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 sample rate.
416 The filter accepts exactly one parameter, the output sample rate. If not
417 specified then the filter will automatically convert between its input
418 and output sample rates.
420 For example, to resample the input audio to 44100Hz:
425 @section asetnsamples
427 Set the number of samples per each output audio frame.
429 The last output packet may contain a different number of samples, as
430 the filter will flush all the remaining samples when the input audio
433 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
438 @item nb_out_samples, n
439 Set the number of frames per each output audio frame. The number is
440 intended as the number of samples @emph{per each channel}.
441 Default value is 1024.
444 If set to 1, the filter will pad the last audio frame with zeroes, so
445 that the last frame will contain the same number of samples as the
446 previous ones. Default value is 1.
449 For example, to set the number of per-frame samples to 1234 and
450 disable padding for the last frame, use:
452 asetnsamples=n=1234:p=0
457 Show a line containing various information for each input audio frame.
458 The input audio is not modified.
460 The shown line contains a sequence of key/value pairs of the form
461 @var{key}:@var{value}.
463 A description of each shown parameter follows:
467 sequential number of the input frame, starting from 0
470 Presentation timestamp of the input frame, in time base units; the time base
471 depends on the filter input pad, and is usually 1/@var{sample_rate}.
474 presentation timestamp of the input frame in seconds
477 position of the frame in the input stream, -1 if this information in
478 unavailable and/or meaningless (for example in case of synthetic audio)
487 sample rate for the audio frame
490 number of samples (per channel) in the frame
493 Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
494 the data is treated as if all the planes were concatenated.
496 @item plane_checksums
497 A list of Adler-32 checksums for each data plane.
502 Split input audio into several identical outputs.
504 The filter accepts a single parameter which specifies the number of outputs. If
505 unspecified, it defaults to 2.
509 [in] asplit [out0][out1]
512 will create two separate outputs from the same input.
514 To create 3 or more outputs, you need to specify the number of
517 [in] asplit=3 [out0][out1][out2]
521 ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
523 will create 5 copies of the input audio.
528 Forward two audio streams and control the order the buffers are forwarded.
530 The argument to the filter is an expression deciding which stream should be
531 forwarded next: if the result is negative, the first stream is forwarded; if
532 the result is positive or zero, the second stream is forwarded. It can use
533 the following variables:
537 number of buffers forwarded so far on each stream
539 number of samples forwarded so far on each stream
541 current timestamp of each stream
544 The default value is @code{t1-t2}, which means to always forward the stream
545 that has a smaller timestamp.
547 Example: stress-test @code{amerge} by randomly sending buffers on the wrong
548 input, while avoiding too much of a desynchronization:
550 amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
551 [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
559 The filter accepts exactly one parameter, the audio tempo. If not
560 specified then the filter will assume nominal 1.0 tempo. Tempo must
561 be in the [0.5, 2.0] range.
563 For example, to slow down audio to 80% tempo:
568 For example, to speed up audio to 125% tempo:
575 Make audio easier to listen to on headphones.
577 This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
578 so that when listened to on headphones the stereo image is moved from
579 inside your head (standard for headphones) to outside and in front of
580 the listener (standard for speakers).
586 Mix channels with specific gain levels. The filter accepts the output
587 channel layout followed by a set of channels definitions.
589 This filter is also designed to remap efficiently the channels of an audio
592 The filter accepts parameters of the form:
593 "@var{l}:@var{outdef}:@var{outdef}:..."
597 output channel layout or number of channels
600 output channel specification, of the form:
601 "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
604 output channel to define, either a channel name (FL, FR, etc.) or a channel
605 number (c0, c1, etc.)
608 multiplicative coefficient for the channel, 1 leaving the volume unchanged
611 input channel to use, see out_name for details; it is not possible to mix
612 named and numbered input channels
615 If the `=' in a channel specification is replaced by `<', then the gains for
616 that specification will be renormalized so that the total is 1, thus
617 avoiding clipping noise.
619 @subsection Mixing examples
621 For example, if you want to down-mix from stereo to mono, but with a bigger
622 factor for the left channel:
624 pan=1:c0=0.9*c0+0.1*c1
627 A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
630 pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
633 Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
634 that should be preferred (see "-ac" option) unless you have very specific
637 @subsection Remapping examples
639 The channel remapping will be effective if, and only if:
642 @item gain coefficients are zeroes or ones,
643 @item only one input per channel output,
646 If all these conditions are satisfied, the filter will notify the user ("Pure
647 channel mapping detected"), and use an optimized and lossless method to do the
650 For example, if you have a 5.1 source and want a stereo audio stream by
651 dropping the extra channels:
653 pan="stereo: c0=FL : c1=FR"
656 Given the same source, you can also switch front left and front right channels
657 and keep the input channel layout:
659 pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
662 If the input is a stereo audio stream, you can mute the front left channel (and
663 still keep the stereo channel layout) with:
668 Still with a stereo audio stream input, you can copy the right channel in both
669 front left and right:
671 pan="stereo: c0=FR : c1=FR"
674 @section silencedetect
676 Detect silence in an audio stream.
678 This filter logs a message when it detects that the input audio volume is less
679 or equal to a noise tolerance value for a duration greater or equal to the
680 minimum detected noise duration.
682 The printed times and duration are expressed in seconds.
686 Set silence duration until notification (default is 2 seconds).
689 Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
690 specified value) or amplitude ratio. Default is -60dB, or 0.001.
693 Detect 5 seconds of silence with -50dB noise tolerance:
695 silencedetect=n=-50dB:d=5
698 Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
699 tolerance in @file{silence.mp3}:
701 ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
706 Adjust the input audio volume.
708 The filter accepts exactly one parameter @var{vol}, which expresses
709 how the audio volume will be increased or decreased.
711 Output values are clipped to the maximum value.
713 If @var{vol} is expressed as a decimal number, the output audio
714 volume is given by the relation:
716 @var{output_volume} = @var{vol} * @var{input_volume}
719 If @var{vol} is expressed as a decimal number followed by the string
720 "dB", the value represents the requested change in decibels of the
721 input audio power, and the output audio volume is given by the
724 @var{output_volume} = 10^(@var{vol}/20) * @var{input_volume}
727 Otherwise @var{vol} is considered an expression and its evaluated
728 value is used for computing the output audio volume according to the
731 Default value for @var{vol} is 1.0.
737 Half the input audio volume:
742 The above example is equivalent to:
748 Decrease input audio power by 12 decibels:
754 @section volumedetect
756 Detect the volume of the input video.
758 The filter has no parameters. The input is not modified. Statistics about
759 the volume will be printed in the log when the input stream end is reached.
761 In particular it will show the mean volume (root mean square), maximum
762 volume (on a per-sample basis), and the beginning of an histogram of the
763 registered volume values (from the maximum value to a cumulated 1/1000 of
766 All volumes are in decibels relative to the maximum PCM value.
768 Here is an excerpt of the output:
770 [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
771 [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
772 [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
773 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
774 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
775 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
776 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
777 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
778 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
784 The mean square energy is approximately -27 dB, or 10^-2.7.
786 The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
788 There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
791 In other words, raising the volume by +4 dB does not cause any clipping,
792 raising it by +5 dB causes clipping for 6 samples, etc.
795 Synchronize audio data with timestamps by squeezing/stretching it and/or
796 dropping samples/adding silence when needed.
798 The filter accepts the following named parameters:
802 Enable stretching/squeezing the data to make it match the timestamps. Disabled
803 by default. When disabled, time gaps are covered with silence.
806 Minimum difference between timestamps and audio data (in seconds) to trigger
807 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
808 this filter, try setting this parameter to 0.
811 Maximum compensation in samples per second. Relevant only with compensate=1.
815 Assume the first pts should be this value.
816 This allows for padding/trimming at the start of stream. By default, no
817 assumption is made about the first frame's expected pts, so no padding or
818 trimming is done. For example, this could be set to 0 to pad the beginning with
819 silence if an audio stream starts after the video stream.
823 @section channelsplit
824 Split each channel in input audio stream into a separate output stream.
826 This filter accepts the following named parameters:
829 Channel layout of the input stream. Default is "stereo".
832 For example, assuming a stereo input MP3 file
834 ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
836 will create an output Matroska file with two audio streams, one containing only
837 the left channel and the other the right channel.
839 To split a 5.1 WAV file into per-channel files
841 ffmpeg -i in.wav -filter_complex
842 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
843 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
844 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
849 Remap input channels to new locations.
851 This filter accepts the following named parameters:
854 Channel layout of the output stream.
857 Map channels from input to output. The argument is a comma-separated list of
858 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
859 @var{in_channel} form. @var{in_channel} can be either the name of the input
860 channel (e.g. FL for front left) or its index in the input channel layout.
861 @var{out_channel} is the name of the output channel or its index in the output
862 channel layout. If @var{out_channel} is not given then it is implicitly an
863 index, starting with zero and increasing by one for each mapping.
866 If no mapping is present, the filter will implicitly map input channels to
867 output channels preserving index.
869 For example, assuming a 5.1+downmix input MOV file
871 ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
873 will create an output WAV file tagged as stereo from the downmix channels of
876 To fix a 5.1 WAV improperly encoded in AAC's native channel order
878 ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
882 Join multiple input streams into one multi-channel stream.
884 The filter accepts the following named parameters:
888 Number of input streams. Defaults to 2.
891 Desired output channel layout. Defaults to stereo.
894 Map channels from inputs to output. The argument is a comma-separated list of
895 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
896 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
897 can be either the name of the input channel (e.g. FL for front left) or its
898 index in the specified input stream. @var{out_channel} is the name of the output
902 The filter will attempt to guess the mappings when those are not specified
903 explicitly. It does so by first trying to find an unused matching input channel
904 and if that fails it picks the first unused input channel.
906 E.g. to join 3 inputs (with properly set channel layouts)
908 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
911 To build a 5.1 output from 6 single-channel streams:
913 ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
914 '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'
919 Convert the audio sample format, sample rate and channel layout. This filter is
920 not meant to be used directly.
922 @c man end AUDIO FILTERS
924 @chapter Audio Sources
925 @c man begin AUDIO SOURCES
927 Below is a description of the currently available audio sources.
931 Buffer audio frames, and make them available to the filter chain.
933 This source is mainly intended for a programmatic use, in particular
934 through the interface defined in @file{libavfilter/asrc_abuffer.h}.
936 It accepts the following mandatory parameters:
937 @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}
942 The sample rate of the incoming audio buffers.
945 The sample format of the incoming audio buffers.
946 Either a sample format name or its corresponging integer representation from
947 the enum AVSampleFormat in @file{libavutil/samplefmt.h}
950 The channel layout of the incoming audio buffers.
951 Either a channel layout name from channel_layout_map in
952 @file{libavutil/channel_layout.c} or its corresponding integer representation
953 from the AV_CH_LAYOUT_* macros in @file{libavutil/channel_layout.h}
959 abuffer=44100:s16p:stereo
962 will instruct the source to accept planar 16bit signed stereo at 44100Hz.
963 Since the sample format with name "s16p" corresponds to the number
964 6 and the "stereo" channel layout corresponds to the value 0x3, this is
972 Generate an audio signal specified by an expression.
974 This source accepts in input one or more expressions (one for each
975 channel), which are evaluated and used to generate a corresponding
978 It accepts the syntax: @var{exprs}[::@var{options}].
979 @var{exprs} is a list of expressions separated by ":", one for each
980 separate channel. In case the @var{channel_layout} is not
981 specified, the selected channel layout depends on the number of
982 provided expressions.
984 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
987 The description of the accepted options follows.
991 @item channel_layout, c
992 Set the channel layout. The number of channels in the specified layout
993 must be equal to the number of specified expressions.
996 Set the minimum duration of the sourced audio. See the function
997 @code{av_parse_time()} for the accepted format.
998 Note that the resulting duration may be greater than the specified
999 duration, as the generated audio is always cut at the end of a
1002 If not specified, or the expressed duration is negative, the audio is
1003 supposed to be generated forever.
1006 Set the number of samples per channel per each output frame,
1009 @item sample_rate, s
1010 Specify the sample rate, default to 44100.
1013 Each expression in @var{exprs} can contain the following constants:
1017 number of the evaluated sample, starting from 0
1020 time of the evaluated sample expressed in seconds, starting from 0
1027 @subsection Examples
1039 Generate a sin signal with frequency of 440 Hz, set sample rate to
1042 aevalsrc="sin(440*2*PI*t)::s=8000"
1046 Generate a two channels signal, specify the channel layout (Front
1047 Center + Back Center) explicitly:
1049 aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
1053 Generate white noise:
1055 aevalsrc="-2+random(0)"
1059 Generate an amplitude modulated signal:
1061 aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
1065 Generate 2.5 Hz binaural beats on a 360 Hz carrier:
1067 aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
1074 Null audio source, return unprocessed audio frames. It is mainly useful
1075 as a template and to be employed in analysis / debugging tools, or as
1076 the source for filters which ignore the input data (for example the sox
1079 It accepts an optional sequence of @var{key}=@var{value} pairs,
1082 The description of the accepted options follows.
1086 @item sample_rate, s
1087 Specify the sample rate, and defaults to 44100.
1089 @item channel_layout, cl
1091 Specify the channel layout, and can be either an integer or a string
1092 representing a channel layout. The default value of @var{channel_layout}
1095 Check the channel_layout_map definition in
1096 @file{libavutil/channel_layout.c} for the mapping between strings and
1097 channel layout values.
1100 Set the number of samples per requested frames.
1104 Follow some examples:
1106 # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
1107 anullsrc=r=48000:cl=4
1110 anullsrc=r=48000:cl=mono
1114 Buffer audio frames, and make them available to the filter chain.
1116 This source is not intended to be part of user-supplied graph descriptions but
1117 for insertion by calling programs through the interface defined in
1118 @file{libavfilter/buffersrc.h}.
1120 It accepts the following named parameters:
1124 Timebase which will be used for timestamps of submitted frames. It must be
1125 either a floating-point number or in @var{numerator}/@var{denominator} form.
1131 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
1133 @item channel_layout
1134 Channel layout of the audio data, in the form that can be accepted by
1135 @code{av_get_channel_layout()}.
1138 All the parameters need to be explicitly defined.
1142 Synthesize a voice utterance using the libflite library.
1144 To enable compilation of this filter you need to configure FFmpeg with
1145 @code{--enable-libflite}.
1147 Note that the flite library is not thread-safe.
1149 The source accepts parameters as a list of @var{key}=@var{value} pairs,
1152 The description of the accepted parameters follows.
1157 If set to 1, list the names of the available voices and exit
1158 immediately. Default value is 0.
1161 Set the maximum number of samples per frame. Default value is 512.
1164 Set the filename containing the text to speak.
1167 Set the text to speak.
1170 Set the voice to use for the speech synthesis. Default value is
1171 @code{kal}. See also the @var{list_voices} option.
1174 @subsection Examples
1178 Read from file @file{speech.txt}, and synthetize the text using the
1179 standard flite voice:
1181 flite=textfile=speech.txt
1185 Read the specified text selecting the @code{slt} voice:
1187 flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1191 Input text to ffmpeg:
1193 ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1197 Make @file{ffplay} speak the specified text, using @code{flite} and
1198 the @code{lavfi} device:
1200 ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
1204 For more information about libflite, check:
1205 @url{http://www.speech.cs.cmu.edu/flite/}
1207 @c man end AUDIO SOURCES
1209 @chapter Audio Sinks
1210 @c man begin AUDIO SINKS
1212 Below is a description of the currently available audio sinks.
1214 @section abuffersink
1216 Buffer audio frames, and make them available to the end of filter chain.
1218 This sink is mainly intended for programmatic use, in particular
1219 through the interface defined in @file{libavfilter/buffersink.h}.
1221 It requires a pointer to an AVABufferSinkContext structure, which
1222 defines the incoming buffers' formats, to be passed as the opaque
1223 parameter to @code{avfilter_init_filter} for initialization.
1227 Null audio sink, do absolutely nothing with the input audio. It is
1228 mainly useful as a template and to be employed in analysis / debugging
1231 @section abuffersink
1232 This sink is intended for programmatic use. Frames that arrive on this sink can
1233 be retrieved by the calling program using the interface defined in
1234 @file{libavfilter/buffersink.h}.
1236 This filter accepts no parameters.
1238 @c man end AUDIO SINKS
1240 @chapter Video Filters
1241 @c man begin VIDEO FILTERS
1243 When you configure your FFmpeg build, you can disable any of the
1244 existing filters using @code{--disable-filters}.
1245 The configure output will show the video filters included in your
1248 Below is a description of the currently available video filters.
1250 @section alphaextract
1252 Extract the alpha component from the input as a grayscale video. This
1253 is especially useful with the @var{alphamerge} filter.
1257 Add or replace the alpha component of the primary input with the
1258 grayscale value of a second input. This is intended for use with
1259 @var{alphaextract} to allow the transmission or storage of frame
1260 sequences that have alpha in a format that doesn't support an alpha
1263 For example, to reconstruct full frames from a normal YUV-encoded video
1264 and a separate video created with @var{alphaextract}, you might use:
1266 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
1269 Since this filter is designed for reconstruction, it operates on frame
1270 sequences without considering timestamps, and terminates when either
1271 input reaches end of stream. This will cause problems if your encoding
1272 pipeline drops frames. If you're trying to apply an image as an
1273 overlay to a video stream, consider the @var{overlay} filter instead.
1277 Draw ASS (Advanced Substation Alpha) subtitles on top of input video
1278 using the libass library.
1280 To enable compilation of this filter you need to configure FFmpeg with
1281 @code{--enable-libass}.
1283 This filter accepts the following named options, expressed as a
1284 sequence of @var{key}=@var{value} pairs, separated by ":".
1288 Set the filename of the ASS file to read. It must be specified.
1291 Specify the size of the original video, the video for which the ASS file
1292 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
1293 necessary to correctly scale the fonts if the aspect ratio has been changed.
1296 If the first key is not specified, it is assumed that the first value
1297 specifies the @option{filename}.
1299 For example, to render the file @file{sub.ass} on top of the input
1300 video, use the command:
1305 which is equivalent to:
1307 ass=filename=sub.ass
1312 Compute the bounding box for the non-black pixels in the input frame
1315 This filter computes the bounding box containing all the pixels with a
1316 luminance value greater than the minimum allowed value.
1317 The parameters describing the bounding box are printed on the filter
1320 @section blackdetect
1322 Detect video intervals that are (almost) completely black. Can be
1323 useful to detect chapter transitions, commercials, or invalid
1324 recordings. Output lines contains the time for the start, end and
1325 duration of the detected black interval expressed in seconds.
1327 In order to display the output lines, you need to set the loglevel at
1328 least to the AV_LOG_INFO value.
1330 This filter accepts a list of options in the form of
1331 @var{key}=@var{value} pairs separated by ":". A description of the
1332 accepted options follows.
1335 @item black_min_duration, d
1336 Set the minimum detected black duration expressed in seconds. It must
1337 be a non-negative floating point number.
1339 Default value is 2.0.
1341 @item picture_black_ratio_th, pic_th
1342 Set the threshold for considering a picture "black".
1343 Express the minimum value for the ratio:
1345 @var{nb_black_pixels} / @var{nb_pixels}
1348 for which a picture is considered black.
1349 Default value is 0.98.
1351 @item pixel_black_th, pix_th
1352 Set the threshold for considering a pixel "black".
1354 The threshold expresses the maximum pixel luminance value for which a
1355 pixel is considered "black". The provided value is scaled according to
1356 the following equation:
1358 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
1361 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
1362 the input video format, the range is [0-255] for YUV full-range
1363 formats and [16-235] for YUV non full-range formats.
1365 Default value is 0.10.
1368 The following example sets the maximum pixel threshold to the minimum
1369 value, and detects only black intervals of 2 or more seconds:
1371 blackdetect=d=2:pix_th=0.00
1376 Detect frames that are (almost) completely black. Can be useful to
1377 detect chapter transitions or commercials. Output lines consist of
1378 the frame number of the detected frame, the percentage of blackness,
1379 the position in the file if known or -1 and the timestamp in seconds.
1381 In order to display the output lines, you need to set the loglevel at
1382 least to the AV_LOG_INFO value.
1384 The filter accepts the syntax:
1386 blackframe[=@var{amount}:[@var{threshold}]]
1389 @var{amount} is the percentage of the pixels that have to be below the
1390 threshold, and defaults to 98.
1392 @var{threshold} is the threshold below which a pixel value is
1393 considered black, and defaults to 32.
1397 Apply boxblur algorithm to the input video.
1399 This filter accepts the parameters:
1400 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
1402 Chroma and alpha parameters are optional, if not specified they default
1403 to the corresponding values set for @var{luma_radius} and
1406 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
1407 the radius in pixels of the box used for blurring the corresponding
1408 input plane. They are expressions, and can contain the following
1412 the input width and height in pixels
1415 the input chroma image width and height in pixels
1418 horizontal and vertical chroma subsample values. For example for the
1419 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1422 The radius must be a non-negative number, and must not be greater than
1423 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
1424 and of @code{min(cw,ch)/2} for the chroma planes.
1426 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
1427 how many times the boxblur filter is applied to the corresponding
1430 Some examples follow:
1435 Apply a boxblur filter with luma, chroma, and alpha radius
1442 Set luma radius to 2, alpha and chroma radius to 0
1448 Set luma and chroma radius to a fraction of the video dimension
1450 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
1455 @section colormatrix
1457 The colormatrix filter allows conversion between any of the following color
1458 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
1459 and FCC (@var{fcc}).
1461 The syntax of the parameters is @var{source}:@var{destination}:
1464 colormatrix=bt601:smpte240m
1469 Copy the input source unchanged to the output. Mainly useful for
1474 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
1476 The @var{keep_aspect} parameter is optional, if specified and set to a
1477 non-zero value will force the output display aspect ratio to be the
1478 same of the input, by changing the output sample aspect ratio.
1480 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1481 expressions containing the following constants:
1485 the computed values for @var{x} and @var{y}. They are evaluated for
1489 the input width and height
1492 same as @var{in_w} and @var{in_h}
1495 the output (cropped) width and height
1498 same as @var{out_w} and @var{out_h}
1501 same as @var{iw} / @var{ih}
1504 input sample aspect ratio
1507 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1510 horizontal and vertical chroma subsample values. For example for the
1511 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1514 the number of input frame, starting from 0
1517 the position in the file of the input frame, NAN if unknown
1520 timestamp expressed in seconds, NAN if the input timestamp is unknown
1524 The @var{out_w} and @var{out_h} parameters specify the expressions for
1525 the width and height of the output (cropped) video. They are
1526 evaluated just at the configuration of the filter.
1528 The default value of @var{out_w} is "in_w", and the default value of
1529 @var{out_h} is "in_h".
1531 The expression for @var{out_w} may depend on the value of @var{out_h},
1532 and the expression for @var{out_h} may depend on @var{out_w}, but they
1533 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1534 evaluated after @var{out_w} and @var{out_h}.
1536 The @var{x} and @var{y} parameters specify the expressions for the
1537 position of the top-left corner of the output (non-cropped) area. They
1538 are evaluated for each frame. If the evaluated value is not valid, it
1539 is approximated to the nearest valid value.
1541 The default value of @var{x} is "(in_w-out_w)/2", and the default
1542 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
1543 the center of the input image.
1545 The expression for @var{x} may depend on @var{y}, and the expression
1546 for @var{y} may depend on @var{x}.
1548 Follow some examples:
1550 # crop the central input area with size 100x100
1553 # crop the central input area with size 2/3 of the input video
1554 "crop=2/3*in_w:2/3*in_h"
1556 # crop the input video central square
1559 # delimit the rectangle with the top-left corner placed at position
1560 # 100:100 and the right-bottom corner corresponding to the right-bottom
1561 # corner of the input image.
1562 crop=in_w-100:in_h-100:100:100
1564 # crop 10 pixels from the left and right borders, and 20 pixels from
1565 # the top and bottom borders
1566 "crop=in_w-2*10:in_h-2*20"
1568 # keep only the bottom right quarter of the input image
1569 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1571 # crop height for getting Greek harmony
1572 "crop=in_w:1/PHI*in_w"
1575 "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)"
1577 # erratic camera effect depending on timestamp
1578 "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)"
1580 # set x depending on the value of y
1581 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1586 Auto-detect crop size.
1588 Calculate necessary cropping parameters and prints the recommended
1589 parameters through the logging system. The detected dimensions
1590 correspond to the non-black area of the input video.
1592 It accepts the syntax:
1594 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1600 Threshold, which can be optionally specified from nothing (0) to
1601 everything (255), defaults to 24.
1604 Value which the width/height should be divisible by, defaults to
1605 16. The offset is automatically adjusted to center the video. Use 2 to
1606 get only even dimensions (needed for 4:2:2 video). 16 is best when
1607 encoding to most video codecs.
1610 Counter that determines after how many frames cropdetect will reset
1611 the previously detected largest video area and start over to detect
1612 the current optimal crop area. Defaults to 0.
1614 This can be useful when channel logos distort the video area. 0
1615 indicates never reset and return the largest area encountered during
1621 This filter drops frames that do not differ greatly from the previous
1622 frame in order to reduce framerate. The main use of this filter is
1623 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1624 it could in theory be used for fixing movies that were
1625 inverse-telecined incorrectly.
1627 It accepts the following parameters:
1628 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1633 Set the maximum number of consecutive frames which can be dropped (if
1634 positive), or the minimum interval between dropped frames (if
1635 negative). If the value is 0, the frame is dropped unregarding the
1636 number of previous sequentially dropped frames.
1641 Set the dropping threshold values.
1643 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1644 represent actual pixel value differences, so a threshold of 64
1645 corresponds to 1 unit of difference for each pixel, or the same spread
1646 out differently over the block.
1648 A frame is a candidate for dropping if no 8x8 blocks differ by more
1649 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1650 meaning the whole image) differ by more than a threshold of @var{lo}.
1652 Default value for @var{hi} is 64*12, default value for @var{lo} is
1653 64*5, and default value for @var{frac} is 0.33.
1658 Suppress a TV station logo by a simple interpolation of the surrounding
1659 pixels. Just set a rectangle covering the logo and watch it disappear
1660 (and sometimes something even uglier appear - your mileage may vary).
1662 The filter accepts parameters as a string of the form
1663 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1664 @var{key}=@var{value} pairs, separated by ":".
1666 The description of the accepted parameters follows.
1671 Specify the top left corner coordinates of the logo. They must be
1675 Specify the width and height of the logo to clear. They must be
1679 Specify the thickness of the fuzzy edge of the rectangle (added to
1680 @var{w} and @var{h}). The default value is 4.
1683 When set to 1, a green rectangle is drawn on the screen to simplify
1684 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1685 @var{band} is set to 4. The default value is 0.
1689 Some examples follow.
1694 Set a rectangle covering the area with top left corner coordinates 0,0
1695 and size 100x77, setting a band of size 10:
1697 delogo=0:0:100:77:10
1701 As the previous example, but use named options:
1703 delogo=x=0:y=0:w=100:h=77:band=10
1710 Attempt to fix small changes in horizontal and/or vertical shift. This
1711 filter helps remove camera shake from hand-holding a camera, bumping a
1712 tripod, moving on a vehicle, etc.
1714 The filter accepts parameters as a string of the form
1715 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1717 A description of the accepted parameters follows.
1722 Specify a rectangular area where to limit the search for motion
1724 If desired the search for motion vectors can be limited to a
1725 rectangular area of the frame defined by its top left corner, width
1726 and height. These parameters have the same meaning as the drawbox
1727 filter which can be used to visualise the position of the bounding
1730 This is useful when simultaneous movement of subjects within the frame
1731 might be confused for camera motion by the motion vector search.
1733 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1734 then the full frame is used. This allows later options to be set
1735 without specifying the bounding box for the motion vector search.
1737 Default - search the whole frame.
1740 Specify the maximum extent of movement in x and y directions in the
1741 range 0-64 pixels. Default 16.
1744 Specify how to generate pixels to fill blanks at the edge of the
1745 frame. An integer from 0 to 3 as follows:
1748 Fill zeroes at blank locations
1750 Original image at blank locations
1752 Extruded edge value at blank locations
1754 Mirrored edge at blank locations
1757 The default setting is mirror edge at blank locations.
1760 Specify the blocksize to use for motion search. Range 4-128 pixels,
1764 Specify the contrast threshold for blocks. Only blocks with more than
1765 the specified contrast (difference between darkest and lightest
1766 pixels) will be considered. Range 1-255, default 125.
1769 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1770 search. Default - exhaustive search.
1773 If set then a detailed log of the motion search is written to the
1780 Draw a colored box on the input image.
1782 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1785 The description of the accepted parameters follows.
1789 Specify the top left corner coordinates of the box. Default to 0.
1793 Specify the width and height of the box, if 0 they are interpreted as
1794 the input width and height. Default to 0.
1797 Specify the color of the box to write, it can be the name of a color
1798 (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
1799 value @code{invert} is used, the box edge color is the same as the
1800 video with inverted luma.
1803 Set the thickness of the box edge. Default value is @code{4}.
1806 If the key of the first options is omitted, the arguments are
1807 interpreted according to the following syntax:
1809 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness}
1812 Some examples follow:
1815 Draw a black box around the edge of the input image:
1821 Draw a box with color red and an opacity of 50%:
1823 drawbox=10:20:200:60:red@@0.5
1826 The previous example can be specified as:
1828 drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
1832 Fill the box with pink color:
1834 drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
1841 Draw text string or text from specified file on top of video using the
1842 libfreetype library.
1844 To enable compilation of this filter you need to configure FFmpeg with
1845 @code{--enable-libfreetype}.
1849 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1852 The description of the accepted parameters follows.
1857 Used to draw a box around text using background color.
1858 Value should be either 1 (enable) or 0 (disable).
1859 The default value of @var{box} is 0.
1862 The color to be used for drawing box around text.
1863 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1864 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1865 The default value of @var{boxcolor} is "white".
1868 Set an expression which specifies if the text should be drawn. If the
1869 expression evaluates to 0, the text is not drawn. This is useful for
1870 specifying that the text should be drawn only when specific conditions
1873 Default value is "1".
1875 See below for the list of accepted constants and functions.
1878 Select how the @var{text} is expanded. Can be either @code{none},
1879 @code{strftime} (default for compatibity reasons but deprecated) or
1880 @code{normal}. See the @ref{drawtext_expansion, Text expansion} section
1884 If true, check and fix text coords to avoid clipping.
1887 The color to be used for drawing fonts.
1888 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1889 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1890 The default value of @var{fontcolor} is "black".
1893 The font file to be used for drawing text. Path must be included.
1894 This parameter is mandatory.
1897 The font size to be used for drawing text.
1898 The default value of @var{fontsize} is 16.
1901 Flags to be used for loading the fonts.
1903 The flags map the corresponding flags supported by libfreetype, and are
1904 a combination of the following values:
1911 @item vertical_layout
1912 @item force_autohint
1915 @item ignore_global_advance_width
1917 @item ignore_transform
1924 Default value is "render".
1926 For more information consult the documentation for the FT_LOAD_*
1930 The color to be used for drawing a shadow behind the drawn text. It
1931 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1932 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1933 The default value of @var{shadowcolor} is "black".
1935 @item shadowx, shadowy
1936 The x and y offsets for the text shadow position with respect to the
1937 position of the text. They can be either positive or negative
1938 values. Default value for both is "0".
1941 The size in number of spaces to use for rendering the tab.
1945 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
1946 format. It can be used with or without text parameter. @var{timecode_rate}
1947 option must be specified.
1949 @item timecode_rate, rate, r
1950 Set the timecode frame rate (timecode only).
1953 The text string to be drawn. The text must be a sequence of UTF-8
1955 This parameter is mandatory if no file is specified with the parameter
1959 A text file containing text to be drawn. The text must be a sequence
1960 of UTF-8 encoded characters.
1962 This parameter is mandatory if no text string is specified with the
1963 parameter @var{text}.
1965 If both @var{text} and @var{textfile} are specified, an error is thrown.
1968 The expressions which specify the offsets where text will be drawn
1969 within the video frame. They are relative to the top/left border of the
1972 The default value of @var{x} and @var{y} is "0".
1974 See below for the list of accepted constants and functions.
1977 The parameters for @var{x} and @var{y} are expressions containing the
1978 following constants and functions:
1982 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
1985 horizontal and vertical chroma subsample values. For example for the
1986 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1989 the height of each text line
1997 @item max_glyph_a, ascent
1998 the maximum distance from the baseline to the highest/upper grid
1999 coordinate used to place a glyph outline point, for all the rendered
2001 It is a positive value, due to the grid's orientation with the Y axis
2004 @item max_glyph_d, descent
2005 the maximum distance from the baseline to the lowest grid coordinate
2006 used to place a glyph outline point, for all the rendered glyphs.
2007 This is a negative value, due to the grid's orientation, with the Y axis
2011 maximum glyph height, that is the maximum height for all the glyphs
2012 contained in the rendered text, it is equivalent to @var{ascent} -
2016 maximum glyph width, that is the maximum width for all the glyphs
2017 contained in the rendered text
2020 the number of input frame, starting from 0
2022 @item rand(min, max)
2023 return a random number included between @var{min} and @var{max}
2026 input sample aspect ratio
2029 timestamp expressed in seconds, NAN if the input timestamp is unknown
2032 the height of the rendered text
2035 the width of the rendered text
2038 the x and y offset coordinates where the text is drawn.
2040 These parameters allow the @var{x} and @var{y} expressions to refer
2041 each other, so you can for example specify @code{y=x/dar}.
2044 If libavfilter was built with @code{--enable-fontconfig}, then
2045 @option{fontfile} can be a fontconfig pattern or omitted.
2047 @anchor{drawtext_expansion}
2048 @subsection Text expansion
2050 If @option{expansion} is set to @code{strftime} (which is the default for
2051 now), the filter recognizes strftime() sequences in the provided text and
2052 expands them accordingly. Check the documentation of strftime(). This
2053 feature is deprecated.
2055 If @option{expansion} is set to @code{none}, the text is printed verbatim.
2057 If @option{expansion} is set to @code{normal} (which will be the default),
2058 the following expansion mechanism is used.
2060 The backslash character '\', followed by any character, always expands to
2061 the second character.
2063 Sequence of the form @code{%@{...@}} are expanded. The text between the
2064 braces is a function name, possibly followed by arguments separated by ':'.
2065 If the arguments contain special characters or delimiters (':' or '@}'),
2066 they should be escaped.
2068 Note that they probably must also be escaped as the value for the
2069 @option{text} option in the filter argument string and as the filter
2070 argument in the filter graph description, and possibly also for the shell,
2071 that makes up to four levels of escaping; using a text file avoids these
2074 The following functions are available:
2079 The expression evaluation result.
2081 It must take one argument specifying the expression to be evaluated,
2082 which accepts the same constants and functions as the @var{x} and
2083 @var{y} values. Note that not all constants should be used, for
2084 example the text size is not known when evaluating the expression, so
2085 the constants @var{text_w} and @var{text_h} will have an undefined
2089 The time at which the filter is running, expressed in UTC.
2090 It can accept an argument: a strftime() format string.
2093 The time at which the filter is running, expressed in the local time zone.
2094 It can accept an argument: a strftime() format string.
2097 The frame number, starting from 0.
2100 The timestamp of the current frame, in seconds, with microsecond accuracy.
2104 @subsection Examples
2106 Some examples follow.
2111 Draw "Test Text" with font FreeSerif, using the default values for the
2112 optional parameters.
2115 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
2119 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
2120 and y=50 (counting from the top-left corner of the screen), text is
2121 yellow with a red box around it. Both the text and the box have an
2125 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
2126 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
2129 Note that the double quotes are not necessary if spaces are not used
2130 within the parameter list.
2133 Show the text at the center of the video frame:
2135 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
2139 Show a text line sliding from right to left in the last row of the video
2140 frame. The file @file{LONG_LINE} is assumed to contain a single line
2143 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
2147 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
2149 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
2153 Draw a single green letter "g", at the center of the input video.
2154 The glyph baseline is placed at half screen height.
2156 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2160 Show text for 1 second every 3 seconds:
2162 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
2166 Use fontconfig to set the font. Note that the colons need to be escaped.
2168 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
2172 Print the date of a real-time encoding (see strftime(3)):
2174 drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%@{localtime:%a %b %d %Y@}'
2179 For more information about libfreetype, check:
2180 @url{http://www.freetype.org/}.
2182 For more information about fontconfig, check:
2183 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2187 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2189 This filter accepts the following optional named parameters:
2193 Set low and high threshold values used by the Canny thresholding
2196 The high threshold selects the "strong" edge pixels, which are then
2197 connected through 8-connectivity with the "weak" edge pixels selected
2198 by the low threshold.
2200 @var{low} and @var{high} threshold values must be choosen in the range
2201 [0,1], and @var{low} should be lesser or equal to @var{high}.
2203 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2209 edgedetect=low=0.1:high=0.4
2214 Apply fade-in/out effect to input video.
2216 It accepts the parameters:
2217 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2219 @var{type} specifies if the effect type, can be either "in" for
2220 fade-in, or "out" for a fade-out effect.
2222 @var{start_frame} specifies the number of the start frame for starting
2223 to apply the fade effect.
2225 @var{nb_frames} specifies the number of frames for which the fade
2226 effect has to last. At the end of the fade-in effect the output video
2227 will have the same intensity as the input video, at the end of the
2228 fade-out transition the output video will be completely black.
2230 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2231 separated by ":". The description of the accepted options follows.
2238 @item start_frame, s
2239 See @var{start_frame}.
2242 See @var{nb_frames}.
2245 If set to 1, fade only alpha channel, if one exists on the input.
2249 A few usage examples follow, usable too as test scenarios.
2251 # fade in first 30 frames of video
2254 # fade out last 45 frames of a 200-frame video
2257 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2258 fade=in:0:25, fade=out:975:25
2260 # make first 5 frames black, then fade in from frame 5-24
2263 # fade in alpha over first 25 frames of video
2264 fade=in:0:25:alpha=1
2269 Extract a single field from an interlaced image using stride
2270 arithmetic to avoid wasting CPU time. The output frames are marked as
2273 This filter accepts the following named options:
2276 Specify whether to extract the top (if the value is @code{0} or
2277 @code{top}) or the bottom field (if the value is @code{1} or
2281 If the option key is not specified, the first value sets the @var{type}
2282 option. For example:
2294 Transform the field order of the input video.
2296 It accepts one parameter which specifies the required field order that
2297 the input interlaced video will be transformed to. The parameter can
2298 assume one of the following values:
2302 output bottom field first
2304 output top field first
2307 Default value is "tff".
2309 Transformation is achieved by shifting the picture content up or down
2310 by one line, and filling the remaining line with appropriate picture content.
2311 This method is consistent with most broadcast field order converters.
2313 If the input video is not flagged as being interlaced, or it is already
2314 flagged as being of the required output field order then this filter does
2315 not alter the incoming video.
2317 This filter is very useful when converting to or from PAL DV material,
2318 which is bottom field first.
2322 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2327 Buffer input images and send them when they are requested.
2329 This filter is mainly useful when auto-inserted by the libavfilter
2332 The filter does not take parameters.
2336 Convert the input video to one of the specified pixel formats.
2337 Libavfilter will try to pick one that is supported for the input to
2340 The filter accepts a list of pixel format names, separated by ":",
2341 for example "yuv420p:monow:rgb24".
2343 Some examples follow:
2345 # convert the input video to the format "yuv420p"
2348 # convert the input video to any of the formats in the list
2349 format=yuv420p:yuv444p:yuv410p
2354 Convert the video to specified constant framerate by duplicating or dropping
2355 frames as necessary.
2357 This filter accepts the following named parameters:
2361 Desired output framerate.
2364 Rounding method. The default is @code{near}.
2370 Select one frame every N.
2372 This filter accepts in input a string representing a positive
2373 integer. Default argument is @code{1}.
2378 Apply a frei0r effect to the input video.
2380 To enable compilation of this filter you need to install the frei0r
2381 header and configure FFmpeg with @code{--enable-frei0r}.
2383 The filter supports the syntax:
2385 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2388 @var{filter_name} is the name of the frei0r effect to load. If the
2389 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2390 is searched in each one of the directories specified by the colon (or
2391 semicolon on Windows platforms) separated list in @env{FREIOR_PATH},
2392 otherwise in the standard frei0r paths, which are in this order:
2393 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
2394 @file{/usr/lib/frei0r-1/}.
2396 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2397 for the frei0r effect.
2399 A frei0r effect parameter can be a boolean (whose values are specified
2400 with "y" and "n"), a double, a color (specified by the syntax
2401 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2402 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2403 description), a position (specified by the syntax @var{X}/@var{Y},
2404 @var{X} and @var{Y} being float numbers) and a string.
2406 The number and kind of parameters depend on the loaded effect. If an
2407 effect parameter is not specified the default value is set.
2409 Some examples follow:
2413 Apply the distort0r effect, set the first two double parameters:
2415 frei0r=distort0r:0.5:0.01
2419 Apply the colordistance effect, take a color as first parameter:
2421 frei0r=colordistance:0.2/0.3/0.4
2422 frei0r=colordistance:violet
2423 frei0r=colordistance:0x112233
2427 Apply the perspective effect, specify the top left and top right image
2430 frei0r=perspective:0.2/0.2:0.8/0.2
2434 For more information see:
2435 @url{http://frei0r.dyne.org}
2439 The filter takes one, two or three equations as parameter, separated by ':'.
2440 The first equation is mandatory and applies to the luma plane. The two
2441 following are respectively for chroma blue and chroma red planes.
2443 The filter syntax allows named parameters:
2447 the luminance expression
2449 the chrominance blue expression
2451 the chrominance red expression
2454 If one of the chrominance expression is not defined, it falls back on the other
2455 one. If none of them are specified, they will evaluate the luminance
2458 The expressions can use the following variables and functions:
2462 The sequential number of the filtered frame, starting from @code{0}.
2465 The coordinates of the current sample.
2468 The width and height of the image.
2471 Width and height scale depending on the currently filtered plane. It is the
2472 ratio between the corresponding luma plane number of pixels and the current
2473 plane ones. E.g. for YUV4:2:0 the values are @code{1,1} for the luma plane, and
2474 @code{0.5,0.5} for chroma planes.
2477 Return the value of the pixel at location (@var{x},@var{y}) of the current
2481 Return the value of the pixel at location (@var{x},@var{y}) of the luminance
2485 Return the value of the pixel at location (@var{x},@var{y}) of the
2486 blue-difference chroma plane.
2489 Return the value of the pixel at location (@var{x},@var{y}) of the
2490 red-difference chroma plane.
2493 For functions, if @var{x} and @var{y} are outside the area, the value will be
2494 automatically clipped to the closer edge.
2496 Some examples follow:
2500 Flip the image horizontally:
2506 Generate a fancy enigmatic moving light:
2508 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
2514 Fix the banding artifacts that are sometimes introduced into nearly flat
2515 regions by truncation to 8bit color depth.
2516 Interpolate the gradients that should go where the bands are, and
2519 This filter is designed for playback only. Do not use it prior to
2520 lossy compression, because compression tends to lose the dither and
2521 bring back the bands.
2523 The filter takes two optional parameters, separated by ':':
2524 @var{strength}:@var{radius}
2526 @var{strength} is the maximum amount by which the filter will change
2527 any one pixel. Also the threshold for detecting nearly flat
2528 regions. Acceptable values range from .51 to 255, default value is
2529 1.2, out-of-range values will be clipped to the valid range.
2531 @var{radius} is the neighborhood to fit the gradient to. A larger
2532 radius makes for smoother gradients, but also prevents the filter from
2533 modifying the pixels near detailed regions. Acceptable values are
2534 8-32, default value is 16, out-of-range values will be clipped to the
2538 # default parameters
2547 Flip the input video horizontally.
2549 For example to horizontally flip the input video with @command{ffmpeg}:
2551 ffmpeg -i in.avi -vf "hflip" out.avi
2556 High precision/quality 3d denoise filter. This filter aims to reduce
2557 image noise producing smooth images and making still images really
2558 still. It should enhance compressibility.
2560 It accepts the following optional parameters:
2561 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2565 a non-negative float number which specifies spatial luma strength,
2568 @item chroma_spatial
2569 a non-negative float number which specifies spatial chroma strength,
2570 defaults to 3.0*@var{luma_spatial}/4.0
2573 a float number which specifies luma temporal strength, defaults to
2574 6.0*@var{luma_spatial}/4.0
2577 a float number which specifies chroma temporal strength, defaults to
2578 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2583 Modify the hue and/or the saturation of the input.
2585 This filter accepts the following optional named options:
2589 Specify the hue angle as a number of degrees. It accepts a float
2590 number or an expression, and defaults to 0.0.
2593 Specify the hue angle as a number of degrees. It accepts a float
2594 number or an expression, and defaults to 0.0.
2597 Specify the saturation in the [-10,10] range. It accepts a float number and
2601 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2602 following constants:
2606 frame count of the input frame starting from 0
2609 presentation timestamp of the input frame expressed in time base units
2612 frame rate of the input video, NAN if the input frame rate is unknown
2615 timestamp expressed in seconds, NAN if the input timestamp is unknown
2618 time base of the input video
2621 The options can also be set using the syntax: @var{hue}:@var{saturation}
2623 In this case @var{hue} is expressed in degrees.
2625 Some examples follow:
2628 Set the hue to 90 degrees and the saturation to 1.0:
2634 Same command but expressing the hue in radians:
2640 Same command without named options, hue must be expressed in degrees:
2646 Note that "h:s" syntax does not support expressions for the values of
2647 h and s, so the following example will issue an error:
2653 Rotate hue and make the saturation swing between 0
2654 and 2 over a period of 1 second:
2656 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2660 Apply a 3 seconds saturation fade-in effect starting at 0:
2665 The general fade-in expression can be written as:
2667 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2671 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2673 hue="s=max(0\, min(1\, (8-t)/3))"
2676 The general fade-out expression can be written as:
2678 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2683 @subsection Commands
2685 This filter supports the following command:
2688 Modify the hue and/or the saturation of the input video.
2689 The command accepts the same named options and syntax than when calling the
2690 filter from the command-line.
2692 If a parameter is omitted, it is kept at its current value.
2697 Interlaceing detect filter. This filter tries to detect if the input is
2698 interlaced or progressive. Top or bottom field first.
2700 @section lut, lutrgb, lutyuv
2702 Compute a look-up table for binding each pixel component input value
2703 to an output value, and apply it to input video.
2705 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2706 to an RGB input video.
2708 These filters accept in input a ":"-separated list of options, which
2709 specify the expressions used for computing the lookup table for the
2710 corresponding pixel component values.
2712 The @var{lut} filter requires either YUV or RGB pixel formats in
2713 input, and accepts the options:
2715 @item @var{c0} (first pixel component)
2716 @item @var{c1} (second pixel component)
2717 @item @var{c2} (third pixel component)
2718 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
2721 The exact component associated to each option depends on the format in
2724 The @var{lutrgb} filter requires RGB pixel formats in input, and
2725 accepts the options:
2727 @item @var{r} (red component)
2728 @item @var{g} (green component)
2729 @item @var{b} (blue component)
2730 @item @var{a} (alpha component)
2733 The @var{lutyuv} filter requires YUV pixel formats in input, and
2734 accepts the options:
2736 @item @var{y} (Y/luminance component)
2737 @item @var{u} (U/Cb component)
2738 @item @var{v} (V/Cr component)
2739 @item @var{a} (alpha component)
2742 The expressions can contain the following constants and functions:
2746 the input width and height
2749 input value for the pixel component
2752 the input value clipped in the @var{minval}-@var{maxval} range
2755 maximum value for the pixel component
2758 minimum value for the pixel component
2761 the negated value for the pixel component value clipped in the
2762 @var{minval}-@var{maxval} range , it corresponds to the expression
2763 "maxval-clipval+minval"
2766 the computed value in @var{val} clipped in the
2767 @var{minval}-@var{maxval} range
2769 @item gammaval(gamma)
2770 the computed gamma correction value of the pixel component value
2771 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2773 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2777 All expressions default to "val".
2779 Some examples follow:
2781 # negate input video
2782 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2783 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2785 # the above is the same as
2786 lutrgb="r=negval:g=negval:b=negval"
2787 lutyuv="y=negval:u=negval:v=negval"
2792 # remove chroma components, turns the video into a graytone image
2793 lutyuv="u=128:v=128"
2795 # apply a luma burning effect
2798 # remove green and blue components
2801 # set a constant alpha channel value on input
2802 format=rgba,lutrgb=a="maxval-minval/2"
2804 # correct luminance gamma by a 0.5 factor
2805 lutyuv=y=gammaval(0.5)
2810 Apply an MPlayer filter to the input video.
2812 This filter provides a wrapper around most of the filters of
2815 This wrapper is considered experimental. Some of the wrapped filters
2816 may not work properly and we may drop support for them, as they will
2817 be implemented natively into FFmpeg. Thus you should avoid
2818 depending on them when writing portable scripts.
2820 The filters accepts the parameters:
2821 @var{filter_name}[:=]@var{filter_params}
2823 @var{filter_name} is the name of a supported MPlayer filter,
2824 @var{filter_params} is a string containing the parameters accepted by
2827 The list of the currently supported filters follows:
2862 The parameter syntax and behavior for the listed filters are the same
2863 of the corresponding MPlayer filters. For detailed instructions check
2864 the "VIDEO FILTERS" section in the MPlayer manual.
2866 Some examples follow:
2869 Adjust gamma, brightness, contrast:
2875 Add temporal noise to input video:
2881 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2887 This filter accepts an integer in input, if non-zero it negates the
2888 alpha component (if available). The default value in input is 0.
2892 Force libavfilter not to use any of the specified pixel formats for the
2893 input to the next filter.
2895 The filter accepts a list of pixel format names, separated by ":",
2896 for example "yuv420p:monow:rgb24".
2898 Some examples follow:
2900 # force libavfilter to use a format different from "yuv420p" for the
2901 # input to the vflip filter
2902 noformat=yuv420p,vflip
2904 # convert the input video to any of the formats not contained in the list
2905 noformat=yuv420p:yuv444p:yuv410p
2910 Pass the video source unchanged to the output.
2914 Apply video transform using libopencv.
2916 To enable this filter install libopencv library and headers and
2917 configure FFmpeg with @code{--enable-libopencv}.
2919 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
2921 @var{filter_name} is the name of the libopencv filter to apply.
2923 @var{filter_params} specifies the parameters to pass to the libopencv
2924 filter. If not specified the default values are assumed.
2926 Refer to the official libopencv documentation for more precise
2928 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
2930 Follows the list of supported libopencv filters.
2935 Dilate an image by using a specific structuring element.
2936 This filter corresponds to the libopencv function @code{cvDilate}.
2938 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
2940 @var{struct_el} represents a structuring element, and has the syntax:
2941 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
2943 @var{cols} and @var{rows} represent the number of columns and rows of
2944 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
2945 point, and @var{shape} the shape for the structuring element, and
2946 can be one of the values "rect", "cross", "ellipse", "custom".
2948 If the value for @var{shape} is "custom", it must be followed by a
2949 string of the form "=@var{filename}". The file with name
2950 @var{filename} is assumed to represent a binary image, with each
2951 printable character corresponding to a bright pixel. When a custom
2952 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
2953 or columns and rows of the read file are assumed instead.
2955 The default value for @var{struct_el} is "3x3+0x0/rect".
2957 @var{nb_iterations} specifies the number of times the transform is
2958 applied to the image, and defaults to 1.
2960 Follow some example:
2962 # use the default values
2965 # dilate using a structuring element with a 5x5 cross, iterate two times
2966 ocv=dilate=5x5+2x2/cross:2
2968 # read the shape from the file diamond.shape, iterate two times
2969 # the file diamond.shape may contain a pattern of characters like this:
2975 # the specified cols and rows are ignored (but not the anchor point coordinates)
2976 ocv=0x0+2x2/custom=diamond.shape:2
2981 Erode an image by using a specific structuring element.
2982 This filter corresponds to the libopencv function @code{cvErode}.
2984 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
2985 with the same syntax and semantics as the @ref{dilate} filter.
2989 Smooth the input video.
2991 The filter takes the following parameters:
2992 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
2994 @var{type} is the type of smooth filter to apply, and can be one of
2995 the following values: "blur", "blur_no_scale", "median", "gaussian",
2996 "bilateral". The default value is "gaussian".
2998 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
2999 parameters whose meanings depend on smooth type. @var{param1} and
3000 @var{param2} accept integer positive values or 0, @var{param3} and
3001 @var{param4} accept float values.
3003 The default value for @var{param1} is 3, the default value for the
3004 other parameters is 0.
3006 These parameters correspond to the parameters assigned to the
3007 libopencv function @code{cvSmooth}.
3012 Overlay one video on top of another.
3014 It takes two inputs and one output, the first input is the "main"
3015 video on which the second input is overlayed.
3017 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
3019 @var{x} is the x coordinate of the overlayed video on the main video,
3020 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
3021 the following parameters:
3024 @item main_w, main_h
3025 main input width and height
3028 same as @var{main_w} and @var{main_h}
3030 @item overlay_w, overlay_h
3031 overlay input width and height
3034 same as @var{overlay_w} and @var{overlay_h}
3037 @var{options} is an optional list of @var{key}=@var{value} pairs,
3040 The description of the accepted options follows.
3044 If set to 1, force the filter to accept inputs in the RGB
3045 color space. Default value is 0.
3048 Be aware that frames are taken from each input video in timestamp
3049 order, hence, if their initial timestamps differ, it is a a good idea
3050 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
3051 have them begin in the same zero timestamp, as it does the example for
3052 the @var{movie} filter.
3054 Follow some examples:
3056 # draw the overlay at 10 pixels from the bottom right
3057 # corner of the main video.
3058 overlay=main_w-overlay_w-10:main_h-overlay_h-10
3060 # insert a transparent PNG logo in the bottom left corner of the input
3061 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
3063 # insert 2 different transparent PNG logos (second logo on bottom
3065 ffmpeg -i input -i logo1 -i logo2 -filter_complex
3066 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
3068 # add a transparent color layer on top of the main video,
3069 # WxH specifies the size of the main input to the overlay filter
3070 color=red@@.3:WxH [over]; [in][over] overlay [out]
3072 # play an original video and a filtered version (here with the deshake filter)
3074 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
3076 # the previous example is the same as:
3077 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
3080 You can chain together more overlays but the efficiency of such
3081 approach is yet to be tested.
3085 Add paddings to the input image, and places the original input at the
3086 given coordinates @var{x}, @var{y}.
3088 It accepts the following parameters:
3089 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
3091 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
3092 expressions containing the following constants:
3096 the input video width and height
3099 same as @var{in_w} and @var{in_h}
3102 the output width and height, that is the size of the padded area as
3103 specified by the @var{width} and @var{height} expressions
3106 same as @var{out_w} and @var{out_h}
3109 x and y offsets as specified by the @var{x} and @var{y}
3110 expressions, or NAN if not yet specified
3113 same as @var{iw} / @var{ih}
3116 input sample aspect ratio
3119 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3122 horizontal and vertical chroma subsample values. For example for the
3123 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3126 Follows the description of the accepted parameters.
3131 Specify the size of the output image with the paddings added. If the
3132 value for @var{width} or @var{height} is 0, the corresponding input size
3133 is used for the output.
3135 The @var{width} expression can reference the value set by the
3136 @var{height} expression, and vice versa.
3138 The default value of @var{width} and @var{height} is 0.
3142 Specify the offsets where to place the input image in the padded area
3143 with respect to the top/left border of the output image.
3145 The @var{x} expression can reference the value set by the @var{y}
3146 expression, and vice versa.
3148 The default value of @var{x} and @var{y} is 0.
3152 Specify the color of the padded area, it can be the name of a color
3153 (case insensitive match) or a 0xRRGGBB[AA] sequence.
3155 The default value of @var{color} is "black".
3159 @subsection Examples
3163 Add paddings with color "violet" to the input video. Output video
3164 size is 640x480, the top-left corner of the input video is placed at
3167 pad=640:480:0:40:violet
3171 Pad the input to get an output with dimensions increased by 3/2,
3172 and put the input video at the center of the padded area:
3174 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
3178 Pad the input to get a squared output with size equal to the maximum
3179 value between the input width and height, and put the input video at
3180 the center of the padded area:
3182 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
3186 Pad the input to get a final w/h ratio of 16:9:
3188 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
3192 In case of anamorphic video, in order to set the output display aspect
3193 correctly, it is necessary to use @var{sar} in the expression,
3194 according to the relation:
3196 (ih * X / ih) * sar = output_dar
3197 X = output_dar / sar
3200 Thus the previous example needs to be modified to:
3202 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
3206 Double output size and put the input video in the bottom-right
3207 corner of the output padded area:
3209 pad="2*iw:2*ih:ow-iw:oh-ih"
3213 @section pixdesctest
3215 Pixel format descriptor test filter, mainly useful for internal
3216 testing. The output video should be equal to the input video.
3220 format=monow, pixdesctest
3223 can be used to test the monowhite pixel format descriptor definition.
3227 Suppress a TV station logo, using an image file to determine which
3228 pixels comprise the logo. It works by filling in the pixels that
3229 comprise the logo with neighboring pixels.
3231 This filter requires one argument which specifies the filter bitmap
3232 file, which can be any image format supported by libavformat. The
3233 width and height of the image file must match those of the video
3234 stream being processed.
3236 Pixels in the provided bitmap image with a value of zero are not
3237 considered part of the logo, non-zero pixels are considered part of
3238 the logo. If you use white (255) for the logo and black (0) for the
3239 rest, you will be safe. For making the filter bitmap, it is
3240 recommended to take a screen capture of a black frame with the logo
3241 visible, and then using a threshold filter followed by the erode
3242 filter once or twice.
3244 If needed, little splotches can be fixed manually. Remember that if
3245 logo pixels are not covered, the filter quality will be much
3246 reduced. Marking too many pixels as part of the logo does not hurt as
3247 much, but it will increase the amount of blurring needed to cover over
3248 the image and will destroy more information than necessary, and extra
3249 pixels will slow things down on a large logo.
3253 Scale (resize) the input video, using the libswscale library.
3255 The scale filter forces the output display aspect ratio to be the same
3256 of the input, by changing the output sample aspect ratio.
3258 This filter accepts a list of named options in the form of
3259 @var{key}=@var{value} pairs separated by ":". If the key for the first
3260 two options is not specified, the assumed keys for the first two
3261 values are @code{w} and @code{h}. If the first option has no key and
3262 can be interpreted like a video size specification, it will be used
3263 to set the video size.
3265 A description of the accepted options follows.
3269 Set the video width expression, default value is @code{iw}. See below
3270 for the list of accepted constants.
3273 Set the video heiht expression, default value is @code{ih}.
3274 See below for the list of accepted constants.
3277 Set the interlacing. It accepts the following values:
3281 force interlaced aware scaling
3284 do not apply interlaced scaling
3287 select interlaced aware scaling depending on whether the source frames
3288 are flagged as interlaced or not
3291 Default value is @code{0}.
3294 Set libswscale scaling flags. If not explictly specified the filter
3295 applies a bilinear scaling algorithm.
3298 Set the video size, the value must be a valid abbreviation or in the
3299 form @var{width}x@var{height}.
3302 The values of the @var{w} and @var{h} options are expressions
3303 containing the following constants:
3307 the input width and height
3310 same as @var{in_w} and @var{in_h}
3313 the output (cropped) width and height
3316 same as @var{out_w} and @var{out_h}
3319 same as @var{iw} / @var{ih}
3322 input sample aspect ratio
3325 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3328 horizontal and vertical chroma subsample values. For example for the
3329 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3332 If the input image format is different from the format requested by
3333 the next filter, the scale filter will convert the input to the
3336 If the value for @var{width} or @var{height} is 0, the respective input
3337 size is used for the output.
3339 If the value for @var{width} or @var{height} is -1, the scale filter will
3340 use, for the respective output size, a value that maintains the aspect
3341 ratio of the input image.
3343 @subsection Examples
3347 Scale the input video to a size of 200x100:
3352 This is equivalent to:
3363 Specify a size abbreviation for the output size:
3368 which can also be written as:
3374 Scale the input to 2x:
3380 The above is the same as:
3386 Scale the input to 2x with forced interlaced scaling:
3388 scale=2*iw:2*ih:interl=1
3392 Scale the input to half size:
3398 Increase the width, and set the height to the same size:
3404 Seek for Greek harmony:
3411 Increase the height, and set the width to 3/2 of the height:
3417 Increase the size, but make the size a multiple of the chroma:
3419 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3423 Increase the width to a maximum of 500 pixels, keep the same input
3426 scale='min(500\, iw*3/2):-1'
3431 Select frames to pass in output.
3433 It accepts in input an expression, which is evaluated for each input
3434 frame. If the expression is evaluated to a non-zero value, the frame
3435 is selected and passed to the output, otherwise it is discarded.
3437 The expression can contain the following constants:
3441 the sequential number of the filtered frame, starting from 0
3444 the sequential number of the selected frame, starting from 0
3446 @item prev_selected_n
3447 the sequential number of the last selected frame, NAN if undefined
3450 timebase of the input timestamps
3453 the PTS (Presentation TimeStamp) of the filtered video frame,
3454 expressed in @var{TB} units, NAN if undefined
3457 the PTS (Presentation TimeStamp) of the filtered video frame,
3458 expressed in seconds, NAN if undefined
3461 the PTS of the previously filtered video frame, NAN if undefined
3463 @item prev_selected_pts
3464 the PTS of the last previously filtered video frame, NAN if undefined
3466 @item prev_selected_t
3467 the PTS of the last previously selected video frame, NAN if undefined
3470 the PTS of the first video frame in the video, NAN if undefined
3473 the time of the first video frame in the video, NAN if undefined
3476 the type of the filtered frame, can assume one of the following
3488 @item interlace_type
3489 the frame interlace type, can assume one of the following values:
3492 the frame is progressive (not interlaced)
3494 the frame is top-field-first
3496 the frame is bottom-field-first
3500 1 if the filtered frame is a key-frame, 0 otherwise
3503 the position in the file of the filtered frame, -1 if the information
3504 is not available (e.g. for synthetic video)
3507 value between 0 and 1 to indicate a new scene; a low value reflects a low
3508 probability for the current frame to introduce a new scene, while a higher
3509 value means the current frame is more likely to be one (see the example below)
3513 The default value of the select expression is "1".
3515 Some examples follow:
3518 # select all frames in input
3521 # the above is the same as:
3527 # select only I-frames
3528 select='eq(pict_type\,I)'
3530 # select one frame every 100
3531 select='not(mod(n\,100))'
3533 # select only frames contained in the 10-20 time interval
3534 select='gte(t\,10)*lte(t\,20)'
3536 # select only I frames contained in the 10-20 time interval
3537 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
3539 # select frames with a minimum distance of 10 seconds
3540 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
3543 Complete example to create a mosaic of the first scenes:
3546 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
3549 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
3552 @section setdar, setsar
3554 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3557 This is done by changing the specified Sample (aka Pixel) Aspect
3558 Ratio, according to the following equation:
3560 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3563 Keep in mind that the @code{setdar} filter does not modify the pixel
3564 dimensions of the video frame. Also the display aspect ratio set by
3565 this filter may be changed by later filters in the filterchain,
3566 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3569 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3570 the filter output video.
3572 Note that as a consequence of the application of this filter, the
3573 output display aspect ratio will change according to the equation
3576 Keep in mind that the sample aspect ratio set by the @code{setsar}
3577 filter may be changed by later filters in the filterchain, e.g. if
3578 another "setsar" or a "setdar" filter is applied.
3580 The @code{setdar} and @code{setsar} filters accept a string in the
3581 form @var{num}:@var{den} expressing an aspect ratio, or the following
3582 named options, expressed as a sequence of @var{key}=@var{value} pairs,
3587 Set the maximum integer value to use for expressing numerator and
3588 denominator when reducing the expressed aspect ratio to a rational.
3589 Default value is @code{100}.
3592 Set the aspect ratio used by the filter.
3594 The parameter can be a floating point number string, an expression, or
3595 a string of the form @var{num}:@var{den}, where @var{num} and
3596 @var{den} are the numerator and denominator of the aspect ratio. If
3597 the parameter is not specified, it is assumed the value "0".
3598 In case the form "@var{num}:@var{den}" the @code{:} character should
3602 If the keys are omitted in the named options list, the specifed values
3603 are assumed to be @var{ratio} and @var{max} in that order.
3605 For example to change the display aspect ratio to 16:9, specify:
3610 The example above is equivalent to:
3615 To change the sample aspect ratio to 10:11, specify:
3620 To set a display aspect ratio of 16:9, and specify a maximum integer value of
3621 1000 in the aspect ratio reduction, use the command:
3623 setdar=ratio='16:9':max=1000
3628 Force field for the output video frame.
3630 The @code{setfield} filter marks the interlace type field for the
3631 output frames. It does not change the input frame, but only sets the
3632 corresponding property, which affects how the frame is treated by
3633 following filters (e.g. @code{fieldorder} or @code{yadif}).
3635 It accepts a string parameter, which can assume the following values:
3638 Keep the same field property.
3641 Mark the frame as bottom-field-first.
3644 Mark the frame as top-field-first.
3647 Mark the frame as progressive.
3652 Show a line containing various information for each input video frame.
3653 The input video is not modified.
3655 The shown line contains a sequence of key/value pairs of the form
3656 @var{key}:@var{value}.
3658 A description of each shown parameter follows:
3662 sequential number of the input frame, starting from 0
3665 Presentation TimeStamp of the input frame, expressed as a number of
3666 time base units. The time base unit depends on the filter input pad.
3669 Presentation TimeStamp of the input frame, expressed as a number of
3673 position of the frame in the input stream, -1 if this information in
3674 unavailable and/or meaningless (for example in case of synthetic video)
3680 sample aspect ratio of the input frame, expressed in the form
3684 size of the input frame, expressed in the form
3685 @var{width}x@var{height}
3688 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3689 for bottom field first)
3692 1 if the frame is a key frame, 0 otherwise
3695 picture type of the input frame ("I" for an I-frame, "P" for a
3696 P-frame, "B" for a B-frame, "?" for unknown type).
3697 Check also the documentation of the @code{AVPictureType} enum and of
3698 the @code{av_get_picture_type_char} function defined in
3699 @file{libavutil/avutil.h}.
3702 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3704 @item plane_checksum
3705 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3706 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3711 Pass the images of input video on to next video filter as multiple
3715 ffmpeg -i in.avi -vf "slicify=32" out.avi
3718 The filter accepts the slice height as parameter. If the parameter is
3719 not specified it will use the default value of 16.
3721 Adding this in the beginning of filter chains should make filtering
3722 faster due to better use of the memory cache.
3726 Blur the input video without impacting the outlines.
3728 The filter accepts the following parameters:
3729 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3731 Parameters prefixed by @var{luma} indicate that they work on the
3732 luminance of the pixels whereas parameters prefixed by @var{chroma}
3733 refer to the chrominance of the pixels.
3735 If the chroma parameters are not set, the luma parameters are used for
3736 either the luminance and the chrominance of the pixels.
3738 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3739 range [0.1,5.0] that specifies the variance of the gaussian filter
3740 used to blur the image (slower if larger).
3742 @var{luma_strength} or @var{chroma_strength} must be a float number in
3743 the range [-1.0,1.0] that configures the blurring. A value included in
3744 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3745 will sharpen the image.
3747 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3748 the range [-30,30] that is used as a coefficient to determine whether
3749 a pixel should be blurred or not. A value of 0 will filter all the
3750 image, a value included in [0,30] will filter flat areas and a value
3751 included in [-30,0] will filter edges.
3755 Split input video into several identical outputs.
3757 The filter accepts a single parameter which specifies the number of outputs. If
3758 unspecified, it defaults to 2.
3762 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3764 will create 5 copies of the input video.
3768 [in] split [splitout1][splitout2];
3769 [splitout1] crop=100:100:0:0 [cropout];
3770 [splitout2] pad=200:200:100:100 [padout];
3773 will create two separate outputs from the same input, one cropped and
3778 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3779 Interpolate) pixel art scaling algorithm.
3781 Useful for enlarging pixel art images without reducing sharpness.
3787 Select the most representative frame in a given sequence of consecutive frames.
3789 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3790 in a set of @var{N} frames, the filter will pick one of them, and then handle
3791 the next batch of @var{N} frames until the end.
3793 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3794 value will result in a higher memory usage, so a high value is not recommended.
3796 The following example extract one picture each 50 frames:
3801 Complete example of a thumbnail creation with @command{ffmpeg}:
3803 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3808 Tile several successive frames together.
3810 It accepts a list of options in the form of @var{key}=@var{value} pairs
3811 separated by ":". A description of the accepted options follows.
3816 Set the grid size (i.e. the number of lines and columns) in the form
3820 Set the outer border margin in pixels.
3823 Set the inner border thickness (i.e. the number of pixels between frames). For
3824 more advanced padding options (such as having different values for the edges),
3825 refer to the pad video filter.
3828 Set the maximum number of frames to render in the given area. It must be less
3829 than or equal to @var{w}x@var{h}. The default value is @code{0}, meaning all
3830 the area will be used.
3834 Alternatively, the options can be specified as a flat string:
3836 @var{layout}[:@var{nb_frames}[:@var{margin}[:@var{padding}]]]
3838 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3841 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3843 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3844 duplicating each output frame to accomodate the originally detected frame
3847 Another example to display @code{5} pictures in an area of @code{3x2} frames,
3848 with @code{7} pixels between them, and @code{2} pixels of initial margin, using
3849 mixed flat and named options:
3851 tile=3x2:nb_frames=5:padding=7:margin=2
3856 Perform various types of temporal field interlacing.
3858 Frames are counted starting from 1, so the first input frame is
3861 This filter accepts a single parameter specifying the mode. Available
3866 Move odd frames into the upper field, even into the lower field,
3867 generating a double height frame at half framerate.
3870 Only output even frames, odd frames are dropped, generating a frame with
3871 unchanged height at half framerate.
3874 Only output odd frames, even frames are dropped, generating a frame with
3875 unchanged height at half framerate.
3878 Expand each frame to full height, but pad alternate lines with black,
3879 generating a frame with double height at the same input framerate.
3881 @item interleave_top, 4
3882 Interleave the upper field from odd frames with the lower field from
3883 even frames, generating a frame with unchanged height at half framerate.
3885 @item interleave_bottom, 5
3886 Interleave the lower field from odd frames with the upper field from
3887 even frames, generating a frame with unchanged height at half framerate.
3889 @item interlacex2, 6
3890 Double frame rate with unchanged height. Frames are inserted each
3891 containing the second temporal field from the previous input frame and
3892 the first temporal field from the next input frame. This mode relies on
3893 the top_field_first flag. Useful for interlaced video displays with no
3894 field synchronisation.
3897 Numeric values are deprecated but are accepted for backward
3898 compatibility reasons.
3900 Default mode is @code{merge}.
3904 Transpose rows with columns in the input video and optionally flip it.
3906 This filter accepts the following named parameters:
3910 Specify the transposition direction. Can assume the following values:
3914 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3922 Rotate by 90 degrees clockwise, that is:
3930 Rotate by 90 degrees counterclockwise, that is:
3938 Rotate by 90 degrees clockwise and vertically flip, that is:
3946 For values between 4-7, the transposition is only done if the input
3947 video geometry is portrait and not landscape. These values are
3948 deprecated, the @code{passthrough} option should be used instead.
3951 Do not apply the transposition if the input geometry matches the one
3952 specified by the specified value. It accepts the following values:
3955 Always apply transposition.
3957 Preserve portrait geometry (when @var{height} >= @var{width}).
3959 Preserve landscape geometry (when @var{width} >= @var{height}).
3962 Default value is @code{none}.
3967 Sharpen or blur the input video.
3969 It accepts the following parameters:
3970 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3972 Negative values for the amount will blur the input video, while positive
3973 values will sharpen. All parameters are optional and default to the
3974 equivalent of the string '5:5:1.0:5:5:0.0'.
3979 Set the luma matrix horizontal size. It can be an integer between 3
3980 and 13, default value is 5.
3983 Set the luma matrix vertical size. It can be an integer between 3
3984 and 13, default value is 5.
3987 Set the luma effect strength. It can be a float number between -2.0
3988 and 5.0, default value is 1.0.
3990 @item chroma_msize_x
3991 Set the chroma matrix horizontal size. It can be an integer between 3
3992 and 13, default value is 5.
3994 @item chroma_msize_y
3995 Set the chroma matrix vertical size. It can be an integer between 3
3996 and 13, default value is 5.
3999 Set the chroma effect strength. It can be a float number between -2.0
4000 and 5.0, default value is 0.0.
4005 # Strong luma sharpen effect parameters
4008 # Strong blur of both luma and chroma parameters
4009 unsharp=7:7:-2:7:7:-2
4011 # Use the default values with @command{ffmpeg}
4012 ffmpeg -i in.avi -vf "unsharp" out.mp4
4017 Flip the input video vertically.
4020 ffmpeg -i in.avi -vf "vflip" out.avi
4025 Deinterlace the input video ("yadif" means "yet another deinterlacing
4028 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
4030 @var{mode} specifies the interlacing mode to adopt, accepts one of the
4035 output 1 frame for each frame
4037 output 1 frame for each field
4039 like 0 but skips spatial interlacing check
4041 like 1 but skips spatial interlacing check
4046 @var{parity} specifies the picture field parity assumed for the input
4047 interlaced video, accepts one of the following values:
4051 assume top field first
4053 assume bottom field first
4055 enable automatic detection
4058 Default value is -1.
4059 If interlacing is unknown or decoder does not export this information,
4060 top field first will be assumed.
4062 @var{auto} specifies if deinterlacer should trust the interlaced flag
4063 and only deinterlace frames marked as interlaced
4067 deinterlace all frames
4069 only deinterlace frames marked as interlaced
4074 @c man end VIDEO FILTERS
4076 @chapter Video Sources
4077 @c man begin VIDEO SOURCES
4079 Below is a description of the currently available video sources.
4083 Buffer video frames, and make them available to the filter chain.
4085 This source is mainly intended for a programmatic use, in particular
4086 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
4088 It accepts a list of options in the form of @var{key}=@var{value} pairs
4089 separated by ":". A description of the accepted options follows.
4094 Specify the size (width and height) of the buffered video frames.
4097 A string representing the pixel format of the buffered video frames.
4098 It may be a number corresponding to a pixel format, or a pixel format
4102 Specify the timebase assumed by the timestamps of the buffered frames.
4105 Specify the frame rate expected for the video stream.
4108 Specify the sample aspect ratio assumed by the video frames.
4111 Specify the optional parameters to be used for the scale filter which
4112 is automatically inserted when an input change is detected in the
4113 input size or format.
4118 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
4121 will instruct the source to accept video frames with size 320x240 and
4122 with format "yuv410p", assuming 1/24 as the timestamps timebase and
4123 square pixels (1:1 sample aspect ratio).
4124 Since the pixel format with name "yuv410p" corresponds to the number 6
4125 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
4126 this example corresponds to:
4128 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
4131 Alternatively, the options can be specified as a flat string, but this
4132 syntax is deprecated:
4134 @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}]
4138 Create a pattern generated by an elementary cellular automaton.
4140 The initial state of the cellular automaton can be defined through the
4141 @option{filename}, and @option{pattern} options. If such options are
4142 not specified an initial state is created randomly.
4144 At each new frame a new row in the video is filled with the result of
4145 the cellular automaton next generation. The behavior when the whole
4146 frame is filled is defined by the @option{scroll} option.
4148 This source accepts a list of options in the form of
4149 @var{key}=@var{value} pairs separated by ":". A description of the
4150 accepted options follows.
4154 Read the initial cellular automaton state, i.e. the starting row, from
4156 In the file, each non-whitespace character is considered an alive
4157 cell, a newline will terminate the row, and further characters in the
4158 file will be ignored.
4161 Read the initial cellular automaton state, i.e. the starting row, from
4162 the specified string.
4164 Each non-whitespace character in the string is considered an alive
4165 cell, a newline will terminate the row, and further characters in the
4166 string will be ignored.
4169 Set the video rate, that is the number of frames generated per second.
4172 @item random_fill_ratio, ratio
4173 Set the random fill ratio for the initial cellular automaton row. It
4174 is a floating point number value ranging from 0 to 1, defaults to
4177 This option is ignored when a file or a pattern is specified.
4179 @item random_seed, seed
4180 Set the seed for filling randomly the initial row, must be an integer
4181 included between 0 and UINT32_MAX. If not specified, or if explicitly
4182 set to -1, the filter will try to use a good random seed on a best
4186 Set the cellular automaton rule, it is a number ranging from 0 to 255.
4187 Default value is 110.
4190 Set the size of the output video.
4192 If @option{filename} or @option{pattern} is specified, the size is set
4193 by default to the width of the specified initial state row, and the
4194 height is set to @var{width} * PHI.
4196 If @option{size} is set, it must contain the width of the specified
4197 pattern string, and the specified pattern will be centered in the
4200 If a filename or a pattern string is not specified, the size value
4201 defaults to "320x518" (used for a randomly generated initial state).
4204 If set to 1, scroll the output upward when all the rows in the output
4205 have been already filled. If set to 0, the new generated row will be
4206 written over the top row just after the bottom row is filled.
4209 @item start_full, full
4210 If set to 1, completely fill the output with generated rows before
4211 outputting the first frame.
4212 This is the default behavior, for disabling set the value to 0.
4215 If set to 1, stitch the left and right row edges together.
4216 This is the default behavior, for disabling set the value to 0.
4219 @subsection Examples
4223 Read the initial state from @file{pattern}, and specify an output of
4226 cellauto=f=pattern:s=200x400
4230 Generate a random initial row with a width of 200 cells, with a fill
4233 cellauto=ratio=2/3:s=200x200
4237 Create a pattern generated by rule 18 starting by a single alive cell
4238 centered on an initial row with width 100:
4240 cellauto=p=@@:s=100x400:full=0:rule=18
4244 Specify a more elaborated initial pattern:
4246 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
4253 Generate a Mandelbrot set fractal, and progressively zoom towards the
4254 point specified with @var{start_x} and @var{start_y}.
4256 This source accepts a list of options in the form of
4257 @var{key}=@var{value} pairs separated by ":". A description of the
4258 accepted options follows.
4263 Set the terminal pts value. Default value is 400.
4266 Set the terminal scale value.
4267 Must be a floating point value. Default value is 0.3.
4270 Set the inner coloring mode, that is the algorithm used to draw the
4271 Mandelbrot fractal internal region.
4273 It shall assume one of the following values:
4278 Show time until convergence.
4280 Set color based on point closest to the origin of the iterations.
4285 Default value is @var{mincol}.
4288 Set the bailout value. Default value is 10.0.
4291 Set the maximum of iterations performed by the rendering
4292 algorithm. Default value is 7189.
4295 Set outer coloring mode.
4296 It shall assume one of following values:
4298 @item iteration_count
4299 Set iteration cound mode.
4300 @item normalized_iteration_count
4301 set normalized iteration count mode.
4303 Default value is @var{normalized_iteration_count}.
4306 Set frame rate, expressed as number of frames per second. Default
4310 Set frame size. Default value is "640x480".
4313 Set the initial scale value. Default value is 3.0.
4316 Set the initial x position. Must be a floating point value between
4317 -100 and 100. Default value is -0.743643887037158704752191506114774.
4320 Set the initial y position. Must be a floating point value between
4321 -100 and 100. Default value is -0.131825904205311970493132056385139.
4326 Generate various test patterns, as generated by the MPlayer test filter.
4328 The size of the generated video is fixed, and is 256x256.
4329 This source is useful in particular for testing encoding features.
4331 This source accepts an optional sequence of @var{key}=@var{value} pairs,
4332 separated by ":". The description of the accepted options follows.
4337 Specify the frame rate of the sourced video, as the number of frames
4338 generated per second. It has to be a string in the format
4339 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4340 number or a valid video frame rate abbreviation. The default value is
4344 Set the video duration of the sourced video. The accepted syntax is:
4349 See also the function @code{av_parse_time()}.
4351 If not specified, or the expressed duration is negative, the video is
4352 supposed to be generated forever.
4356 Set the number or the name of the test to perform. Supported tests are:
4371 Default value is "all", which will cycle through the list of all tests.
4374 For example the following:
4379 will generate a "dc_luma" test pattern.
4383 Provide a frei0r source.
4385 To enable compilation of this filter you need to install the frei0r
4386 header and configure FFmpeg with @code{--enable-frei0r}.
4388 The source supports the syntax:
4390 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
4393 @var{size} is the size of the video to generate, may be a string of the
4394 form @var{width}x@var{height} or a frame size abbreviation.
4395 @var{rate} is the rate of the video to generate, may be a string of
4396 the form @var{num}/@var{den} or a frame rate abbreviation.
4397 @var{src_name} is the name to the frei0r source to load. For more
4398 information regarding frei0r and how to set the parameters read the
4399 section @ref{frei0r} in the description of the video filters.
4401 For example, to generate a frei0r partik0l source with size 200x200
4402 and frame rate 10 which is overlayed on the overlay filter main input:
4404 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4409 Generate a life pattern.
4411 This source is based on a generalization of John Conway's life game.
4413 The sourced input represents a life grid, each pixel represents a cell
4414 which can be in one of two possible states, alive or dead. Every cell
4415 interacts with its eight neighbours, which are the cells that are
4416 horizontally, vertically, or diagonally adjacent.
4418 At each interaction the grid evolves according to the adopted rule,
4419 which specifies the number of neighbor alive cells which will make a
4420 cell stay alive or born. The @option{rule} option allows to specify
4423 This source accepts a list of options in the form of
4424 @var{key}=@var{value} pairs separated by ":". A description of the
4425 accepted options follows.
4429 Set the file from which to read the initial grid state. In the file,
4430 each non-whitespace character is considered an alive cell, and newline
4431 is used to delimit the end of each row.
4433 If this option is not specified, the initial grid is generated
4437 Set the video rate, that is the number of frames generated per second.
4440 @item random_fill_ratio, ratio
4441 Set the random fill ratio for the initial random grid. It is a
4442 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4443 It is ignored when a file is specified.
4445 @item random_seed, seed
4446 Set the seed for filling the initial random grid, must be an integer
4447 included between 0 and UINT32_MAX. If not specified, or if explicitly
4448 set to -1, the filter will try to use a good random seed on a best
4454 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4455 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4456 @var{NS} specifies the number of alive neighbor cells which make a
4457 live cell stay alive, and @var{NB} the number of alive neighbor cells
4458 which make a dead cell to become alive (i.e. to "born").
4459 "s" and "b" can be used in place of "S" and "B", respectively.
4461 Alternatively a rule can be specified by an 18-bits integer. The 9
4462 high order bits are used to encode the next cell state if it is alive
4463 for each number of neighbor alive cells, the low order bits specify
4464 the rule for "borning" new cells. Higher order bits encode for an
4465 higher number of neighbor cells.
4466 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4467 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4469 Default value is "S23/B3", which is the original Conway's game of life
4470 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4471 cells, and will born a new cell if there are three alive cells around
4475 Set the size of the output video.
4477 If @option{filename} is specified, the size is set by default to the
4478 same size of the input file. If @option{size} is set, it must contain
4479 the size specified in the input file, and the initial grid defined in
4480 that file is centered in the larger resulting area.
4482 If a filename is not specified, the size value defaults to "320x240"
4483 (used for a randomly generated initial grid).
4486 If set to 1, stitch the left and right grid edges together, and the
4487 top and bottom edges also. Defaults to 1.
4490 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4491 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4492 value from 0 to 255.
4495 Set the color of living (or new born) cells.
4498 Set the color of dead cells. If @option{mold} is set, this is the first color
4499 used to represent a dead cell.
4502 Set mold color, for definitely dead and moldy cells.
4505 @subsection Examples
4509 Read a grid from @file{pattern}, and center it on a grid of size
4512 life=f=pattern:s=300x300
4516 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4518 life=ratio=2/3:s=200x200
4522 Specify a custom rule for evolving a randomly generated grid:
4528 Full example with slow death effect (mold) using @command{ffplay}:
4530 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4534 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4536 The @code{color} source provides an uniformly colored input.
4538 The @code{nullsrc} source returns unprocessed video frames. It is
4539 mainly useful to be employed in analysis / debugging tools, or as the
4540 source for filters which ignore the input data.
4542 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4543 detecting RGB vs BGR issues. You should see a red, green and blue
4544 stripe from top to bottom.
4546 The @code{smptebars} source generates a color bars pattern, based on
4547 the SMPTE Engineering Guideline EG 1-1990.
4549 The @code{testsrc} source generates a test video pattern, showing a
4550 color pattern, a scrolling gradient and a timestamp. This is mainly
4551 intended for testing purposes.
4553 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4554 separated by ":". The description of the accepted options follows.
4559 Specify the color of the source, only used in the @code{color}
4560 source. It can be the name of a color (case insensitive match) or a
4561 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4562 default value is "black".
4565 Specify the size of the sourced video, it may be a string of the form
4566 @var{width}x@var{height}, or the name of a size abbreviation. The
4567 default value is "320x240".
4570 Specify the frame rate of the sourced video, as the number of frames
4571 generated per second. It has to be a string in the format
4572 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4573 number or a valid video frame rate abbreviation. The default value is
4577 Set the sample aspect ratio of the sourced video.
4580 Set the video duration of the sourced video. The accepted syntax is:
4582 [-]HH[:MM[:SS[.m...]]]
4585 See also the function @code{av_parse_time()}.
4587 If not specified, or the expressed duration is negative, the video is
4588 supposed to be generated forever.
4591 Set the number of decimals to show in the timestamp, only used in the
4592 @code{testsrc} source.
4594 The displayed timestamp value will correspond to the original
4595 timestamp value multiplied by the power of 10 of the specified
4596 value. Default value is 0.
4599 For example the following:
4601 testsrc=duration=5.3:size=qcif:rate=10
4604 will generate a video with a duration of 5.3 seconds, with size
4605 176x144 and a frame rate of 10 frames per second.
4607 The following graph description will generate a red source
4608 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4611 color=c=red@@0.2:s=qcif:r=10
4614 If the input content is to be ignored, @code{nullsrc} can be used. The
4615 following command generates noise in the luminance plane by employing
4616 the @code{geq} filter:
4618 nullsrc=s=256x256, geq=random(1)*255:128:128
4621 @c man end VIDEO SOURCES
4623 @chapter Video Sinks
4624 @c man begin VIDEO SINKS
4626 Below is a description of the currently available video sinks.
4630 Buffer video frames, and make them available to the end of the filter
4633 This sink is mainly intended for a programmatic use, in particular
4634 through the interface defined in @file{libavfilter/buffersink.h}.
4636 It does not require a string parameter in input, but you need to
4637 specify a pointer to a list of supported pixel formats terminated by
4638 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4639 when initializing this sink.
4643 Null video sink, do absolutely nothing with the input video. It is
4644 mainly useful as a template and to be employed in analysis / debugging
4647 @c man end VIDEO SINKS
4649 @chapter Multimedia Filters
4650 @c man begin MULTIMEDIA FILTERS
4652 Below is a description of the currently available multimedia filters.
4654 @section asendcmd, sendcmd
4656 Send commands to filters in the filtergraph.
4658 These filters read commands to be sent to other filters in the
4661 @code{asendcmd} must be inserted between two audio filters,
4662 @code{sendcmd} must be inserted between two video filters, but apart
4663 from that they act the same way.
4665 The specification of commands can be provided in the filter arguments
4666 with the @var{commands} option, or in a file specified by the
4667 @var{filename} option.
4669 These filters accept the following options:
4672 Set the commands to be read and sent to the other filters.
4674 Set the filename of the commands to be read and sent to the other
4678 @subsection Commands syntax
4680 A commands description consists of a sequence of interval
4681 specifications, comprising a list of commands to be executed when a
4682 particular event related to that interval occurs. The occurring event
4683 is typically the current frame time entering or leaving a given time
4686 An interval is specified by the following syntax:
4688 @var{START}[-@var{END}] @var{COMMANDS};
4691 The time interval is specified by the @var{START} and @var{END} times.
4692 @var{END} is optional and defaults to the maximum time.
4694 The current frame time is considered within the specified interval if
4695 it is included in the interval [@var{START}, @var{END}), that is when
4696 the time is greater or equal to @var{START} and is lesser than
4699 @var{COMMANDS} consists of a sequence of one or more command
4700 specifications, separated by ",", relating to that interval. The
4701 syntax of a command specification is given by:
4703 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4706 @var{FLAGS} is optional and specifies the type of events relating to
4707 the time interval which enable sending the specified command, and must
4708 be a non-null sequence of identifier flags separated by "+" or "|" and
4709 enclosed between "[" and "]".
4711 The following flags are recognized:
4714 The command is sent when the current frame timestamp enters the
4715 specified interval. In other words, the command is sent when the
4716 previous frame timestamp was not in the given interval, and the
4720 The command is sent when the current frame timestamp leaves the
4721 specified interval. In other words, the command is sent when the
4722 previous frame timestamp was in the given interval, and the
4726 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4729 @var{TARGET} specifies the target of the command, usually the name of
4730 the filter class or a specific filter instance name.
4732 @var{COMMAND} specifies the name of the command for the target filter.
4734 @var{ARG} is optional and specifies the optional list of argument for
4735 the given @var{COMMAND}.
4737 Between one interval specification and another, whitespaces, or
4738 sequences of characters starting with @code{#} until the end of line,
4739 are ignored and can be used to annotate comments.
4741 A simplified BNF description of the commands specification syntax
4744 @var{COMMAND_FLAG} ::= "enter" | "leave"
4745 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4746 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4747 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4748 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4749 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4752 @subsection Examples
4756 Specify audio tempo change at second 4:
4758 asendcmd=c='4.0 atempo tempo 1.5',atempo
4762 Specify a list of drawtext and hue commands in a file.
4764 # show text in the interval 5-10
4765 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4766 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4768 # desaturate the image in the interval 15-20
4769 15.0-20.0 [enter] hue reinit s=0,
4770 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4771 [leave] hue reinit s=1,
4772 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4774 # apply an exponential saturation fade-out effect, starting from time 25
4775 25 [enter] hue s=exp(t-25)
4778 A filtergraph allowing to read and process the above command list
4779 stored in a file @file{test.cmd}, can be specified with:
4781 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4785 @section asetpts, setpts
4787 Change the PTS (presentation timestamp) of the input frames.
4789 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4791 Accept in input an expression evaluated through the eval API, which
4792 can contain the following constants:
4796 frame rate, only defined for constant frame-rate video
4799 the presentation timestamp in input
4802 the count of the input frame, starting from 0.
4804 @item NB_CONSUMED_SAMPLES
4805 the number of consumed samples, not including the current frame (only
4809 the number of samples in the current frame (only audio)
4815 the PTS of the first frame
4818 the time in seconds of the first frame
4821 tell if the current frame is interlaced
4824 the time in seconds of the current frame
4830 original position in the file of the frame, or undefined if undefined
4831 for the current frame
4837 previous input time in seconds
4843 previous output time in seconds
4846 @subsection Examples
4850 Start counting PTS from zero
4856 Apply fast motion effect:
4862 Apply slow motion effect:
4868 Set fixed rate of 25 frames per second:
4874 Set fixed rate 25 fps with some jitter:
4876 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
4880 Apply an offset of 10 seconds to the input PTS:
4888 EBU R128 scanner filter. This filter takes an audio stream as input and outputs
4889 it unchanged. By default, it logs a message at a frequency of 10Hz with the
4890 Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
4891 Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
4893 The filter also has a video output (see the @var{video} option) with a real
4894 time graph to observe the loudness evolution. The graphic contains the logged
4895 message mentioned above, so it is not printed anymore when this option is set,
4896 unless the verbose logging is set. The main graphing area contains the
4897 short-term loudness (3 seconds of analysis), and the gauge on the right is for
4898 the momentary loudness (400 milliseconds).
4900 More information about the Loudness Recommendation EBU R128 on
4901 @url{http://tech.ebu.ch/loudness}.
4903 The filter accepts the following named parameters:
4908 Activate the video output. The audio stream is passed unchanged whether this
4909 option is set or no. The video stream will be the first output stream if
4910 activated. Default is @code{0}.
4913 Set the video size. This option is for video only. Default and minimum
4914 resolution is @code{640x480}.
4917 Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
4918 @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
4919 other integer value between this range is allowed.
4923 Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
4925 ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
4928 Run an analysis with @command{ffmpeg}:
4930 ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
4933 @section settb, asettb
4935 Set the timebase to use for the output frames timestamps.
4936 It is mainly useful for testing timebase configuration.
4938 It accepts in input an arithmetic expression representing a rational.
4939 The expression can contain the constants "AVTB" (the
4940 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
4943 The default value for the input is "intb".
4945 @subsection Examples
4949 Set the timebase to 1/25:
4955 Set the timebase to 1/10:
4961 Set the timebase to 1001/1000:
4967 Set the timebase to 2*intb:
4973 Set the default timebase value:
4981 Concatenate audio and video streams, joining them together one after the
4984 The filter works on segments of synchronized video and audio streams. All
4985 segments must have the same number of streams of each type, and that will
4986 also be the number of streams at output.
4988 The filter accepts the following named parameters:
4992 Set the number of segments. Default is 2.
4995 Set the number of output video streams, that is also the number of video
4996 streams in each segment. Default is 1.
4999 Set the number of output audio streams, that is also the number of video
5000 streams in each segment. Default is 0.
5003 Activate unsafe mode: do not fail if segments have a different format.
5007 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
5008 @var{a} audio outputs.
5010 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
5011 segment, in the same order as the outputs, then the inputs for the second
5014 Related streams do not always have exactly the same duration, for various
5015 reasons including codec frame size or sloppy authoring. For that reason,
5016 related synchronized streams (e.g. a video and its audio track) should be
5017 concatenated at once. The concat filter will use the duration of the longest
5018 stream in each segment (except the last one), and if necessary pad shorter
5019 audio streams with silence.
5021 For this filter to work correctly, all segments must start at timestamp 0.
5023 All corresponding streams must have the same parameters in all segments; the
5024 filtering system will automatically select a common pixel format for video
5025 streams, and a common sample format, sample rate and channel layout for
5026 audio streams, but other settings, such as resolution, must be converted
5027 explicitly by the user.
5029 Different frame rates are acceptable but will result in variable frame rate
5030 at output; be sure to configure the output file to handle it.
5035 Concatenate an opening, an episode and an ending, all in bilingual version
5036 (video in stream 0, audio in streams 1 and 2):
5038 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
5039 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
5040 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
5041 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
5045 Concatenate two parts, handling audio and video separately, using the
5046 (a)movie sources, and adjusting the resolution:
5048 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
5049 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
5050 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
5052 Note that a desync will happen at the stitch if the audio and video streams
5053 do not have exactly the same duration in the first file.
5057 @section showspectrum
5059 Convert input audio to a video output, representing the audio frequency
5062 The filter accepts the following named parameters:
5065 Specify the video size for the output. Default value is @code{640x480}.
5067 Specify if the spectrum should slide along the window. Default value is
5071 The usage is very similar to the showwaves filter; see the examples in that
5076 Convert input audio to a video output, representing the samples waves.
5078 The filter accepts the following named parameters:
5082 Set the number of samples which are printed on the same column. A
5083 larger value will decrease the frame rate. Must be a positive
5084 integer. This option can be set only if the value for @var{rate}
5085 is not explicitly specified.
5088 Set the (approximate) output frame rate. This is done by setting the
5089 option @var{n}. Default value is "25".
5092 Specify the video size for the output. Default value is "600x240".
5095 Some examples follow.
5098 Output the input file audio and the corresponding video representation
5101 amovie=a.mp3,asplit[out0],showwaves[out1]
5105 Create a synthetic signal and show it with showwaves, forcing a
5106 framerate of 30 frames per second:
5108 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
5112 @c man end MULTIMEDIA FILTERS
5114 @chapter Multimedia Sources
5115 @c man begin MULTIMEDIA SOURCES
5117 Below is a description of the currently available multimedia sources.
5121 This is the same as @ref{src_movie} source, except it selects an audio
5127 Read audio and/or video stream(s) from a movie container.
5129 It accepts the syntax: @var{movie_name}[:@var{options}] where
5130 @var{movie_name} is the name of the resource to read (not necessarily
5131 a file but also a device or a stream accessed through some protocol),
5132 and @var{options} is an optional sequence of @var{key}=@var{value}
5133 pairs, separated by ":".
5135 The description of the accepted options follows.
5139 @item format_name, f
5140 Specifies the format assumed for the movie to read, and can be either
5141 the name of a container or an input device. If not specified the
5142 format is guessed from @var{movie_name} or by probing.
5144 @item seek_point, sp
5145 Specifies the seek point in seconds, the frames will be output
5146 starting from this seek point, the parameter is evaluated with
5147 @code{av_strtod} so the numerical value may be suffixed by an IS
5148 postfix. Default value is "0".
5151 Specifies the streams to read. Several streams can be specified, separated
5152 by "+". The source will then have as many outputs, in the same order. The
5153 syntax is explained in the @ref{Stream specifiers} chapter. Two special
5154 names, "dv" and "da" specify respectively the default (best suited) video
5155 and audio stream. Default is "dv", or "da" if the filter is called as
5158 @item stream_index, si
5159 Specifies the index of the video stream to read. If the value is -1,
5160 the best suited video stream will be automatically selected. Default
5161 value is "-1". Deprecated. If the filter is called "amovie", it will select
5162 audio instead of video.
5165 Specifies how many times to read the stream in sequence.
5166 If the value is less than 1, the stream will be read again and again.
5167 Default value is "1".
5169 Note that when the movie is looped the source timestamps are not
5170 changed, so it will generate non monotonically increasing timestamps.
5173 This filter allows to overlay a second video on top of main input of
5174 a filtergraph as shown in this graph:
5176 input -----------> deltapts0 --> overlay --> output
5179 movie --> scale--> deltapts1 -------+
5182 Some examples follow.
5186 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
5187 on top of the input labelled as "in":
5189 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5190 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5194 Read from a video4linux2 device, and overlay it on top of the input
5197 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5198 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5202 Read the first video stream and the audio stream with id 0x81 from
5203 dvd.vob; the video is connected to the pad named "video" and the audio is
5204 connected to the pad named "audio":
5206 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
5210 @c man end MULTIMEDIA SOURCES