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 to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
1523 The @var{keep_aspect} parameter is optional, if specified and set to a
1524 non-zero value will force the output display aspect ratio to be the
1525 same of the input, by changing the output sample aspect ratio.
1527 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1528 expressions containing the following constants:
1532 the computed values for @var{x} and @var{y}. They are evaluated for
1536 the input width and height
1539 same as @var{in_w} and @var{in_h}
1542 the output (cropped) width and height
1545 same as @var{out_w} and @var{out_h}
1548 same as @var{iw} / @var{ih}
1551 input sample aspect ratio
1554 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1557 horizontal and vertical chroma subsample values. For example for the
1558 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1561 the number of input frame, starting from 0
1564 the position in the file of the input frame, NAN if unknown
1567 timestamp expressed in seconds, NAN if the input timestamp is unknown
1571 The @var{out_w} and @var{out_h} parameters specify the expressions for
1572 the width and height of the output (cropped) video. They are
1573 evaluated just at the configuration of the filter.
1575 The default value of @var{out_w} is "in_w", and the default value of
1576 @var{out_h} is "in_h".
1578 The expression for @var{out_w} may depend on the value of @var{out_h},
1579 and the expression for @var{out_h} may depend on @var{out_w}, but they
1580 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1581 evaluated after @var{out_w} and @var{out_h}.
1583 The @var{x} and @var{y} parameters specify the expressions for the
1584 position of the top-left corner of the output (non-cropped) area. They
1585 are evaluated for each frame. If the evaluated value is not valid, it
1586 is approximated to the nearest valid value.
1588 The default value of @var{x} is "(in_w-out_w)/2", and the default
1589 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
1590 the center of the input image.
1592 The expression for @var{x} may depend on @var{y}, and the expression
1593 for @var{y} may depend on @var{x}.
1595 Follow some examples:
1597 # crop the central input area with size 100x100
1600 # crop the central input area with size 2/3 of the input video
1601 "crop=2/3*in_w:2/3*in_h"
1603 # crop the input video central square
1606 # delimit the rectangle with the top-left corner placed at position
1607 # 100:100 and the right-bottom corner corresponding to the right-bottom
1608 # corner of the input image.
1609 crop=in_w-100:in_h-100:100:100
1611 # crop 10 pixels from the left and right borders, and 20 pixels from
1612 # the top and bottom borders
1613 "crop=in_w-2*10:in_h-2*20"
1615 # keep only the bottom right quarter of the input image
1616 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1618 # crop height for getting Greek harmony
1619 "crop=in_w:1/PHI*in_w"
1622 "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)"
1624 # erratic camera effect depending on timestamp
1625 "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)"
1627 # set x depending on the value of y
1628 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1633 Auto-detect crop size.
1635 Calculate necessary cropping parameters and prints the recommended
1636 parameters through the logging system. The detected dimensions
1637 correspond to the non-black area of the input video.
1639 It accepts the syntax:
1641 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1647 Threshold, which can be optionally specified from nothing (0) to
1648 everything (255), defaults to 24.
1651 Value which the width/height should be divisible by, defaults to
1652 16. The offset is automatically adjusted to center the video. Use 2 to
1653 get only even dimensions (needed for 4:2:2 video). 16 is best when
1654 encoding to most video codecs.
1657 Counter that determines after how many frames cropdetect will reset
1658 the previously detected largest video area and start over to detect
1659 the current optimal crop area. Defaults to 0.
1661 This can be useful when channel logos distort the video area. 0
1662 indicates never reset and return the largest area encountered during
1668 This filter drops frames that do not differ greatly from the previous
1669 frame in order to reduce framerate. The main use of this filter is
1670 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1671 it could in theory be used for fixing movies that were
1672 inverse-telecined incorrectly.
1674 It accepts the following parameters:
1675 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1680 Set the maximum number of consecutive frames which can be dropped (if
1681 positive), or the minimum interval between dropped frames (if
1682 negative). If the value is 0, the frame is dropped unregarding the
1683 number of previous sequentially dropped frames.
1688 Set the dropping threshold values.
1690 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1691 represent actual pixel value differences, so a threshold of 64
1692 corresponds to 1 unit of difference for each pixel, or the same spread
1693 out differently over the block.
1695 A frame is a candidate for dropping if no 8x8 blocks differ by more
1696 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1697 meaning the whole image) differ by more than a threshold of @var{lo}.
1699 Default value for @var{hi} is 64*12, default value for @var{lo} is
1700 64*5, and default value for @var{frac} is 0.33.
1705 Suppress a TV station logo by a simple interpolation of the surrounding
1706 pixels. Just set a rectangle covering the logo and watch it disappear
1707 (and sometimes something even uglier appear - your mileage may vary).
1709 The filter accepts parameters as a string of the form
1710 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1711 @var{key}=@var{value} pairs, separated by ":".
1713 The description of the accepted parameters follows.
1718 Specify the top left corner coordinates of the logo. They must be
1722 Specify the width and height of the logo to clear. They must be
1726 Specify the thickness of the fuzzy edge of the rectangle (added to
1727 @var{w} and @var{h}). The default value is 4.
1730 When set to 1, a green rectangle is drawn on the screen to simplify
1731 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1732 @var{band} is set to 4. The default value is 0.
1736 Some examples follow.
1741 Set a rectangle covering the area with top left corner coordinates 0,0
1742 and size 100x77, setting a band of size 10:
1744 delogo=0:0:100:77:10
1748 As the previous example, but use named options:
1750 delogo=x=0:y=0:w=100:h=77:band=10
1757 Attempt to fix small changes in horizontal and/or vertical shift. This
1758 filter helps remove camera shake from hand-holding a camera, bumping a
1759 tripod, moving on a vehicle, etc.
1761 The filter accepts parameters as a string of the form
1762 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1764 A description of the accepted parameters follows.
1769 Specify a rectangular area where to limit the search for motion
1771 If desired the search for motion vectors can be limited to a
1772 rectangular area of the frame defined by its top left corner, width
1773 and height. These parameters have the same meaning as the drawbox
1774 filter which can be used to visualise the position of the bounding
1777 This is useful when simultaneous movement of subjects within the frame
1778 might be confused for camera motion by the motion vector search.
1780 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1781 then the full frame is used. This allows later options to be set
1782 without specifying the bounding box for the motion vector search.
1784 Default - search the whole frame.
1787 Specify the maximum extent of movement in x and y directions in the
1788 range 0-64 pixels. Default 16.
1791 Specify how to generate pixels to fill blanks at the edge of the
1792 frame. An integer from 0 to 3 as follows:
1795 Fill zeroes at blank locations
1797 Original image at blank locations
1799 Extruded edge value at blank locations
1801 Mirrored edge at blank locations
1804 The default setting is mirror edge at blank locations.
1807 Specify the blocksize to use for motion search. Range 4-128 pixels,
1811 Specify the contrast threshold for blocks. Only blocks with more than
1812 the specified contrast (difference between darkest and lightest
1813 pixels) will be considered. Range 1-255, default 125.
1816 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1817 search. Default - exhaustive search.
1820 If set then a detailed log of the motion search is written to the
1827 Draw a colored box on the input image.
1829 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1832 The description of the accepted parameters follows.
1836 Specify the top left corner coordinates of the box. Default to 0.
1840 Specify the width and height of the box, if 0 they are interpreted as
1841 the input width and height. Default to 0.
1844 Specify the color of the box to write, it can be the name of a color
1845 (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
1846 value @code{invert} is used, the box edge color is the same as the
1847 video with inverted luma.
1850 Set the thickness of the box edge. Default value is @code{4}.
1853 If the key of the first options is omitted, the arguments are
1854 interpreted according to the following syntax:
1856 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness}
1859 Some examples follow:
1862 Draw a black box around the edge of the input image:
1868 Draw a box with color red and an opacity of 50%:
1870 drawbox=10:20:200:60:red@@0.5
1873 The previous example can be specified as:
1875 drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
1879 Fill the box with pink color:
1881 drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
1888 Draw text string or text from specified file on top of video using the
1889 libfreetype library.
1891 To enable compilation of this filter you need to configure FFmpeg with
1892 @code{--enable-libfreetype}.
1896 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1899 The description of the accepted parameters follows.
1904 Used to draw a box around text using background color.
1905 Value should be either 1 (enable) or 0 (disable).
1906 The default value of @var{box} is 0.
1909 The color to be used for drawing box around text.
1910 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1911 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1912 The default value of @var{boxcolor} is "white".
1915 Set an expression which specifies if the text should be drawn. If the
1916 expression evaluates to 0, the text is not drawn. This is useful for
1917 specifying that the text should be drawn only when specific conditions
1920 Default value is "1".
1922 See below for the list of accepted constants and functions.
1925 Select how the @var{text} is expanded. Can be either @code{none},
1926 @code{strftime} (default for compatibity reasons but deprecated) or
1927 @code{normal}. See the @ref{drawtext_expansion, Text expansion} section
1931 If true, check and fix text coords to avoid clipping.
1934 The color to be used for drawing fonts.
1935 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1936 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1937 The default value of @var{fontcolor} is "black".
1940 The font file to be used for drawing text. Path must be included.
1941 This parameter is mandatory.
1944 The font size to be used for drawing text.
1945 The default value of @var{fontsize} is 16.
1948 Flags to be used for loading the fonts.
1950 The flags map the corresponding flags supported by libfreetype, and are
1951 a combination of the following values:
1958 @item vertical_layout
1959 @item force_autohint
1962 @item ignore_global_advance_width
1964 @item ignore_transform
1971 Default value is "render".
1973 For more information consult the documentation for the FT_LOAD_*
1977 The color to be used for drawing a shadow behind the drawn text. It
1978 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1979 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1980 The default value of @var{shadowcolor} is "black".
1982 @item shadowx, shadowy
1983 The x and y offsets for the text shadow position with respect to the
1984 position of the text. They can be either positive or negative
1985 values. Default value for both is "0".
1988 The size in number of spaces to use for rendering the tab.
1992 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
1993 format. It can be used with or without text parameter. @var{timecode_rate}
1994 option must be specified.
1996 @item timecode_rate, rate, r
1997 Set the timecode frame rate (timecode only).
2000 The text string to be drawn. The text must be a sequence of UTF-8
2002 This parameter is mandatory if no file is specified with the parameter
2006 A text file containing text to be drawn. The text must be a sequence
2007 of UTF-8 encoded characters.
2009 This parameter is mandatory if no text string is specified with the
2010 parameter @var{text}.
2012 If both @var{text} and @var{textfile} are specified, an error is thrown.
2015 If set to 1, the @var{textfile} will be reloaded before each frame.
2016 Be sure to update it atomically, or it may be read partially, or even fail.
2019 The expressions which specify the offsets where text will be drawn
2020 within the video frame. They are relative to the top/left border of the
2023 The default value of @var{x} and @var{y} is "0".
2025 See below for the list of accepted constants and functions.
2028 The parameters for @var{x} and @var{y} are expressions containing the
2029 following constants and functions:
2033 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
2036 horizontal and vertical chroma subsample values. For example for the
2037 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2040 the height of each text line
2048 @item max_glyph_a, ascent
2049 the maximum distance from the baseline to the highest/upper grid
2050 coordinate used to place a glyph outline point, for all the rendered
2052 It is a positive value, due to the grid's orientation with the Y axis
2055 @item max_glyph_d, descent
2056 the maximum distance from the baseline to the lowest grid coordinate
2057 used to place a glyph outline point, for all the rendered glyphs.
2058 This is a negative value, due to the grid's orientation, with the Y axis
2062 maximum glyph height, that is the maximum height for all the glyphs
2063 contained in the rendered text, it is equivalent to @var{ascent} -
2067 maximum glyph width, that is the maximum width for all the glyphs
2068 contained in the rendered text
2071 the number of input frame, starting from 0
2073 @item rand(min, max)
2074 return a random number included between @var{min} and @var{max}
2077 input sample aspect ratio
2080 timestamp expressed in seconds, NAN if the input timestamp is unknown
2083 the height of the rendered text
2086 the width of the rendered text
2089 the x and y offset coordinates where the text is drawn.
2091 These parameters allow the @var{x} and @var{y} expressions to refer
2092 each other, so you can for example specify @code{y=x/dar}.
2095 If libavfilter was built with @code{--enable-fontconfig}, then
2096 @option{fontfile} can be a fontconfig pattern or omitted.
2098 @anchor{drawtext_expansion}
2099 @subsection Text expansion
2101 If @option{expansion} is set to @code{strftime} (which is the default for
2102 now), the filter recognizes strftime() sequences in the provided text and
2103 expands them accordingly. Check the documentation of strftime(). This
2104 feature is deprecated.
2106 If @option{expansion} is set to @code{none}, the text is printed verbatim.
2108 If @option{expansion} is set to @code{normal} (which will be the default),
2109 the following expansion mechanism is used.
2111 The backslash character '\', followed by any character, always expands to
2112 the second character.
2114 Sequence of the form @code{%@{...@}} are expanded. The text between the
2115 braces is a function name, possibly followed by arguments separated by ':'.
2116 If the arguments contain special characters or delimiters (':' or '@}'),
2117 they should be escaped.
2119 Note that they probably must also be escaped as the value for the
2120 @option{text} option in the filter argument string and as the filter
2121 argument in the filter graph description, and possibly also for the shell,
2122 that makes up to four levels of escaping; using a text file avoids these
2125 The following functions are available:
2130 The expression evaluation result.
2132 It must take one argument specifying the expression to be evaluated,
2133 which accepts the same constants and functions as the @var{x} and
2134 @var{y} values. Note that not all constants should be used, for
2135 example the text size is not known when evaluating the expression, so
2136 the constants @var{text_w} and @var{text_h} will have an undefined
2140 The time at which the filter is running, expressed in UTC.
2141 It can accept an argument: a strftime() format string.
2144 The time at which the filter is running, expressed in the local time zone.
2145 It can accept an argument: a strftime() format string.
2148 The frame number, starting from 0.
2151 The timestamp of the current frame, in seconds, with microsecond accuracy.
2155 @subsection Examples
2157 Some examples follow.
2162 Draw "Test Text" with font FreeSerif, using the default values for the
2163 optional parameters.
2166 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
2170 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
2171 and y=50 (counting from the top-left corner of the screen), text is
2172 yellow with a red box around it. Both the text and the box have an
2176 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
2177 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
2180 Note that the double quotes are not necessary if spaces are not used
2181 within the parameter list.
2184 Show the text at the center of the video frame:
2186 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
2190 Show a text line sliding from right to left in the last row of the video
2191 frame. The file @file{LONG_LINE} is assumed to contain a single line
2194 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
2198 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
2200 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
2204 Draw a single green letter "g", at the center of the input video.
2205 The glyph baseline is placed at half screen height.
2207 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2211 Show text for 1 second every 3 seconds:
2213 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
2217 Use fontconfig to set the font. Note that the colons need to be escaped.
2219 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
2223 Print the date of a real-time encoding (see strftime(3)):
2225 drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%@{localtime:%a %b %d %Y@}'
2230 For more information about libfreetype, check:
2231 @url{http://www.freetype.org/}.
2233 For more information about fontconfig, check:
2234 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2238 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2240 This filter accepts the following optional named parameters:
2244 Set low and high threshold values used by the Canny thresholding
2247 The high threshold selects the "strong" edge pixels, which are then
2248 connected through 8-connectivity with the "weak" edge pixels selected
2249 by the low threshold.
2251 @var{low} and @var{high} threshold values must be choosen in the range
2252 [0,1], and @var{low} should be lesser or equal to @var{high}.
2254 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2260 edgedetect=low=0.1:high=0.4
2265 Apply fade-in/out effect to input video.
2267 It accepts the parameters:
2268 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2270 @var{type} specifies if the effect type, can be either "in" for
2271 fade-in, or "out" for a fade-out effect.
2273 @var{start_frame} specifies the number of the start frame for starting
2274 to apply the fade effect.
2276 @var{nb_frames} specifies the number of frames for which the fade
2277 effect has to last. At the end of the fade-in effect the output video
2278 will have the same intensity as the input video, at the end of the
2279 fade-out transition the output video will be completely black.
2281 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2282 separated by ":". The description of the accepted options follows.
2289 @item start_frame, s
2290 See @var{start_frame}.
2293 See @var{nb_frames}.
2296 If set to 1, fade only alpha channel, if one exists on the input.
2300 A few usage examples follow, usable too as test scenarios.
2302 # fade in first 30 frames of video
2305 # fade out last 45 frames of a 200-frame video
2308 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2309 fade=in:0:25, fade=out:975:25
2311 # make first 5 frames black, then fade in from frame 5-24
2314 # fade in alpha over first 25 frames of video
2315 fade=in:0:25:alpha=1
2320 Extract a single field from an interlaced image using stride
2321 arithmetic to avoid wasting CPU time. The output frames are marked as
2324 This filter accepts the following named options:
2327 Specify whether to extract the top (if the value is @code{0} or
2328 @code{top}) or the bottom field (if the value is @code{1} or
2332 If the option key is not specified, the first value sets the @var{type}
2333 option. For example:
2345 Transform the field order of the input video.
2347 It accepts one parameter which specifies the required field order that
2348 the input interlaced video will be transformed to. The parameter can
2349 assume one of the following values:
2353 output bottom field first
2355 output top field first
2358 Default value is "tff".
2360 Transformation is achieved by shifting the picture content up or down
2361 by one line, and filling the remaining line with appropriate picture content.
2362 This method is consistent with most broadcast field order converters.
2364 If the input video is not flagged as being interlaced, or it is already
2365 flagged as being of the required output field order then this filter does
2366 not alter the incoming video.
2368 This filter is very useful when converting to or from PAL DV material,
2369 which is bottom field first.
2373 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2378 Buffer input images and send them when they are requested.
2380 This filter is mainly useful when auto-inserted by the libavfilter
2383 The filter does not take parameters.
2387 Convert the input video to one of the specified pixel formats.
2388 Libavfilter will try to pick one that is supported for the input to
2391 The filter accepts a list of pixel format names, separated by ":",
2392 for example "yuv420p:monow:rgb24".
2394 Some examples follow:
2396 # convert the input video to the format "yuv420p"
2399 # convert the input video to any of the formats in the list
2400 format=yuv420p:yuv444p:yuv410p
2405 Convert the video to specified constant framerate by duplicating or dropping
2406 frames as necessary.
2408 This filter accepts the following named parameters:
2412 Desired output framerate. The default is @code{25}.
2417 Possible values are:
2420 zero round towards 0
2424 round towards -infinity
2426 round towards +infinity
2430 The default is @code{near}.
2434 Alternatively, the options can be specified as a flat string:
2435 @var{fps}[:@var{round}].
2437 See also the @ref{setpts} filter.
2441 Select one frame every N.
2443 This filter accepts in input a string representing a positive
2444 integer. Default argument is @code{1}.
2449 Apply a frei0r effect to the input video.
2451 To enable compilation of this filter you need to install the frei0r
2452 header and configure FFmpeg with @code{--enable-frei0r}.
2454 The filter supports the syntax:
2456 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2459 @var{filter_name} is the name of the frei0r effect to load. If the
2460 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2461 is searched in each one of the directories specified by the colon (or
2462 semicolon on Windows platforms) separated list in @env{FREIOR_PATH},
2463 otherwise in the standard frei0r paths, which are in this order:
2464 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
2465 @file{/usr/lib/frei0r-1/}.
2467 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2468 for the frei0r effect.
2470 A frei0r effect parameter can be a boolean (whose values are specified
2471 with "y" and "n"), a double, a color (specified by the syntax
2472 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2473 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2474 description), a position (specified by the syntax @var{X}/@var{Y},
2475 @var{X} and @var{Y} being float numbers) and a string.
2477 The number and kind of parameters depend on the loaded effect. If an
2478 effect parameter is not specified the default value is set.
2480 Some examples follow:
2484 Apply the distort0r effect, set the first two double parameters:
2486 frei0r=distort0r:0.5:0.01
2490 Apply the colordistance effect, take a color as first parameter:
2492 frei0r=colordistance:0.2/0.3/0.4
2493 frei0r=colordistance:violet
2494 frei0r=colordistance:0x112233
2498 Apply the perspective effect, specify the top left and top right image
2501 frei0r=perspective:0.2/0.2:0.8/0.2
2505 For more information see:
2506 @url{http://frei0r.dyne.org}
2510 The filter takes one, two or three equations as parameter, separated by ':'.
2511 The first equation is mandatory and applies to the luma plane. The two
2512 following are respectively for chroma blue and chroma red planes.
2514 The filter syntax allows named parameters:
2518 the luminance expression
2520 the chrominance blue expression
2522 the chrominance red expression
2525 If one of the chrominance expression is not defined, it falls back on the other
2526 one. If none of them are specified, they will evaluate the luminance
2529 The expressions can use the following variables and functions:
2533 The sequential number of the filtered frame, starting from @code{0}.
2536 The coordinates of the current sample.
2539 The width and height of the image.
2542 Width and height scale depending on the currently filtered plane. It is the
2543 ratio between the corresponding luma plane number of pixels and the current
2544 plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
2545 @code{0.5,0.5} for chroma planes.
2548 Time of the current frame, expressed in seconds.
2551 Return the value of the pixel at location (@var{x},@var{y}) of the current
2555 Return the value of the pixel at location (@var{x},@var{y}) of the luminance
2559 Return the value of the pixel at location (@var{x},@var{y}) of the
2560 blue-difference chroma plane.
2563 Return the value of the pixel at location (@var{x},@var{y}) of the
2564 red-difference chroma plane.
2567 For functions, if @var{x} and @var{y} are outside the area, the value will be
2568 automatically clipped to the closer edge.
2570 Some examples follow:
2574 Flip the image horizontally:
2580 Generate a bidimensional sine wave, with angle @code{PI/3} and a
2581 wavelength of 100 pixels:
2583 geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
2587 Generate a fancy enigmatic moving light:
2589 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
2595 Fix the banding artifacts that are sometimes introduced into nearly flat
2596 regions by truncation to 8bit color depth.
2597 Interpolate the gradients that should go where the bands are, and
2600 This filter is designed for playback only. Do not use it prior to
2601 lossy compression, because compression tends to lose the dither and
2602 bring back the bands.
2604 The filter takes two optional parameters, separated by ':':
2605 @var{strength}:@var{radius}
2607 @var{strength} is the maximum amount by which the filter will change
2608 any one pixel. Also the threshold for detecting nearly flat
2609 regions. Acceptable values range from .51 to 255, default value is
2610 1.2, out-of-range values will be clipped to the valid range.
2612 @var{radius} is the neighborhood to fit the gradient to. A larger
2613 radius makes for smoother gradients, but also prevents the filter from
2614 modifying the pixels near detailed regions. Acceptable values are
2615 8-32, default value is 16, out-of-range values will be clipped to the
2619 # default parameters
2628 Flip the input video horizontally.
2630 For example to horizontally flip the input video with @command{ffmpeg}:
2632 ffmpeg -i in.avi -vf "hflip" out.avi
2637 High precision/quality 3d denoise filter. This filter aims to reduce
2638 image noise producing smooth images and making still images really
2639 still. It should enhance compressibility.
2641 It accepts the following optional parameters:
2642 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2646 a non-negative float number which specifies spatial luma strength,
2649 @item chroma_spatial
2650 a non-negative float number which specifies spatial chroma strength,
2651 defaults to 3.0*@var{luma_spatial}/4.0
2654 a float number which specifies luma temporal strength, defaults to
2655 6.0*@var{luma_spatial}/4.0
2658 a float number which specifies chroma temporal strength, defaults to
2659 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2664 Modify the hue and/or the saturation of the input.
2666 This filter accepts the following optional named options:
2670 Specify the hue angle as a number of degrees. It accepts a float
2671 number or an expression, and defaults to 0.0.
2674 Specify the hue angle as a number of degrees. It accepts a float
2675 number or an expression, and defaults to 0.0.
2678 Specify the saturation in the [-10,10] range. It accepts a float number and
2682 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2683 following constants:
2687 frame count of the input frame starting from 0
2690 presentation timestamp of the input frame expressed in time base units
2693 frame rate of the input video, NAN if the input frame rate is unknown
2696 timestamp expressed in seconds, NAN if the input timestamp is unknown
2699 time base of the input video
2702 The options can also be set using the syntax: @var{hue}:@var{saturation}
2704 In this case @var{hue} is expressed in degrees.
2706 Some examples follow:
2709 Set the hue to 90 degrees and the saturation to 1.0:
2715 Same command but expressing the hue in radians:
2721 Same command without named options, hue must be expressed in degrees:
2727 Note that "h:s" syntax does not support expressions for the values of
2728 h and s, so the following example will issue an error:
2734 Rotate hue and make the saturation swing between 0
2735 and 2 over a period of 1 second:
2737 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2741 Apply a 3 seconds saturation fade-in effect starting at 0:
2746 The general fade-in expression can be written as:
2748 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2752 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2754 hue="s=max(0\, min(1\, (8-t)/3))"
2757 The general fade-out expression can be written as:
2759 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2764 @subsection Commands
2766 This filter supports the following command:
2769 Modify the hue and/or the saturation of the input video.
2770 The command accepts the same named options and syntax than when calling the
2771 filter from the command-line.
2773 If a parameter is omitted, it is kept at its current value.
2778 Interlaceing detect filter. This filter tries to detect if the input is
2779 interlaced or progressive. Top or bottom field first.
2781 @section lut, lutrgb, lutyuv
2783 Compute a look-up table for binding each pixel component input value
2784 to an output value, and apply it to input video.
2786 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2787 to an RGB input video.
2789 These filters accept in input a ":"-separated list of options, which
2790 specify the expressions used for computing the lookup table for the
2791 corresponding pixel component values.
2793 The @var{lut} filter requires either YUV or RGB pixel formats in
2794 input, and accepts the options:
2796 @item @var{c0} (first pixel component)
2797 @item @var{c1} (second pixel component)
2798 @item @var{c2} (third pixel component)
2799 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
2802 The exact component associated to each option depends on the format in
2805 The @var{lutrgb} filter requires RGB pixel formats in input, and
2806 accepts the options:
2808 @item @var{r} (red component)
2809 @item @var{g} (green component)
2810 @item @var{b} (blue component)
2811 @item @var{a} (alpha component)
2814 The @var{lutyuv} filter requires YUV pixel formats in input, and
2815 accepts the options:
2817 @item @var{y} (Y/luminance component)
2818 @item @var{u} (U/Cb component)
2819 @item @var{v} (V/Cr component)
2820 @item @var{a} (alpha component)
2823 The expressions can contain the following constants and functions:
2827 the input width and height
2830 input value for the pixel component
2833 the input value clipped in the @var{minval}-@var{maxval} range
2836 maximum value for the pixel component
2839 minimum value for the pixel component
2842 the negated value for the pixel component value clipped in the
2843 @var{minval}-@var{maxval} range , it corresponds to the expression
2844 "maxval-clipval+minval"
2847 the computed value in @var{val} clipped in the
2848 @var{minval}-@var{maxval} range
2850 @item gammaval(gamma)
2851 the computed gamma correction value of the pixel component value
2852 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2854 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2858 All expressions default to "val".
2860 Some examples follow:
2862 # negate input video
2863 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2864 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2866 # the above is the same as
2867 lutrgb="r=negval:g=negval:b=negval"
2868 lutyuv="y=negval:u=negval:v=negval"
2873 # remove chroma components, turns the video into a graytone image
2874 lutyuv="u=128:v=128"
2876 # apply a luma burning effect
2879 # remove green and blue components
2882 # set a constant alpha channel value on input
2883 format=rgba,lutrgb=a="maxval-minval/2"
2885 # correct luminance gamma by a 0.5 factor
2886 lutyuv=y=gammaval(0.5)
2891 Apply an MPlayer filter to the input video.
2893 This filter provides a wrapper around most of the filters of
2896 This wrapper is considered experimental. Some of the wrapped filters
2897 may not work properly and we may drop support for them, as they will
2898 be implemented natively into FFmpeg. Thus you should avoid
2899 depending on them when writing portable scripts.
2901 The filters accepts the parameters:
2902 @var{filter_name}[:=]@var{filter_params}
2904 @var{filter_name} is the name of a supported MPlayer filter,
2905 @var{filter_params} is a string containing the parameters accepted by
2908 The list of the currently supported filters follows:
2942 The parameter syntax and behavior for the listed filters are the same
2943 of the corresponding MPlayer filters. For detailed instructions check
2944 the "VIDEO FILTERS" section in the MPlayer manual.
2946 Some examples follow:
2949 Adjust gamma, brightness, contrast:
2955 Add temporal noise to input video:
2961 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2967 This filter accepts an integer in input, if non-zero it negates the
2968 alpha component (if available). The default value in input is 0.
2972 Force libavfilter not to use any of the specified pixel formats for the
2973 input to the next filter.
2975 The filter accepts a list of pixel format names, separated by ":",
2976 for example "yuv420p:monow:rgb24".
2978 Some examples follow:
2980 # force libavfilter to use a format different from "yuv420p" for the
2981 # input to the vflip filter
2982 noformat=yuv420p,vflip
2984 # convert the input video to any of the formats not contained in the list
2985 noformat=yuv420p:yuv444p:yuv410p
2990 Pass the video source unchanged to the output.
2994 Apply video transform using libopencv.
2996 To enable this filter install libopencv library and headers and
2997 configure FFmpeg with @code{--enable-libopencv}.
2999 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
3001 @var{filter_name} is the name of the libopencv filter to apply.
3003 @var{filter_params} specifies the parameters to pass to the libopencv
3004 filter. If not specified the default values are assumed.
3006 Refer to the official libopencv documentation for more precise
3008 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
3010 Follows the list of supported libopencv filters.
3015 Dilate an image by using a specific structuring element.
3016 This filter corresponds to the libopencv function @code{cvDilate}.
3018 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
3020 @var{struct_el} represents a structuring element, and has the syntax:
3021 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
3023 @var{cols} and @var{rows} represent the number of columns and rows of
3024 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
3025 point, and @var{shape} the shape for the structuring element, and
3026 can be one of the values "rect", "cross", "ellipse", "custom".
3028 If the value for @var{shape} is "custom", it must be followed by a
3029 string of the form "=@var{filename}". The file with name
3030 @var{filename} is assumed to represent a binary image, with each
3031 printable character corresponding to a bright pixel. When a custom
3032 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
3033 or columns and rows of the read file are assumed instead.
3035 The default value for @var{struct_el} is "3x3+0x0/rect".
3037 @var{nb_iterations} specifies the number of times the transform is
3038 applied to the image, and defaults to 1.
3040 Follow some example:
3042 # use the default values
3045 # dilate using a structuring element with a 5x5 cross, iterate two times
3046 ocv=dilate=5x5+2x2/cross:2
3048 # read the shape from the file diamond.shape, iterate two times
3049 # the file diamond.shape may contain a pattern of characters like this:
3055 # the specified cols and rows are ignored (but not the anchor point coordinates)
3056 ocv=0x0+2x2/custom=diamond.shape:2
3061 Erode an image by using a specific structuring element.
3062 This filter corresponds to the libopencv function @code{cvErode}.
3064 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
3065 with the same syntax and semantics as the @ref{dilate} filter.
3069 Smooth the input video.
3071 The filter takes the following parameters:
3072 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
3074 @var{type} is the type of smooth filter to apply, and can be one of
3075 the following values: "blur", "blur_no_scale", "median", "gaussian",
3076 "bilateral". The default value is "gaussian".
3078 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
3079 parameters whose meanings depend on smooth type. @var{param1} and
3080 @var{param2} accept integer positive values or 0, @var{param3} and
3081 @var{param4} accept float values.
3083 The default value for @var{param1} is 3, the default value for the
3084 other parameters is 0.
3086 These parameters correspond to the parameters assigned to the
3087 libopencv function @code{cvSmooth}.
3092 Overlay one video on top of another.
3094 It takes two inputs and one output, the first input is the "main"
3095 video on which the second input is overlayed.
3097 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
3099 @var{x} is the x coordinate of the overlayed video on the main video,
3100 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
3101 the following parameters:
3104 @item main_w, main_h
3105 main input width and height
3108 same as @var{main_w} and @var{main_h}
3110 @item overlay_w, overlay_h
3111 overlay input width and height
3114 same as @var{overlay_w} and @var{overlay_h}
3117 @var{options} is an optional list of @var{key}=@var{value} pairs,
3120 The description of the accepted options follows.
3124 If set to 1, force the filter to accept inputs in the RGB
3125 color space. Default value is 0.
3128 Be aware that frames are taken from each input video in timestamp
3129 order, hence, if their initial timestamps differ, it is a a good idea
3130 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
3131 have them begin in the same zero timestamp, as it does the example for
3132 the @var{movie} filter.
3134 Follow some examples:
3136 # draw the overlay at 10 pixels from the bottom right
3137 # corner of the main video.
3138 overlay=main_w-overlay_w-10:main_h-overlay_h-10
3140 # insert a transparent PNG logo in the bottom left corner of the input
3141 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
3143 # insert 2 different transparent PNG logos (second logo on bottom
3145 ffmpeg -i input -i logo1 -i logo2 -filter_complex
3146 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
3148 # add a transparent color layer on top of the main video,
3149 # WxH specifies the size of the main input to the overlay filter
3150 color=red@@.3:WxH [over]; [in][over] overlay [out]
3152 # play an original video and a filtered version (here with the deshake filter)
3154 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
3156 # the previous example is the same as:
3157 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
3160 You can chain together more overlays but the efficiency of such
3161 approach is yet to be tested.
3165 Add paddings to the input image, and places the original input at the
3166 given coordinates @var{x}, @var{y}.
3168 It accepts the following parameters:
3169 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
3171 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
3172 expressions containing the following constants:
3176 the input video width and height
3179 same as @var{in_w} and @var{in_h}
3182 the output width and height, that is the size of the padded area as
3183 specified by the @var{width} and @var{height} expressions
3186 same as @var{out_w} and @var{out_h}
3189 x and y offsets as specified by the @var{x} and @var{y}
3190 expressions, or NAN if not yet specified
3193 same as @var{iw} / @var{ih}
3196 input sample aspect ratio
3199 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3202 horizontal and vertical chroma subsample values. For example for the
3203 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3206 Follows the description of the accepted parameters.
3211 Specify the size of the output image with the paddings added. If the
3212 value for @var{width} or @var{height} is 0, the corresponding input size
3213 is used for the output.
3215 The @var{width} expression can reference the value set by the
3216 @var{height} expression, and vice versa.
3218 The default value of @var{width} and @var{height} is 0.
3222 Specify the offsets where to place the input image in the padded area
3223 with respect to the top/left border of the output image.
3225 The @var{x} expression can reference the value set by the @var{y}
3226 expression, and vice versa.
3228 The default value of @var{x} and @var{y} is 0.
3232 Specify the color of the padded area, it can be the name of a color
3233 (case insensitive match) or a 0xRRGGBB[AA] sequence.
3235 The default value of @var{color} is "black".
3239 @subsection Examples
3243 Add paddings with color "violet" to the input video. Output video
3244 size is 640x480, the top-left corner of the input video is placed at
3247 pad=640:480:0:40:violet
3251 Pad the input to get an output with dimensions increased by 3/2,
3252 and put the input video at the center of the padded area:
3254 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
3258 Pad the input to get a squared output with size equal to the maximum
3259 value between the input width and height, and put the input video at
3260 the center of the padded area:
3262 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
3266 Pad the input to get a final w/h ratio of 16:9:
3268 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
3272 In case of anamorphic video, in order to set the output display aspect
3273 correctly, it is necessary to use @var{sar} in the expression,
3274 according to the relation:
3276 (ih * X / ih) * sar = output_dar
3277 X = output_dar / sar
3280 Thus the previous example needs to be modified to:
3282 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
3286 Double output size and put the input video in the bottom-right
3287 corner of the output padded area:
3289 pad="2*iw:2*ih:ow-iw:oh-ih"
3293 @section pixdesctest
3295 Pixel format descriptor test filter, mainly useful for internal
3296 testing. The output video should be equal to the input video.
3300 format=monow, pixdesctest
3303 can be used to test the monowhite pixel format descriptor definition.
3307 Suppress a TV station logo, using an image file to determine which
3308 pixels comprise the logo. It works by filling in the pixels that
3309 comprise the logo with neighboring pixels.
3311 This filter requires one argument which specifies the filter bitmap
3312 file, which can be any image format supported by libavformat. The
3313 width and height of the image file must match those of the video
3314 stream being processed.
3316 Pixels in the provided bitmap image with a value of zero are not
3317 considered part of the logo, non-zero pixels are considered part of
3318 the logo. If you use white (255) for the logo and black (0) for the
3319 rest, you will be safe. For making the filter bitmap, it is
3320 recommended to take a screen capture of a black frame with the logo
3321 visible, and then using a threshold filter followed by the erode
3322 filter once or twice.
3324 If needed, little splotches can be fixed manually. Remember that if
3325 logo pixels are not covered, the filter quality will be much
3326 reduced. Marking too many pixels as part of the logo does not hurt as
3327 much, but it will increase the amount of blurring needed to cover over
3328 the image and will destroy more information than necessary, and extra
3329 pixels will slow things down on a large logo.
3333 Scale (resize) the input video, using the libswscale library.
3335 The scale filter forces the output display aspect ratio to be the same
3336 of the input, by changing the output sample aspect ratio.
3338 This filter accepts a list of named options in the form of
3339 @var{key}=@var{value} pairs separated by ":". If the key for the first
3340 two options is not specified, the assumed keys for the first two
3341 values are @code{w} and @code{h}. If the first option has no key and
3342 can be interpreted like a video size specification, it will be used
3343 to set the video size.
3345 A description of the accepted options follows.
3349 Set the video width expression, default value is @code{iw}. See below
3350 for the list of accepted constants.
3353 Set the video heiht expression, default value is @code{ih}.
3354 See below for the list of accepted constants.
3357 Set the interlacing. It accepts the following values:
3361 force interlaced aware scaling
3364 do not apply interlaced scaling
3367 select interlaced aware scaling depending on whether the source frames
3368 are flagged as interlaced or not
3371 Default value is @code{0}.
3374 Set libswscale scaling flags. If not explictly specified the filter
3375 applies a bilinear scaling algorithm.
3378 Set the video size, the value must be a valid abbreviation or in the
3379 form @var{width}x@var{height}.
3382 The values of the @var{w} and @var{h} options are expressions
3383 containing the following constants:
3387 the input width and height
3390 same as @var{in_w} and @var{in_h}
3393 the output (cropped) width and height
3396 same as @var{out_w} and @var{out_h}
3399 same as @var{iw} / @var{ih}
3402 input sample aspect ratio
3405 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3408 horizontal and vertical chroma subsample values. For example for the
3409 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3412 If the input image format is different from the format requested by
3413 the next filter, the scale filter will convert the input to the
3416 If the value for @var{width} or @var{height} is 0, the respective input
3417 size is used for the output.
3419 If the value for @var{width} or @var{height} is -1, the scale filter will
3420 use, for the respective output size, a value that maintains the aspect
3421 ratio of the input image.
3423 @subsection Examples
3427 Scale the input video to a size of 200x100:
3432 This is equivalent to:
3443 Specify a size abbreviation for the output size:
3448 which can also be written as:
3454 Scale the input to 2x:
3460 The above is the same as:
3466 Scale the input to 2x with forced interlaced scaling:
3468 scale=2*iw:2*ih:interl=1
3472 Scale the input to half size:
3478 Increase the width, and set the height to the same size:
3484 Seek for Greek harmony:
3491 Increase the height, and set the width to 3/2 of the height:
3497 Increase the size, but make the size a multiple of the chroma:
3499 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3503 Increase the width to a maximum of 500 pixels, keep the same input
3506 scale='min(500\, iw*3/2):-1'
3510 @section setdar, setsar
3512 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3515 This is done by changing the specified Sample (aka Pixel) Aspect
3516 Ratio, according to the following equation:
3518 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3521 Keep in mind that the @code{setdar} filter does not modify the pixel
3522 dimensions of the video frame. Also the display aspect ratio set by
3523 this filter may be changed by later filters in the filterchain,
3524 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3527 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3528 the filter output video.
3530 Note that as a consequence of the application of this filter, the
3531 output display aspect ratio will change according to the equation
3534 Keep in mind that the sample aspect ratio set by the @code{setsar}
3535 filter may be changed by later filters in the filterchain, e.g. if
3536 another "setsar" or a "setdar" filter is applied.
3538 The @code{setdar} and @code{setsar} filters accept a string in the
3539 form @var{num}:@var{den} expressing an aspect ratio, or the following
3540 named options, expressed as a sequence of @var{key}=@var{value} pairs,
3545 Set the maximum integer value to use for expressing numerator and
3546 denominator when reducing the expressed aspect ratio to a rational.
3547 Default value is @code{100}.
3550 Set the aspect ratio used by the filter.
3552 The parameter can be a floating point number string, an expression, or
3553 a string of the form @var{num}:@var{den}, where @var{num} and
3554 @var{den} are the numerator and denominator of the aspect ratio. If
3555 the parameter is not specified, it is assumed the value "0".
3556 In case the form "@var{num}:@var{den}" the @code{:} character should
3560 If the keys are omitted in the named options list, the specifed values
3561 are assumed to be @var{ratio} and @var{max} in that order.
3563 For example to change the display aspect ratio to 16:9, specify:
3568 The example above is equivalent to:
3573 To change the sample aspect ratio to 10:11, specify:
3578 To set a display aspect ratio of 16:9, and specify a maximum integer value of
3579 1000 in the aspect ratio reduction, use the command:
3581 setdar=ratio='16:9':max=1000
3586 Force field for the output video frame.
3588 The @code{setfield} filter marks the interlace type field for the
3589 output frames. It does not change the input frame, but only sets the
3590 corresponding property, which affects how the frame is treated by
3591 following filters (e.g. @code{fieldorder} or @code{yadif}).
3593 This filter accepts a single option @option{mode}, which can be
3594 specified either by setting @code{mode=VALUE} or setting the value
3595 alone. Available values are:
3599 Keep the same field property.
3602 Mark the frame as bottom-field-first.
3605 Mark the frame as top-field-first.
3608 Mark the frame as progressive.
3613 Show a line containing various information for each input video frame.
3614 The input video is not modified.
3616 The shown line contains a sequence of key/value pairs of the form
3617 @var{key}:@var{value}.
3619 A description of each shown parameter follows:
3623 sequential number of the input frame, starting from 0
3626 Presentation TimeStamp of the input frame, expressed as a number of
3627 time base units. The time base unit depends on the filter input pad.
3630 Presentation TimeStamp of the input frame, expressed as a number of
3634 position of the frame in the input stream, -1 if this information in
3635 unavailable and/or meaningless (for example in case of synthetic video)
3641 sample aspect ratio of the input frame, expressed in the form
3645 size of the input frame, expressed in the form
3646 @var{width}x@var{height}
3649 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3650 for bottom field first)
3653 1 if the frame is a key frame, 0 otherwise
3656 picture type of the input frame ("I" for an I-frame, "P" for a
3657 P-frame, "B" for a B-frame, "?" for unknown type).
3658 Check also the documentation of the @code{AVPictureType} enum and of
3659 the @code{av_get_picture_type_char} function defined in
3660 @file{libavutil/avutil.h}.
3663 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3665 @item plane_checksum
3666 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3667 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3672 Blur the input video without impacting the outlines.
3674 The filter accepts the following parameters:
3675 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3677 Parameters prefixed by @var{luma} indicate that they work on the
3678 luminance of the pixels whereas parameters prefixed by @var{chroma}
3679 refer to the chrominance of the pixels.
3681 If the chroma parameters are not set, the luma parameters are used for
3682 either the luminance and the chrominance of the pixels.
3684 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3685 range [0.1,5.0] that specifies the variance of the gaussian filter
3686 used to blur the image (slower if larger).
3688 @var{luma_strength} or @var{chroma_strength} must be a float number in
3689 the range [-1.0,1.0] that configures the blurring. A value included in
3690 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3691 will sharpen the image.
3693 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3694 the range [-30,30] that is used as a coefficient to determine whether
3695 a pixel should be blurred or not. A value of 0 will filter all the
3696 image, a value included in [0,30] will filter flat areas and a value
3697 included in [-30,0] will filter edges.
3702 Draw subtitles on top of input video using the libass library.
3704 To enable compilation of this filter you need to configure FFmpeg with
3705 @code{--enable-libass}. This filter also requires a build with libavcodec and
3706 libavformat to convert the passed subtitles file to ASS (Advanced Substation
3707 Alpha) subtitles format.
3709 This filter accepts the following named options, expressed as a
3710 sequence of @var{key}=@var{value} pairs, separated by ":".
3714 Set the filename of the subtitle file to read. It must be specified.
3717 Specify the size of the original video, the video for which the ASS file
3718 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
3719 necessary to correctly scale the fonts if the aspect ratio has been changed.
3722 If the first key is not specified, it is assumed that the first value
3723 specifies the @option{filename}.
3725 For example, to render the file @file{sub.srt} on top of the input
3726 video, use the command:
3731 which is equivalent to:
3733 subtitles=filename=sub.srt
3738 Split input video into several identical outputs.
3740 The filter accepts a single parameter which specifies the number of outputs. If
3741 unspecified, it defaults to 2.
3745 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3747 will create 5 copies of the input video.
3751 [in] split [splitout1][splitout2];
3752 [splitout1] crop=100:100:0:0 [cropout];
3753 [splitout2] pad=200:200:100:100 [padout];
3756 will create two separate outputs from the same input, one cropped and
3761 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3762 Interpolate) pixel art scaling algorithm.
3764 Useful for enlarging pixel art images without reducing sharpness.
3770 Select the most representative frame in a given sequence of consecutive frames.
3772 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3773 in a set of @var{N} frames, the filter will pick one of them, and then handle
3774 the next batch of @var{N} frames until the end.
3776 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3777 value will result in a higher memory usage, so a high value is not recommended.
3779 The following example extract one picture each 50 frames:
3784 Complete example of a thumbnail creation with @command{ffmpeg}:
3786 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3791 Tile several successive frames together.
3793 It accepts a list of options in the form of @var{key}=@var{value} pairs
3794 separated by ":". A description of the accepted options follows.
3799 Set the grid size (i.e. the number of lines and columns) in the form
3803 Set the outer border margin in pixels.
3806 Set the inner border thickness (i.e. the number of pixels between frames). For
3807 more advanced padding options (such as having different values for the edges),
3808 refer to the pad video filter.
3811 Set the maximum number of frames to render in the given area. It must be less
3812 than or equal to @var{w}x@var{h}. The default value is @code{0}, meaning all
3813 the area will be used.
3817 Alternatively, the options can be specified as a flat string:
3819 @var{layout}[:@var{nb_frames}[:@var{margin}[:@var{padding}]]]
3821 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3824 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3826 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3827 duplicating each output frame to accomodate the originally detected frame
3830 Another example to display @code{5} pictures in an area of @code{3x2} frames,
3831 with @code{7} pixels between them, and @code{2} pixels of initial margin, using
3832 mixed flat and named options:
3834 tile=3x2:nb_frames=5:padding=7:margin=2
3839 Perform various types of temporal field interlacing.
3841 Frames are counted starting from 1, so the first input frame is
3844 This filter accepts a single option @option{mode} specifying the mode,
3845 which can be specified either by specyfing @code{mode=VALUE} either
3846 specifying the value alone. Available values are:
3850 Move odd frames into the upper field, even into the lower field,
3851 generating a double height frame at half framerate.
3854 Only output even frames, odd frames are dropped, generating a frame with
3855 unchanged height at half framerate.
3858 Only output odd frames, even frames are dropped, generating a frame with
3859 unchanged height at half framerate.
3862 Expand each frame to full height, but pad alternate lines with black,
3863 generating a frame with double height at the same input framerate.
3865 @item interleave_top, 4
3866 Interleave the upper field from odd frames with the lower field from
3867 even frames, generating a frame with unchanged height at half framerate.
3869 @item interleave_bottom, 5
3870 Interleave the lower field from odd frames with the upper field from
3871 even frames, generating a frame with unchanged height at half framerate.
3873 @item interlacex2, 6
3874 Double frame rate with unchanged height. Frames are inserted each
3875 containing the second temporal field from the previous input frame and
3876 the first temporal field from the next input frame. This mode relies on
3877 the top_field_first flag. Useful for interlaced video displays with no
3878 field synchronisation.
3881 Numeric values are deprecated but are accepted for backward
3882 compatibility reasons.
3884 Default mode is @code{merge}.
3888 Transpose rows with columns in the input video and optionally flip it.
3890 This filter accepts the following named parameters:
3894 Specify the transposition direction. Can assume the following values:
3898 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3906 Rotate by 90 degrees clockwise, that is:
3914 Rotate by 90 degrees counterclockwise, that is:
3922 Rotate by 90 degrees clockwise and vertically flip, that is:
3930 For values between 4-7, the transposition is only done if the input
3931 video geometry is portrait and not landscape. These values are
3932 deprecated, the @code{passthrough} option should be used instead.
3935 Do not apply the transposition if the input geometry matches the one
3936 specified by the specified value. It accepts the following values:
3939 Always apply transposition.
3941 Preserve portrait geometry (when @var{height} >= @var{width}).
3943 Preserve landscape geometry (when @var{width} >= @var{height}).
3946 Default value is @code{none}.
3951 Sharpen or blur the input video.
3953 It accepts the following parameters:
3954 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3956 Negative values for the amount will blur the input video, while positive
3957 values will sharpen. All parameters are optional and default to the
3958 equivalent of the string '5:5:1.0:5:5:0.0'.
3963 Set the luma matrix horizontal size. It can be an integer between 3
3964 and 13, default value is 5.
3967 Set the luma matrix vertical size. It can be an integer between 3
3968 and 13, default value is 5.
3971 Set the luma effect strength. It can be a float number between -2.0
3972 and 5.0, default value is 1.0.
3974 @item chroma_msize_x
3975 Set the chroma matrix horizontal size. It can be an integer between 3
3976 and 13, default value is 5.
3978 @item chroma_msize_y
3979 Set the chroma matrix vertical size. It can be an integer between 3
3980 and 13, default value is 5.
3983 Set the chroma effect strength. It can be a float number between -2.0
3984 and 5.0, default value is 0.0.
3989 # Strong luma sharpen effect parameters
3992 # Strong blur of both luma and chroma parameters
3993 unsharp=7:7:-2:7:7:-2
3995 # Use the default values with @command{ffmpeg}
3996 ffmpeg -i in.avi -vf "unsharp" out.mp4
4001 Flip the input video vertically.
4004 ffmpeg -i in.avi -vf "vflip" out.avi
4009 Deinterlace the input video ("yadif" means "yet another deinterlacing
4012 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
4014 @var{mode} specifies the interlacing mode to adopt, accepts one of the
4019 output 1 frame for each frame
4021 output 1 frame for each field
4023 like 0 but skips spatial interlacing check
4025 like 1 but skips spatial interlacing check
4030 @var{parity} specifies the picture field parity assumed for the input
4031 interlaced video, accepts one of the following values:
4035 assume top field first
4037 assume bottom field first
4039 enable automatic detection
4042 Default value is -1.
4043 If interlacing is unknown or decoder does not export this information,
4044 top field first will be assumed.
4046 @var{auto} specifies if deinterlacer should trust the interlaced flag
4047 and only deinterlace frames marked as interlaced
4051 deinterlace all frames
4053 only deinterlace frames marked as interlaced
4058 @c man end VIDEO FILTERS
4060 @chapter Video Sources
4061 @c man begin VIDEO SOURCES
4063 Below is a description of the currently available video sources.
4067 Buffer video frames, and make them available to the filter chain.
4069 This source is mainly intended for a programmatic use, in particular
4070 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
4072 It accepts a list of options in the form of @var{key}=@var{value} pairs
4073 separated by ":". A description of the accepted options follows.
4078 Specify the size (width and height) of the buffered video frames.
4081 A string representing the pixel format of the buffered video frames.
4082 It may be a number corresponding to a pixel format, or a pixel format
4086 Specify the timebase assumed by the timestamps of the buffered frames.
4089 Specify the frame rate expected for the video stream.
4092 Specify the sample aspect ratio assumed by the video frames.
4095 Specify the optional parameters to be used for the scale filter which
4096 is automatically inserted when an input change is detected in the
4097 input size or format.
4102 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
4105 will instruct the source to accept video frames with size 320x240 and
4106 with format "yuv410p", assuming 1/24 as the timestamps timebase and
4107 square pixels (1:1 sample aspect ratio).
4108 Since the pixel format with name "yuv410p" corresponds to the number 6
4109 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
4110 this example corresponds to:
4112 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
4115 Alternatively, the options can be specified as a flat string, but this
4116 syntax is deprecated:
4118 @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}]
4122 Create a pattern generated by an elementary cellular automaton.
4124 The initial state of the cellular automaton can be defined through the
4125 @option{filename}, and @option{pattern} options. If such options are
4126 not specified an initial state is created randomly.
4128 At each new frame a new row in the video is filled with the result of
4129 the cellular automaton next generation. The behavior when the whole
4130 frame is filled is defined by the @option{scroll} option.
4132 This source accepts a list of options in the form of
4133 @var{key}=@var{value} pairs separated by ":". A description of the
4134 accepted options follows.
4138 Read the initial cellular automaton state, i.e. the starting row, from
4140 In the file, each non-whitespace character is considered an alive
4141 cell, a newline will terminate the row, and further characters in the
4142 file will be ignored.
4145 Read the initial cellular automaton state, i.e. the starting row, from
4146 the specified string.
4148 Each non-whitespace character in the string is considered an alive
4149 cell, a newline will terminate the row, and further characters in the
4150 string will be ignored.
4153 Set the video rate, that is the number of frames generated per second.
4156 @item random_fill_ratio, ratio
4157 Set the random fill ratio for the initial cellular automaton row. It
4158 is a floating point number value ranging from 0 to 1, defaults to
4161 This option is ignored when a file or a pattern is specified.
4163 @item random_seed, seed
4164 Set the seed for filling randomly the initial row, must be an integer
4165 included between 0 and UINT32_MAX. If not specified, or if explicitly
4166 set to -1, the filter will try to use a good random seed on a best
4170 Set the cellular automaton rule, it is a number ranging from 0 to 255.
4171 Default value is 110.
4174 Set the size of the output video.
4176 If @option{filename} or @option{pattern} is specified, the size is set
4177 by default to the width of the specified initial state row, and the
4178 height is set to @var{width} * PHI.
4180 If @option{size} is set, it must contain the width of the specified
4181 pattern string, and the specified pattern will be centered in the
4184 If a filename or a pattern string is not specified, the size value
4185 defaults to "320x518" (used for a randomly generated initial state).
4188 If set to 1, scroll the output upward when all the rows in the output
4189 have been already filled. If set to 0, the new generated row will be
4190 written over the top row just after the bottom row is filled.
4193 @item start_full, full
4194 If set to 1, completely fill the output with generated rows before
4195 outputting the first frame.
4196 This is the default behavior, for disabling set the value to 0.
4199 If set to 1, stitch the left and right row edges together.
4200 This is the default behavior, for disabling set the value to 0.
4203 @subsection Examples
4207 Read the initial state from @file{pattern}, and specify an output of
4210 cellauto=f=pattern:s=200x400
4214 Generate a random initial row with a width of 200 cells, with a fill
4217 cellauto=ratio=2/3:s=200x200
4221 Create a pattern generated by rule 18 starting by a single alive cell
4222 centered on an initial row with width 100:
4224 cellauto=p=@@:s=100x400:full=0:rule=18
4228 Specify a more elaborated initial pattern:
4230 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
4237 Generate a Mandelbrot set fractal, and progressively zoom towards the
4238 point specified with @var{start_x} and @var{start_y}.
4240 This source accepts a list of options in the form of
4241 @var{key}=@var{value} pairs separated by ":". A description of the
4242 accepted options follows.
4247 Set the terminal pts value. Default value is 400.
4250 Set the terminal scale value.
4251 Must be a floating point value. Default value is 0.3.
4254 Set the inner coloring mode, that is the algorithm used to draw the
4255 Mandelbrot fractal internal region.
4257 It shall assume one of the following values:
4262 Show time until convergence.
4264 Set color based on point closest to the origin of the iterations.
4269 Default value is @var{mincol}.
4272 Set the bailout value. Default value is 10.0.
4275 Set the maximum of iterations performed by the rendering
4276 algorithm. Default value is 7189.
4279 Set outer coloring mode.
4280 It shall assume one of following values:
4282 @item iteration_count
4283 Set iteration cound mode.
4284 @item normalized_iteration_count
4285 set normalized iteration count mode.
4287 Default value is @var{normalized_iteration_count}.
4290 Set frame rate, expressed as number of frames per second. Default
4294 Set frame size. Default value is "640x480".
4297 Set the initial scale value. Default value is 3.0.
4300 Set the initial x position. Must be a floating point value between
4301 -100 and 100. Default value is -0.743643887037158704752191506114774.
4304 Set the initial y position. Must be a floating point value between
4305 -100 and 100. Default value is -0.131825904205311970493132056385139.
4310 Generate various test patterns, as generated by the MPlayer test filter.
4312 The size of the generated video is fixed, and is 256x256.
4313 This source is useful in particular for testing encoding features.
4315 This source accepts an optional sequence of @var{key}=@var{value} pairs,
4316 separated by ":". The description of the accepted options follows.
4321 Specify the frame rate of the sourced video, as the number of frames
4322 generated per second. It has to be a string in the format
4323 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4324 number or a valid video frame rate abbreviation. The default value is
4328 Set the video duration of the sourced video. The accepted syntax is:
4333 See also the function @code{av_parse_time()}.
4335 If not specified, or the expressed duration is negative, the video is
4336 supposed to be generated forever.
4340 Set the number or the name of the test to perform. Supported tests are:
4355 Default value is "all", which will cycle through the list of all tests.
4358 For example the following:
4363 will generate a "dc_luma" test pattern.
4367 Provide a frei0r source.
4369 To enable compilation of this filter you need to install the frei0r
4370 header and configure FFmpeg with @code{--enable-frei0r}.
4372 The source supports the syntax:
4374 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
4377 @var{size} is the size of the video to generate, may be a string of the
4378 form @var{width}x@var{height} or a frame size abbreviation.
4379 @var{rate} is the rate of the video to generate, may be a string of
4380 the form @var{num}/@var{den} or a frame rate abbreviation.
4381 @var{src_name} is the name to the frei0r source to load. For more
4382 information regarding frei0r and how to set the parameters read the
4383 section @ref{frei0r} in the description of the video filters.
4385 For example, to generate a frei0r partik0l source with size 200x200
4386 and frame rate 10 which is overlayed on the overlay filter main input:
4388 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4393 Generate a life pattern.
4395 This source is based on a generalization of John Conway's life game.
4397 The sourced input represents a life grid, each pixel represents a cell
4398 which can be in one of two possible states, alive or dead. Every cell
4399 interacts with its eight neighbours, which are the cells that are
4400 horizontally, vertically, or diagonally adjacent.
4402 At each interaction the grid evolves according to the adopted rule,
4403 which specifies the number of neighbor alive cells which will make a
4404 cell stay alive or born. The @option{rule} option allows to specify
4407 This source accepts a list of options in the form of
4408 @var{key}=@var{value} pairs separated by ":". A description of the
4409 accepted options follows.
4413 Set the file from which to read the initial grid state. In the file,
4414 each non-whitespace character is considered an alive cell, and newline
4415 is used to delimit the end of each row.
4417 If this option is not specified, the initial grid is generated
4421 Set the video rate, that is the number of frames generated per second.
4424 @item random_fill_ratio, ratio
4425 Set the random fill ratio for the initial random grid. It is a
4426 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4427 It is ignored when a file is specified.
4429 @item random_seed, seed
4430 Set the seed for filling the initial random grid, must be an integer
4431 included between 0 and UINT32_MAX. If not specified, or if explicitly
4432 set to -1, the filter will try to use a good random seed on a best
4438 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4439 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4440 @var{NS} specifies the number of alive neighbor cells which make a
4441 live cell stay alive, and @var{NB} the number of alive neighbor cells
4442 which make a dead cell to become alive (i.e. to "born").
4443 "s" and "b" can be used in place of "S" and "B", respectively.
4445 Alternatively a rule can be specified by an 18-bits integer. The 9
4446 high order bits are used to encode the next cell state if it is alive
4447 for each number of neighbor alive cells, the low order bits specify
4448 the rule for "borning" new cells. Higher order bits encode for an
4449 higher number of neighbor cells.
4450 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4451 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4453 Default value is "S23/B3", which is the original Conway's game of life
4454 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4455 cells, and will born a new cell if there are three alive cells around
4459 Set the size of the output video.
4461 If @option{filename} is specified, the size is set by default to the
4462 same size of the input file. If @option{size} is set, it must contain
4463 the size specified in the input file, and the initial grid defined in
4464 that file is centered in the larger resulting area.
4466 If a filename is not specified, the size value defaults to "320x240"
4467 (used for a randomly generated initial grid).
4470 If set to 1, stitch the left and right grid edges together, and the
4471 top and bottom edges also. Defaults to 1.
4474 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4475 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4476 value from 0 to 255.
4479 Set the color of living (or new born) cells.
4482 Set the color of dead cells. If @option{mold} is set, this is the first color
4483 used to represent a dead cell.
4486 Set mold color, for definitely dead and moldy cells.
4489 @subsection Examples
4493 Read a grid from @file{pattern}, and center it on a grid of size
4496 life=f=pattern:s=300x300
4500 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4502 life=ratio=2/3:s=200x200
4506 Specify a custom rule for evolving a randomly generated grid:
4512 Full example with slow death effect (mold) using @command{ffplay}:
4514 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4518 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4520 The @code{color} source provides an uniformly colored input.
4522 The @code{nullsrc} source returns unprocessed video frames. It is
4523 mainly useful to be employed in analysis / debugging tools, or as the
4524 source for filters which ignore the input data.
4526 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4527 detecting RGB vs BGR issues. You should see a red, green and blue
4528 stripe from top to bottom.
4530 The @code{smptebars} source generates a color bars pattern, based on
4531 the SMPTE Engineering Guideline EG 1-1990.
4533 The @code{testsrc} source generates a test video pattern, showing a
4534 color pattern, a scrolling gradient and a timestamp. This is mainly
4535 intended for testing purposes.
4537 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4538 separated by ":". The description of the accepted options follows.
4543 Specify the color of the source, only used in the @code{color}
4544 source. It can be the name of a color (case insensitive match) or a
4545 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4546 default value is "black".
4549 Specify the size of the sourced video, it may be a string of the form
4550 @var{width}x@var{height}, or the name of a size abbreviation. The
4551 default value is "320x240".
4554 Specify the frame rate of the sourced video, as the number of frames
4555 generated per second. It has to be a string in the format
4556 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4557 number or a valid video frame rate abbreviation. The default value is
4561 Set the sample aspect ratio of the sourced video.
4564 Set the video duration of the sourced video. The accepted syntax is:
4566 [-]HH[:MM[:SS[.m...]]]
4569 See also the function @code{av_parse_time()}.
4571 If not specified, or the expressed duration is negative, the video is
4572 supposed to be generated forever.
4575 Set the number of decimals to show in the timestamp, only used in the
4576 @code{testsrc} source.
4578 The displayed timestamp value will correspond to the original
4579 timestamp value multiplied by the power of 10 of the specified
4580 value. Default value is 0.
4583 For example the following:
4585 testsrc=duration=5.3:size=qcif:rate=10
4588 will generate a video with a duration of 5.3 seconds, with size
4589 176x144 and a frame rate of 10 frames per second.
4591 The following graph description will generate a red source
4592 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4595 color=c=red@@0.2:s=qcif:r=10
4598 If the input content is to be ignored, @code{nullsrc} can be used. The
4599 following command generates noise in the luminance plane by employing
4600 the @code{geq} filter:
4602 nullsrc=s=256x256, geq=random(1)*255:128:128
4605 @c man end VIDEO SOURCES
4607 @chapter Video Sinks
4608 @c man begin VIDEO SINKS
4610 Below is a description of the currently available video sinks.
4614 Buffer video frames, and make them available to the end of the filter
4617 This sink is mainly intended for a programmatic use, in particular
4618 through the interface defined in @file{libavfilter/buffersink.h}.
4620 It does not require a string parameter in input, but you need to
4621 specify a pointer to a list of supported pixel formats terminated by
4622 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4623 when initializing this sink.
4627 Null video sink, do absolutely nothing with the input video. It is
4628 mainly useful as a template and to be employed in analysis / debugging
4631 @c man end VIDEO SINKS
4633 @chapter Multimedia Filters
4634 @c man begin MULTIMEDIA FILTERS
4636 Below is a description of the currently available multimedia filters.
4638 @section aselect, select
4639 Select frames to pass in output.
4641 These filters accept a single option @option{expr} or @option{e}
4642 specifying the select expression, which can be specified either by
4643 specyfing @code{expr=VALUE} or specifying the expression
4646 The select expression is evaluated for each input frame. If the
4647 evaluation result is a non-zero value, the frame is selected and
4648 passed to the output, otherwise it is discarded.
4650 The expression can contain the following constants:
4654 the sequential number of the filtered frame, starting from 0
4657 the sequential number of the selected frame, starting from 0
4659 @item prev_selected_n
4660 the sequential number of the last selected frame, NAN if undefined
4663 timebase of the input timestamps
4666 the PTS (Presentation TimeStamp) of the filtered video frame,
4667 expressed in @var{TB} units, NAN if undefined
4670 the PTS (Presentation TimeStamp) of the filtered video frame,
4671 expressed in seconds, NAN if undefined
4674 the PTS of the previously filtered video frame, NAN if undefined
4676 @item prev_selected_pts
4677 the PTS of the last previously filtered video frame, NAN if undefined
4679 @item prev_selected_t
4680 the PTS of the last previously selected video frame, NAN if undefined
4683 the PTS of the first video frame in the video, NAN if undefined
4686 the time of the first video frame in the video, NAN if undefined
4688 @item pict_type @emph{(video only)}
4689 the type of the filtered frame, can assume one of the following
4701 @item interlace_type @emph{(video only)}
4702 the frame interlace type, can assume one of the following values:
4705 the frame is progressive (not interlaced)
4707 the frame is top-field-first
4709 the frame is bottom-field-first
4712 @item consumed_sample_n @emph{(audio only)}
4713 the number of selected samples before the current frame
4715 @item samples_n @emph{(audio only)}
4716 the number of samples in the current frame
4718 @item sample_rate @emph{(audio only)}
4719 the input sample rate
4722 1 if the filtered frame is a key-frame, 0 otherwise
4725 the position in the file of the filtered frame, -1 if the information
4726 is not available (e.g. for synthetic video)
4728 @item scene @emph{(video only)}
4729 value between 0 and 1 to indicate a new scene; a low value reflects a low
4730 probability for the current frame to introduce a new scene, while a higher
4731 value means the current frame is more likely to be one (see the example below)
4735 The default value of the select expression is "1".
4737 @subsection Examples
4741 Select all frames in input:
4746 The example above is the same as:
4758 Select only I-frames:
4760 select='eq(pict_type\,I)'
4764 Select one frame every 100:
4766 select='not(mod(n\,100))'
4770 Select only frames contained in the 10-20 time interval:
4772 select='gte(t\,10)*lte(t\,20)'
4776 Select only I frames contained in the 10-20 time interval:
4778 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
4782 Select frames with a minimum distance of 10 seconds:
4784 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
4788 Use aselect to select only audio frames with samples number > 100:
4790 aselect='gt(samples_n\,100)'
4794 Create a mosaic of the first scenes:
4796 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
4799 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
4803 @section asendcmd, sendcmd
4805 Send commands to filters in the filtergraph.
4807 These filters read commands to be sent to other filters in the
4810 @code{asendcmd} must be inserted between two audio filters,
4811 @code{sendcmd} must be inserted between two video filters, but apart
4812 from that they act the same way.
4814 The specification of commands can be provided in the filter arguments
4815 with the @var{commands} option, or in a file specified by the
4816 @var{filename} option.
4818 These filters accept the following options:
4821 Set the commands to be read and sent to the other filters.
4823 Set the filename of the commands to be read and sent to the other
4827 @subsection Commands syntax
4829 A commands description consists of a sequence of interval
4830 specifications, comprising a list of commands to be executed when a
4831 particular event related to that interval occurs. The occurring event
4832 is typically the current frame time entering or leaving a given time
4835 An interval is specified by the following syntax:
4837 @var{START}[-@var{END}] @var{COMMANDS};
4840 The time interval is specified by the @var{START} and @var{END} times.
4841 @var{END} is optional and defaults to the maximum time.
4843 The current frame time is considered within the specified interval if
4844 it is included in the interval [@var{START}, @var{END}), that is when
4845 the time is greater or equal to @var{START} and is lesser than
4848 @var{COMMANDS} consists of a sequence of one or more command
4849 specifications, separated by ",", relating to that interval. The
4850 syntax of a command specification is given by:
4852 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4855 @var{FLAGS} is optional and specifies the type of events relating to
4856 the time interval which enable sending the specified command, and must
4857 be a non-null sequence of identifier flags separated by "+" or "|" and
4858 enclosed between "[" and "]".
4860 The following flags are recognized:
4863 The command is sent when the current frame timestamp enters the
4864 specified interval. In other words, the command is sent when the
4865 previous frame timestamp was not in the given interval, and the
4869 The command is sent when the current frame timestamp leaves the
4870 specified interval. In other words, the command is sent when the
4871 previous frame timestamp was in the given interval, and the
4875 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4878 @var{TARGET} specifies the target of the command, usually the name of
4879 the filter class or a specific filter instance name.
4881 @var{COMMAND} specifies the name of the command for the target filter.
4883 @var{ARG} is optional and specifies the optional list of argument for
4884 the given @var{COMMAND}.
4886 Between one interval specification and another, whitespaces, or
4887 sequences of characters starting with @code{#} until the end of line,
4888 are ignored and can be used to annotate comments.
4890 A simplified BNF description of the commands specification syntax
4893 @var{COMMAND_FLAG} ::= "enter" | "leave"
4894 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4895 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4896 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4897 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4898 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4901 @subsection Examples
4905 Specify audio tempo change at second 4:
4907 asendcmd=c='4.0 atempo tempo 1.5',atempo
4911 Specify a list of drawtext and hue commands in a file.
4913 # show text in the interval 5-10
4914 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4915 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4917 # desaturate the image in the interval 15-20
4918 15.0-20.0 [enter] hue reinit s=0,
4919 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4920 [leave] hue reinit s=1,
4921 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4923 # apply an exponential saturation fade-out effect, starting from time 25
4924 25 [enter] hue s=exp(t-25)
4927 A filtergraph allowing to read and process the above command list
4928 stored in a file @file{test.cmd}, can be specified with:
4930 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4935 @section asetpts, setpts
4937 Change the PTS (presentation timestamp) of the input frames.
4939 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4941 Accept in input an expression evaluated through the eval API, which
4942 can contain the following constants:
4946 frame rate, only defined for constant frame-rate video
4949 the presentation timestamp in input
4952 the count of the input frame, starting from 0.
4954 @item NB_CONSUMED_SAMPLES
4955 the number of consumed samples, not including the current frame (only
4959 the number of samples in the current frame (only audio)
4965 the PTS of the first frame
4968 the time in seconds of the first frame
4971 tell if the current frame is interlaced
4974 the time in seconds of the current frame
4980 original position in the file of the frame, or undefined if undefined
4981 for the current frame
4987 previous input time in seconds
4993 previous output time in seconds
4996 @subsection Examples
5000 Start counting PTS from zero
5006 Apply fast motion effect:
5012 Apply slow motion effect:
5018 Set fixed rate of 25 frames per second:
5024 Set fixed rate 25 fps with some jitter:
5026 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
5030 Apply an offset of 10 seconds to the input PTS:
5038 EBU R128 scanner filter. This filter takes an audio stream as input and outputs
5039 it unchanged. By default, it logs a message at a frequency of 10Hz with the
5040 Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
5041 Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
5043 The filter also has a video output (see the @var{video} option) with a real
5044 time graph to observe the loudness evolution. The graphic contains the logged
5045 message mentioned above, so it is not printed anymore when this option is set,
5046 unless the verbose logging is set. The main graphing area contains the
5047 short-term loudness (3 seconds of analysis), and the gauge on the right is for
5048 the momentary loudness (400 milliseconds).
5050 More information about the Loudness Recommendation EBU R128 on
5051 @url{http://tech.ebu.ch/loudness}.
5053 The filter accepts the following named parameters:
5058 Activate the video output. The audio stream is passed unchanged whether this
5059 option is set or no. The video stream will be the first output stream if
5060 activated. Default is @code{0}.
5063 Set the video size. This option is for video only. Default and minimum
5064 resolution is @code{640x480}.
5067 Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
5068 @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
5069 other integer value between this range is allowed.
5073 Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
5075 ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
5078 Run an analysis with @command{ffmpeg}:
5080 ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
5083 @section settb, asettb
5085 Set the timebase to use for the output frames timestamps.
5086 It is mainly useful for testing timebase configuration.
5088 It accepts in input an arithmetic expression representing a rational.
5089 The expression can contain the constants "AVTB" (the
5090 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
5093 The default value for the input is "intb".
5095 @subsection Examples
5099 Set the timebase to 1/25:
5105 Set the timebase to 1/10:
5111 Set the timebase to 1001/1000:
5117 Set the timebase to 2*intb:
5123 Set the default timebase value:
5131 Concatenate audio and video streams, joining them together one after the
5134 The filter works on segments of synchronized video and audio streams. All
5135 segments must have the same number of streams of each type, and that will
5136 also be the number of streams at output.
5138 The filter accepts the following named parameters:
5142 Set the number of segments. Default is 2.
5145 Set the number of output video streams, that is also the number of video
5146 streams in each segment. Default is 1.
5149 Set the number of output audio streams, that is also the number of video
5150 streams in each segment. Default is 0.
5153 Activate unsafe mode: do not fail if segments have a different format.
5157 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
5158 @var{a} audio outputs.
5160 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
5161 segment, in the same order as the outputs, then the inputs for the second
5164 Related streams do not always have exactly the same duration, for various
5165 reasons including codec frame size or sloppy authoring. For that reason,
5166 related synchronized streams (e.g. a video and its audio track) should be
5167 concatenated at once. The concat filter will use the duration of the longest
5168 stream in each segment (except the last one), and if necessary pad shorter
5169 audio streams with silence.
5171 For this filter to work correctly, all segments must start at timestamp 0.
5173 All corresponding streams must have the same parameters in all segments; the
5174 filtering system will automatically select a common pixel format for video
5175 streams, and a common sample format, sample rate and channel layout for
5176 audio streams, but other settings, such as resolution, must be converted
5177 explicitly by the user.
5179 Different frame rates are acceptable but will result in variable frame rate
5180 at output; be sure to configure the output file to handle it.
5185 Concatenate an opening, an episode and an ending, all in bilingual version
5186 (video in stream 0, audio in streams 1 and 2):
5188 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
5189 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
5190 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
5191 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
5195 Concatenate two parts, handling audio and video separately, using the
5196 (a)movie sources, and adjusting the resolution:
5198 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
5199 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
5200 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
5202 Note that a desync will happen at the stitch if the audio and video streams
5203 do not have exactly the same duration in the first file.
5207 @section showspectrum
5209 Convert input audio to a video output, representing the audio frequency
5212 The filter accepts the following named parameters:
5215 Specify the video size for the output. Default value is @code{640x480}.
5217 Specify if the spectrum should slide along the window. Default value is
5221 The usage is very similar to the showwaves filter; see the examples in that
5226 Convert input audio to a video output, representing the samples waves.
5228 The filter accepts the following named parameters:
5232 Set the number of samples which are printed on the same column. A
5233 larger value will decrease the frame rate. Must be a positive
5234 integer. This option can be set only if the value for @var{rate}
5235 is not explicitly specified.
5238 Set the (approximate) output frame rate. This is done by setting the
5239 option @var{n}. Default value is "25".
5242 Specify the video size for the output. Default value is "600x240".
5245 Some examples follow.
5248 Output the input file audio and the corresponding video representation
5251 amovie=a.mp3,asplit[out0],showwaves[out1]
5255 Create a synthetic signal and show it with showwaves, forcing a
5256 framerate of 30 frames per second:
5258 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
5262 @c man end MULTIMEDIA FILTERS
5264 @chapter Multimedia Sources
5265 @c man begin MULTIMEDIA SOURCES
5267 Below is a description of the currently available multimedia sources.
5271 This is the same as @ref{src_movie} source, except it selects an audio
5277 Read audio and/or video stream(s) from a movie container.
5279 It accepts the syntax: @var{movie_name}[:@var{options}] where
5280 @var{movie_name} is the name of the resource to read (not necessarily
5281 a file but also a device or a stream accessed through some protocol),
5282 and @var{options} is an optional sequence of @var{key}=@var{value}
5283 pairs, separated by ":".
5285 The description of the accepted options follows.
5289 @item format_name, f
5290 Specifies the format assumed for the movie to read, and can be either
5291 the name of a container or an input device. If not specified the
5292 format is guessed from @var{movie_name} or by probing.
5294 @item seek_point, sp
5295 Specifies the seek point in seconds, the frames will be output
5296 starting from this seek point, the parameter is evaluated with
5297 @code{av_strtod} so the numerical value may be suffixed by an IS
5298 postfix. Default value is "0".
5301 Specifies the streams to read. Several streams can be specified, separated
5302 by "+". The source will then have as many outputs, in the same order. The
5303 syntax is explained in the @ref{Stream specifiers} chapter. Two special
5304 names, "dv" and "da" specify respectively the default (best suited) video
5305 and audio stream. Default is "dv", or "da" if the filter is called as
5308 @item stream_index, si
5309 Specifies the index of the video stream to read. If the value is -1,
5310 the best suited video stream will be automatically selected. Default
5311 value is "-1". Deprecated. If the filter is called "amovie", it will select
5312 audio instead of video.
5315 Specifies how many times to read the stream in sequence.
5316 If the value is less than 1, the stream will be read again and again.
5317 Default value is "1".
5319 Note that when the movie is looped the source timestamps are not
5320 changed, so it will generate non monotonically increasing timestamps.
5323 This filter allows to overlay a second video on top of main input of
5324 a filtergraph as shown in this graph:
5326 input -----------> deltapts0 --> overlay --> output
5329 movie --> scale--> deltapts1 -------+
5332 Some examples follow.
5336 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
5337 on top of the input labelled as "in":
5339 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5340 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5344 Read from a video4linux2 device, and overlay it on top of the input
5347 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5348 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5352 Read the first video stream and the audio stream with id 0x81 from
5353 dvd.vob; the video is connected to the pad named "video" and the audio is
5354 connected to the pad named "audio":
5356 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
5360 @c man end MULTIMEDIA SOURCES