1 @chapter Filtering Introduction
2 @c man begin FILTERING INTRODUCTION
4 Filtering in FFmpeg is enabled through the libavfilter library.
6 Libavfilter is the filtering API of FFmpeg. It is the substitute of
7 the now deprecated 'vhooks' and started as a Google Summer of Code
10 Audio filtering integration into the main FFmpeg repository is a work in
11 progress, so audio API and ABI should not be considered stable yet.
13 In libavfilter, it is possible for filters to have multiple inputs and
15 To illustrate the sorts of things that are possible, we can
16 use a complex filter graph. For example, the following one:
19 input --> split --> fifo -----------------------> overlay --> output
22 +------> fifo --> crop --> vflip --------+
25 splits the stream in two streams, sends one stream through the crop filter
26 and the vflip filter before merging it back with the other stream by
27 overlaying it on top. You can use the following command to achieve this:
30 ffmpeg -i input -vf "[in] split [T1], fifo, [T2] overlay=0:H/2 [out]; [T1] fifo, crop=iw:ih/2:0:ih/2, vflip [T2]" output
33 The result will be that in output the top half of the video is mirrored
36 Filters are loaded using the @var{-vf} or @var{-af} option passed to
37 @command{ffmpeg} or to @command{ffplay}. Filters in the same linear
38 chain are separated by commas. In our example, @var{split, fifo,
39 overlay} are in one linear chain, and @var{fifo, crop, vflip} are in
40 another. The points where the linear chains join are labeled by names
41 enclosed in square brackets. In our example, that is @var{[T1]} and
42 @var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points
43 where video is input and output.
45 Some filters take in input a list of parameters: they are specified
46 after the filter name and an equal sign, and are separated from each other
49 There exist so-called @var{source filters} that do not have an
50 audio/video input, and @var{sink filters} that will not have audio/video
53 @c man end FILTERING INTRODUCTION
56 @c man begin GRAPH2DOT
58 The @file{graph2dot} program included in the FFmpeg @file{tools}
59 directory can be used to parse a filter graph description and issue a
60 corresponding textual representation in the dot language.
67 to see how to use @file{graph2dot}.
69 You can then pass the dot description to the @file{dot} program (from
70 the graphviz suite of programs) and obtain a graphical representation
73 For example the sequence of commands:
75 echo @var{GRAPH_DESCRIPTION} | \
76 tools/graph2dot -o graph.tmp && \
77 dot -Tpng graph.tmp -o graph.png && \
81 can be used to create and display an image representing the graph
82 described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be
83 a complete self-contained graph, with its inputs and outputs explicitly defined.
84 For example if your command line is of the form:
86 ffmpeg -i infile -vf scale=640:360 outfile
88 your @var{GRAPH_DESCRIPTION} string will need to be of the form:
90 nullsrc,scale=640:360,nullsink
92 you may also need to set the @var{nullsrc} parameters and add a @var{format}
93 filter in order to simulate a specific input file.
97 @chapter Filtergraph description
98 @c man begin FILTERGRAPH DESCRIPTION
100 A filtergraph is a directed graph of connected filters. It can contain
101 cycles, and there can be multiple links between a pair of
102 filters. Each link has one input pad on one side connecting it to one
103 filter from which it takes its input, and one output pad on the other
104 side connecting it to the one filter accepting its output.
106 Each filter in a filtergraph is an instance of a filter class
107 registered in the application, which defines the features and the
108 number of input and output pads of the filter.
110 A filter with no input pads is called a "source", a filter with no
111 output pads is called a "sink".
113 @anchor{Filtergraph syntax}
114 @section Filtergraph syntax
116 A filtergraph can be represented using a textual representation, which is
117 recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}
118 options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the
119 @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in
120 @file{libavfilter/avfiltergraph.h}.
122 A filterchain consists of a sequence of connected filters, each one
123 connected to the previous one in the sequence. A filterchain is
124 represented by a list of ","-separated filter descriptions.
126 A filtergraph consists of a sequence of filterchains. A sequence of
127 filterchains is represented by a list of ";"-separated filterchain
130 A filter is represented by a string of the form:
131 [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
133 @var{filter_name} is the name of the filter class of which the
134 described filter is an instance of, and has to be the name of one of
135 the filter classes registered in the program.
136 The name of the filter class is optionally followed by a string
139 @var{arguments} is a string which contains the parameters used to
140 initialize the filter instance, and are described in the filter
143 The list of arguments can be quoted using the character "'" as initial
144 and ending mark, and the character '\' for escaping the characters
145 within the quoted text; otherwise the argument string is considered
146 terminated when the next special character (belonging to the set
147 "[]=;,") is encountered.
149 The name and arguments of the filter are optionally preceded and
150 followed by a list of link labels.
151 A link label allows to name a link and associate it to a filter output
152 or input pad. The preceding labels @var{in_link_1}
153 ... @var{in_link_N}, are associated to the filter input pads,
154 the following labels @var{out_link_1} ... @var{out_link_M}, are
155 associated to the output pads.
157 When two link labels with the same name are found in the
158 filtergraph, a link between the corresponding input and output pad is
161 If an output pad is not labelled, it is linked by default to the first
162 unlabelled input pad of the next filter in the filterchain.
163 For example in the filterchain:
165 nullsrc, split[L1], [L2]overlay, nullsink
167 the split filter instance has two output pads, and the overlay filter
168 instance two input pads. The first output pad of split is labelled
169 "L1", the first input pad of overlay is labelled "L2", and the second
170 output pad of split is linked to the second input pad of overlay,
171 which are both unlabelled.
173 In a complete filterchain all the unlabelled filter input and output
174 pads must be connected. A filtergraph is considered valid if all the
175 filter input and output pads of all the filterchains are connected.
177 Libavfilter will automatically insert scale filters where format
178 conversion is required. It is possible to specify swscale flags
179 for those automatically inserted scalers by prepending
180 @code{sws_flags=@var{flags};}
181 to the filtergraph description.
183 Follows a BNF description for the filtergraph syntax:
185 @var{NAME} ::= sequence of alphanumeric characters and '_'
186 @var{LINKLABEL} ::= "[" @var{NAME} "]"
187 @var{LINKLABELS} ::= @var{LINKLABEL} [@var{LINKLABELS}]
188 @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
189 @var{FILTER} ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]
190 @var{FILTERCHAIN} ::= @var{FILTER} [,@var{FILTERCHAIN}]
191 @var{FILTERGRAPH} ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
194 @section Notes on filtergraph escaping
196 Some filter arguments require the use of special characters, typically
197 @code{:} to separate key=value pairs in a named options list. In this
198 case the user should perform a first level escaping when specifying
199 the filter arguments. For example, consider the following literal
200 string to be embedded in the @ref{drawtext} filter arguments:
202 this is a 'string': may contain one, or more, special characters
205 Since @code{:} is special for the filter arguments syntax, it needs to
206 be escaped, so you get:
208 text=this is a \'string\'\: may contain one, or more, special characters
211 A second level of escaping is required when embedding the filter
212 arguments in a filtergraph description, in order to escape all the
213 filtergraph special characters. Thus the example above becomes:
215 drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
218 Finally an additional level of escaping may be needed when writing the
219 filtergraph description in a shell command, which depends on the
220 escaping rules of the adopted shell. For example, assuming that
221 @code{\} is special and needs to be escaped with another @code{\}, the
222 previous string will finally result in:
224 -vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
227 Sometimes, it might be more convenient to employ quoting in place of
228 escaping. For example the string:
230 Caesar: tu quoque, Brute, fili mi
233 Can be quoted in the filter arguments as:
235 text='Caesar: tu quoque, Brute, fili mi'
238 And finally inserted in a filtergraph like:
240 drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
243 See the @ref{quoting_and_escaping, Quoting and escaping} section for
244 more information about the escaping and quoting rules adopted by
247 @c man end FILTERGRAPH DESCRIPTION
249 @chapter Audio Filters
250 @c man begin AUDIO FILTERS
252 When you configure your FFmpeg build, you can disable any of the
253 existing filters using @code{--disable-filters}.
254 The configure output will show the audio filters included in your
257 Below is a description of the currently available audio filters.
261 Convert the input audio format to the specified formats.
263 The filter accepts a string of the form:
264 "@var{sample_format}:@var{channel_layout}".
266 @var{sample_format} specifies the sample format, and can be a string or the
267 corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p'
268 suffix for a planar sample format.
270 @var{channel_layout} specifies the channel layout, and can be a string
271 or the corresponding number value defined in @file{libavutil/channel_layout.h}.
273 The special parameter "auto", signifies that the filter will
274 automatically select the output format depending on the output filter.
276 Some examples follow.
280 Convert input to float, planar, stereo:
286 Convert input to unsigned 8-bit, automatically select out channel layout:
294 Convert the input audio to one of the specified formats. The framework will
295 negotiate the most appropriate format to minimize conversions.
297 The filter accepts the following named parameters:
301 A comma-separated list of requested sample formats.
304 A comma-separated list of requested sample rates.
306 @item channel_layouts
307 A comma-separated list of requested channel layouts.
311 If a parameter is omitted, all values are allowed.
313 For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
315 aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo
320 Merge two or more audio streams into a single multi-channel stream.
322 The filter accepts the following named options:
327 Set the number of inputs. Default is 2.
331 If the channel layouts of the inputs are disjoint, and therefore compatible,
332 the channel layout of the output will be set accordingly and the channels
333 will be reordered as necessary. If the channel layouts of the inputs are not
334 disjoint, the output will have all the channels of the first input then all
335 the channels of the second input, in that order, and the channel layout of
336 the output will be the default value corresponding to the total number of
339 For example, if the first input is in 2.1 (FL+FR+LF) and the second input
340 is FC+BL+BR, then the output will be in 5.1, with the channels in the
341 following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
342 first input, b1 is the first channel of the second input).
344 On the other hand, if both input are in stereo, the output channels will be
345 in the default order: a1, a2, b1, b2, and the channel layout will be
346 arbitrarily set to 4.0, which may or may not be the expected value.
348 All inputs must have the same sample rate, and format.
350 If inputs do not have the same duration, the output will stop with the
353 Example: merge two mono files into a stereo stream:
355 amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
358 Example: multiple merges:
361 amovie=input.mkv:si=0 [a0];
362 amovie=input.mkv:si=1 [a1];
363 amovie=input.mkv:si=2 [a2];
364 amovie=input.mkv:si=3 [a3];
365 amovie=input.mkv:si=4 [a4];
366 amovie=input.mkv:si=5 [a5];
367 [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
372 Mixes multiple audio inputs into a single output.
376 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
378 will mix 3 input audio streams to a single output with the same duration as the
379 first input and a dropout transition time of 3 seconds.
381 The filter accepts the following named parameters:
385 Number of inputs. If unspecified, it defaults to 2.
388 How to determine the end-of-stream.
392 Duration of longest input. (default)
395 Duration of shortest input.
398 Duration of first input.
402 @item dropout_transition
403 Transition time, in seconds, for volume renormalization when an input
404 stream ends. The default value is 2 seconds.
410 Pass the audio source unchanged to the output.
414 Resample the input audio to the specified parameters. If none are specified
415 then the filter will automatically convert between its input
418 This filter is also able to stretch/squeeze the audio data to make it match
419 the timestamps or to inject silence / cut out audio to make it match the
420 timestamps, do a combination of both or do neither.
422 The filter accepts the following named parameters:
426 Minimum difference between timestamps and audio data (in seconds) to trigger
427 stretching/squeezing/filling or trimming of the data to make it match the
428 timestamps. The default is that stretching/squeezing/filling and
429 trimming is disabled (min_comp = infinite).
432 Minimum difference between timestamps and audio data (in seconds) to trigger
433 adding/dropping samples to make it match the timestamps.
434 This option effectively is a threshold to select between hard (trim/fill) and
435 soft (squeeze/stretch) compensation. Note that all compensation is by default
436 disabled through min_comp.
437 The default is 0.1 seconds.
440 Maximum stretch/squeeze factor.
443 @item tsf, internal_sample_fmt
444 Internal sampling format.
445 Default is automatic selection
447 @item clev, center_mix_level
448 center mix level, for rematrixing
451 @item slev, surround_mix_level
452 surround mix level, for rematrixing
455 @item rmvol, rematrix_volume
460 Low frequency effects mix level.
463 @item matrix_encoding
464 matrixed stereo encoding
467 No matrixed stereo encoding
470 Dolby matrixed stereo encoding
473 Dolby Pro Logic II matrixed stereo encoding
476 Default value is @code{none}.
480 For example, to resample the input audio to 44100Hz:
485 @section asetnsamples
487 Set the number of samples per each output audio frame.
489 The last output packet may contain a different number of samples, as
490 the filter will flush all the remaining samples when the input audio
493 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
498 @item nb_out_samples, n
499 Set the number of frames per each output audio frame. The number is
500 intended as the number of samples @emph{per each channel}.
501 Default value is 1024.
504 If set to 1, the filter will pad the last audio frame with zeroes, so
505 that the last frame will contain the same number of samples as the
506 previous ones. Default value is 1.
509 For example, to set the number of per-frame samples to 1234 and
510 disable padding for the last frame, use:
512 asetnsamples=n=1234:p=0
517 Show a line containing various information for each input audio frame.
518 The input audio is not modified.
520 The shown line contains a sequence of key/value pairs of the form
521 @var{key}:@var{value}.
523 A description of each shown parameter follows:
527 sequential number of the input frame, starting from 0
530 Presentation timestamp of the input frame, in time base units; the time base
531 depends on the filter input pad, and is usually 1/@var{sample_rate}.
534 presentation timestamp of the input frame in seconds
537 position of the frame in the input stream, -1 if this information in
538 unavailable and/or meaningless (for example in case of synthetic audio)
547 sample rate for the audio frame
550 number of samples (per channel) in the frame
553 Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
554 the data is treated as if all the planes were concatenated.
556 @item plane_checksums
557 A list of Adler-32 checksums for each data plane.
562 Split input audio into several identical outputs.
564 The filter accepts a single parameter which specifies the number of outputs. If
565 unspecified, it defaults to 2.
569 [in] asplit [out0][out1]
572 will create two separate outputs from the same input.
574 To create 3 or more outputs, you need to specify the number of
577 [in] asplit=3 [out0][out1][out2]
581 ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
583 will create 5 copies of the input audio.
588 Forward two audio streams and control the order the buffers are forwarded.
590 The argument to the filter is an expression deciding which stream should be
591 forwarded next: if the result is negative, the first stream is forwarded; if
592 the result is positive or zero, the second stream is forwarded. It can use
593 the following variables:
597 number of buffers forwarded so far on each stream
599 number of samples forwarded so far on each stream
601 current timestamp of each stream
604 The default value is @code{t1-t2}, which means to always forward the stream
605 that has a smaller timestamp.
607 Example: stress-test @code{amerge} by randomly sending buffers on the wrong
608 input, while avoiding too much of a desynchronization:
610 amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
611 [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
619 The filter accepts exactly one parameter, the audio tempo. If not
620 specified then the filter will assume nominal 1.0 tempo. Tempo must
621 be in the [0.5, 2.0] range.
623 For example, to slow down audio to 80% tempo:
628 For example, to speed up audio to 125% tempo:
635 Make audio easier to listen to on headphones.
637 This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
638 so that when listened to on headphones the stereo image is moved from
639 inside your head (standard for headphones) to outside and in front of
640 the listener (standard for speakers).
646 Mix channels with specific gain levels. The filter accepts the output
647 channel layout followed by a set of channels definitions.
649 This filter is also designed to remap efficiently the channels of an audio
652 The filter accepts parameters of the form:
653 "@var{l}:@var{outdef}:@var{outdef}:..."
657 output channel layout or number of channels
660 output channel specification, of the form:
661 "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
664 output channel to define, either a channel name (FL, FR, etc.) or a channel
665 number (c0, c1, etc.)
668 multiplicative coefficient for the channel, 1 leaving the volume unchanged
671 input channel to use, see out_name for details; it is not possible to mix
672 named and numbered input channels
675 If the `=' in a channel specification is replaced by `<', then the gains for
676 that specification will be renormalized so that the total is 1, thus
677 avoiding clipping noise.
679 @subsection Mixing examples
681 For example, if you want to down-mix from stereo to mono, but with a bigger
682 factor for the left channel:
684 pan=1:c0=0.9*c0+0.1*c1
687 A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
690 pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
693 Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
694 that should be preferred (see "-ac" option) unless you have very specific
697 @subsection Remapping examples
699 The channel remapping will be effective if, and only if:
702 @item gain coefficients are zeroes or ones,
703 @item only one input per channel output,
706 If all these conditions are satisfied, the filter will notify the user ("Pure
707 channel mapping detected"), and use an optimized and lossless method to do the
710 For example, if you have a 5.1 source and want a stereo audio stream by
711 dropping the extra channels:
713 pan="stereo: c0=FL : c1=FR"
716 Given the same source, you can also switch front left and front right channels
717 and keep the input channel layout:
719 pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
722 If the input is a stereo audio stream, you can mute the front left channel (and
723 still keep the stereo channel layout) with:
728 Still with a stereo audio stream input, you can copy the right channel in both
729 front left and right:
731 pan="stereo: c0=FR : c1=FR"
734 @section silencedetect
736 Detect silence in an audio stream.
738 This filter logs a message when it detects that the input audio volume is less
739 or equal to a noise tolerance value for a duration greater or equal to the
740 minimum detected noise duration.
742 The printed times and duration are expressed in seconds.
746 Set silence duration until notification (default is 2 seconds).
749 Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
750 specified value) or amplitude ratio. Default is -60dB, or 0.001.
753 Detect 5 seconds of silence with -50dB noise tolerance:
755 silencedetect=n=-50dB:d=5
758 Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
759 tolerance in @file{silence.mp3}:
761 ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
765 Synchronize audio data with timestamps by squeezing/stretching it and/or
766 dropping samples/adding silence when needed.
768 The filter accepts the following named parameters:
772 Enable stretching/squeezing the data to make it match the timestamps. Disabled
773 by default. When disabled, time gaps are covered with silence.
776 Minimum difference between timestamps and audio data (in seconds) to trigger
777 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
778 this filter, try setting this parameter to 0.
781 Maximum compensation in samples per second. Relevant only with compensate=1.
785 Assume the first pts should be this value. The time base is 1 / sample rate.
786 This allows for padding/trimming at the start of stream. By default, no
787 assumption is made about the first frame's expected pts, so no padding or
788 trimming is done. For example, this could be set to 0 to pad the beginning with
789 silence if an audio stream starts after the video stream or to trim any samples
790 with a negative pts due to encoder delay.
794 @section channelsplit
795 Split each channel in input audio stream into a separate output stream.
797 This filter accepts the following named parameters:
800 Channel layout of the input stream. Default is "stereo".
803 For example, assuming a stereo input MP3 file
805 ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
807 will create an output Matroska file with two audio streams, one containing only
808 the left channel and the other the right channel.
810 To split a 5.1 WAV file into per-channel files
812 ffmpeg -i in.wav -filter_complex
813 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
814 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
815 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
820 Remap input channels to new locations.
822 This filter accepts the following named parameters:
825 Channel layout of the output stream.
828 Map channels from input to output. The argument is a comma-separated list of
829 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
830 @var{in_channel} form. @var{in_channel} can be either the name of the input
831 channel (e.g. FL for front left) or its index in the input channel layout.
832 @var{out_channel} is the name of the output channel or its index in the output
833 channel layout. If @var{out_channel} is not given then it is implicitly an
834 index, starting with zero and increasing by one for each mapping.
837 If no mapping is present, the filter will implicitly map input channels to
838 output channels preserving index.
840 For example, assuming a 5.1+downmix input MOV file
842 ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
844 will create an output WAV file tagged as stereo from the downmix channels of
847 To fix a 5.1 WAV improperly encoded in AAC's native channel order
849 ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
853 Join multiple input streams into one multi-channel stream.
855 The filter accepts the following named parameters:
859 Number of input streams. Defaults to 2.
862 Desired output channel layout. Defaults to stereo.
865 Map channels from inputs to output. The argument is a comma-separated list of
866 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
867 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
868 can be either the name of the input channel (e.g. FL for front left) or its
869 index in the specified input stream. @var{out_channel} is the name of the output
873 The filter will attempt to guess the mappings when those are not specified
874 explicitly. It does so by first trying to find an unused matching input channel
875 and if that fails it picks the first unused input channel.
877 E.g. to join 3 inputs (with properly set channel layouts)
879 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
882 To build a 5.1 output from 6 single-channel streams:
884 ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
885 'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE'
890 Convert the audio sample format, sample rate and channel layout. This filter is
891 not meant to be used directly.
895 Adjust the input audio volume.
897 The filter accepts the following named parameters. If the key of the
898 first options is omitted, the arguments are interpreted according to
899 the following syntax:
901 volume=@var{volume}:@var{precision}
907 Expresses how the audio volume will be increased or decreased.
909 Output values are clipped to the maximum value.
911 The output audio volume is given by the relation:
913 @var{output_volume} = @var{volume} * @var{input_volume}
916 Default value for @var{volume} is 1.0.
919 Set the mathematical precision.
921 This determines which input sample formats will be allowed, which affects the
922 precision of the volume scaling.
926 8-bit fixed-point; limits input sample format to U8, S16, and S32.
928 32-bit floating-point; limits input sample format to FLT. (default)
930 64-bit floating-point; limits input sample format to DBL.
938 Halve the input audio volume:
942 volume=volume=-6.0206dB
945 In all the above example the named key for @option{volume} can be
946 omitted, for example like in:
952 Increase input audio power by 6 decibels using fixed-point precision:
954 volume=volume=6dB:precision=fixed
958 @section volumedetect
960 Detect the volume of the input video.
962 The filter has no parameters. The input is not modified. Statistics about
963 the volume will be printed in the log when the input stream end is reached.
965 In particular it will show the mean volume (root mean square), maximum
966 volume (on a per-sample basis), and the beginning of an histogram of the
967 registered volume values (from the maximum value to a cumulated 1/1000 of
970 All volumes are in decibels relative to the maximum PCM value.
972 Here is an excerpt of the output:
974 [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
975 [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
976 [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
977 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
978 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
979 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
980 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
981 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
982 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
988 The mean square energy is approximately -27 dB, or 10^-2.7.
990 The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
992 There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
995 In other words, raising the volume by +4 dB does not cause any clipping,
996 raising it by +5 dB causes clipping for 6 samples, etc.
998 @c man end AUDIO FILTERS
1000 @chapter Audio Sources
1001 @c man begin AUDIO SOURCES
1003 Below is a description of the currently available audio sources.
1007 Buffer audio frames, and make them available to the filter chain.
1009 This source is mainly intended for a programmatic use, in particular
1010 through the interface defined in @file{libavfilter/asrc_abuffer.h}.
1012 It accepts the following mandatory parameters:
1013 @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}
1018 The sample rate of the incoming audio buffers.
1021 The sample format of the incoming audio buffers.
1022 Either a sample format name or its corresponging integer representation from
1023 the enum AVSampleFormat in @file{libavutil/samplefmt.h}
1025 @item channel_layout
1026 The channel layout of the incoming audio buffers.
1027 Either a channel layout name from channel_layout_map in
1028 @file{libavutil/channel_layout.c} or its corresponding integer representation
1029 from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h}
1035 abuffer=44100:s16p:stereo
1038 will instruct the source to accept planar 16bit signed stereo at 44100Hz.
1039 Since the sample format with name "s16p" corresponds to the number
1040 6 and the "stereo" channel layout corresponds to the value 0x3, this is
1048 Generate an audio signal specified by an expression.
1050 This source accepts in input one or more expressions (one for each
1051 channel), which are evaluated and used to generate a corresponding
1054 It accepts the syntax: @var{exprs}[::@var{options}].
1055 @var{exprs} is a list of expressions separated by ":", one for each
1056 separate channel. In case the @var{channel_layout} is not
1057 specified, the selected channel layout depends on the number of
1058 provided expressions.
1060 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
1063 The description of the accepted options follows.
1067 @item channel_layout, c
1068 Set the channel layout. The number of channels in the specified layout
1069 must be equal to the number of specified expressions.
1072 Set the minimum duration of the sourced audio. See the function
1073 @code{av_parse_time()} for the accepted format.
1074 Note that the resulting duration may be greater than the specified
1075 duration, as the generated audio is always cut at the end of a
1078 If not specified, or the expressed duration is negative, the audio is
1079 supposed to be generated forever.
1082 Set the number of samples per channel per each output frame,
1085 @item sample_rate, s
1086 Specify the sample rate, default to 44100.
1089 Each expression in @var{exprs} can contain the following constants:
1093 number of the evaluated sample, starting from 0
1096 time of the evaluated sample expressed in seconds, starting from 0
1103 @subsection Examples
1115 Generate a sin signal with frequency of 440 Hz, set sample rate to
1118 aevalsrc="sin(440*2*PI*t)::s=8000"
1122 Generate a two channels signal, specify the channel layout (Front
1123 Center + Back Center) explicitly:
1125 aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
1129 Generate white noise:
1131 aevalsrc="-2+random(0)"
1135 Generate an amplitude modulated signal:
1137 aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
1141 Generate 2.5 Hz binaural beats on a 360 Hz carrier:
1143 aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
1150 Null audio source, return unprocessed audio frames. It is mainly useful
1151 as a template and to be employed in analysis / debugging tools, or as
1152 the source for filters which ignore the input data (for example the sox
1155 It accepts an optional sequence of @var{key}=@var{value} pairs,
1158 The description of the accepted options follows.
1162 @item sample_rate, s
1163 Specify the sample rate, and defaults to 44100.
1165 @item channel_layout, cl
1167 Specify the channel layout, and can be either an integer or a string
1168 representing a channel layout. The default value of @var{channel_layout}
1171 Check the channel_layout_map definition in
1172 @file{libavutil/channel_layout.c} for the mapping between strings and
1173 channel layout values.
1176 Set the number of samples per requested frames.
1180 Follow some examples:
1182 # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
1183 anullsrc=r=48000:cl=4
1186 anullsrc=r=48000:cl=mono
1190 Buffer audio frames, and make them available to the filter chain.
1192 This source is not intended to be part of user-supplied graph descriptions but
1193 for insertion by calling programs through the interface defined in
1194 @file{libavfilter/buffersrc.h}.
1196 It accepts the following named parameters:
1200 Timebase which will be used for timestamps of submitted frames. It must be
1201 either a floating-point number or in @var{numerator}/@var{denominator} form.
1207 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
1209 @item channel_layout
1210 Channel layout of the audio data, in the form that can be accepted by
1211 @code{av_get_channel_layout()}.
1214 All the parameters need to be explicitly defined.
1218 Synthesize a voice utterance using the libflite library.
1220 To enable compilation of this filter you need to configure FFmpeg with
1221 @code{--enable-libflite}.
1223 Note that the flite library is not thread-safe.
1225 The source accepts parameters as a list of @var{key}=@var{value} pairs,
1228 The description of the accepted parameters follows.
1233 If set to 1, list the names of the available voices and exit
1234 immediately. Default value is 0.
1237 Set the maximum number of samples per frame. Default value is 512.
1240 Set the filename containing the text to speak.
1243 Set the text to speak.
1246 Set the voice to use for the speech synthesis. Default value is
1247 @code{kal}. See also the @var{list_voices} option.
1250 @subsection Examples
1254 Read from file @file{speech.txt}, and synthetize the text using the
1255 standard flite voice:
1257 flite=textfile=speech.txt
1261 Read the specified text selecting the @code{slt} voice:
1263 flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1267 Input text to ffmpeg:
1269 ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1273 Make @file{ffplay} speak the specified text, using @code{flite} and
1274 the @code{lavfi} device:
1276 ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
1280 For more information about libflite, check:
1281 @url{http://www.speech.cs.cmu.edu/flite/}
1283 @c man end AUDIO SOURCES
1285 @chapter Audio Sinks
1286 @c man begin AUDIO SINKS
1288 Below is a description of the currently available audio sinks.
1290 @section abuffersink
1292 Buffer audio frames, and make them available to the end of filter chain.
1294 This sink is mainly intended for programmatic use, in particular
1295 through the interface defined in @file{libavfilter/buffersink.h}.
1297 It requires a pointer to an AVABufferSinkContext structure, which
1298 defines the incoming buffers' formats, to be passed as the opaque
1299 parameter to @code{avfilter_init_filter} for initialization.
1303 Null audio sink, do absolutely nothing with the input audio. It is
1304 mainly useful as a template and to be employed in analysis / debugging
1307 @section abuffersink
1308 This sink is intended for programmatic use. Frames that arrive on this sink can
1309 be retrieved by the calling program using the interface defined in
1310 @file{libavfilter/buffersink.h}.
1312 This filter accepts no parameters.
1314 @c man end AUDIO SINKS
1316 @chapter Video Filters
1317 @c man begin VIDEO FILTERS
1319 When you configure your FFmpeg build, you can disable any of the
1320 existing filters using @code{--disable-filters}.
1321 The configure output will show the video filters included in your
1324 Below is a description of the currently available video filters.
1326 @section alphaextract
1328 Extract the alpha component from the input as a grayscale video. This
1329 is especially useful with the @var{alphamerge} filter.
1333 Add or replace the alpha component of the primary input with the
1334 grayscale value of a second input. This is intended for use with
1335 @var{alphaextract} to allow the transmission or storage of frame
1336 sequences that have alpha in a format that doesn't support an alpha
1339 For example, to reconstruct full frames from a normal YUV-encoded video
1340 and a separate video created with @var{alphaextract}, you might use:
1342 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
1345 Since this filter is designed for reconstruction, it operates on frame
1346 sequences without considering timestamps, and terminates when either
1347 input reaches end of stream. This will cause problems if your encoding
1348 pipeline drops frames. If you're trying to apply an image as an
1349 overlay to a video stream, consider the @var{overlay} filter instead.
1353 Same as the @ref{subtitles} filter, except that it doesn't require libavcodec
1354 and libavformat to work. On the other hand, it is limited to ASS (Advanced
1355 Substation Alpha) subtitles files.
1359 Compute the bounding box for the non-black pixels in the input frame
1362 This filter computes the bounding box containing all the pixels with a
1363 luminance value greater than the minimum allowed value.
1364 The parameters describing the bounding box are printed on the filter
1367 @section blackdetect
1369 Detect video intervals that are (almost) completely black. Can be
1370 useful to detect chapter transitions, commercials, or invalid
1371 recordings. Output lines contains the time for the start, end and
1372 duration of the detected black interval expressed in seconds.
1374 In order to display the output lines, you need to set the loglevel at
1375 least to the AV_LOG_INFO value.
1377 This filter accepts a list of options in the form of
1378 @var{key}=@var{value} pairs separated by ":". A description of the
1379 accepted options follows.
1382 @item black_min_duration, d
1383 Set the minimum detected black duration expressed in seconds. It must
1384 be a non-negative floating point number.
1386 Default value is 2.0.
1388 @item picture_black_ratio_th, pic_th
1389 Set the threshold for considering a picture "black".
1390 Express the minimum value for the ratio:
1392 @var{nb_black_pixels} / @var{nb_pixels}
1395 for which a picture is considered black.
1396 Default value is 0.98.
1398 @item pixel_black_th, pix_th
1399 Set the threshold for considering a pixel "black".
1401 The threshold expresses the maximum pixel luminance value for which a
1402 pixel is considered "black". The provided value is scaled according to
1403 the following equation:
1405 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
1408 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
1409 the input video format, the range is [0-255] for YUV full-range
1410 formats and [16-235] for YUV non full-range formats.
1412 Default value is 0.10.
1415 The following example sets the maximum pixel threshold to the minimum
1416 value, and detects only black intervals of 2 or more seconds:
1418 blackdetect=d=2:pix_th=0.00
1423 Detect frames that are (almost) completely black. Can be useful to
1424 detect chapter transitions or commercials. Output lines consist of
1425 the frame number of the detected frame, the percentage of blackness,
1426 the position in the file if known or -1 and the timestamp in seconds.
1428 In order to display the output lines, you need to set the loglevel at
1429 least to the AV_LOG_INFO value.
1431 The filter accepts the syntax:
1433 blackframe[=@var{amount}:[@var{threshold}]]
1436 @var{amount} is the percentage of the pixels that have to be below the
1437 threshold, and defaults to 98.
1439 @var{threshold} is the threshold below which a pixel value is
1440 considered black, and defaults to 32.
1444 Apply boxblur algorithm to the input video.
1446 This filter accepts the parameters:
1447 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
1449 Chroma and alpha parameters are optional, if not specified they default
1450 to the corresponding values set for @var{luma_radius} and
1453 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
1454 the radius in pixels of the box used for blurring the corresponding
1455 input plane. They are expressions, and can contain the following
1459 the input width and height in pixels
1462 the input chroma image width and height in pixels
1465 horizontal and vertical chroma subsample values. For example for the
1466 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1469 The radius must be a non-negative number, and must not be greater than
1470 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
1471 and of @code{min(cw,ch)/2} for the chroma planes.
1473 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
1474 how many times the boxblur filter is applied to the corresponding
1477 Some examples follow:
1482 Apply a boxblur filter with luma, chroma, and alpha radius
1489 Set luma radius to 2, alpha and chroma radius to 0
1495 Set luma and chroma radius to a fraction of the video dimension
1497 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
1502 @section colormatrix
1504 The colormatrix filter allows conversion between any of the following color
1505 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
1506 and FCC (@var{fcc}).
1508 The syntax of the parameters is @var{source}:@var{destination}:
1511 colormatrix=bt601:smpte240m
1516 Copy the input source unchanged to the output. Mainly useful for
1521 Crop the input video.
1523 This filter accepts a list of @var{key}=@var{value} pairs as argument,
1524 separated by ':'. If the key of the first options is omitted, the
1525 arguments are interpreted according to the syntax
1526 @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}.
1528 A description of the accepted options follows:
1531 Set the crop area width. It defaults to @code{iw}.
1532 This expression is evaluated only once during the filter
1536 Set the crop area width. It defaults to @code{ih}.
1537 This expression is evaluated only once during the filter
1541 Set the expression for the x top-left coordinate of the cropped area.
1542 It defaults to @code{(in_w-out_w)/2}.
1543 This expression is evaluated per-frame.
1546 Set the expression for the y top-left coordinate of the cropped area.
1547 It defaults to @code{(in_h-out_h)/2}.
1548 This expression is evaluated per-frame.
1551 If set to 1 will force the output display aspect ratio
1552 to be the same of the input, by changing the output sample aspect
1553 ratio. It defaults to 0.
1556 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1557 expressions containing the following constants:
1561 the computed values for @var{x} and @var{y}. They are evaluated for
1565 the input width and height
1568 same as @var{in_w} and @var{in_h}
1571 the output (cropped) width and height
1574 same as @var{out_w} and @var{out_h}
1577 same as @var{iw} / @var{ih}
1580 input sample aspect ratio
1583 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1586 horizontal and vertical chroma subsample values. For example for the
1587 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1590 the number of input frame, starting from 0
1593 the position in the file of the input frame, NAN if unknown
1596 timestamp expressed in seconds, NAN if the input timestamp is unknown
1600 The expression for @var{out_w} may depend on the value of @var{out_h},
1601 and the expression for @var{out_h} may depend on @var{out_w}, but they
1602 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1603 evaluated after @var{out_w} and @var{out_h}.
1605 The @var{x} and @var{y} parameters specify the expressions for the
1606 position of the top-left corner of the output (non-cropped) area. They
1607 are evaluated for each frame. If the evaluated value is not valid, it
1608 is approximated to the nearest valid value.
1610 The expression for @var{x} may depend on @var{y}, and the expression
1611 for @var{y} may depend on @var{x}.
1613 Follow some examples:
1615 # crop the central input area with size 100x100
1618 # crop the central input area with size 2/3 of the input video
1619 "crop=2/3*in_w:2/3*in_h"
1621 # crop the input video central square
1624 # delimit the rectangle with the top-left corner placed at position
1625 # 100:100 and the right-bottom corner corresponding to the right-bottom
1626 # corner of the input image.
1627 crop=in_w-100:in_h-100:100:100
1629 # crop 10 pixels from the left and right borders, and 20 pixels from
1630 # the top and bottom borders
1631 "crop=in_w-2*10:in_h-2*20"
1633 # keep only the bottom right quarter of the input image
1634 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1636 # crop height for getting Greek harmony
1637 "crop=in_w:1/PHI*in_w"
1640 "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
1642 # erratic camera effect depending on timestamp
1643 "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
1645 # set x depending on the value of y
1646 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1651 Auto-detect crop size.
1653 Calculate necessary cropping parameters and prints the recommended
1654 parameters through the logging system. The detected dimensions
1655 correspond to the non-black area of the input video.
1657 It accepts the syntax:
1659 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1665 Threshold, which can be optionally specified from nothing (0) to
1666 everything (255), defaults to 24.
1669 Value which the width/height should be divisible by, defaults to
1670 16. The offset is automatically adjusted to center the video. Use 2 to
1671 get only even dimensions (needed for 4:2:2 video). 16 is best when
1672 encoding to most video codecs.
1675 Counter that determines after how many frames cropdetect will reset
1676 the previously detected largest video area and start over to detect
1677 the current optimal crop area. Defaults to 0.
1679 This can be useful when channel logos distort the video area. 0
1680 indicates never reset and return the largest area encountered during
1686 This filter drops frames that do not differ greatly from the previous
1687 frame in order to reduce framerate. The main use of this filter is
1688 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1689 it could in theory be used for fixing movies that were
1690 inverse-telecined incorrectly.
1692 It accepts the following parameters:
1693 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1698 Set the maximum number of consecutive frames which can be dropped (if
1699 positive), or the minimum interval between dropped frames (if
1700 negative). If the value is 0, the frame is dropped unregarding the
1701 number of previous sequentially dropped frames.
1706 Set the dropping threshold values.
1708 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1709 represent actual pixel value differences, so a threshold of 64
1710 corresponds to 1 unit of difference for each pixel, or the same spread
1711 out differently over the block.
1713 A frame is a candidate for dropping if no 8x8 blocks differ by more
1714 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1715 meaning the whole image) differ by more than a threshold of @var{lo}.
1717 Default value for @var{hi} is 64*12, default value for @var{lo} is
1718 64*5, and default value for @var{frac} is 0.33.
1723 Suppress a TV station logo by a simple interpolation of the surrounding
1724 pixels. Just set a rectangle covering the logo and watch it disappear
1725 (and sometimes something even uglier appear - your mileage may vary).
1727 The filter accepts parameters as a string of the form
1728 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1729 @var{key}=@var{value} pairs, separated by ":".
1731 The description of the accepted parameters follows.
1736 Specify the top left corner coordinates of the logo. They must be
1740 Specify the width and height of the logo to clear. They must be
1744 Specify the thickness of the fuzzy edge of the rectangle (added to
1745 @var{w} and @var{h}). The default value is 4.
1748 When set to 1, a green rectangle is drawn on the screen to simplify
1749 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1750 @var{band} is set to 4. The default value is 0.
1754 Some examples follow.
1759 Set a rectangle covering the area with top left corner coordinates 0,0
1760 and size 100x77, setting a band of size 10:
1762 delogo=0:0:100:77:10
1766 As the previous example, but use named options:
1768 delogo=x=0:y=0:w=100:h=77:band=10
1775 Attempt to fix small changes in horizontal and/or vertical shift. This
1776 filter helps remove camera shake from hand-holding a camera, bumping a
1777 tripod, moving on a vehicle, etc.
1779 The filter accepts parameters as a string of the form
1780 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1782 A description of the accepted parameters follows.
1787 Specify a rectangular area where to limit the search for motion
1789 If desired the search for motion vectors can be limited to a
1790 rectangular area of the frame defined by its top left corner, width
1791 and height. These parameters have the same meaning as the drawbox
1792 filter which can be used to visualise the position of the bounding
1795 This is useful when simultaneous movement of subjects within the frame
1796 might be confused for camera motion by the motion vector search.
1798 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1799 then the full frame is used. This allows later options to be set
1800 without specifying the bounding box for the motion vector search.
1802 Default - search the whole frame.
1805 Specify the maximum extent of movement in x and y directions in the
1806 range 0-64 pixels. Default 16.
1809 Specify how to generate pixels to fill blanks at the edge of the
1810 frame. An integer from 0 to 3 as follows:
1813 Fill zeroes at blank locations
1815 Original image at blank locations
1817 Extruded edge value at blank locations
1819 Mirrored edge at blank locations
1822 The default setting is mirror edge at blank locations.
1825 Specify the blocksize to use for motion search. Range 4-128 pixels,
1829 Specify the contrast threshold for blocks. Only blocks with more than
1830 the specified contrast (difference between darkest and lightest
1831 pixels) will be considered. Range 1-255, default 125.
1834 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1835 search. Default - exhaustive search.
1838 If set then a detailed log of the motion search is written to the
1845 Draw a colored box on the input image.
1847 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1850 The description of the accepted parameters follows.
1854 Specify the top left corner coordinates of the box. Default to 0.
1858 Specify the width and height of the box, if 0 they are interpreted as
1859 the input width and height. Default to 0.
1862 Specify the color of the box to write, it can be the name of a color
1863 (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
1864 value @code{invert} is used, the box edge color is the same as the
1865 video with inverted luma.
1868 Set the thickness of the box edge. Default value is @code{4}.
1871 If the key of the first options is omitted, the arguments are
1872 interpreted according to the following syntax:
1874 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness}
1877 Some examples follow:
1880 Draw a black box around the edge of the input image:
1886 Draw a box with color red and an opacity of 50%:
1888 drawbox=10:20:200:60:red@@0.5
1891 The previous example can be specified as:
1893 drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
1897 Fill the box with pink color:
1899 drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
1906 Draw text string or text from specified file on top of video using the
1907 libfreetype library.
1909 To enable compilation of this filter you need to configure FFmpeg with
1910 @code{--enable-libfreetype}.
1914 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1917 The description of the accepted parameters follows.
1922 Used to draw a box around text using background color.
1923 Value should be either 1 (enable) or 0 (disable).
1924 The default value of @var{box} is 0.
1927 The color to be used for drawing box around text.
1928 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1929 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1930 The default value of @var{boxcolor} is "white".
1933 Set an expression which specifies if the text should be drawn. If the
1934 expression evaluates to 0, the text is not drawn. This is useful for
1935 specifying that the text should be drawn only when specific conditions
1938 Default value is "1".
1940 See below for the list of accepted constants and functions.
1943 Select how the @var{text} is expanded. Can be either @code{none},
1944 @code{strftime} (default for compatibity reasons but deprecated) or
1945 @code{normal}. See the @ref{drawtext_expansion, Text expansion} section
1949 If true, check and fix text coords to avoid clipping.
1952 The color to be used for drawing fonts.
1953 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1954 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1955 The default value of @var{fontcolor} is "black".
1958 The font file to be used for drawing text. Path must be included.
1959 This parameter is mandatory.
1962 The font size to be used for drawing text.
1963 The default value of @var{fontsize} is 16.
1966 Flags to be used for loading the fonts.
1968 The flags map the corresponding flags supported by libfreetype, and are
1969 a combination of the following values:
1976 @item vertical_layout
1977 @item force_autohint
1980 @item ignore_global_advance_width
1982 @item ignore_transform
1989 Default value is "render".
1991 For more information consult the documentation for the FT_LOAD_*
1995 The color to be used for drawing a shadow behind the drawn text. It
1996 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1997 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1998 The default value of @var{shadowcolor} is "black".
2000 @item shadowx, shadowy
2001 The x and y offsets for the text shadow position with respect to the
2002 position of the text. They can be either positive or negative
2003 values. Default value for both is "0".
2006 The size in number of spaces to use for rendering the tab.
2010 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
2011 format. It can be used with or without text parameter. @var{timecode_rate}
2012 option must be specified.
2014 @item timecode_rate, rate, r
2015 Set the timecode frame rate (timecode only).
2018 The text string to be drawn. The text must be a sequence of UTF-8
2020 This parameter is mandatory if no file is specified with the parameter
2024 A text file containing text to be drawn. The text must be a sequence
2025 of UTF-8 encoded characters.
2027 This parameter is mandatory if no text string is specified with the
2028 parameter @var{text}.
2030 If both @var{text} and @var{textfile} are specified, an error is thrown.
2033 If set to 1, the @var{textfile} will be reloaded before each frame.
2034 Be sure to update it atomically, or it may be read partially, or even fail.
2037 The expressions which specify the offsets where text will be drawn
2038 within the video frame. They are relative to the top/left border of the
2041 The default value of @var{x} and @var{y} is "0".
2043 See below for the list of accepted constants and functions.
2046 The parameters for @var{x} and @var{y} are expressions containing the
2047 following constants and functions:
2051 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
2054 horizontal and vertical chroma subsample values. For example for the
2055 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2058 the height of each text line
2066 @item max_glyph_a, ascent
2067 the maximum distance from the baseline to the highest/upper grid
2068 coordinate used to place a glyph outline point, for all the rendered
2070 It is a positive value, due to the grid's orientation with the Y axis
2073 @item max_glyph_d, descent
2074 the maximum distance from the baseline to the lowest grid coordinate
2075 used to place a glyph outline point, for all the rendered glyphs.
2076 This is a negative value, due to the grid's orientation, with the Y axis
2080 maximum glyph height, that is the maximum height for all the glyphs
2081 contained in the rendered text, it is equivalent to @var{ascent} -
2085 maximum glyph width, that is the maximum width for all the glyphs
2086 contained in the rendered text
2089 the number of input frame, starting from 0
2091 @item rand(min, max)
2092 return a random number included between @var{min} and @var{max}
2095 input sample aspect ratio
2098 timestamp expressed in seconds, NAN if the input timestamp is unknown
2101 the height of the rendered text
2104 the width of the rendered text
2107 the x and y offset coordinates where the text is drawn.
2109 These parameters allow the @var{x} and @var{y} expressions to refer
2110 each other, so you can for example specify @code{y=x/dar}.
2113 If libavfilter was built with @code{--enable-fontconfig}, then
2114 @option{fontfile} can be a fontconfig pattern or omitted.
2116 @anchor{drawtext_expansion}
2117 @subsection Text expansion
2119 If @option{expansion} is set to @code{strftime} (which is the default for
2120 now), the filter recognizes strftime() sequences in the provided text and
2121 expands them accordingly. Check the documentation of strftime(). This
2122 feature is deprecated.
2124 If @option{expansion} is set to @code{none}, the text is printed verbatim.
2126 If @option{expansion} is set to @code{normal} (which will be the default),
2127 the following expansion mechanism is used.
2129 The backslash character '\', followed by any character, always expands to
2130 the second character.
2132 Sequence of the form @code{%@{...@}} are expanded. The text between the
2133 braces is a function name, possibly followed by arguments separated by ':'.
2134 If the arguments contain special characters or delimiters (':' or '@}'),
2135 they should be escaped.
2137 Note that they probably must also be escaped as the value for the
2138 @option{text} option in the filter argument string and as the filter
2139 argument in the filter graph description, and possibly also for the shell,
2140 that makes up to four levels of escaping; using a text file avoids these
2143 The following functions are available:
2148 The expression evaluation result.
2150 It must take one argument specifying the expression to be evaluated,
2151 which accepts the same constants and functions as the @var{x} and
2152 @var{y} values. Note that not all constants should be used, for
2153 example the text size is not known when evaluating the expression, so
2154 the constants @var{text_w} and @var{text_h} will have an undefined
2158 The time at which the filter is running, expressed in UTC.
2159 It can accept an argument: a strftime() format string.
2162 The time at which the filter is running, expressed in the local time zone.
2163 It can accept an argument: a strftime() format string.
2166 The frame number, starting from 0.
2169 The timestamp of the current frame, in seconds, with microsecond accuracy.
2173 @subsection Examples
2175 Some examples follow.
2180 Draw "Test Text" with font FreeSerif, using the default values for the
2181 optional parameters.
2184 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
2188 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
2189 and y=50 (counting from the top-left corner of the screen), text is
2190 yellow with a red box around it. Both the text and the box have an
2194 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
2195 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
2198 Note that the double quotes are not necessary if spaces are not used
2199 within the parameter list.
2202 Show the text at the center of the video frame:
2204 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
2208 Show a text line sliding from right to left in the last row of the video
2209 frame. The file @file{LONG_LINE} is assumed to contain a single line
2212 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
2216 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
2218 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
2222 Draw a single green letter "g", at the center of the input video.
2223 The glyph baseline is placed at half screen height.
2225 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2229 Show text for 1 second every 3 seconds:
2231 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
2235 Use fontconfig to set the font. Note that the colons need to be escaped.
2237 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
2241 Print the date of a real-time encoding (see strftime(3)):
2243 drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%@{localtime:%a %b %d %Y@}'
2248 For more information about libfreetype, check:
2249 @url{http://www.freetype.org/}.
2251 For more information about fontconfig, check:
2252 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2256 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2258 This filter accepts the following optional named parameters:
2262 Set low and high threshold values used by the Canny thresholding
2265 The high threshold selects the "strong" edge pixels, which are then
2266 connected through 8-connectivity with the "weak" edge pixels selected
2267 by the low threshold.
2269 @var{low} and @var{high} threshold values must be choosen in the range
2270 [0,1], and @var{low} should be lesser or equal to @var{high}.
2272 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2278 edgedetect=low=0.1:high=0.4
2283 Apply fade-in/out effect to input video.
2285 It accepts the parameters:
2286 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2288 @var{type} specifies if the effect type, can be either "in" for
2289 fade-in, or "out" for a fade-out effect.
2291 @var{start_frame} specifies the number of the start frame for starting
2292 to apply the fade effect.
2294 @var{nb_frames} specifies the number of frames for which the fade
2295 effect has to last. At the end of the fade-in effect the output video
2296 will have the same intensity as the input video, at the end of the
2297 fade-out transition the output video will be completely black.
2299 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2300 separated by ":". The description of the accepted options follows.
2307 @item start_frame, s
2308 See @var{start_frame}.
2311 See @var{nb_frames}.
2314 If set to 1, fade only alpha channel, if one exists on the input.
2318 A few usage examples follow, usable too as test scenarios.
2320 # fade in first 30 frames of video
2323 # fade out last 45 frames of a 200-frame video
2326 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2327 fade=in:0:25, fade=out:975:25
2329 # make first 5 frames black, then fade in from frame 5-24
2332 # fade in alpha over first 25 frames of video
2333 fade=in:0:25:alpha=1
2338 Extract a single field from an interlaced image using stride
2339 arithmetic to avoid wasting CPU time. The output frames are marked as
2342 This filter accepts the following named options:
2345 Specify whether to extract the top (if the value is @code{0} or
2346 @code{top}) or the bottom field (if the value is @code{1} or
2350 If the option key is not specified, the first value sets the @var{type}
2351 option. For example:
2363 Transform the field order of the input video.
2365 It accepts one parameter which specifies the required field order that
2366 the input interlaced video will be transformed to. The parameter can
2367 assume one of the following values:
2371 output bottom field first
2373 output top field first
2376 Default value is "tff".
2378 Transformation is achieved by shifting the picture content up or down
2379 by one line, and filling the remaining line with appropriate picture content.
2380 This method is consistent with most broadcast field order converters.
2382 If the input video is not flagged as being interlaced, or it is already
2383 flagged as being of the required output field order then this filter does
2384 not alter the incoming video.
2386 This filter is very useful when converting to or from PAL DV material,
2387 which is bottom field first.
2391 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2396 Buffer input images and send them when they are requested.
2398 This filter is mainly useful when auto-inserted by the libavfilter
2401 The filter does not take parameters.
2405 Convert the input video to one of the specified pixel formats.
2406 Libavfilter will try to pick one that is supported for the input to
2409 The filter accepts a list of pixel format names, separated by ":",
2410 for example "yuv420p:monow:rgb24".
2412 Some examples follow:
2414 # convert the input video to the format "yuv420p"
2417 # convert the input video to any of the formats in the list
2418 format=yuv420p:yuv444p:yuv410p
2423 Convert the video to specified constant framerate by duplicating or dropping
2424 frames as necessary.
2426 This filter accepts the following named parameters:
2430 Desired output framerate. The default is @code{25}.
2435 Possible values are:
2438 zero round towards 0
2442 round towards -infinity
2444 round towards +infinity
2448 The default is @code{near}.
2452 Alternatively, the options can be specified as a flat string:
2453 @var{fps}[:@var{round}].
2455 See also the @ref{setpts} filter.
2459 Select one frame every N.
2461 This filter accepts in input a string representing a positive
2462 integer. Default argument is @code{1}.
2467 Apply a frei0r effect to the input video.
2469 To enable compilation of this filter you need to install the frei0r
2470 header and configure FFmpeg with @code{--enable-frei0r}.
2472 The filter supports the syntax:
2474 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2477 @var{filter_name} is the name of the frei0r effect to load. If the
2478 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2479 is searched in each one of the directories specified by the colon (or
2480 semicolon on Windows platforms) separated list in @env{FREIOR_PATH},
2481 otherwise in the standard frei0r paths, which are in this order:
2482 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
2483 @file{/usr/lib/frei0r-1/}.
2485 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2486 for the frei0r effect.
2488 A frei0r effect parameter can be a boolean (whose values are specified
2489 with "y" and "n"), a double, a color (specified by the syntax
2490 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2491 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2492 description), a position (specified by the syntax @var{X}/@var{Y},
2493 @var{X} and @var{Y} being float numbers) and a string.
2495 The number and kind of parameters depend on the loaded effect. If an
2496 effect parameter is not specified the default value is set.
2498 Some examples follow:
2502 Apply the distort0r effect, set the first two double parameters:
2504 frei0r=distort0r:0.5:0.01
2508 Apply the colordistance effect, take a color as first parameter:
2510 frei0r=colordistance:0.2/0.3/0.4
2511 frei0r=colordistance:violet
2512 frei0r=colordistance:0x112233
2516 Apply the perspective effect, specify the top left and top right image
2519 frei0r=perspective:0.2/0.2:0.8/0.2
2523 For more information see:
2524 @url{http://frei0r.dyne.org}
2528 The filter takes one, two or three equations as parameter, separated by ':'.
2529 The first equation is mandatory and applies to the luma plane. The two
2530 following are respectively for chroma blue and chroma red planes.
2532 The filter syntax allows named parameters:
2536 the luminance expression
2538 the chrominance blue expression
2540 the chrominance red expression
2543 If one of the chrominance expression is not defined, it falls back on the other
2544 one. If none of them are specified, they will evaluate the luminance
2547 The expressions can use the following variables and functions:
2551 The sequential number of the filtered frame, starting from @code{0}.
2554 The coordinates of the current sample.
2557 The width and height of the image.
2560 Width and height scale depending on the currently filtered plane. It is the
2561 ratio between the corresponding luma plane number of pixels and the current
2562 plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
2563 @code{0.5,0.5} for chroma planes.
2566 Time of the current frame, expressed in seconds.
2569 Return the value of the pixel at location (@var{x},@var{y}) of the current
2573 Return the value of the pixel at location (@var{x},@var{y}) of the luminance
2577 Return the value of the pixel at location (@var{x},@var{y}) of the
2578 blue-difference chroma plane.
2581 Return the value of the pixel at location (@var{x},@var{y}) of the
2582 red-difference chroma plane.
2585 For functions, if @var{x} and @var{y} are outside the area, the value will be
2586 automatically clipped to the closer edge.
2588 Some examples follow:
2592 Flip the image horizontally:
2598 Generate a bidimensional sine wave, with angle @code{PI/3} and a
2599 wavelength of 100 pixels:
2601 geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
2605 Generate a fancy enigmatic moving light:
2607 nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128
2613 Fix the banding artifacts that are sometimes introduced into nearly flat
2614 regions by truncation to 8bit color depth.
2615 Interpolate the gradients that should go where the bands are, and
2618 This filter is designed for playback only. Do not use it prior to
2619 lossy compression, because compression tends to lose the dither and
2620 bring back the bands.
2622 The filter takes two optional parameters, separated by ':':
2623 @var{strength}:@var{radius}
2625 @var{strength} is the maximum amount by which the filter will change
2626 any one pixel. Also the threshold for detecting nearly flat
2627 regions. Acceptable values range from .51 to 255, default value is
2628 1.2, out-of-range values will be clipped to the valid range.
2630 @var{radius} is the neighborhood to fit the gradient to. A larger
2631 radius makes for smoother gradients, but also prevents the filter from
2632 modifying the pixels near detailed regions. Acceptable values are
2633 8-32, default value is 16, out-of-range values will be clipped to the
2637 # default parameters
2646 Flip the input video horizontally.
2648 For example to horizontally flip the input video with @command{ffmpeg}:
2650 ffmpeg -i in.avi -vf "hflip" out.avi
2655 High precision/quality 3d denoise filter. This filter aims to reduce
2656 image noise producing smooth images and making still images really
2657 still. It should enhance compressibility.
2659 It accepts the following optional parameters:
2660 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2664 a non-negative float number which specifies spatial luma strength,
2667 @item chroma_spatial
2668 a non-negative float number which specifies spatial chroma strength,
2669 defaults to 3.0*@var{luma_spatial}/4.0
2672 a float number which specifies luma temporal strength, defaults to
2673 6.0*@var{luma_spatial}/4.0
2676 a float number which specifies chroma temporal strength, defaults to
2677 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2682 Modify the hue and/or the saturation of the input.
2684 This filter accepts the following optional named options:
2688 Specify the hue angle as a number of degrees. It accepts a float
2689 number or an expression, and defaults to 0.0.
2692 Specify the hue angle as a number of degrees. It accepts a float
2693 number or an expression, and defaults to 0.0.
2696 Specify the saturation in the [-10,10] range. It accepts a float number and
2700 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2701 following constants:
2705 frame count of the input frame starting from 0
2708 presentation timestamp of the input frame expressed in time base units
2711 frame rate of the input video, NAN if the input frame rate is unknown
2714 timestamp expressed in seconds, NAN if the input timestamp is unknown
2717 time base of the input video
2720 The options can also be set using the syntax: @var{hue}:@var{saturation}
2722 In this case @var{hue} is expressed in degrees.
2724 Some examples follow:
2727 Set the hue to 90 degrees and the saturation to 1.0:
2733 Same command but expressing the hue in radians:
2739 Same command without named options, hue must be expressed in degrees:
2745 Note that "h:s" syntax does not support expressions for the values of
2746 h and s, so the following example will issue an error:
2752 Rotate hue and make the saturation swing between 0
2753 and 2 over a period of 1 second:
2755 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2759 Apply a 3 seconds saturation fade-in effect starting at 0:
2764 The general fade-in expression can be written as:
2766 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2770 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2772 hue="s=max(0\, min(1\, (8-t)/3))"
2775 The general fade-out expression can be written as:
2777 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2782 @subsection Commands
2784 This filter supports the following command:
2787 Modify the hue and/or the saturation of the input video.
2788 The command accepts the same named options and syntax than when calling the
2789 filter from the command-line.
2791 If a parameter is omitted, it is kept at its current value.
2796 Interlaceing detect filter. This filter tries to detect if the input is
2797 interlaced or progressive. Top or bottom field first.
2799 @section lut, lutrgb, lutyuv
2801 Compute a look-up table for binding each pixel component input value
2802 to an output value, and apply it to input video.
2804 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2805 to an RGB input video.
2807 These filters accept in input a ":"-separated list of options, which
2808 specify the expressions used for computing the lookup table for the
2809 corresponding pixel component values.
2811 The @var{lut} filter requires either YUV or RGB pixel formats in
2812 input, and accepts the options:
2814 @item @var{c0} (first pixel component)
2815 @item @var{c1} (second pixel component)
2816 @item @var{c2} (third pixel component)
2817 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
2820 The exact component associated to each option depends on the format in
2823 The @var{lutrgb} filter requires RGB pixel formats in input, and
2824 accepts the options:
2826 @item @var{r} (red component)
2827 @item @var{g} (green component)
2828 @item @var{b} (blue component)
2829 @item @var{a} (alpha component)
2832 The @var{lutyuv} filter requires YUV pixel formats in input, and
2833 accepts the options:
2835 @item @var{y} (Y/luminance component)
2836 @item @var{u} (U/Cb component)
2837 @item @var{v} (V/Cr component)
2838 @item @var{a} (alpha component)
2841 The expressions can contain the following constants and functions:
2845 the input width and height
2848 input value for the pixel component
2851 the input value clipped in the @var{minval}-@var{maxval} range
2854 maximum value for the pixel component
2857 minimum value for the pixel component
2860 the negated value for the pixel component value clipped in the
2861 @var{minval}-@var{maxval} range , it corresponds to the expression
2862 "maxval-clipval+minval"
2865 the computed value in @var{val} clipped in the
2866 @var{minval}-@var{maxval} range
2868 @item gammaval(gamma)
2869 the computed gamma correction value of the pixel component value
2870 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2872 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2876 All expressions default to "val".
2878 Some examples follow:
2880 # negate input video
2881 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2882 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2884 # the above is the same as
2885 lutrgb="r=negval:g=negval:b=negval"
2886 lutyuv="y=negval:u=negval:v=negval"
2891 # remove chroma components, turns the video into a graytone image
2892 lutyuv="u=128:v=128"
2894 # apply a luma burning effect
2897 # remove green and blue components
2900 # set a constant alpha channel value on input
2901 format=rgba,lutrgb=a="maxval-minval/2"
2903 # correct luminance gamma by a 0.5 factor
2904 lutyuv=y=gammaval(0.5)
2909 Apply an MPlayer filter to the input video.
2911 This filter provides a wrapper around most of the filters of
2914 This wrapper is considered experimental. Some of the wrapped filters
2915 may not work properly and we may drop support for them, as they will
2916 be implemented natively into FFmpeg. Thus you should avoid
2917 depending on them when writing portable scripts.
2919 The filters accepts the parameters:
2920 @var{filter_name}[:=]@var{filter_params}
2922 @var{filter_name} is the name of a supported MPlayer filter,
2923 @var{filter_params} is a string containing the parameters accepted by
2926 The list of the currently supported filters follows:
2960 The parameter syntax and behavior for the listed filters are the same
2961 of the corresponding MPlayer filters. For detailed instructions check
2962 the "VIDEO FILTERS" section in the MPlayer manual.
2964 Some examples follow:
2967 Adjust gamma, brightness, contrast:
2973 Add temporal noise to input video:
2979 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2985 This filter accepts an integer in input, if non-zero it negates the
2986 alpha component (if available). The default value in input is 0.
2990 Force libavfilter not to use any of the specified pixel formats for the
2991 input to the next filter.
2993 The filter accepts a list of pixel format names, separated by ":",
2994 for example "yuv420p:monow:rgb24".
2996 Some examples follow:
2998 # force libavfilter to use a format different from "yuv420p" for the
2999 # input to the vflip filter
3000 noformat=yuv420p,vflip
3002 # convert the input video to any of the formats not contained in the list
3003 noformat=yuv420p:yuv444p:yuv410p
3008 Pass the video source unchanged to the output.
3012 Apply video transform using libopencv.
3014 To enable this filter install libopencv library and headers and
3015 configure FFmpeg with @code{--enable-libopencv}.
3017 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
3019 @var{filter_name} is the name of the libopencv filter to apply.
3021 @var{filter_params} specifies the parameters to pass to the libopencv
3022 filter. If not specified the default values are assumed.
3024 Refer to the official libopencv documentation for more precise
3026 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
3028 Follows the list of supported libopencv filters.
3033 Dilate an image by using a specific structuring element.
3034 This filter corresponds to the libopencv function @code{cvDilate}.
3036 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
3038 @var{struct_el} represents a structuring element, and has the syntax:
3039 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
3041 @var{cols} and @var{rows} represent the number of columns and rows of
3042 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
3043 point, and @var{shape} the shape for the structuring element, and
3044 can be one of the values "rect", "cross", "ellipse", "custom".
3046 If the value for @var{shape} is "custom", it must be followed by a
3047 string of the form "=@var{filename}". The file with name
3048 @var{filename} is assumed to represent a binary image, with each
3049 printable character corresponding to a bright pixel. When a custom
3050 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
3051 or columns and rows of the read file are assumed instead.
3053 The default value for @var{struct_el} is "3x3+0x0/rect".
3055 @var{nb_iterations} specifies the number of times the transform is
3056 applied to the image, and defaults to 1.
3058 Follow some example:
3060 # use the default values
3063 # dilate using a structuring element with a 5x5 cross, iterate two times
3064 ocv=dilate=5x5+2x2/cross:2
3066 # read the shape from the file diamond.shape, iterate two times
3067 # the file diamond.shape may contain a pattern of characters like this:
3073 # the specified cols and rows are ignored (but not the anchor point coordinates)
3074 ocv=0x0+2x2/custom=diamond.shape:2
3079 Erode an image by using a specific structuring element.
3080 This filter corresponds to the libopencv function @code{cvErode}.
3082 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
3083 with the same syntax and semantics as the @ref{dilate} filter.
3087 Smooth the input video.
3089 The filter takes the following parameters:
3090 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
3092 @var{type} is the type of smooth filter to apply, and can be one of
3093 the following values: "blur", "blur_no_scale", "median", "gaussian",
3094 "bilateral". The default value is "gaussian".
3096 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
3097 parameters whose meanings depend on smooth type. @var{param1} and
3098 @var{param2} accept integer positive values or 0, @var{param3} and
3099 @var{param4} accept float values.
3101 The default value for @var{param1} is 3, the default value for the
3102 other parameters is 0.
3104 These parameters correspond to the parameters assigned to the
3105 libopencv function @code{cvSmooth}.
3110 Overlay one video on top of another.
3112 It takes two inputs and one output, the first input is the "main"
3113 video on which the second input is overlayed.
3115 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
3117 @var{x} is the x coordinate of the overlayed video on the main video,
3118 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
3119 the following parameters:
3122 @item main_w, main_h
3123 main input width and height
3126 same as @var{main_w} and @var{main_h}
3128 @item overlay_w, overlay_h
3129 overlay input width and height
3132 same as @var{overlay_w} and @var{overlay_h}
3135 @var{options} is an optional list of @var{key}=@var{value} pairs,
3138 The description of the accepted options follows.
3142 If set to 1, force the filter to accept inputs in the RGB
3143 color space. Default value is 0.
3146 Be aware that frames are taken from each input video in timestamp
3147 order, hence, if their initial timestamps differ, it is a a good idea
3148 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
3149 have them begin in the same zero timestamp, as it does the example for
3150 the @var{movie} filter.
3152 Follow some examples:
3154 # draw the overlay at 10 pixels from the bottom right
3155 # corner of the main video.
3156 overlay=main_w-overlay_w-10:main_h-overlay_h-10
3158 # insert a transparent PNG logo in the bottom left corner of the input
3159 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
3161 # insert 2 different transparent PNG logos (second logo on bottom
3163 ffmpeg -i input -i logo1 -i logo2 -filter_complex
3164 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
3166 # add a transparent color layer on top of the main video,
3167 # WxH specifies the size of the main input to the overlay filter
3168 color=red@@.3:WxH [over]; [in][over] overlay [out]
3170 # play an original video and a filtered version (here with the deshake filter)
3172 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
3174 # the previous example is the same as:
3175 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
3178 You can chain together more overlays but the efficiency of such
3179 approach is yet to be tested.
3183 Add paddings to the input image, and places the original input at the
3184 given coordinates @var{x}, @var{y}.
3186 It accepts the following parameters:
3187 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
3189 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
3190 expressions containing the following constants:
3194 the input video width and height
3197 same as @var{in_w} and @var{in_h}
3200 the output width and height, that is the size of the padded area as
3201 specified by the @var{width} and @var{height} expressions
3204 same as @var{out_w} and @var{out_h}
3207 x and y offsets as specified by the @var{x} and @var{y}
3208 expressions, or NAN if not yet specified
3211 same as @var{iw} / @var{ih}
3214 input sample aspect ratio
3217 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3220 horizontal and vertical chroma subsample values. For example for the
3221 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3224 Follows the description of the accepted parameters.
3229 Specify the size of the output image with the paddings added. If the
3230 value for @var{width} or @var{height} is 0, the corresponding input size
3231 is used for the output.
3233 The @var{width} expression can reference the value set by the
3234 @var{height} expression, and vice versa.
3236 The default value of @var{width} and @var{height} is 0.
3240 Specify the offsets where to place the input image in the padded area
3241 with respect to the top/left border of the output image.
3243 The @var{x} expression can reference the value set by the @var{y}
3244 expression, and vice versa.
3246 The default value of @var{x} and @var{y} is 0.
3250 Specify the color of the padded area, it can be the name of a color
3251 (case insensitive match) or a 0xRRGGBB[AA] sequence.
3253 The default value of @var{color} is "black".
3257 @subsection Examples
3261 Add paddings with color "violet" to the input video. Output video
3262 size is 640x480, the top-left corner of the input video is placed at
3265 pad=640:480:0:40:violet
3269 Pad the input to get an output with dimensions increased by 3/2,
3270 and put the input video at the center of the padded area:
3272 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
3276 Pad the input to get a squared output with size equal to the maximum
3277 value between the input width and height, and put the input video at
3278 the center of the padded area:
3280 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
3284 Pad the input to get a final w/h ratio of 16:9:
3286 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
3290 In case of anamorphic video, in order to set the output display aspect
3291 correctly, it is necessary to use @var{sar} in the expression,
3292 according to the relation:
3294 (ih * X / ih) * sar = output_dar
3295 X = output_dar / sar
3298 Thus the previous example needs to be modified to:
3300 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
3304 Double output size and put the input video in the bottom-right
3305 corner of the output padded area:
3307 pad="2*iw:2*ih:ow-iw:oh-ih"
3311 @section pixdesctest
3313 Pixel format descriptor test filter, mainly useful for internal
3314 testing. The output video should be equal to the input video.
3318 format=monow, pixdesctest
3321 can be used to test the monowhite pixel format descriptor definition.
3325 Suppress a TV station logo, using an image file to determine which
3326 pixels comprise the logo. It works by filling in the pixels that
3327 comprise the logo with neighboring pixels.
3329 This filter requires one argument which specifies the filter bitmap
3330 file, which can be any image format supported by libavformat. The
3331 width and height of the image file must match those of the video
3332 stream being processed.
3334 Pixels in the provided bitmap image with a value of zero are not
3335 considered part of the logo, non-zero pixels are considered part of
3336 the logo. If you use white (255) for the logo and black (0) for the
3337 rest, you will be safe. For making the filter bitmap, it is
3338 recommended to take a screen capture of a black frame with the logo
3339 visible, and then using a threshold filter followed by the erode
3340 filter once or twice.
3342 If needed, little splotches can be fixed manually. Remember that if
3343 logo pixels are not covered, the filter quality will be much
3344 reduced. Marking too many pixels as part of the logo does not hurt as
3345 much, but it will increase the amount of blurring needed to cover over
3346 the image and will destroy more information than necessary, and extra
3347 pixels will slow things down on a large logo.
3351 Scale (resize) the input video, using the libswscale library.
3353 The scale filter forces the output display aspect ratio to be the same
3354 of the input, by changing the output sample aspect ratio.
3356 This filter accepts a list of named options in the form of
3357 @var{key}=@var{value} pairs separated by ":". If the key for the first
3358 two options is not specified, the assumed keys for the first two
3359 values are @code{w} and @code{h}. If the first option has no key and
3360 can be interpreted like a video size specification, it will be used
3361 to set the video size.
3363 A description of the accepted options follows.
3367 Set the video width expression, default value is @code{iw}. See below
3368 for the list of accepted constants.
3371 Set the video heiht expression, default value is @code{ih}.
3372 See below for the list of accepted constants.
3375 Set the interlacing. It accepts the following values:
3379 force interlaced aware scaling
3382 do not apply interlaced scaling
3385 select interlaced aware scaling depending on whether the source frames
3386 are flagged as interlaced or not
3389 Default value is @code{0}.
3392 Set libswscale scaling flags. If not explictly specified the filter
3393 applies a bilinear scaling algorithm.
3396 Set the video size, the value must be a valid abbreviation or in the
3397 form @var{width}x@var{height}.
3400 The values of the @var{w} and @var{h} options are expressions
3401 containing the following constants:
3405 the input width and height
3408 same as @var{in_w} and @var{in_h}
3411 the output (cropped) width and height
3414 same as @var{out_w} and @var{out_h}
3417 same as @var{iw} / @var{ih}
3420 input sample aspect ratio
3423 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3426 horizontal and vertical chroma subsample values. For example for the
3427 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3430 If the input image format is different from the format requested by
3431 the next filter, the scale filter will convert the input to the
3434 If the value for @var{width} or @var{height} is 0, the respective input
3435 size is used for the output.
3437 If the value for @var{width} or @var{height} is -1, the scale filter will
3438 use, for the respective output size, a value that maintains the aspect
3439 ratio of the input image.
3441 @subsection Examples
3445 Scale the input video to a size of 200x100:
3450 This is equivalent to:
3461 Specify a size abbreviation for the output size:
3466 which can also be written as:
3472 Scale the input to 2x:
3478 The above is the same as:
3484 Scale the input to 2x with forced interlaced scaling:
3486 scale=2*iw:2*ih:interl=1
3490 Scale the input to half size:
3496 Increase the width, and set the height to the same size:
3502 Seek for Greek harmony:
3509 Increase the height, and set the width to 3/2 of the height:
3515 Increase the size, but make the size a multiple of the chroma:
3517 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3521 Increase the width to a maximum of 500 pixels, keep the same input
3524 scale='min(500\, iw*3/2):-1'
3528 @section setdar, setsar
3530 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3533 This is done by changing the specified Sample (aka Pixel) Aspect
3534 Ratio, according to the following equation:
3536 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3539 Keep in mind that the @code{setdar} filter does not modify the pixel
3540 dimensions of the video frame. Also the display aspect ratio set by
3541 this filter may be changed by later filters in the filterchain,
3542 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3545 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3546 the filter output video.
3548 Note that as a consequence of the application of this filter, the
3549 output display aspect ratio will change according to the equation
3552 Keep in mind that the sample aspect ratio set by the @code{setsar}
3553 filter may be changed by later filters in the filterchain, e.g. if
3554 another "setsar" or a "setdar" filter is applied.
3556 The @code{setdar} and @code{setsar} filters accept a string in the
3557 form @var{num}:@var{den} expressing an aspect ratio, or the following
3558 named options, expressed as a sequence of @var{key}=@var{value} pairs,
3563 Set the maximum integer value to use for expressing numerator and
3564 denominator when reducing the expressed aspect ratio to a rational.
3565 Default value is @code{100}.
3568 Set the aspect ratio used by the filter.
3570 The parameter can be a floating point number string, an expression, or
3571 a string of the form @var{num}:@var{den}, where @var{num} and
3572 @var{den} are the numerator and denominator of the aspect ratio. If
3573 the parameter is not specified, it is assumed the value "0".
3574 In case the form "@var{num}:@var{den}" the @code{:} character should
3578 If the keys are omitted in the named options list, the specifed values
3579 are assumed to be @var{ratio} and @var{max} in that order.
3581 For example to change the display aspect ratio to 16:9, specify:
3586 The example above is equivalent to:
3591 To change the sample aspect ratio to 10:11, specify:
3596 To set a display aspect ratio of 16:9, and specify a maximum integer value of
3597 1000 in the aspect ratio reduction, use the command:
3599 setdar=ratio='16:9':max=1000
3604 Force field for the output video frame.
3606 The @code{setfield} filter marks the interlace type field for the
3607 output frames. It does not change the input frame, but only sets the
3608 corresponding property, which affects how the frame is treated by
3609 following filters (e.g. @code{fieldorder} or @code{yadif}).
3611 This filter accepts a single option @option{mode}, which can be
3612 specified either by setting @code{mode=VALUE} or setting the value
3613 alone. Available values are:
3617 Keep the same field property.
3620 Mark the frame as bottom-field-first.
3623 Mark the frame as top-field-first.
3626 Mark the frame as progressive.
3631 Show a line containing various information for each input video frame.
3632 The input video is not modified.
3634 The shown line contains a sequence of key/value pairs of the form
3635 @var{key}:@var{value}.
3637 A description of each shown parameter follows:
3641 sequential number of the input frame, starting from 0
3644 Presentation TimeStamp of the input frame, expressed as a number of
3645 time base units. The time base unit depends on the filter input pad.
3648 Presentation TimeStamp of the input frame, expressed as a number of
3652 position of the frame in the input stream, -1 if this information in
3653 unavailable and/or meaningless (for example in case of synthetic video)
3659 sample aspect ratio of the input frame, expressed in the form
3663 size of the input frame, expressed in the form
3664 @var{width}x@var{height}
3667 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3668 for bottom field first)
3671 1 if the frame is a key frame, 0 otherwise
3674 picture type of the input frame ("I" for an I-frame, "P" for a
3675 P-frame, "B" for a B-frame, "?" for unknown type).
3676 Check also the documentation of the @code{AVPictureType} enum and of
3677 the @code{av_get_picture_type_char} function defined in
3678 @file{libavutil/avutil.h}.
3681 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3683 @item plane_checksum
3684 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3685 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3690 Blur the input video without impacting the outlines.
3692 The filter accepts the following parameters:
3693 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3695 Parameters prefixed by @var{luma} indicate that they work on the
3696 luminance of the pixels whereas parameters prefixed by @var{chroma}
3697 refer to the chrominance of the pixels.
3699 If the chroma parameters are not set, the luma parameters are used for
3700 either the luminance and the chrominance of the pixels.
3702 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3703 range [0.1,5.0] that specifies the variance of the gaussian filter
3704 used to blur the image (slower if larger).
3706 @var{luma_strength} or @var{chroma_strength} must be a float number in
3707 the range [-1.0,1.0] that configures the blurring. A value included in
3708 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3709 will sharpen the image.
3711 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3712 the range [-30,30] that is used as a coefficient to determine whether
3713 a pixel should be blurred or not. A value of 0 will filter all the
3714 image, a value included in [0,30] will filter flat areas and a value
3715 included in [-30,0] will filter edges.
3720 Draw subtitles on top of input video using the libass library.
3722 To enable compilation of this filter you need to configure FFmpeg with
3723 @code{--enable-libass}. This filter also requires a build with libavcodec and
3724 libavformat to convert the passed subtitles file to ASS (Advanced Substation
3725 Alpha) subtitles format.
3727 This filter accepts the following named options, expressed as a
3728 sequence of @var{key}=@var{value} pairs, separated by ":".
3732 Set the filename of the subtitle file to read. It must be specified.
3735 Specify the size of the original video, the video for which the ASS file
3736 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
3737 necessary to correctly scale the fonts if the aspect ratio has been changed.
3740 If the first key is not specified, it is assumed that the first value
3741 specifies the @option{filename}.
3743 For example, to render the file @file{sub.srt} on top of the input
3744 video, use the command:
3749 which is equivalent to:
3751 subtitles=filename=sub.srt
3756 Split input video into several identical outputs.
3758 The filter accepts a single parameter which specifies the number of outputs. If
3759 unspecified, it defaults to 2.
3763 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3765 will create 5 copies of the input video.
3769 [in] split [splitout1][splitout2];
3770 [splitout1] crop=100:100:0:0 [cropout];
3771 [splitout2] pad=200:200:100:100 [padout];
3774 will create two separate outputs from the same input, one cropped and
3779 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3780 Interpolate) pixel art scaling algorithm.
3782 Useful for enlarging pixel art images without reducing sharpness.
3788 Select the most representative frame in a given sequence of consecutive frames.
3790 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3791 in a set of @var{N} frames, the filter will pick one of them, and then handle
3792 the next batch of @var{N} frames until the end.
3794 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3795 value will result in a higher memory usage, so a high value is not recommended.
3797 The following example extract one picture each 50 frames:
3802 Complete example of a thumbnail creation with @command{ffmpeg}:
3804 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3809 Tile several successive frames together.
3811 It accepts a list of options in the form of @var{key}=@var{value} pairs
3812 separated by ":". A description of the accepted options follows.
3817 Set the grid size (i.e. the number of lines and columns) in the form
3821 Set the outer border margin in pixels.
3824 Set the inner border thickness (i.e. the number of pixels between frames). For
3825 more advanced padding options (such as having different values for the edges),
3826 refer to the pad video filter.
3829 Set the maximum number of frames to render in the given area. It must be less
3830 than or equal to @var{w}x@var{h}. The default value is @code{0}, meaning all
3831 the area will be used.
3835 Alternatively, the options can be specified as a flat string:
3837 @var{layout}[:@var{nb_frames}[:@var{margin}[:@var{padding}]]]
3839 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3842 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3844 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3845 duplicating each output frame to accomodate the originally detected frame
3848 Another example to display @code{5} pictures in an area of @code{3x2} frames,
3849 with @code{7} pixels between them, and @code{2} pixels of initial margin, using
3850 mixed flat and named options:
3852 tile=3x2:nb_frames=5:padding=7:margin=2
3857 Perform various types of temporal field interlacing.
3859 Frames are counted starting from 1, so the first input frame is
3862 This filter accepts a single option @option{mode} specifying the mode,
3863 which can be specified either by specyfing @code{mode=VALUE} either
3864 specifying the value alone. Available values are:
3868 Move odd frames into the upper field, even into the lower field,
3869 generating a double height frame at half framerate.
3872 Only output even frames, odd frames are dropped, generating a frame with
3873 unchanged height at half framerate.
3876 Only output odd frames, even frames are dropped, generating a frame with
3877 unchanged height at half framerate.
3880 Expand each frame to full height, but pad alternate lines with black,
3881 generating a frame with double height at the same input framerate.
3883 @item interleave_top, 4
3884 Interleave the upper field from odd frames with the lower field from
3885 even frames, generating a frame with unchanged height at half framerate.
3887 @item interleave_bottom, 5
3888 Interleave the lower field from odd frames with the upper field from
3889 even frames, generating a frame with unchanged height at half framerate.
3891 @item interlacex2, 6
3892 Double frame rate with unchanged height. Frames are inserted each
3893 containing the second temporal field from the previous input frame and
3894 the first temporal field from the next input frame. This mode relies on
3895 the top_field_first flag. Useful for interlaced video displays with no
3896 field synchronisation.
3899 Numeric values are deprecated but are accepted for backward
3900 compatibility reasons.
3902 Default mode is @code{merge}.
3906 Transpose rows with columns in the input video and optionally flip it.
3908 This filter accepts the following named parameters:
3912 Specify the transposition direction. Can assume the following values:
3916 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3924 Rotate by 90 degrees clockwise, that is:
3932 Rotate by 90 degrees counterclockwise, that is:
3940 Rotate by 90 degrees clockwise and vertically flip, that is:
3948 For values between 4-7, the transposition is only done if the input
3949 video geometry is portrait and not landscape. These values are
3950 deprecated, the @code{passthrough} option should be used instead.
3953 Do not apply the transposition if the input geometry matches the one
3954 specified by the specified value. It accepts the following values:
3957 Always apply transposition.
3959 Preserve portrait geometry (when @var{height} >= @var{width}).
3961 Preserve landscape geometry (when @var{width} >= @var{height}).
3964 Default value is @code{none}.
3969 Sharpen or blur the input video.
3971 It accepts the following parameters:
3972 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3974 Negative values for the amount will blur the input video, while positive
3975 values will sharpen. All parameters are optional and default to the
3976 equivalent of the string '5:5:1.0:5:5:0.0'.
3981 Set the luma matrix horizontal size. It can be an integer between 3
3982 and 13, default value is 5.
3985 Set the luma matrix vertical size. It can be an integer between 3
3986 and 13, default value is 5.
3989 Set the luma effect strength. It can be a float number between -2.0
3990 and 5.0, default value is 1.0.
3992 @item chroma_msize_x
3993 Set the chroma matrix horizontal size. It can be an integer between 3
3994 and 13, default value is 5.
3996 @item chroma_msize_y
3997 Set the chroma matrix vertical size. It can be an integer between 3
3998 and 13, default value is 5.
4001 Set the chroma effect strength. It can be a float number between -2.0
4002 and 5.0, default value is 0.0.
4007 # Strong luma sharpen effect parameters
4010 # Strong blur of both luma and chroma parameters
4011 unsharp=7:7:-2:7:7:-2
4013 # Use the default values with @command{ffmpeg}
4014 ffmpeg -i in.avi -vf "unsharp" out.mp4
4019 Flip the input video vertically.
4022 ffmpeg -i in.avi -vf "vflip" out.avi
4027 Deinterlace the input video ("yadif" means "yet another deinterlacing
4030 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
4032 @var{mode} specifies the interlacing mode to adopt, accepts one of the
4037 output 1 frame for each frame
4039 output 1 frame for each field
4041 like 0 but skips spatial interlacing check
4043 like 1 but skips spatial interlacing check
4048 @var{parity} specifies the picture field parity assumed for the input
4049 interlaced video, accepts one of the following values:
4053 assume top field first
4055 assume bottom field first
4057 enable automatic detection
4060 Default value is -1.
4061 If interlacing is unknown or decoder does not export this information,
4062 top field first will be assumed.
4064 @var{auto} specifies if deinterlacer should trust the interlaced flag
4065 and only deinterlace frames marked as interlaced
4069 deinterlace all frames
4071 only deinterlace frames marked as interlaced
4076 @c man end VIDEO FILTERS
4078 @chapter Video Sources
4079 @c man begin VIDEO SOURCES
4081 Below is a description of the currently available video sources.
4085 Buffer video frames, and make them available to the filter chain.
4087 This source is mainly intended for a programmatic use, in particular
4088 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
4090 It accepts a list of options in the form of @var{key}=@var{value} pairs
4091 separated by ":". A description of the accepted options follows.
4096 Specify the size (width and height) of the buffered video frames.
4099 A string representing the pixel format of the buffered video frames.
4100 It may be a number corresponding to a pixel format, or a pixel format
4104 Specify the timebase assumed by the timestamps of the buffered frames.
4107 Specify the frame rate expected for the video stream.
4110 Specify the sample aspect ratio assumed by the video frames.
4113 Specify the optional parameters to be used for the scale filter which
4114 is automatically inserted when an input change is detected in the
4115 input size or format.
4120 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
4123 will instruct the source to accept video frames with size 320x240 and
4124 with format "yuv410p", assuming 1/24 as the timestamps timebase and
4125 square pixels (1:1 sample aspect ratio).
4126 Since the pixel format with name "yuv410p" corresponds to the number 6
4127 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
4128 this example corresponds to:
4130 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
4133 Alternatively, the options can be specified as a flat string, but this
4134 syntax is deprecated:
4136 @var{width}:@var{height}:@var{pix_fmt}:@var{time_base.num}:@var{time_base.den}:@var{pixel_aspect.num}:@var{pixel_aspect.den}[:@var{sws_param}]
4140 Create a pattern generated by an elementary cellular automaton.
4142 The initial state of the cellular automaton can be defined through the
4143 @option{filename}, and @option{pattern} options. If such options are
4144 not specified an initial state is created randomly.
4146 At each new frame a new row in the video is filled with the result of
4147 the cellular automaton next generation. The behavior when the whole
4148 frame is filled is defined by the @option{scroll} option.
4150 This source accepts a list of options in the form of
4151 @var{key}=@var{value} pairs separated by ":". A description of the
4152 accepted options follows.
4156 Read the initial cellular automaton state, i.e. the starting row, from
4158 In the file, each non-whitespace character is considered an alive
4159 cell, a newline will terminate the row, and further characters in the
4160 file will be ignored.
4163 Read the initial cellular automaton state, i.e. the starting row, from
4164 the specified string.
4166 Each non-whitespace character in the string is considered an alive
4167 cell, a newline will terminate the row, and further characters in the
4168 string will be ignored.
4171 Set the video rate, that is the number of frames generated per second.
4174 @item random_fill_ratio, ratio
4175 Set the random fill ratio for the initial cellular automaton row. It
4176 is a floating point number value ranging from 0 to 1, defaults to
4179 This option is ignored when a file or a pattern is specified.
4181 @item random_seed, seed
4182 Set the seed for filling randomly the initial row, must be an integer
4183 included between 0 and UINT32_MAX. If not specified, or if explicitly
4184 set to -1, the filter will try to use a good random seed on a best
4188 Set the cellular automaton rule, it is a number ranging from 0 to 255.
4189 Default value is 110.
4192 Set the size of the output video.
4194 If @option{filename} or @option{pattern} is specified, the size is set
4195 by default to the width of the specified initial state row, and the
4196 height is set to @var{width} * PHI.
4198 If @option{size} is set, it must contain the width of the specified
4199 pattern string, and the specified pattern will be centered in the
4202 If a filename or a pattern string is not specified, the size value
4203 defaults to "320x518" (used for a randomly generated initial state).
4206 If set to 1, scroll the output upward when all the rows in the output
4207 have been already filled. If set to 0, the new generated row will be
4208 written over the top row just after the bottom row is filled.
4211 @item start_full, full
4212 If set to 1, completely fill the output with generated rows before
4213 outputting the first frame.
4214 This is the default behavior, for disabling set the value to 0.
4217 If set to 1, stitch the left and right row edges together.
4218 This is the default behavior, for disabling set the value to 0.
4221 @subsection Examples
4225 Read the initial state from @file{pattern}, and specify an output of
4228 cellauto=f=pattern:s=200x400
4232 Generate a random initial row with a width of 200 cells, with a fill
4235 cellauto=ratio=2/3:s=200x200
4239 Create a pattern generated by rule 18 starting by a single alive cell
4240 centered on an initial row with width 100:
4242 cellauto=p=@@:s=100x400:full=0:rule=18
4246 Specify a more elaborated initial pattern:
4248 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
4255 Generate a Mandelbrot set fractal, and progressively zoom towards the
4256 point specified with @var{start_x} and @var{start_y}.
4258 This source accepts a list of options in the form of
4259 @var{key}=@var{value} pairs separated by ":". A description of the
4260 accepted options follows.
4265 Set the terminal pts value. Default value is 400.
4268 Set the terminal scale value.
4269 Must be a floating point value. Default value is 0.3.
4272 Set the inner coloring mode, that is the algorithm used to draw the
4273 Mandelbrot fractal internal region.
4275 It shall assume one of the following values:
4280 Show time until convergence.
4282 Set color based on point closest to the origin of the iterations.
4287 Default value is @var{mincol}.
4290 Set the bailout value. Default value is 10.0.
4293 Set the maximum of iterations performed by the rendering
4294 algorithm. Default value is 7189.
4297 Set outer coloring mode.
4298 It shall assume one of following values:
4300 @item iteration_count
4301 Set iteration cound mode.
4302 @item normalized_iteration_count
4303 set normalized iteration count mode.
4305 Default value is @var{normalized_iteration_count}.
4308 Set frame rate, expressed as number of frames per second. Default
4312 Set frame size. Default value is "640x480".
4315 Set the initial scale value. Default value is 3.0.
4318 Set the initial x position. Must be a floating point value between
4319 -100 and 100. Default value is -0.743643887037158704752191506114774.
4322 Set the initial y position. Must be a floating point value between
4323 -100 and 100. Default value is -0.131825904205311970493132056385139.
4328 Generate various test patterns, as generated by the MPlayer test filter.
4330 The size of the generated video is fixed, and is 256x256.
4331 This source is useful in particular for testing encoding features.
4333 This source accepts an optional sequence of @var{key}=@var{value} pairs,
4334 separated by ":". The description of the accepted options follows.
4339 Specify the frame rate of the sourced video, as the number of frames
4340 generated per second. It has to be a string in the format
4341 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4342 number or a valid video frame rate abbreviation. The default value is
4346 Set the video duration of the sourced video. The accepted syntax is:
4351 See also the function @code{av_parse_time()}.
4353 If not specified, or the expressed duration is negative, the video is
4354 supposed to be generated forever.
4358 Set the number or the name of the test to perform. Supported tests are:
4373 Default value is "all", which will cycle through the list of all tests.
4376 For example the following:
4381 will generate a "dc_luma" test pattern.
4385 Provide a frei0r source.
4387 To enable compilation of this filter you need to install the frei0r
4388 header and configure FFmpeg with @code{--enable-frei0r}.
4390 The source supports the syntax:
4392 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
4395 @var{size} is the size of the video to generate, may be a string of the
4396 form @var{width}x@var{height} or a frame size abbreviation.
4397 @var{rate} is the rate of the video to generate, may be a string of
4398 the form @var{num}/@var{den} or a frame rate abbreviation.
4399 @var{src_name} is the name to the frei0r source to load. For more
4400 information regarding frei0r and how to set the parameters read the
4401 section @ref{frei0r} in the description of the video filters.
4403 For example, to generate a frei0r partik0l source with size 200x200
4404 and frame rate 10 which is overlayed on the overlay filter main input:
4406 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4411 Generate a life pattern.
4413 This source is based on a generalization of John Conway's life game.
4415 The sourced input represents a life grid, each pixel represents a cell
4416 which can be in one of two possible states, alive or dead. Every cell
4417 interacts with its eight neighbours, which are the cells that are
4418 horizontally, vertically, or diagonally adjacent.
4420 At each interaction the grid evolves according to the adopted rule,
4421 which specifies the number of neighbor alive cells which will make a
4422 cell stay alive or born. The @option{rule} option allows to specify
4425 This source accepts a list of options in the form of
4426 @var{key}=@var{value} pairs separated by ":". A description of the
4427 accepted options follows.
4431 Set the file from which to read the initial grid state. In the file,
4432 each non-whitespace character is considered an alive cell, and newline
4433 is used to delimit the end of each row.
4435 If this option is not specified, the initial grid is generated
4439 Set the video rate, that is the number of frames generated per second.
4442 @item random_fill_ratio, ratio
4443 Set the random fill ratio for the initial random grid. It is a
4444 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4445 It is ignored when a file is specified.
4447 @item random_seed, seed
4448 Set the seed for filling the initial random grid, must be an integer
4449 included between 0 and UINT32_MAX. If not specified, or if explicitly
4450 set to -1, the filter will try to use a good random seed on a best
4456 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4457 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4458 @var{NS} specifies the number of alive neighbor cells which make a
4459 live cell stay alive, and @var{NB} the number of alive neighbor cells
4460 which make a dead cell to become alive (i.e. to "born").
4461 "s" and "b" can be used in place of "S" and "B", respectively.
4463 Alternatively a rule can be specified by an 18-bits integer. The 9
4464 high order bits are used to encode the next cell state if it is alive
4465 for each number of neighbor alive cells, the low order bits specify
4466 the rule for "borning" new cells. Higher order bits encode for an
4467 higher number of neighbor cells.
4468 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4469 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4471 Default value is "S23/B3", which is the original Conway's game of life
4472 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4473 cells, and will born a new cell if there are three alive cells around
4477 Set the size of the output video.
4479 If @option{filename} is specified, the size is set by default to the
4480 same size of the input file. If @option{size} is set, it must contain
4481 the size specified in the input file, and the initial grid defined in
4482 that file is centered in the larger resulting area.
4484 If a filename is not specified, the size value defaults to "320x240"
4485 (used for a randomly generated initial grid).
4488 If set to 1, stitch the left and right grid edges together, and the
4489 top and bottom edges also. Defaults to 1.
4492 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4493 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4494 value from 0 to 255.
4497 Set the color of living (or new born) cells.
4500 Set the color of dead cells. If @option{mold} is set, this is the first color
4501 used to represent a dead cell.
4504 Set mold color, for definitely dead and moldy cells.
4507 @subsection Examples
4511 Read a grid from @file{pattern}, and center it on a grid of size
4514 life=f=pattern:s=300x300
4518 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4520 life=ratio=2/3:s=200x200
4524 Specify a custom rule for evolving a randomly generated grid:
4530 Full example with slow death effect (mold) using @command{ffplay}:
4532 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4536 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4538 The @code{color} source provides an uniformly colored input.
4540 The @code{nullsrc} source returns unprocessed video frames. It is
4541 mainly useful to be employed in analysis / debugging tools, or as the
4542 source for filters which ignore the input data.
4544 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4545 detecting RGB vs BGR issues. You should see a red, green and blue
4546 stripe from top to bottom.
4548 The @code{smptebars} source generates a color bars pattern, based on
4549 the SMPTE Engineering Guideline EG 1-1990.
4551 The @code{testsrc} source generates a test video pattern, showing a
4552 color pattern, a scrolling gradient and a timestamp. This is mainly
4553 intended for testing purposes.
4555 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4556 separated by ":". The description of the accepted options follows.
4561 Specify the color of the source, only used in the @code{color}
4562 source. It can be the name of a color (case insensitive match) or a
4563 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4564 default value is "black".
4567 Specify the size of the sourced video, it may be a string of the form
4568 @var{width}x@var{height}, or the name of a size abbreviation. The
4569 default value is "320x240".
4572 Specify the frame rate of the sourced video, as the number of frames
4573 generated per second. It has to be a string in the format
4574 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4575 number or a valid video frame rate abbreviation. The default value is
4579 Set the sample aspect ratio of the sourced video.
4582 Set the video duration of the sourced video. The accepted syntax is:
4584 [-]HH[:MM[:SS[.m...]]]
4587 See also the function @code{av_parse_time()}.
4589 If not specified, or the expressed duration is negative, the video is
4590 supposed to be generated forever.
4593 Set the number of decimals to show in the timestamp, only used in the
4594 @code{testsrc} source.
4596 The displayed timestamp value will correspond to the original
4597 timestamp value multiplied by the power of 10 of the specified
4598 value. Default value is 0.
4601 For example the following:
4603 testsrc=duration=5.3:size=qcif:rate=10
4606 will generate a video with a duration of 5.3 seconds, with size
4607 176x144 and a frame rate of 10 frames per second.
4609 The following graph description will generate a red source
4610 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4613 color=c=red@@0.2:s=qcif:r=10
4616 If the input content is to be ignored, @code{nullsrc} can be used. The
4617 following command generates noise in the luminance plane by employing
4618 the @code{geq} filter:
4620 nullsrc=s=256x256, geq=random(1)*255:128:128
4623 @c man end VIDEO SOURCES
4625 @chapter Video Sinks
4626 @c man begin VIDEO SINKS
4628 Below is a description of the currently available video sinks.
4632 Buffer video frames, and make them available to the end of the filter
4635 This sink is mainly intended for a programmatic use, in particular
4636 through the interface defined in @file{libavfilter/buffersink.h}.
4638 It does not require a string parameter in input, but you need to
4639 specify a pointer to a list of supported pixel formats terminated by
4640 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4641 when initializing this sink.
4645 Null video sink, do absolutely nothing with the input video. It is
4646 mainly useful as a template and to be employed in analysis / debugging
4649 @c man end VIDEO SINKS
4651 @chapter Multimedia Filters
4652 @c man begin MULTIMEDIA FILTERS
4654 Below is a description of the currently available multimedia filters.
4656 @section aselect, select
4657 Select frames to pass in output.
4659 These filters accept a single option @option{expr} or @option{e}
4660 specifying the select expression, which can be specified either by
4661 specyfing @code{expr=VALUE} or specifying the expression
4664 The select expression is evaluated for each input frame. If the
4665 evaluation result is a non-zero value, the frame is selected and
4666 passed to the output, otherwise it is discarded.
4668 The expression can contain the following constants:
4672 the sequential number of the filtered frame, starting from 0
4675 the sequential number of the selected frame, starting from 0
4677 @item prev_selected_n
4678 the sequential number of the last selected frame, NAN if undefined
4681 timebase of the input timestamps
4684 the PTS (Presentation TimeStamp) of the filtered video frame,
4685 expressed in @var{TB} units, NAN if undefined
4688 the PTS (Presentation TimeStamp) of the filtered video frame,
4689 expressed in seconds, NAN if undefined
4692 the PTS of the previously filtered video frame, NAN if undefined
4694 @item prev_selected_pts
4695 the PTS of the last previously filtered video frame, NAN if undefined
4697 @item prev_selected_t
4698 the PTS of the last previously selected video frame, NAN if undefined
4701 the PTS of the first video frame in the video, NAN if undefined
4704 the time of the first video frame in the video, NAN if undefined
4706 @item pict_type @emph{(video only)}
4707 the type of the filtered frame, can assume one of the following
4719 @item interlace_type @emph{(video only)}
4720 the frame interlace type, can assume one of the following values:
4723 the frame is progressive (not interlaced)
4725 the frame is top-field-first
4727 the frame is bottom-field-first
4730 @item consumed_sample_n @emph{(audio only)}
4731 the number of selected samples before the current frame
4733 @item samples_n @emph{(audio only)}
4734 the number of samples in the current frame
4736 @item sample_rate @emph{(audio only)}
4737 the input sample rate
4740 1 if the filtered frame is a key-frame, 0 otherwise
4743 the position in the file of the filtered frame, -1 if the information
4744 is not available (e.g. for synthetic video)
4746 @item scene @emph{(video only)}
4747 value between 0 and 1 to indicate a new scene; a low value reflects a low
4748 probability for the current frame to introduce a new scene, while a higher
4749 value means the current frame is more likely to be one (see the example below)
4753 The default value of the select expression is "1".
4755 @subsection Examples
4759 Select all frames in input:
4764 The example above is the same as:
4776 Select only I-frames:
4778 select='eq(pict_type\,I)'
4782 Select one frame every 100:
4784 select='not(mod(n\,100))'
4788 Select only frames contained in the 10-20 time interval:
4790 select='gte(t\,10)*lte(t\,20)'
4794 Select only I frames contained in the 10-20 time interval:
4796 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
4800 Select frames with a minimum distance of 10 seconds:
4802 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
4806 Use aselect to select only audio frames with samples number > 100:
4808 aselect='gt(samples_n\,100)'
4812 Create a mosaic of the first scenes:
4814 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
4817 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
4821 @section asendcmd, sendcmd
4823 Send commands to filters in the filtergraph.
4825 These filters read commands to be sent to other filters in the
4828 @code{asendcmd} must be inserted between two audio filters,
4829 @code{sendcmd} must be inserted between two video filters, but apart
4830 from that they act the same way.
4832 The specification of commands can be provided in the filter arguments
4833 with the @var{commands} option, or in a file specified by the
4834 @var{filename} option.
4836 These filters accept the following options:
4839 Set the commands to be read and sent to the other filters.
4841 Set the filename of the commands to be read and sent to the other
4845 @subsection Commands syntax
4847 A commands description consists of a sequence of interval
4848 specifications, comprising a list of commands to be executed when a
4849 particular event related to that interval occurs. The occurring event
4850 is typically the current frame time entering or leaving a given time
4853 An interval is specified by the following syntax:
4855 @var{START}[-@var{END}] @var{COMMANDS};
4858 The time interval is specified by the @var{START} and @var{END} times.
4859 @var{END} is optional and defaults to the maximum time.
4861 The current frame time is considered within the specified interval if
4862 it is included in the interval [@var{START}, @var{END}), that is when
4863 the time is greater or equal to @var{START} and is lesser than
4866 @var{COMMANDS} consists of a sequence of one or more command
4867 specifications, separated by ",", relating to that interval. The
4868 syntax of a command specification is given by:
4870 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4873 @var{FLAGS} is optional and specifies the type of events relating to
4874 the time interval which enable sending the specified command, and must
4875 be a non-null sequence of identifier flags separated by "+" or "|" and
4876 enclosed between "[" and "]".
4878 The following flags are recognized:
4881 The command is sent when the current frame timestamp enters the
4882 specified interval. In other words, the command is sent when the
4883 previous frame timestamp was not in the given interval, and the
4887 The command is sent when the current frame timestamp leaves the
4888 specified interval. In other words, the command is sent when the
4889 previous frame timestamp was in the given interval, and the
4893 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4896 @var{TARGET} specifies the target of the command, usually the name of
4897 the filter class or a specific filter instance name.
4899 @var{COMMAND} specifies the name of the command for the target filter.
4901 @var{ARG} is optional and specifies the optional list of argument for
4902 the given @var{COMMAND}.
4904 Between one interval specification and another, whitespaces, or
4905 sequences of characters starting with @code{#} until the end of line,
4906 are ignored and can be used to annotate comments.
4908 A simplified BNF description of the commands specification syntax
4911 @var{COMMAND_FLAG} ::= "enter" | "leave"
4912 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4913 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4914 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4915 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4916 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4919 @subsection Examples
4923 Specify audio tempo change at second 4:
4925 asendcmd=c='4.0 atempo tempo 1.5',atempo
4929 Specify a list of drawtext and hue commands in a file.
4931 # show text in the interval 5-10
4932 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4933 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4935 # desaturate the image in the interval 15-20
4936 15.0-20.0 [enter] hue reinit s=0,
4937 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4938 [leave] hue reinit s=1,
4939 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4941 # apply an exponential saturation fade-out effect, starting from time 25
4942 25 [enter] hue s=exp(t-25)
4945 A filtergraph allowing to read and process the above command list
4946 stored in a file @file{test.cmd}, can be specified with:
4948 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4953 @section asetpts, setpts
4955 Change the PTS (presentation timestamp) of the input frames.
4957 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4959 Accept in input an expression evaluated through the eval API, which
4960 can contain the following constants:
4964 frame rate, only defined for constant frame-rate video
4967 the presentation timestamp in input
4970 the count of the input frame, starting from 0.
4972 @item NB_CONSUMED_SAMPLES
4973 the number of consumed samples, not including the current frame (only
4977 the number of samples in the current frame (only audio)
4983 the PTS of the first frame
4986 the time in seconds of the first frame
4989 tell if the current frame is interlaced
4992 the time in seconds of the current frame
4998 original position in the file of the frame, or undefined if undefined
4999 for the current frame
5005 previous input time in seconds
5011 previous output time in seconds
5014 @subsection Examples
5018 Start counting PTS from zero
5024 Apply fast motion effect:
5030 Apply slow motion effect:
5036 Set fixed rate of 25 frames per second:
5042 Set fixed rate 25 fps with some jitter:
5044 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
5048 Apply an offset of 10 seconds to the input PTS:
5056 EBU R128 scanner filter. This filter takes an audio stream as input and outputs
5057 it unchanged. By default, it logs a message at a frequency of 10Hz with the
5058 Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
5059 Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
5061 The filter also has a video output (see the @var{video} option) with a real
5062 time graph to observe the loudness evolution. The graphic contains the logged
5063 message mentioned above, so it is not printed anymore when this option is set,
5064 unless the verbose logging is set. The main graphing area contains the
5065 short-term loudness (3 seconds of analysis), and the gauge on the right is for
5066 the momentary loudness (400 milliseconds).
5068 More information about the Loudness Recommendation EBU R128 on
5069 @url{http://tech.ebu.ch/loudness}.
5071 The filter accepts the following named parameters:
5076 Activate the video output. The audio stream is passed unchanged whether this
5077 option is set or no. The video stream will be the first output stream if
5078 activated. Default is @code{0}.
5081 Set the video size. This option is for video only. Default and minimum
5082 resolution is @code{640x480}.
5085 Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
5086 @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
5087 other integer value between this range is allowed.
5091 Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
5093 ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
5096 Run an analysis with @command{ffmpeg}:
5098 ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
5101 @section settb, asettb
5103 Set the timebase to use for the output frames timestamps.
5104 It is mainly useful for testing timebase configuration.
5106 It accepts in input an arithmetic expression representing a rational.
5107 The expression can contain the constants "AVTB" (the
5108 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
5111 The default value for the input is "intb".
5113 @subsection Examples
5117 Set the timebase to 1/25:
5123 Set the timebase to 1/10:
5129 Set the timebase to 1001/1000:
5135 Set the timebase to 2*intb:
5141 Set the default timebase value:
5149 Concatenate audio and video streams, joining them together one after the
5152 The filter works on segments of synchronized video and audio streams. All
5153 segments must have the same number of streams of each type, and that will
5154 also be the number of streams at output.
5156 The filter accepts the following named parameters:
5160 Set the number of segments. Default is 2.
5163 Set the number of output video streams, that is also the number of video
5164 streams in each segment. Default is 1.
5167 Set the number of output audio streams, that is also the number of video
5168 streams in each segment. Default is 0.
5171 Activate unsafe mode: do not fail if segments have a different format.
5175 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
5176 @var{a} audio outputs.
5178 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
5179 segment, in the same order as the outputs, then the inputs for the second
5182 Related streams do not always have exactly the same duration, for various
5183 reasons including codec frame size or sloppy authoring. For that reason,
5184 related synchronized streams (e.g. a video and its audio track) should be
5185 concatenated at once. The concat filter will use the duration of the longest
5186 stream in each segment (except the last one), and if necessary pad shorter
5187 audio streams with silence.
5189 For this filter to work correctly, all segments must start at timestamp 0.
5191 All corresponding streams must have the same parameters in all segments; the
5192 filtering system will automatically select a common pixel format for video
5193 streams, and a common sample format, sample rate and channel layout for
5194 audio streams, but other settings, such as resolution, must be converted
5195 explicitly by the user.
5197 Different frame rates are acceptable but will result in variable frame rate
5198 at output; be sure to configure the output file to handle it.
5203 Concatenate an opening, an episode and an ending, all in bilingual version
5204 (video in stream 0, audio in streams 1 and 2):
5206 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
5207 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
5208 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
5209 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
5213 Concatenate two parts, handling audio and video separately, using the
5214 (a)movie sources, and adjusting the resolution:
5216 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
5217 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
5218 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
5220 Note that a desync will happen at the stitch if the audio and video streams
5221 do not have exactly the same duration in the first file.
5225 @section showspectrum
5227 Convert input audio to a video output, representing the audio frequency
5230 The filter accepts the following named parameters:
5233 Specify the video size for the output. Default value is @code{640x480}.
5235 Specify if the spectrum should slide along the window. Default value is
5239 The usage is very similar to the showwaves filter; see the examples in that
5244 Convert input audio to a video output, representing the samples waves.
5246 The filter accepts the following named parameters:
5250 Set the number of samples which are printed on the same column. A
5251 larger value will decrease the frame rate. Must be a positive
5252 integer. This option can be set only if the value for @var{rate}
5253 is not explicitly specified.
5256 Set the (approximate) output frame rate. This is done by setting the
5257 option @var{n}. Default value is "25".
5260 Specify the video size for the output. Default value is "600x240".
5263 Some examples follow.
5266 Output the input file audio and the corresponding video representation
5269 amovie=a.mp3,asplit[out0],showwaves[out1]
5273 Create a synthetic signal and show it with showwaves, forcing a
5274 framerate of 30 frames per second:
5276 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
5280 @c man end MULTIMEDIA FILTERS
5282 @chapter Multimedia Sources
5283 @c man begin MULTIMEDIA SOURCES
5285 Below is a description of the currently available multimedia sources.
5289 This is the same as @ref{src_movie} source, except it selects an audio
5295 Read audio and/or video stream(s) from a movie container.
5297 It accepts the syntax: @var{movie_name}[:@var{options}] where
5298 @var{movie_name} is the name of the resource to read (not necessarily
5299 a file but also a device or a stream accessed through some protocol),
5300 and @var{options} is an optional sequence of @var{key}=@var{value}
5301 pairs, separated by ":".
5303 The description of the accepted options follows.
5307 @item format_name, f
5308 Specifies the format assumed for the movie to read, and can be either
5309 the name of a container or an input device. If not specified the
5310 format is guessed from @var{movie_name} or by probing.
5312 @item seek_point, sp
5313 Specifies the seek point in seconds, the frames will be output
5314 starting from this seek point, the parameter is evaluated with
5315 @code{av_strtod} so the numerical value may be suffixed by an IS
5316 postfix. Default value is "0".
5319 Specifies the streams to read. Several streams can be specified, separated
5320 by "+". The source will then have as many outputs, in the same order. The
5321 syntax is explained in the @ref{Stream specifiers} chapter. Two special
5322 names, "dv" and "da" specify respectively the default (best suited) video
5323 and audio stream. Default is "dv", or "da" if the filter is called as
5326 @item stream_index, si
5327 Specifies the index of the video stream to read. If the value is -1,
5328 the best suited video stream will be automatically selected. Default
5329 value is "-1". Deprecated. If the filter is called "amovie", it will select
5330 audio instead of video.
5333 Specifies how many times to read the stream in sequence.
5334 If the value is less than 1, the stream will be read again and again.
5335 Default value is "1".
5337 Note that when the movie is looped the source timestamps are not
5338 changed, so it will generate non monotonically increasing timestamps.
5341 This filter allows to overlay a second video on top of main input of
5342 a filtergraph as shown in this graph:
5344 input -----------> deltapts0 --> overlay --> output
5347 movie --> scale--> deltapts1 -------+
5350 Some examples follow.
5354 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
5355 on top of the input labelled as "in":
5357 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5358 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5362 Read from a video4linux2 device, and overlay it on top of the input
5365 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5366 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5370 Read the first video stream and the audio stream with id 0x81 from
5371 dvd.vob; the video is connected to the pad named "video" and the audio is
5372 connected to the pad named "audio":
5374 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
5378 @c man end MULTIMEDIA SOURCES