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 @c man end FILTERGRAPH DESCRIPTION
196 @chapter Audio Filters
197 @c man begin AUDIO FILTERS
199 When you configure your FFmpeg build, you can disable any of the
200 existing filters using @code{--disable-filters}.
201 The configure output will show the audio filters included in your
204 Below is a description of the currently available audio filters.
208 Convert the input audio format to the specified formats.
210 The filter accepts a string of the form:
211 "@var{sample_format}:@var{channel_layout}".
213 @var{sample_format} specifies the sample format, and can be a string or the
214 corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p'
215 suffix for a planar sample format.
217 @var{channel_layout} specifies the channel layout, and can be a string
218 or the corresponding number value defined in @file{libavutil/audioconvert.h}.
220 The special parameter "auto", signifies that the filter will
221 automatically select the output format depending on the output filter.
223 Some examples follow.
227 Convert input to float, planar, stereo:
233 Convert input to unsigned 8-bit, automatically select out channel layout:
241 Convert the input audio to one of the specified formats. The framework will
242 negotiate the most appropriate format to minimize conversions.
244 The filter accepts the following named parameters:
248 A comma-separated list of requested sample formats.
251 A comma-separated list of requested sample rates.
253 @item channel_layouts
254 A comma-separated list of requested channel layouts.
258 If a parameter is omitted, all values are allowed.
260 For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
262 aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo
267 Merge two or more audio streams into a single multi-channel stream.
269 The filter accepts the following named options:
274 Set the number of inputs. Default is 2.
278 If the channel layouts of the inputs are disjoint, and therefore compatible,
279 the channel layout of the output will be set accordingly and the channels
280 will be reordered as necessary. If the channel layouts of the inputs are not
281 disjoint, the output will have all the channels of the first input then all
282 the channels of the second input, in that order, and the channel layout of
283 the output will be the default value corresponding to the total number of
286 For example, if the first input is in 2.1 (FL+FR+LF) and the second input
287 is FC+BL+BR, then the output will be in 5.1, with the channels in the
288 following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
289 first input, b1 is the first channel of the second input).
291 On the other hand, if both input are in stereo, the output channels will be
292 in the default order: a1, a2, b1, b2, and the channel layout will be
293 arbitrarily set to 4.0, which may or may not be the expected value.
295 All inputs must have the same sample rate, and format.
297 If inputs do not have the same duration, the output will stop with the
300 Example: merge two mono files into a stereo stream:
302 amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
305 Example: multiple merges:
308 amovie=input.mkv:si=0 [a0];
309 amovie=input.mkv:si=1 [a1];
310 amovie=input.mkv:si=2 [a2];
311 amovie=input.mkv:si=3 [a3];
312 amovie=input.mkv:si=4 [a4];
313 amovie=input.mkv:si=5 [a5];
314 [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
319 Mixes multiple audio inputs into a single output.
323 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
325 will mix 3 input audio streams to a single output with the same duration as the
326 first input and a dropout transition time of 3 seconds.
328 The filter accepts the following named parameters:
332 Number of inputs. If unspecified, it defaults to 2.
335 How to determine the end-of-stream.
339 Duration of longest input. (default)
342 Duration of shortest input.
345 Duration of first input.
349 @item dropout_transition
350 Transition time, in seconds, for volume renormalization when an input
351 stream ends. The default value is 2 seconds.
357 Pass the audio source unchanged to the output.
361 Resample the input audio to the specified sample rate.
363 The filter accepts exactly one parameter, the output sample rate. If not
364 specified then the filter will automatically convert between its input
365 and output sample rates.
367 For example, to resample the input audio to 44100Hz:
372 @section asetnsamples
374 Set the number of samples per each output audio frame.
376 The last output packet may contain a different number of samples, as
377 the filter will flush all the remaining samples when the input audio
380 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
385 @item nb_out_samples, n
386 Set the number of frames per each output audio frame. The number is
387 intended as the number of samples @emph{per each channel}.
388 Default value is 1024.
391 If set to 1, the filter will pad the last audio frame with zeroes, so
392 that the last frame will contain the same number of samples as the
393 previous ones. Default value is 1.
396 For example, to set the number of per-frame samples to 1234 and
397 disable padding for the last frame, use:
399 asetnsamples=n=1234:p=0
404 Show a line containing various information for each input audio frame.
405 The input audio is not modified.
407 The shown line contains a sequence of key/value pairs of the form
408 @var{key}:@var{value}.
410 A description of each shown parameter follows:
414 sequential number of the input frame, starting from 0
417 presentation TimeStamp of the input frame, expressed as a number of
418 time base units. The time base unit depends on the filter input pad, and
419 is usually 1/@var{sample_rate}.
422 presentation TimeStamp of the input frame, expressed as a number of
426 position of the frame in the input stream, -1 if this information in
427 unavailable and/or meaningless (for example in case of synthetic audio)
433 channel layout description
436 number of samples (per each channel) contained in the filtered frame
439 sample rate for the audio frame
442 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
445 Adler-32 checksum (printed in hexadecimal) for each input frame plane,
446 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3} @var{c4} @var{c5}
452 Split input audio into several identical outputs.
454 The filter accepts a single parameter which specifies the number of outputs. If
455 unspecified, it defaults to 2.
459 [in] asplit [out0][out1]
462 will create two separate outputs from the same input.
464 To create 3 or more outputs, you need to specify the number of
467 [in] asplit=3 [out0][out1][out2]
471 ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
473 will create 5 copies of the input audio.
478 Forward two audio streams and control the order the buffers are forwarded.
480 The argument to the filter is an expression deciding which stream should be
481 forwarded next: if the result is negative, the first stream is forwarded; if
482 the result is positive or zero, the second stream is forwarded. It can use
483 the following variables:
487 number of buffers forwarded so far on each stream
489 number of samples forwarded so far on each stream
491 current timestamp of each stream
494 The default value is @code{t1-t2}, which means to always forward the stream
495 that has a smaller timestamp.
497 Example: stress-test @code{amerge} by randomly sending buffers on the wrong
498 input, while avoiding too much of a desynchronization:
500 amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
501 [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
509 The filter accepts exactly one parameter, the audio tempo. If not
510 specified then the filter will assume nominal 1.0 tempo. Tempo must
511 be in the [0.5, 2.0] range.
513 For example, to slow down audio to 80% tempo:
518 For example, to speed up audio to 125% tempo:
525 Make audio easier to listen to on headphones.
527 This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
528 so that when listened to on headphones the stereo image is moved from
529 inside your head (standard for headphones) to outside and in front of
530 the listener (standard for speakers).
536 Mix channels with specific gain levels. The filter accepts the output
537 channel layout followed by a set of channels definitions.
539 This filter is also designed to remap efficiently the channels of an audio
542 The filter accepts parameters of the form:
543 "@var{l}:@var{outdef}:@var{outdef}:..."
547 output channel layout or number of channels
550 output channel specification, of the form:
551 "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
554 output channel to define, either a channel name (FL, FR, etc.) or a channel
555 number (c0, c1, etc.)
558 multiplicative coefficient for the channel, 1 leaving the volume unchanged
561 input channel to use, see out_name for details; it is not possible to mix
562 named and numbered input channels
565 If the `=' in a channel specification is replaced by `<', then the gains for
566 that specification will be renormalized so that the total is 1, thus
567 avoiding clipping noise.
569 @subsection Mixing examples
571 For example, if you want to down-mix from stereo to mono, but with a bigger
572 factor for the left channel:
574 pan=1:c0=0.9*c0+0.1*c1
577 A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
580 pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
583 Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
584 that should be preferred (see "-ac" option) unless you have very specific
587 @subsection Remapping examples
589 The channel remapping will be effective if, and only if:
592 @item gain coefficients are zeroes or ones,
593 @item only one input per channel output,
596 If all these conditions are satisfied, the filter will notify the user ("Pure
597 channel mapping detected"), and use an optimized and lossless method to do the
600 For example, if you have a 5.1 source and want a stereo audio stream by
601 dropping the extra channels:
603 pan="stereo: c0=FL : c1=FR"
606 Given the same source, you can also switch front left and front right channels
607 and keep the input channel layout:
609 pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
612 If the input is a stereo audio stream, you can mute the front left channel (and
613 still keep the stereo channel layout) with:
618 Still with a stereo audio stream input, you can copy the right channel in both
619 front left and right:
621 pan="stereo: c0=FR : c1=FR"
624 @section silencedetect
626 Detect silence in an audio stream.
628 This filter logs a message when it detects that the input audio volume is less
629 or equal to a noise tolerance value for a duration greater or equal to the
630 minimum detected noise duration.
632 The printed times and duration are expressed in seconds.
636 Set silence duration until notification (default is 2 seconds).
639 Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
640 specified value) or amplitude ratio. Default is -60dB, or 0.001.
643 Detect 5 seconds of silence with -50dB noise tolerance:
645 silencedetect=n=-50dB:d=5
648 Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
649 tolerance in @file{silence.mp3}:
651 ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
656 Adjust the input audio volume.
658 The filter accepts exactly one parameter @var{vol}, which expresses
659 how the audio volume will be increased or decreased.
661 Output values are clipped to the maximum value.
663 If @var{vol} is expressed as a decimal number, the output audio
664 volume is given by the relation:
666 @var{output_volume} = @var{vol} * @var{input_volume}
669 If @var{vol} is expressed as a decimal number followed by the string
670 "dB", the value represents the requested change in decibels of the
671 input audio power, and the output audio volume is given by the
674 @var{output_volume} = 10^(@var{vol}/20) * @var{input_volume}
677 Otherwise @var{vol} is considered an expression and its evaluated
678 value is used for computing the output audio volume according to the
681 Default value for @var{vol} is 1.0.
687 Half the input audio volume:
692 The above example is equivalent to:
698 Decrease input audio power by 12 decibels:
704 @section volumedetect
706 Detect the volume of the input video.
708 The filter has no parameters. The input is not modified. Statistics about
709 the volume will be printed in the log when the input stream end is reached.
711 In particular it will show the mean volume (root mean square), maximum
712 volume (on a per-sample basis), and the beginning of an histogram of the
713 registered volume values (from the maximum value to a cumulated 1/1000 of
716 All volumes are in decibels relative to the maximum PCM value.
718 Here is an excerpt of the output:
720 [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
721 [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
722 [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
723 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
724 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
725 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
726 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
727 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
728 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
734 The mean square energy is approximately -27 dB, or 10^-2.7.
736 The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
738 There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
741 In other words, raising the volume by +4 dB does not cause any clipping,
742 raising it by +5 dB causes clipping for 6 samples, etc.
745 Synchronize audio data with timestamps by squeezing/stretching it and/or
746 dropping samples/adding silence when needed.
748 The filter accepts the following named parameters:
752 Enable stretching/squeezing the data to make it match the timestamps. Disabled
753 by default. When disabled, time gaps are covered with silence.
756 Minimum difference between timestamps and audio data (in seconds) to trigger
757 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
758 this filter, try setting this parameter to 0.
761 Maximum compensation in samples per second. Relevant only with compensate=1.
765 Assume the first pts should be this value.
766 This allows for padding/trimming at the start of stream. By default, no
767 assumption is made about the first frame's expected pts, so no padding or
768 trimming is done. For example, this could be set to 0 to pad the beginning with
769 silence if an audio stream starts after the video stream.
773 @section channelsplit
774 Split each channel in input audio stream into a separate output stream.
776 This filter accepts the following named parameters:
779 Channel layout of the input stream. Default is "stereo".
782 For example, assuming a stereo input MP3 file
784 ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
786 will create an output Matroska file with two audio streams, one containing only
787 the left channel and the other the right channel.
789 To split a 5.1 WAV file into per-channel files
791 ffmpeg -i in.wav -filter_complex
792 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
793 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
794 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
799 Remap input channels to new locations.
801 This filter accepts the following named parameters:
804 Channel layout of the output stream.
807 Map channels from input to output. The argument is a comma-separated list of
808 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
809 @var{in_channel} form. @var{in_channel} can be either the name of the input
810 channel (e.g. FL for front left) or its index in the input channel layout.
811 @var{out_channel} is the name of the output channel or its index in the output
812 channel layout. If @var{out_channel} is not given then it is implicitly an
813 index, starting with zero and increasing by one for each mapping.
816 If no mapping is present, the filter will implicitly map input channels to
817 output channels preserving index.
819 For example, assuming a 5.1+downmix input MOV file
821 ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
823 will create an output WAV file tagged as stereo from the downmix channels of
826 To fix a 5.1 WAV improperly encoded in AAC's native channel order
828 ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
832 Join multiple input streams into one multi-channel stream.
834 The filter accepts the following named parameters:
838 Number of input streams. Defaults to 2.
841 Desired output channel layout. Defaults to stereo.
844 Map channels from inputs to output. The argument is a comma-separated list of
845 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
846 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
847 can be either the name of the input channel (e.g. FL for front left) or its
848 index in the specified input stream. @var{out_channel} is the name of the output
852 The filter will attempt to guess the mappings when those are not specified
853 explicitly. It does so by first trying to find an unused matching input channel
854 and if that fails it picks the first unused input channel.
856 E.g. to join 3 inputs (with properly set channel layouts)
858 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
861 To build a 5.1 output from 6 single-channel streams:
863 ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
864 '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'
869 Convert the audio sample format, sample rate and channel layout. This filter is
870 not meant to be used directly.
872 @c man end AUDIO FILTERS
874 @chapter Audio Sources
875 @c man begin AUDIO SOURCES
877 Below is a description of the currently available audio sources.
881 Buffer audio frames, and make them available to the filter chain.
883 This source is mainly intended for a programmatic use, in particular
884 through the interface defined in @file{libavfilter/asrc_abuffer.h}.
886 It accepts the following mandatory parameters:
887 @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}
892 The sample rate of the incoming audio buffers.
895 The sample format of the incoming audio buffers.
896 Either a sample format name or its corresponging integer representation from
897 the enum AVSampleFormat in @file{libavutil/samplefmt.h}
900 The channel layout of the incoming audio buffers.
901 Either a channel layout name from channel_layout_map in
902 @file{libavutil/audioconvert.c} or its corresponding integer representation
903 from the AV_CH_LAYOUT_* macros in @file{libavutil/audioconvert.h}
909 abuffer=44100:s16p:stereo
912 will instruct the source to accept planar 16bit signed stereo at 44100Hz.
913 Since the sample format with name "s16p" corresponds to the number
914 6 and the "stereo" channel layout corresponds to the value 0x3, this is
922 Generate an audio signal specified by an expression.
924 This source accepts in input one or more expressions (one for each
925 channel), which are evaluated and used to generate a corresponding
928 It accepts the syntax: @var{exprs}[::@var{options}].
929 @var{exprs} is a list of expressions separated by ":", one for each
930 separate channel. In case the @var{channel_layout} is not
931 specified, the selected channel layout depends on the number of
932 provided expressions.
934 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
937 The description of the accepted options follows.
941 @item channel_layout, c
942 Set the channel layout. The number of channels in the specified layout
943 must be equal to the number of specified expressions.
946 Set the minimum duration of the sourced audio. See the function
947 @code{av_parse_time()} for the accepted format.
948 Note that the resulting duration may be greater than the specified
949 duration, as the generated audio is always cut at the end of a
952 If not specified, or the expressed duration is negative, the audio is
953 supposed to be generated forever.
956 Set the number of samples per channel per each output frame,
960 Specify the sample rate, default to 44100.
963 Each expression in @var{exprs} can contain the following constants:
967 number of the evaluated sample, starting from 0
970 time of the evaluated sample expressed in seconds, starting from 0
989 Generate a sin signal with frequency of 440 Hz, set sample rate to
992 aevalsrc="sin(440*2*PI*t)::s=8000"
996 Generate a two channels signal, specify the channel layout (Front
997 Center + Back Center) explicitly:
999 aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
1003 Generate white noise:
1005 aevalsrc="-2+random(0)"
1009 Generate an amplitude modulated signal:
1011 aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
1015 Generate 2.5 Hz binaural beats on a 360 Hz carrier:
1017 aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
1024 Null audio source, return unprocessed audio frames. It is mainly useful
1025 as a template and to be employed in analysis / debugging tools, or as
1026 the source for filters which ignore the input data (for example the sox
1029 It accepts an optional sequence of @var{key}=@var{value} pairs,
1032 The description of the accepted options follows.
1036 @item sample_rate, s
1037 Specify the sample rate, and defaults to 44100.
1039 @item channel_layout, cl
1041 Specify the channel layout, and can be either an integer or a string
1042 representing a channel layout. The default value of @var{channel_layout}
1045 Check the channel_layout_map definition in
1046 @file{libavcodec/audioconvert.c} for the mapping between strings and
1047 channel layout values.
1050 Set the number of samples per requested frames.
1054 Follow some examples:
1056 # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
1057 anullsrc=r=48000:cl=4
1060 anullsrc=r=48000:cl=mono
1064 Buffer audio frames, and make them available to the filter chain.
1066 This source is not intended to be part of user-supplied graph descriptions but
1067 for insertion by calling programs through the interface defined in
1068 @file{libavfilter/buffersrc.h}.
1070 It accepts the following named parameters:
1074 Timebase which will be used for timestamps of submitted frames. It must be
1075 either a floating-point number or in @var{numerator}/@var{denominator} form.
1081 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
1083 @item channel_layout
1084 Channel layout of the audio data, in the form that can be accepted by
1085 @code{av_get_channel_layout()}.
1088 All the parameters need to be explicitly defined.
1092 Synthesize a voice utterance using the libflite library.
1094 To enable compilation of this filter you need to configure FFmpeg with
1095 @code{--enable-libflite}.
1097 Note that the flite library is not thread-safe.
1099 The source accepts parameters as a list of @var{key}=@var{value} pairs,
1102 The description of the accepted parameters follows.
1107 If set to 1, list the names of the available voices and exit
1108 immediately. Default value is 0.
1111 Set the maximum number of samples per frame. Default value is 512.
1114 Set the filename containing the text to speak.
1117 Set the text to speak.
1120 Set the voice to use for the speech synthesis. Default value is
1121 @code{kal}. See also the @var{list_voices} option.
1124 @subsection Examples
1128 Read from file @file{speech.txt}, and synthetize the text using the
1129 standard flite voice:
1131 flite=textfile=speech.txt
1135 Read the specified text selecting the @code{slt} voice:
1137 flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1141 Input text to ffmpeg:
1143 ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1147 Make @file{ffplay} speak the specified text, using @code{flite} and
1148 the @code{lavfi} device:
1150 ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
1154 For more information about libflite, check:
1155 @url{http://www.speech.cs.cmu.edu/flite/}
1157 @c man end AUDIO SOURCES
1159 @chapter Audio Sinks
1160 @c man begin AUDIO SINKS
1162 Below is a description of the currently available audio sinks.
1164 @section abuffersink
1166 Buffer audio frames, and make them available to the end of filter chain.
1168 This sink is mainly intended for programmatic use, in particular
1169 through the interface defined in @file{libavfilter/buffersink.h}.
1171 It requires a pointer to an AVABufferSinkContext structure, which
1172 defines the incoming buffers' formats, to be passed as the opaque
1173 parameter to @code{avfilter_init_filter} for initialization.
1177 Null audio sink, do absolutely nothing with the input audio. It is
1178 mainly useful as a template and to be employed in analysis / debugging
1181 @section abuffersink
1182 This sink is intended for programmatic use. Frames that arrive on this sink can
1183 be retrieved by the calling program using the interface defined in
1184 @file{libavfilter/buffersink.h}.
1186 This filter accepts no parameters.
1188 @c man end AUDIO SINKS
1190 @chapter Video Filters
1191 @c man begin VIDEO FILTERS
1193 When you configure your FFmpeg build, you can disable any of the
1194 existing filters using @code{--disable-filters}.
1195 The configure output will show the video filters included in your
1198 Below is a description of the currently available video filters.
1200 @section alphaextract
1202 Extract the alpha component from the input as a grayscale video. This
1203 is especially useful with the @var{alphamerge} filter.
1207 Add or replace the alpha component of the primary input with the
1208 grayscale value of a second input. This is intended for use with
1209 @var{alphaextract} to allow the transmission or storage of frame
1210 sequences that have alpha in a format that doesn't support an alpha
1213 For example, to reconstruct full frames from a normal YUV-encoded video
1214 and a separate video created with @var{alphaextract}, you might use:
1216 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
1219 Since this filter is designed for reconstruction, it operates on frame
1220 sequences without considering timestamps, and terminates when either
1221 input reaches end of stream. This will cause problems if your encoding
1222 pipeline drops frames. If you're trying to apply an image as an
1223 overlay to a video stream, consider the @var{overlay} filter instead.
1227 Draw ASS (Advanced Substation Alpha) subtitles on top of input video
1228 using the libass library.
1230 To enable compilation of this filter you need to configure FFmpeg with
1231 @code{--enable-libass}.
1233 This filter accepts the following named options, expressed as a
1234 sequence of @var{key}=@var{value} pairs, separated by ":".
1238 Set the filename of the ASS file to read. It must be specified.
1241 Specify the size of the original video, the video for which the ASS file
1242 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
1243 necessary to correctly scale the fonts if the aspect ratio has been changed.
1246 If the first key is not specified, it is assumed that the first value
1247 specifies the @option{filename}.
1249 For example, to render the file @file{sub.ass} on top of the input
1250 video, use the command:
1255 which is equivalent to:
1257 ass=filename=sub.ass
1262 Compute the bounding box for the non-black pixels in the input frame
1265 This filter computes the bounding box containing all the pixels with a
1266 luminance value greater than the minimum allowed value.
1267 The parameters describing the bounding box are printed on the filter
1270 @section blackdetect
1272 Detect video intervals that are (almost) completely black. Can be
1273 useful to detect chapter transitions, commercials, or invalid
1274 recordings. Output lines contains the time for the start, end and
1275 duration of the detected black interval expressed in seconds.
1277 In order to display the output lines, you need to set the loglevel at
1278 least to the AV_LOG_INFO value.
1280 This filter accepts a list of options in the form of
1281 @var{key}=@var{value} pairs separated by ":". A description of the
1282 accepted options follows.
1285 @item black_min_duration, d
1286 Set the minimum detected black duration expressed in seconds. It must
1287 be a non-negative floating point number.
1289 Default value is 2.0.
1291 @item picture_black_ratio_th, pic_th
1292 Set the threshold for considering a picture "black".
1293 Express the minimum value for the ratio:
1295 @var{nb_black_pixels} / @var{nb_pixels}
1298 for which a picture is considered black.
1299 Default value is 0.98.
1301 @item pixel_black_th, pix_th
1302 Set the threshold for considering a pixel "black".
1304 The threshold expresses the maximum pixel luminance value for which a
1305 pixel is considered "black". The provided value is scaled according to
1306 the following equation:
1308 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
1311 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
1312 the input video format, the range is [0-255] for YUV full-range
1313 formats and [16-235] for YUV non full-range formats.
1315 Default value is 0.10.
1318 The following example sets the maximum pixel threshold to the minimum
1319 value, and detects only black intervals of 2 or more seconds:
1321 blackdetect=d=2:pix_th=0.00
1326 Detect frames that are (almost) completely black. Can be useful to
1327 detect chapter transitions or commercials. Output lines consist of
1328 the frame number of the detected frame, the percentage of blackness,
1329 the position in the file if known or -1 and the timestamp in seconds.
1331 In order to display the output lines, you need to set the loglevel at
1332 least to the AV_LOG_INFO value.
1334 The filter accepts the syntax:
1336 blackframe[=@var{amount}:[@var{threshold}]]
1339 @var{amount} is the percentage of the pixels that have to be below the
1340 threshold, and defaults to 98.
1342 @var{threshold} is the threshold below which a pixel value is
1343 considered black, and defaults to 32.
1347 Apply boxblur algorithm to the input video.
1349 This filter accepts the parameters:
1350 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
1352 Chroma and alpha parameters are optional, if not specified they default
1353 to the corresponding values set for @var{luma_radius} and
1356 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
1357 the radius in pixels of the box used for blurring the corresponding
1358 input plane. They are expressions, and can contain the following
1362 the input width and height in pixels
1365 the input chroma image width and height in pixels
1368 horizontal and vertical chroma subsample values. For example for the
1369 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1372 The radius must be a non-negative number, and must not be greater than
1373 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
1374 and of @code{min(cw,ch)/2} for the chroma planes.
1376 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
1377 how many times the boxblur filter is applied to the corresponding
1380 Some examples follow:
1385 Apply a boxblur filter with luma, chroma, and alpha radius
1392 Set luma radius to 2, alpha and chroma radius to 0
1398 Set luma and chroma radius to a fraction of the video dimension
1400 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
1405 @section colormatrix
1407 The colormatrix filter allows conversion between any of the following color
1408 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
1409 and FCC (@var{fcc}).
1411 The syntax of the parameters is @var{source}:@var{destination}:
1414 colormatrix=bt601:smpte240m
1419 Copy the input source unchanged to the output. Mainly useful for
1424 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
1426 The @var{keep_aspect} parameter is optional, if specified and set to a
1427 non-zero value will force the output display aspect ratio to be the
1428 same of the input, by changing the output sample aspect ratio.
1430 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1431 expressions containing the following constants:
1435 the computed values for @var{x} and @var{y}. They are evaluated for
1439 the input width and height
1442 same as @var{in_w} and @var{in_h}
1445 the output (cropped) width and height
1448 same as @var{out_w} and @var{out_h}
1451 same as @var{iw} / @var{ih}
1454 input sample aspect ratio
1457 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1460 horizontal and vertical chroma subsample values. For example for the
1461 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1464 the number of input frame, starting from 0
1467 the position in the file of the input frame, NAN if unknown
1470 timestamp expressed in seconds, NAN if the input timestamp is unknown
1474 The @var{out_w} and @var{out_h} parameters specify the expressions for
1475 the width and height of the output (cropped) video. They are
1476 evaluated just at the configuration of the filter.
1478 The default value of @var{out_w} is "in_w", and the default value of
1479 @var{out_h} is "in_h".
1481 The expression for @var{out_w} may depend on the value of @var{out_h},
1482 and the expression for @var{out_h} may depend on @var{out_w}, but they
1483 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1484 evaluated after @var{out_w} and @var{out_h}.
1486 The @var{x} and @var{y} parameters specify the expressions for the
1487 position of the top-left corner of the output (non-cropped) area. They
1488 are evaluated for each frame. If the evaluated value is not valid, it
1489 is approximated to the nearest valid value.
1491 The default value of @var{x} is "(in_w-out_w)/2", and the default
1492 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
1493 the center of the input image.
1495 The expression for @var{x} may depend on @var{y}, and the expression
1496 for @var{y} may depend on @var{x}.
1498 Follow some examples:
1500 # crop the central input area with size 100x100
1503 # crop the central input area with size 2/3 of the input video
1504 "crop=2/3*in_w:2/3*in_h"
1506 # crop the input video central square
1509 # delimit the rectangle with the top-left corner placed at position
1510 # 100:100 and the right-bottom corner corresponding to the right-bottom
1511 # corner of the input image.
1512 crop=in_w-100:in_h-100:100:100
1514 # crop 10 pixels from the left and right borders, and 20 pixels from
1515 # the top and bottom borders
1516 "crop=in_w-2*10:in_h-2*20"
1518 # keep only the bottom right quarter of the input image
1519 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1521 # crop height for getting Greek harmony
1522 "crop=in_w:1/PHI*in_w"
1525 "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)"
1527 # erratic camera effect depending on timestamp
1528 "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)"
1530 # set x depending on the value of y
1531 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1536 Auto-detect crop size.
1538 Calculate necessary cropping parameters and prints the recommended
1539 parameters through the logging system. The detected dimensions
1540 correspond to the non-black area of the input video.
1542 It accepts the syntax:
1544 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1550 Threshold, which can be optionally specified from nothing (0) to
1551 everything (255), defaults to 24.
1554 Value which the width/height should be divisible by, defaults to
1555 16. The offset is automatically adjusted to center the video. Use 2 to
1556 get only even dimensions (needed for 4:2:2 video). 16 is best when
1557 encoding to most video codecs.
1560 Counter that determines after how many frames cropdetect will reset
1561 the previously detected largest video area and start over to detect
1562 the current optimal crop area. Defaults to 0.
1564 This can be useful when channel logos distort the video area. 0
1565 indicates never reset and return the largest area encountered during
1571 This filter drops frames that do not differ greatly from the previous
1572 frame in order to reduce framerate. The main use of this filter is
1573 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1574 it could in theory be used for fixing movies that were
1575 inverse-telecined incorrectly.
1577 It accepts the following parameters:
1578 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1583 Set the maximum number of consecutive frames which can be dropped (if
1584 positive), or the minimum interval between dropped frames (if
1585 negative). If the value is 0, the frame is dropped unregarding the
1586 number of previous sequentially dropped frames.
1591 Set the dropping threshold values.
1593 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1594 represent actual pixel value differences, so a threshold of 64
1595 corresponds to 1 unit of difference for each pixel, or the same spread
1596 out differently over the block.
1598 A frame is a candidate for dropping if no 8x8 blocks differ by more
1599 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1600 meaning the whole image) differ by more than a threshold of @var{lo}.
1602 Default value for @var{hi} is 64*12, default value for @var{lo} is
1603 64*5, and default value for @var{frac} is 0.33.
1608 Suppress a TV station logo by a simple interpolation of the surrounding
1609 pixels. Just set a rectangle covering the logo and watch it disappear
1610 (and sometimes something even uglier appear - your mileage may vary).
1612 The filter accepts parameters as a string of the form
1613 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1614 @var{key}=@var{value} pairs, separated by ":".
1616 The description of the accepted parameters follows.
1621 Specify the top left corner coordinates of the logo. They must be
1625 Specify the width and height of the logo to clear. They must be
1629 Specify the thickness of the fuzzy edge of the rectangle (added to
1630 @var{w} and @var{h}). The default value is 4.
1633 When set to 1, a green rectangle is drawn on the screen to simplify
1634 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1635 @var{band} is set to 4. The default value is 0.
1639 Some examples follow.
1644 Set a rectangle covering the area with top left corner coordinates 0,0
1645 and size 100x77, setting a band of size 10:
1647 delogo=0:0:100:77:10
1651 As the previous example, but use named options:
1653 delogo=x=0:y=0:w=100:h=77:band=10
1660 Attempt to fix small changes in horizontal and/or vertical shift. This
1661 filter helps remove camera shake from hand-holding a camera, bumping a
1662 tripod, moving on a vehicle, etc.
1664 The filter accepts parameters as a string of the form
1665 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1667 A description of the accepted parameters follows.
1672 Specify a rectangular area where to limit the search for motion
1674 If desired the search for motion vectors can be limited to a
1675 rectangular area of the frame defined by its top left corner, width
1676 and height. These parameters have the same meaning as the drawbox
1677 filter which can be used to visualise the position of the bounding
1680 This is useful when simultaneous movement of subjects within the frame
1681 might be confused for camera motion by the motion vector search.
1683 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1684 then the full frame is used. This allows later options to be set
1685 without specifying the bounding box for the motion vector search.
1687 Default - search the whole frame.
1690 Specify the maximum extent of movement in x and y directions in the
1691 range 0-64 pixels. Default 16.
1694 Specify how to generate pixels to fill blanks at the edge of the
1695 frame. An integer from 0 to 3 as follows:
1698 Fill zeroes at blank locations
1700 Original image at blank locations
1702 Extruded edge value at blank locations
1704 Mirrored edge at blank locations
1707 The default setting is mirror edge at blank locations.
1710 Specify the blocksize to use for motion search. Range 4-128 pixels,
1714 Specify the contrast threshold for blocks. Only blocks with more than
1715 the specified contrast (difference between darkest and lightest
1716 pixels) will be considered. Range 1-255, default 125.
1719 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1720 search. Default - exhaustive search.
1723 If set then a detailed log of the motion search is written to the
1730 Draw a colored box on the input image.
1732 It accepts the syntax:
1734 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}
1740 Specify the top left corner coordinates of the box. Default to 0.
1743 Specify the width and height of the box, if 0 they are interpreted as
1744 the input width and height. Default to 0.
1747 Specify the color of the box to write, it can be the name of a color
1748 (case insensitive match) or a 0xRRGGBB[AA] sequence.
1751 Follow some examples:
1753 # draw a black box around the edge of the input image
1756 # draw a box with color red and an opacity of 50%
1757 drawbox=10:20:200:60:red@@0.5"
1762 Draw text string or text from specified file on top of video using the
1763 libfreetype library.
1765 To enable compilation of this filter you need to configure FFmpeg with
1766 @code{--enable-libfreetype}.
1768 The filter also recognizes strftime() sequences in the provided text
1769 and expands them accordingly. Check the documentation of strftime().
1771 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1774 The description of the accepted parameters follows.
1779 Used to draw a box around text using background color.
1780 Value should be either 1 (enable) or 0 (disable).
1781 The default value of @var{box} is 0.
1784 The color to be used for drawing box around text.
1785 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1786 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1787 The default value of @var{boxcolor} is "white".
1790 Set an expression which specifies if the text should be drawn. If the
1791 expression evaluates to 0, the text is not drawn. This is useful for
1792 specifying that the text should be drawn only when specific conditions
1795 Default value is "1".
1797 See below for the list of accepted constants and functions.
1800 If true, check and fix text coords to avoid clipping.
1803 The color to be used for drawing fonts.
1804 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1805 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1806 The default value of @var{fontcolor} is "black".
1809 The font file to be used for drawing text. Path must be included.
1810 This parameter is mandatory.
1813 The font size to be used for drawing text.
1814 The default value of @var{fontsize} is 16.
1817 Flags to be used for loading the fonts.
1819 The flags map the corresponding flags supported by libfreetype, and are
1820 a combination of the following values:
1827 @item vertical_layout
1828 @item force_autohint
1831 @item ignore_global_advance_width
1833 @item ignore_transform
1840 Default value is "render".
1842 For more information consult the documentation for the FT_LOAD_*
1846 The color to be used for drawing a shadow behind the drawn text. It
1847 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1848 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1849 The default value of @var{shadowcolor} is "black".
1851 @item shadowx, shadowy
1852 The x and y offsets for the text shadow position with respect to the
1853 position of the text. They can be either positive or negative
1854 values. Default value for both is "0".
1857 The size in number of spaces to use for rendering the tab.
1861 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
1862 format. It can be used with or without text parameter. @var{timecode_rate}
1863 option must be specified.
1865 @item timecode_rate, rate, r
1866 Set the timecode frame rate (timecode only).
1869 The text string to be drawn. The text must be a sequence of UTF-8
1871 This parameter is mandatory if no file is specified with the parameter
1875 A text file containing text to be drawn. The text must be a sequence
1876 of UTF-8 encoded characters.
1878 This parameter is mandatory if no text string is specified with the
1879 parameter @var{text}.
1881 If both @var{text} and @var{textfile} are specified, an error is thrown.
1884 The expressions which specify the offsets where text will be drawn
1885 within the video frame. They are relative to the top/left border of the
1888 The default value of @var{x} and @var{y} is "0".
1890 See below for the list of accepted constants and functions.
1893 The parameters for @var{x} and @var{y} are expressions containing the
1894 following constants and functions:
1898 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
1901 horizontal and vertical chroma subsample values. For example for the
1902 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1905 the height of each text line
1913 @item max_glyph_a, ascent
1914 the maximum distance from the baseline to the highest/upper grid
1915 coordinate used to place a glyph outline point, for all the rendered
1917 It is a positive value, due to the grid's orientation with the Y axis
1920 @item max_glyph_d, descent
1921 the maximum distance from the baseline to the lowest grid coordinate
1922 used to place a glyph outline point, for all the rendered glyphs.
1923 This is a negative value, due to the grid's orientation, with the Y axis
1927 maximum glyph height, that is the maximum height for all the glyphs
1928 contained in the rendered text, it is equivalent to @var{ascent} -
1932 maximum glyph width, that is the maximum width for all the glyphs
1933 contained in the rendered text
1936 the number of input frame, starting from 0
1938 @item rand(min, max)
1939 return a random number included between @var{min} and @var{max}
1942 input sample aspect ratio
1945 timestamp expressed in seconds, NAN if the input timestamp is unknown
1948 the height of the rendered text
1951 the width of the rendered text
1954 the x and y offset coordinates where the text is drawn.
1956 These parameters allow the @var{x} and @var{y} expressions to refer
1957 each other, so you can for example specify @code{y=x/dar}.
1960 If libavfilter was built with @code{--enable-fontconfig}, then
1961 @option{fontfile} can be a fontconfig pattern or omitted.
1963 Some examples follow.
1968 Draw "Test Text" with font FreeSerif, using the default values for the
1969 optional parameters.
1972 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
1976 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
1977 and y=50 (counting from the top-left corner of the screen), text is
1978 yellow with a red box around it. Both the text and the box have an
1982 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
1983 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
1986 Note that the double quotes are not necessary if spaces are not used
1987 within the parameter list.
1990 Show the text at the center of the video frame:
1992 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
1996 Show a text line sliding from right to left in the last row of the video
1997 frame. The file @file{LONG_LINE} is assumed to contain a single line
2000 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
2004 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
2006 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
2010 Draw a single green letter "g", at the center of the input video.
2011 The glyph baseline is placed at half screen height.
2013 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2017 Show text for 1 second every 3 seconds:
2019 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\\,3)\\,1):text='blink'"
2023 Use fontconfig to set the font. Note that the colons need to be escaped.
2025 drawtext='fontfile=Linux Libertine O-40\\:style=Semibold:text=FFmpeg'
2030 For more information about libfreetype, check:
2031 @url{http://www.freetype.org/}.
2033 For more information about fontconfig, check:
2034 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2038 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2040 This filter accepts the following optional named parameters:
2044 Set low and high threshold values used by the Canny thresholding
2047 The high threshold selects the "strong" edge pixels, which are then
2048 connected through 8-connectivity with the "weak" edge pixels selected
2049 by the low threshold.
2051 @var{low} and @var{high} threshold values must be choosen in the range
2052 [0,1], and @var{low} should be lesser or equal to @var{high}.
2054 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2060 edgedetect=low=0.1:high=0.4
2065 Apply fade-in/out effect to input video.
2067 It accepts the parameters:
2068 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2070 @var{type} specifies if the effect type, can be either "in" for
2071 fade-in, or "out" for a fade-out effect.
2073 @var{start_frame} specifies the number of the start frame for starting
2074 to apply the fade effect.
2076 @var{nb_frames} specifies the number of frames for which the fade
2077 effect has to last. At the end of the fade-in effect the output video
2078 will have the same intensity as the input video, at the end of the
2079 fade-out transition the output video will be completely black.
2081 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2082 separated by ":". The description of the accepted options follows.
2089 @item start_frame, s
2090 See @var{start_frame}.
2093 See @var{nb_frames}.
2096 If set to 1, fade only alpha channel, if one exists on the input.
2100 A few usage examples follow, usable too as test scenarios.
2102 # fade in first 30 frames of video
2105 # fade out last 45 frames of a 200-frame video
2108 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2109 fade=in:0:25, fade=out:975:25
2111 # make first 5 frames black, then fade in from frame 5-24
2114 # fade in alpha over first 25 frames of video
2115 fade=in:0:25:alpha=1
2120 Transform the field order of the input video.
2122 It accepts one parameter which specifies the required field order that
2123 the input interlaced video will be transformed to. The parameter can
2124 assume one of the following values:
2128 output bottom field first
2130 output top field first
2133 Default value is "tff".
2135 Transformation is achieved by shifting the picture content up or down
2136 by one line, and filling the remaining line with appropriate picture content.
2137 This method is consistent with most broadcast field order converters.
2139 If the input video is not flagged as being interlaced, or it is already
2140 flagged as being of the required output field order then this filter does
2141 not alter the incoming video.
2143 This filter is very useful when converting to or from PAL DV material,
2144 which is bottom field first.
2148 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2153 Buffer input images and send them when they are requested.
2155 This filter is mainly useful when auto-inserted by the libavfilter
2158 The filter does not take parameters.
2162 Convert the input video to one of the specified pixel formats.
2163 Libavfilter will try to pick one that is supported for the input to
2166 The filter accepts a list of pixel format names, separated by ":",
2167 for example "yuv420p:monow:rgb24".
2169 Some examples follow:
2171 # convert the input video to the format "yuv420p"
2174 # convert the input video to any of the formats in the list
2175 format=yuv420p:yuv444p:yuv410p
2180 Convert the video to specified constant framerate by duplicating or dropping
2181 frames as necessary.
2183 This filter accepts the following named parameters:
2187 Desired output framerate.
2193 Select one frame every N.
2195 This filter accepts in input a string representing a positive
2196 integer. Default argument is @code{1}.
2201 Apply a frei0r effect to the input video.
2203 To enable compilation of this filter you need to install the frei0r
2204 header and configure FFmpeg with @code{--enable-frei0r}.
2206 The filter supports the syntax:
2208 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2211 @var{filter_name} is the name to the frei0r effect to load. If the
2212 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2213 is searched in each one of the directories specified by the colon
2214 separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r
2215 paths, which are in this order: @file{HOME/.frei0r-1/lib/},
2216 @file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}.
2218 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2219 for the frei0r effect.
2221 A frei0r effect parameter can be a boolean (whose values are specified
2222 with "y" and "n"), a double, a color (specified by the syntax
2223 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2224 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2225 description), a position (specified by the syntax @var{X}/@var{Y},
2226 @var{X} and @var{Y} being float numbers) and a string.
2228 The number and kind of parameters depend on the loaded effect. If an
2229 effect parameter is not specified the default value is set.
2231 Some examples follow:
2235 Apply the distort0r effect, set the first two double parameters:
2237 frei0r=distort0r:0.5:0.01
2241 Apply the colordistance effect, takes a color as first parameter:
2243 frei0r=colordistance:0.2/0.3/0.4
2244 frei0r=colordistance:violet
2245 frei0r=colordistance:0x112233
2249 Apply the perspective effect, specify the top left and top right image
2252 frei0r=perspective:0.2/0.2:0.8/0.2
2256 For more information see:
2257 @url{http://frei0r.dyne.org}
2261 Fix the banding artifacts that are sometimes introduced into nearly flat
2262 regions by truncation to 8bit color depth.
2263 Interpolate the gradients that should go where the bands are, and
2266 This filter is designed for playback only. Do not use it prior to
2267 lossy compression, because compression tends to lose the dither and
2268 bring back the bands.
2270 The filter takes two optional parameters, separated by ':':
2271 @var{strength}:@var{radius}
2273 @var{strength} is the maximum amount by which the filter will change
2274 any one pixel. Also the threshold for detecting nearly flat
2275 regions. Acceptable values range from .51 to 255, default value is
2276 1.2, out-of-range values will be clipped to the valid range.
2278 @var{radius} is the neighborhood to fit the gradient to. A larger
2279 radius makes for smoother gradients, but also prevents the filter from
2280 modifying the pixels near detailed regions. Acceptable values are
2281 8-32, default value is 16, out-of-range values will be clipped to the
2285 # default parameters
2294 Flip the input video horizontally.
2296 For example to horizontally flip the input video with @command{ffmpeg}:
2298 ffmpeg -i in.avi -vf "hflip" out.avi
2303 High precision/quality 3d denoise filter. This filter aims to reduce
2304 image noise producing smooth images and making still images really
2305 still. It should enhance compressibility.
2307 It accepts the following optional parameters:
2308 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2312 a non-negative float number which specifies spatial luma strength,
2315 @item chroma_spatial
2316 a non-negative float number which specifies spatial chroma strength,
2317 defaults to 3.0*@var{luma_spatial}/4.0
2320 a float number which specifies luma temporal strength, defaults to
2321 6.0*@var{luma_spatial}/4.0
2324 a float number which specifies chroma temporal strength, defaults to
2325 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2330 Modify the hue and/or the saturation of the input.
2332 This filter accepts the following optional named options:
2336 Specify the hue angle as a number of degrees. It accepts a float
2337 number or an expression, and defaults to 0.0.
2340 Specify the hue angle as a number of degrees. It accepts a float
2341 number or an expression, and defaults to 0.0.
2344 Specify the saturation in the [-10,10] range. It accepts a float number and
2348 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2349 following constants:
2353 frame count of the input frame starting from 0
2356 presentation timestamp of the input frame expressed in time base units
2359 frame rate of the input video, NAN if the input frame rate is unknown
2362 timestamp expressed in seconds, NAN if the input timestamp is unknown
2365 time base of the input video
2368 The options can also be set using the syntax: @var{hue}:@var{saturation}
2370 In this case @var{hue} is expressed in degrees.
2372 Some examples follow:
2375 Set the hue to 90 degrees and the saturation to 1.0:
2381 Same command but expressing the hue in radians:
2387 Same command without named options, hue must be expressed in degrees:
2393 Note that "h:s" syntax does not support expressions for the values of
2394 h and s, so the following example will issue an error:
2400 Rotate hue and make the saturation swing between 0
2401 and 2 over a period of 1 second:
2403 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2407 Apply a 3 seconds saturation fade-in effect starting at 0:
2412 The general fade-in expression can be written as:
2414 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2418 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2420 hue="s=max(0\, min(1\, (8-t)/3))"
2423 The general fade-out expression can be written as:
2425 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2430 @subsection Commands
2432 This filter supports the following command:
2435 Modify the hue and/or the saturation of the input video.
2436 The command accepts the same named options and syntax than when calling the
2437 filter from the command-line.
2439 If a parameter is omitted, it is kept at its current value.
2444 Interlaceing detect filter. This filter tries to detect if the input is
2445 interlaced or progressive. Top or bottom field first.
2447 @section lut, lutrgb, lutyuv
2449 Compute a look-up table for binding each pixel component input value
2450 to an output value, and apply it to input video.
2452 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2453 to an RGB input video.
2455 These filters accept in input a ":"-separated list of options, which
2456 specify the expressions used for computing the lookup table for the
2457 corresponding pixel component values.
2459 The @var{lut} filter requires either YUV or RGB pixel formats in
2460 input, and accepts the options:
2462 @item @var{c0} (first pixel component)
2463 @item @var{c1} (second pixel component)
2464 @item @var{c2} (third pixel component)
2465 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
2468 The exact component associated to each option depends on the format in
2471 The @var{lutrgb} filter requires RGB pixel formats in input, and
2472 accepts the options:
2474 @item @var{r} (red component)
2475 @item @var{g} (green component)
2476 @item @var{b} (blue component)
2477 @item @var{a} (alpha component)
2480 The @var{lutyuv} filter requires YUV pixel formats in input, and
2481 accepts the options:
2483 @item @var{y} (Y/luminance component)
2484 @item @var{u} (U/Cb component)
2485 @item @var{v} (V/Cr component)
2486 @item @var{a} (alpha component)
2489 The expressions can contain the following constants and functions:
2493 the input width and height
2496 input value for the pixel component
2499 the input value clipped in the @var{minval}-@var{maxval} range
2502 maximum value for the pixel component
2505 minimum value for the pixel component
2508 the negated value for the pixel component value clipped in the
2509 @var{minval}-@var{maxval} range , it corresponds to the expression
2510 "maxval-clipval+minval"
2513 the computed value in @var{val} clipped in the
2514 @var{minval}-@var{maxval} range
2516 @item gammaval(gamma)
2517 the computed gamma correction value of the pixel component value
2518 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2520 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2524 All expressions default to "val".
2526 Some examples follow:
2528 # negate input video
2529 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2530 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2532 # the above is the same as
2533 lutrgb="r=negval:g=negval:b=negval"
2534 lutyuv="y=negval:u=negval:v=negval"
2539 # remove chroma components, turns the video into a graytone image
2540 lutyuv="u=128:v=128"
2542 # apply a luma burning effect
2545 # remove green and blue components
2548 # set a constant alpha channel value on input
2549 format=rgba,lutrgb=a="maxval-minval/2"
2551 # correct luminance gamma by a 0.5 factor
2552 lutyuv=y=gammaval(0.5)
2557 Apply an MPlayer filter to the input video.
2559 This filter provides a wrapper around most of the filters of
2562 This wrapper is considered experimental. Some of the wrapped filters
2563 may not work properly and we may drop support for them, as they will
2564 be implemented natively into FFmpeg. Thus you should avoid
2565 depending on them when writing portable scripts.
2567 The filters accepts the parameters:
2568 @var{filter_name}[:=]@var{filter_params}
2570 @var{filter_name} is the name of a supported MPlayer filter,
2571 @var{filter_params} is a string containing the parameters accepted by
2574 The list of the currently supported filters follows:
2618 The parameter syntax and behavior for the listed filters are the same
2619 of the corresponding MPlayer filters. For detailed instructions check
2620 the "VIDEO FILTERS" section in the MPlayer manual.
2622 Some examples follow:
2625 Adjust gamma, brightness, contrast:
2631 Add temporal noise to input video:
2637 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2643 This filter accepts an integer in input, if non-zero it negates the
2644 alpha component (if available). The default value in input is 0.
2648 Force libavfilter not to use any of the specified pixel formats for the
2649 input to the next filter.
2651 The filter accepts a list of pixel format names, separated by ":",
2652 for example "yuv420p:monow:rgb24".
2654 Some examples follow:
2656 # force libavfilter to use a format different from "yuv420p" for the
2657 # input to the vflip filter
2658 noformat=yuv420p,vflip
2660 # convert the input video to any of the formats not contained in the list
2661 noformat=yuv420p:yuv444p:yuv410p
2666 Pass the video source unchanged to the output.
2670 Apply video transform using libopencv.
2672 To enable this filter install libopencv library and headers and
2673 configure FFmpeg with @code{--enable-libopencv}.
2675 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
2677 @var{filter_name} is the name of the libopencv filter to apply.
2679 @var{filter_params} specifies the parameters to pass to the libopencv
2680 filter. If not specified the default values are assumed.
2682 Refer to the official libopencv documentation for more precise
2684 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
2686 Follows the list of supported libopencv filters.
2691 Dilate an image by using a specific structuring element.
2692 This filter corresponds to the libopencv function @code{cvDilate}.
2694 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
2696 @var{struct_el} represents a structuring element, and has the syntax:
2697 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
2699 @var{cols} and @var{rows} represent the number of columns and rows of
2700 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
2701 point, and @var{shape} the shape for the structuring element, and
2702 can be one of the values "rect", "cross", "ellipse", "custom".
2704 If the value for @var{shape} is "custom", it must be followed by a
2705 string of the form "=@var{filename}". The file with name
2706 @var{filename} is assumed to represent a binary image, with each
2707 printable character corresponding to a bright pixel. When a custom
2708 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
2709 or columns and rows of the read file are assumed instead.
2711 The default value for @var{struct_el} is "3x3+0x0/rect".
2713 @var{nb_iterations} specifies the number of times the transform is
2714 applied to the image, and defaults to 1.
2716 Follow some example:
2718 # use the default values
2721 # dilate using a structuring element with a 5x5 cross, iterate two times
2722 ocv=dilate=5x5+2x2/cross:2
2724 # read the shape from the file diamond.shape, iterate two times
2725 # the file diamond.shape may contain a pattern of characters like this:
2731 # the specified cols and rows are ignored (but not the anchor point coordinates)
2732 ocv=0x0+2x2/custom=diamond.shape:2
2737 Erode an image by using a specific structuring element.
2738 This filter corresponds to the libopencv function @code{cvErode}.
2740 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
2741 with the same syntax and semantics as the @ref{dilate} filter.
2745 Smooth the input video.
2747 The filter takes the following parameters:
2748 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
2750 @var{type} is the type of smooth filter to apply, and can be one of
2751 the following values: "blur", "blur_no_scale", "median", "gaussian",
2752 "bilateral". The default value is "gaussian".
2754 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
2755 parameters whose meanings depend on smooth type. @var{param1} and
2756 @var{param2} accept integer positive values or 0, @var{param3} and
2757 @var{param4} accept float values.
2759 The default value for @var{param1} is 3, the default value for the
2760 other parameters is 0.
2762 These parameters correspond to the parameters assigned to the
2763 libopencv function @code{cvSmooth}.
2768 Overlay one video on top of another.
2770 It takes two inputs and one output, the first input is the "main"
2771 video on which the second input is overlayed.
2773 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
2775 @var{x} is the x coordinate of the overlayed video on the main video,
2776 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
2777 the following parameters:
2780 @item main_w, main_h
2781 main input width and height
2784 same as @var{main_w} and @var{main_h}
2786 @item overlay_w, overlay_h
2787 overlay input width and height
2790 same as @var{overlay_w} and @var{overlay_h}
2793 @var{options} is an optional list of @var{key}=@var{value} pairs,
2796 The description of the accepted options follows.
2800 If set to 1, force the filter to accept inputs in the RGB
2801 color space. Default value is 0.
2804 Be aware that frames are taken from each input video in timestamp
2805 order, hence, if their initial timestamps differ, it is a a good idea
2806 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
2807 have them begin in the same zero timestamp, as it does the example for
2808 the @var{movie} filter.
2810 Follow some examples:
2812 # draw the overlay at 10 pixels from the bottom right
2813 # corner of the main video.
2814 overlay=main_w-overlay_w-10:main_h-overlay_h-10
2816 # insert a transparent PNG logo in the bottom left corner of the input
2817 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
2819 # insert 2 different transparent PNG logos (second logo on bottom
2821 ffmpeg -i input -i logo1 -i logo2 -filter_complex
2822 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
2824 # add a transparent color layer on top of the main video,
2825 # WxH specifies the size of the main input to the overlay filter
2826 color=red@.3:WxH [over]; [in][over] overlay [out]
2828 # play an original video and a filtered version (here with the deshake filter)
2830 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
2832 # the previous example is the same as:
2833 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
2836 You can chain together more overlays but the efficiency of such
2837 approach is yet to be tested.
2841 Add paddings to the input image, and places the original input at the
2842 given coordinates @var{x}, @var{y}.
2844 It accepts the following parameters:
2845 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
2847 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
2848 expressions containing the following constants:
2852 the input video width and height
2855 same as @var{in_w} and @var{in_h}
2858 the output width and height, that is the size of the padded area as
2859 specified by the @var{width} and @var{height} expressions
2862 same as @var{out_w} and @var{out_h}
2865 x and y offsets as specified by the @var{x} and @var{y}
2866 expressions, or NAN if not yet specified
2869 same as @var{iw} / @var{ih}
2872 input sample aspect ratio
2875 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
2878 horizontal and vertical chroma subsample values. For example for the
2879 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2882 Follows the description of the accepted parameters.
2887 Specify the size of the output image with the paddings added. If the
2888 value for @var{width} or @var{height} is 0, the corresponding input size
2889 is used for the output.
2891 The @var{width} expression can reference the value set by the
2892 @var{height} expression, and vice versa.
2894 The default value of @var{width} and @var{height} is 0.
2898 Specify the offsets where to place the input image in the padded area
2899 with respect to the top/left border of the output image.
2901 The @var{x} expression can reference the value set by the @var{y}
2902 expression, and vice versa.
2904 The default value of @var{x} and @var{y} is 0.
2908 Specify the color of the padded area, it can be the name of a color
2909 (case insensitive match) or a 0xRRGGBB[AA] sequence.
2911 The default value of @var{color} is "black".
2915 @subsection Examples
2919 Add paddings with color "violet" to the input video. Output video
2920 size is 640x480, the top-left corner of the input video is placed at
2923 pad=640:480:0:40:violet
2927 Pad the input to get an output with dimensions increased by 3/2,
2928 and put the input video at the center of the padded area:
2930 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
2934 Pad the input to get a squared output with size equal to the maximum
2935 value between the input width and height, and put the input video at
2936 the center of the padded area:
2938 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
2942 Pad the input to get a final w/h ratio of 16:9:
2944 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
2948 In case of anamorphic video, in order to set the output display aspect
2949 correctly, it is necessary to use @var{sar} in the expression,
2950 according to the relation:
2952 (ih * X / ih) * sar = output_dar
2953 X = output_dar / sar
2956 Thus the previous example needs to be modified to:
2958 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
2962 Double output size and put the input video in the bottom-right
2963 corner of the output padded area:
2965 pad="2*iw:2*ih:ow-iw:oh-ih"
2969 @section pixdesctest
2971 Pixel format descriptor test filter, mainly useful for internal
2972 testing. The output video should be equal to the input video.
2976 format=monow, pixdesctest
2979 can be used to test the monowhite pixel format descriptor definition.
2983 Suppress a TV station logo, using an image file to determine which
2984 pixels comprise the logo. It works by filling in the pixels that
2985 comprise the logo with neighboring pixels.
2987 This filter requires one argument which specifies the filter bitmap
2988 file, which can be any image format supported by libavformat. The
2989 width and height of the image file must match those of the video
2990 stream being processed.
2992 Pixels in the provided bitmap image with a value of zero are not
2993 considered part of the logo, non-zero pixels are considered part of
2994 the logo. If you use white (255) for the logo and black (0) for the
2995 rest, you will be safe. For making the filter bitmap, it is
2996 recommended to take a screen capture of a black frame with the logo
2997 visible, and then using a threshold filter followed by the erode
2998 filter once or twice.
3000 If needed, little splotches can be fixed manually. Remember that if
3001 logo pixels are not covered, the filter quality will be much
3002 reduced. Marking too many pixels as part of the logo does not hurt as
3003 much, but it will increase the amount of blurring needed to cover over
3004 the image and will destroy more information than necessary, and extra
3005 pixels will slow things down on a large logo.
3009 Scale (resize) the input video to @var{width}:@var{height}[:@var{interl}=@{1|-1@}] and/or convert the image format.
3011 The scale filter forces the output display aspect ratio to be the same
3012 of the input, by changing the output sample aspect ratio.
3014 The parameters @var{width} and @var{height} are expressions containing
3015 the following constants:
3019 the input width and height
3022 same as @var{in_w} and @var{in_h}
3025 the output (cropped) width and height
3028 same as @var{out_w} and @var{out_h}
3031 same as @var{iw} / @var{ih}
3034 input sample aspect ratio
3037 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3040 horizontal and vertical chroma subsample values. For example for the
3041 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3044 If the input image format is different from the format requested by
3045 the next filter, the scale filter will convert the input to the
3048 If the value for @var{width} or @var{height} is 0, the respective input
3049 size is used for the output.
3051 If the value for @var{width} or @var{height} is -1, the scale filter will
3052 use, for the respective output size, a value that maintains the aspect
3053 ratio of the input image.
3055 The default value of @var{width} and @var{height} is 0.
3057 Valid values for the optional parameter @var{interl} are:
3061 force interlaced aware scaling
3064 select interlaced aware scaling depending on whether the source frames
3065 are flagged as interlaced or not
3068 Unless @var{interl} is set to one of the above options, interlaced scaling will not be used.
3070 Some examples follow:
3072 # scale the input video to a size of 200x100.
3075 # scale the input to 2x
3077 # the above is the same as
3080 # scale the input to 2x with forced interlaced scaling
3081 scale=2*iw:2*ih:interl=1
3083 # scale the input to half size
3086 # increase the width, and set the height to the same size
3089 # seek for Greek harmony
3093 # increase the height, and set the width to 3/2 of the height
3096 # increase the size, but make the size a multiple of the chroma
3097 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3099 # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
3100 scale='min(500\, iw*3/2):-1'
3104 Select frames to pass in output.
3106 It accepts in input an expression, which is evaluated for each input
3107 frame. If the expression is evaluated to a non-zero value, the frame
3108 is selected and passed to the output, otherwise it is discarded.
3110 The expression can contain the following constants:
3114 the sequential number of the filtered frame, starting from 0
3117 the sequential number of the selected frame, starting from 0
3119 @item prev_selected_n
3120 the sequential number of the last selected frame, NAN if undefined
3123 timebase of the input timestamps
3126 the PTS (Presentation TimeStamp) of the filtered video frame,
3127 expressed in @var{TB} units, NAN if undefined
3130 the PTS (Presentation TimeStamp) of the filtered video frame,
3131 expressed in seconds, NAN if undefined
3134 the PTS of the previously filtered video frame, NAN if undefined
3136 @item prev_selected_pts
3137 the PTS of the last previously filtered video frame, NAN if undefined
3139 @item prev_selected_t
3140 the PTS of the last previously selected video frame, NAN if undefined
3143 the PTS of the first video frame in the video, NAN if undefined
3146 the time of the first video frame in the video, NAN if undefined
3149 the type of the filtered frame, can assume one of the following
3161 @item interlace_type
3162 the frame interlace type, can assume one of the following values:
3165 the frame is progressive (not interlaced)
3167 the frame is top-field-first
3169 the frame is bottom-field-first
3173 1 if the filtered frame is a key-frame, 0 otherwise
3176 the position in the file of the filtered frame, -1 if the information
3177 is not available (e.g. for synthetic video)
3180 value between 0 and 1 to indicate a new scene; a low value reflects a low
3181 probability for the current frame to introduce a new scene, while a higher
3182 value means the current frame is more likely to be one (see the example below)
3186 The default value of the select expression is "1".
3188 Some examples follow:
3191 # select all frames in input
3194 # the above is the same as:
3200 # select only I-frames
3201 select='eq(pict_type\,I)'
3203 # select one frame every 100
3204 select='not(mod(n\,100))'
3206 # select only frames contained in the 10-20 time interval
3207 select='gte(t\,10)*lte(t\,20)'
3209 # select only I frames contained in the 10-20 time interval
3210 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
3212 # select frames with a minimum distance of 10 seconds
3213 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
3216 Complete example to create a mosaic of the first scenes:
3219 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
3222 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
3225 @section setdar, setsar
3227 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3230 This is done by changing the specified Sample (aka Pixel) Aspect
3231 Ratio, according to the following equation:
3233 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3236 Keep in mind that the @code{setdar} filter does not modify the pixel
3237 dimensions of the video frame. Also the display aspect ratio set by
3238 this filter may be changed by later filters in the filterchain,
3239 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3242 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3243 the filter output video.
3245 Note that as a consequence of the application of this filter, the
3246 output display aspect ratio will change according to the equation
3249 Keep in mind that the sample aspect ratio set by the @code{setsar}
3250 filter may be changed by later filters in the filterchain, e.g. if
3251 another "setsar" or a "setdar" filter is applied.
3253 The @code{setdar} and @code{setsar} filters accept a parameter string
3254 which represents the wanted aspect ratio. The parameter can
3255 be a floating point number string, an expression, or a string of the form
3256 @var{num}:@var{den}, where @var{num} and @var{den} are the numerator
3257 and denominator of the aspect ratio. If the parameter is not
3258 specified, it is assumed the value "0:1".
3260 For example to change the display aspect ratio to 16:9, specify:
3265 The example above is equivalent to:
3270 To change the sample aspect ratio to 10:11, specify:
3277 Force field for the output video frame.
3279 The @code{setfield} filter marks the interlace type field for the
3280 output frames. It does not change the input frame, but only sets the
3281 corresponding property, which affects how the frame is treated by
3282 following filters (e.g. @code{fieldorder} or @code{yadif}).
3284 It accepts a string parameter, which can assume the following values:
3287 Keep the same field property.
3290 Mark the frame as bottom-field-first.
3293 Mark the frame as top-field-first.
3296 Mark the frame as progressive.
3301 Show a line containing various information for each input video frame.
3302 The input video is not modified.
3304 The shown line contains a sequence of key/value pairs of the form
3305 @var{key}:@var{value}.
3307 A description of each shown parameter follows:
3311 sequential number of the input frame, starting from 0
3314 Presentation TimeStamp of the input frame, expressed as a number of
3315 time base units. The time base unit depends on the filter input pad.
3318 Presentation TimeStamp of the input frame, expressed as a number of
3322 position of the frame in the input stream, -1 if this information in
3323 unavailable and/or meaningless (for example in case of synthetic video)
3329 sample aspect ratio of the input frame, expressed in the form
3333 size of the input frame, expressed in the form
3334 @var{width}x@var{height}
3337 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3338 for bottom field first)
3341 1 if the frame is a key frame, 0 otherwise
3344 picture type of the input frame ("I" for an I-frame, "P" for a
3345 P-frame, "B" for a B-frame, "?" for unknown type).
3346 Check also the documentation of the @code{AVPictureType} enum and of
3347 the @code{av_get_picture_type_char} function defined in
3348 @file{libavutil/avutil.h}.
3351 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3353 @item plane_checksum
3354 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3355 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3360 Pass the images of input video on to next video filter as multiple
3364 ffmpeg -i in.avi -vf "slicify=32" out.avi
3367 The filter accepts the slice height as parameter. If the parameter is
3368 not specified it will use the default value of 16.
3370 Adding this in the beginning of filter chains should make filtering
3371 faster due to better use of the memory cache.
3375 Blur the input video without impacting the outlines.
3377 The filter accepts the following parameters:
3378 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3380 Parameters prefixed by @var{luma} indicate that they work on the
3381 luminance of the pixels whereas parameters prefixed by @var{chroma}
3382 refer to the chrominance of the pixels.
3384 If the chroma parameters are not set, the luma parameters are used for
3385 either the luminance and the chrominance of the pixels.
3387 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3388 range [0.1,5.0] that specifies the variance of the gaussian filter
3389 used to blur the image (slower if larger).
3391 @var{luma_strength} or @var{chroma_strength} must be a float number in
3392 the range [-1.0,1.0] that configures the blurring. A value included in
3393 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3394 will sharpen the image.
3396 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3397 the range [-30,30] that is used as a coefficient to determine whether
3398 a pixel should be blurred or not. A value of 0 will filter all the
3399 image, a value included in [0,30] will filter flat areas and a value
3400 included in [-30,0] will filter edges.
3404 Split input video into several identical outputs.
3406 The filter accepts a single parameter which specifies the number of outputs. If
3407 unspecified, it defaults to 2.
3411 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3413 will create 5 copies of the input video.
3417 [in] split [splitout1][splitout2];
3418 [splitout1] crop=100:100:0:0 [cropout];
3419 [splitout2] pad=200:200:100:100 [padout];
3422 will create two separate outputs from the same input, one cropped and
3427 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3428 Interpolate) pixel art scaling algorithm.
3430 Useful for enlarging pixel art images without reducing sharpness.
3436 Select the most representative frame in a given sequence of consecutive frames.
3438 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3439 in a set of @var{N} frames, the filter will pick one of them, and then handle
3440 the next batch of @var{N} frames until the end.
3442 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3443 value will result in a higher memory usage, so a high value is not recommended.
3445 The following example extract one picture each 50 frames:
3450 Complete example of a thumbnail creation with @command{ffmpeg}:
3452 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3457 Tile several successive frames together.
3459 It accepts as argument the tile size (i.e. the number of lines and columns)
3460 in the form "@var{w}x@var{h}".
3462 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3465 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3467 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3468 duplicating each output frame to accomodate the originally detected frame
3473 Perform various types of temporal field interlacing.
3475 Frames are counted starting from 1, so the first input frame is
3478 This filter accepts a single parameter specifying the mode. Available
3483 Move odd frames into the upper field, even into the lower field,
3484 generating a double height frame at half framerate.
3487 Only output even frames, odd frames are dropped, generating a frame with
3488 unchanged height at half framerate.
3491 Only output odd frames, even frames are dropped, generating a frame with
3492 unchanged height at half framerate.
3495 Expand each frame to full height, but pad alternate lines with black,
3496 generating a frame with double height at the same input framerate.
3498 @item interleave_top, 4
3499 Interleave the upper field from odd frames with the lower field from
3500 even frames, generating a frame with unchanged height at half framerate.
3502 @item interleave_bottom, 5
3503 Interleave the lower field from odd frames with the upper field from
3504 even frames, generating a frame with unchanged height at half framerate.
3506 @item interlacex2, 6
3507 Double frame rate with unchanged height. Frames are inserted each
3508 containing the second temporal field from the previous input frame and
3509 the first temporal field from the next input frame. This mode relies on
3510 the top_field_first flag. Useful for interlaced video displays with no
3511 field synchronisation.
3514 Numeric values are deprecated but are accepted for backward
3515 compatibility reasons.
3517 Default mode is @code{merge}.
3521 Transpose rows with columns in the input video and optionally flip it.
3523 This filter accepts the following named parameters:
3527 Specify the transposition direction. Can assume the following values:
3531 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3539 Rotate by 90 degrees clockwise, that is:
3547 Rotate by 90 degrees counterclockwise, that is:
3555 Rotate by 90 degrees clockwise and vertically flip, that is:
3563 For values between 4-7, the transposition is only done if the input
3564 video geometry is portrait and not landscape. These values are
3565 deprecated, the @code{passthrough} option should be used instead.
3568 Do not apply the transposition if the input geometry matches the one
3569 specified by the specified value. It accepts the following values:
3572 Always apply transposition.
3574 Preserve portrait geometry (when @var{height} >= @var{width}).
3576 Preserve landscape geometry (when @var{width} >= @var{height}).
3579 Default value is @code{none}.
3584 Sharpen or blur the input video.
3586 It accepts the following parameters:
3587 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3589 Negative values for the amount will blur the input video, while positive
3590 values will sharpen. All parameters are optional and default to the
3591 equivalent of the string '5:5:1.0:5:5:0.0'.
3596 Set the luma matrix horizontal size. It can be an integer between 3
3597 and 13, default value is 5.
3600 Set the luma matrix vertical size. It can be an integer between 3
3601 and 13, default value is 5.
3604 Set the luma effect strength. It can be a float number between -2.0
3605 and 5.0, default value is 1.0.
3607 @item chroma_msize_x
3608 Set the chroma matrix horizontal size. It can be an integer between 3
3609 and 13, default value is 5.
3611 @item chroma_msize_y
3612 Set the chroma matrix vertical size. It can be an integer between 3
3613 and 13, default value is 5.
3616 Set the chroma effect strength. It can be a float number between -2.0
3617 and 5.0, default value is 0.0.
3622 # Strong luma sharpen effect parameters
3625 # Strong blur of both luma and chroma parameters
3626 unsharp=7:7:-2:7:7:-2
3628 # Use the default values with @command{ffmpeg}
3629 ffmpeg -i in.avi -vf "unsharp" out.mp4
3634 Flip the input video vertically.
3637 ffmpeg -i in.avi -vf "vflip" out.avi
3642 Deinterlace the input video ("yadif" means "yet another deinterlacing
3645 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
3647 @var{mode} specifies the interlacing mode to adopt, accepts one of the
3652 output 1 frame for each frame
3654 output 1 frame for each field
3656 like 0 but skips spatial interlacing check
3658 like 1 but skips spatial interlacing check
3663 @var{parity} specifies the picture field parity assumed for the input
3664 interlaced video, accepts one of the following values:
3668 assume top field first
3670 assume bottom field first
3672 enable automatic detection
3675 Default value is -1.
3676 If interlacing is unknown or decoder does not export this information,
3677 top field first will be assumed.
3679 @var{auto} specifies if deinterlacer should trust the interlaced flag
3680 and only deinterlace frames marked as interlaced
3684 deinterlace all frames
3686 only deinterlace frames marked as interlaced
3691 @c man end VIDEO FILTERS
3693 @chapter Video Sources
3694 @c man begin VIDEO SOURCES
3696 Below is a description of the currently available video sources.
3700 Buffer video frames, and make them available to the filter chain.
3702 This source is mainly intended for a programmatic use, in particular
3703 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
3705 It accepts a list of options in the form of @var{key}=@var{value} pairs
3706 separated by ":". A description of the accepted options follows.
3711 Specify the size (width and height) of the buffered video frames.
3714 A string representing the pixel format of the buffered video frames.
3715 It may be a number corresponding to a pixel format, or a pixel format
3719 Specify the timebase assumed by the timestamps of the buffered frames.
3722 Specify the frame rate expected for the video stream.
3725 Specify the sample aspect ratio assumed by the video frames.
3728 Specify the optional parameters to be used for the scale filter which
3729 is automatically inserted when an input change is detected in the
3730 input size or format.
3735 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
3738 will instruct the source to accept video frames with size 320x240 and
3739 with format "yuv410p", assuming 1/24 as the timestamps timebase and
3740 square pixels (1:1 sample aspect ratio).
3741 Since the pixel format with name "yuv410p" corresponds to the number 6
3742 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
3743 this example corresponds to:
3745 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
3748 Alternatively, the options can be specified as a flat string, but this
3749 syntax is deprecated:
3751 @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}]
3755 Create a pattern generated by an elementary cellular automaton.
3757 The initial state of the cellular automaton can be defined through the
3758 @option{filename}, and @option{pattern} options. If such options are
3759 not specified an initial state is created randomly.
3761 At each new frame a new row in the video is filled with the result of
3762 the cellular automaton next generation. The behavior when the whole
3763 frame is filled is defined by the @option{scroll} option.
3765 This source accepts a list of options in the form of
3766 @var{key}=@var{value} pairs separated by ":". A description of the
3767 accepted options follows.
3771 Read the initial cellular automaton state, i.e. the starting row, from
3773 In the file, each non-whitespace character is considered an alive
3774 cell, a newline will terminate the row, and further characters in the
3775 file will be ignored.
3778 Read the initial cellular automaton state, i.e. the starting row, from
3779 the specified string.
3781 Each non-whitespace character in the string is considered an alive
3782 cell, a newline will terminate the row, and further characters in the
3783 string will be ignored.
3786 Set the video rate, that is the number of frames generated per second.
3789 @item random_fill_ratio, ratio
3790 Set the random fill ratio for the initial cellular automaton row. It
3791 is a floating point number value ranging from 0 to 1, defaults to
3794 This option is ignored when a file or a pattern is specified.
3796 @item random_seed, seed
3797 Set the seed for filling randomly the initial row, must be an integer
3798 included between 0 and UINT32_MAX. If not specified, or if explicitly
3799 set to -1, the filter will try to use a good random seed on a best
3803 Set the cellular automaton rule, it is a number ranging from 0 to 255.
3804 Default value is 110.
3807 Set the size of the output video.
3809 If @option{filename} or @option{pattern} is specified, the size is set
3810 by default to the width of the specified initial state row, and the
3811 height is set to @var{width} * PHI.
3813 If @option{size} is set, it must contain the width of the specified
3814 pattern string, and the specified pattern will be centered in the
3817 If a filename or a pattern string is not specified, the size value
3818 defaults to "320x518" (used for a randomly generated initial state).
3821 If set to 1, scroll the output upward when all the rows in the output
3822 have been already filled. If set to 0, the new generated row will be
3823 written over the top row just after the bottom row is filled.
3826 @item start_full, full
3827 If set to 1, completely fill the output with generated rows before
3828 outputting the first frame.
3829 This is the default behavior, for disabling set the value to 0.
3832 If set to 1, stitch the left and right row edges together.
3833 This is the default behavior, for disabling set the value to 0.
3836 @subsection Examples
3840 Read the initial state from @file{pattern}, and specify an output of
3843 cellauto=f=pattern:s=200x400
3847 Generate a random initial row with a width of 200 cells, with a fill
3850 cellauto=ratio=2/3:s=200x200
3854 Create a pattern generated by rule 18 starting by a single alive cell
3855 centered on an initial row with width 100:
3857 cellauto=p=@@:s=100x400:full=0:rule=18
3861 Specify a more elaborated initial pattern:
3863 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
3870 Generate a Mandelbrot set fractal, and progressively zoom towards the
3871 point specified with @var{start_x} and @var{start_y}.
3873 This source accepts a list of options in the form of
3874 @var{key}=@var{value} pairs separated by ":". A description of the
3875 accepted options follows.
3880 Set the terminal pts value. Default value is 400.
3883 Set the terminal scale value.
3884 Must be a floating point value. Default value is 0.3.
3887 Set the inner coloring mode, that is the algorithm used to draw the
3888 Mandelbrot fractal internal region.
3890 It shall assume one of the following values:
3895 Show time until convergence.
3897 Set color based on point closest to the origin of the iterations.
3902 Default value is @var{mincol}.
3905 Set the bailout value. Default value is 10.0.
3908 Set the maximum of iterations performed by the rendering
3909 algorithm. Default value is 7189.
3912 Set outer coloring mode.
3913 It shall assume one of following values:
3915 @item iteration_count
3916 Set iteration cound mode.
3917 @item normalized_iteration_count
3918 set normalized iteration count mode.
3920 Default value is @var{normalized_iteration_count}.
3923 Set frame rate, expressed as number of frames per second. Default
3927 Set frame size. Default value is "640x480".
3930 Set the initial scale value. Default value is 3.0.
3933 Set the initial x position. Must be a floating point value between
3934 -100 and 100. Default value is -0.743643887037158704752191506114774.
3937 Set the initial y position. Must be a floating point value between
3938 -100 and 100. Default value is -0.131825904205311970493132056385139.
3943 Generate various test patterns, as generated by the MPlayer test filter.
3945 The size of the generated video is fixed, and is 256x256.
3946 This source is useful in particular for testing encoding features.
3948 This source accepts an optional sequence of @var{key}=@var{value} pairs,
3949 separated by ":". The description of the accepted options follows.
3954 Specify the frame rate of the sourced video, as the number of frames
3955 generated per second. It has to be a string in the format
3956 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
3957 number or a valid video frame rate abbreviation. The default value is
3961 Set the video duration of the sourced video. The accepted syntax is:
3966 See also the function @code{av_parse_time()}.
3968 If not specified, or the expressed duration is negative, the video is
3969 supposed to be generated forever.
3973 Set the number or the name of the test to perform. Supported tests are:
3988 Default value is "all", which will cycle through the list of all tests.
3991 For example the following:
3996 will generate a "dc_luma" test pattern.
4000 Provide a frei0r source.
4002 To enable compilation of this filter you need to install the frei0r
4003 header and configure FFmpeg with @code{--enable-frei0r}.
4005 The source supports the syntax:
4007 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
4010 @var{size} is the size of the video to generate, may be a string of the
4011 form @var{width}x@var{height} or a frame size abbreviation.
4012 @var{rate} is the rate of the video to generate, may be a string of
4013 the form @var{num}/@var{den} or a frame rate abbreviation.
4014 @var{src_name} is the name to the frei0r source to load. For more
4015 information regarding frei0r and how to set the parameters read the
4016 section @ref{frei0r} in the description of the video filters.
4018 For example, to generate a frei0r partik0l source with size 200x200
4019 and frame rate 10 which is overlayed on the overlay filter main input:
4021 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4026 Generate a life pattern.
4028 This source is based on a generalization of John Conway's life game.
4030 The sourced input represents a life grid, each pixel represents a cell
4031 which can be in one of two possible states, alive or dead. Every cell
4032 interacts with its eight neighbours, which are the cells that are
4033 horizontally, vertically, or diagonally adjacent.
4035 At each interaction the grid evolves according to the adopted rule,
4036 which specifies the number of neighbor alive cells which will make a
4037 cell stay alive or born. The @option{rule} option allows to specify
4040 This source accepts a list of options in the form of
4041 @var{key}=@var{value} pairs separated by ":". A description of the
4042 accepted options follows.
4046 Set the file from which to read the initial grid state. In the file,
4047 each non-whitespace character is considered an alive cell, and newline
4048 is used to delimit the end of each row.
4050 If this option is not specified, the initial grid is generated
4054 Set the video rate, that is the number of frames generated per second.
4057 @item random_fill_ratio, ratio
4058 Set the random fill ratio for the initial random grid. It is a
4059 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4060 It is ignored when a file is specified.
4062 @item random_seed, seed
4063 Set the seed for filling the initial random grid, must be an integer
4064 included between 0 and UINT32_MAX. If not specified, or if explicitly
4065 set to -1, the filter will try to use a good random seed on a best
4071 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4072 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4073 @var{NS} specifies the number of alive neighbor cells which make a
4074 live cell stay alive, and @var{NB} the number of alive neighbor cells
4075 which make a dead cell to become alive (i.e. to "born").
4076 "s" and "b" can be used in place of "S" and "B", respectively.
4078 Alternatively a rule can be specified by an 18-bits integer. The 9
4079 high order bits are used to encode the next cell state if it is alive
4080 for each number of neighbor alive cells, the low order bits specify
4081 the rule for "borning" new cells. Higher order bits encode for an
4082 higher number of neighbor cells.
4083 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4084 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4086 Default value is "S23/B3", which is the original Conway's game of life
4087 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4088 cells, and will born a new cell if there are three alive cells around
4092 Set the size of the output video.
4094 If @option{filename} is specified, the size is set by default to the
4095 same size of the input file. If @option{size} is set, it must contain
4096 the size specified in the input file, and the initial grid defined in
4097 that file is centered in the larger resulting area.
4099 If a filename is not specified, the size value defaults to "320x240"
4100 (used for a randomly generated initial grid).
4103 If set to 1, stitch the left and right grid edges together, and the
4104 top and bottom edges also. Defaults to 1.
4107 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4108 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4109 value from 0 to 255.
4112 Set the color of living (or new born) cells.
4115 Set the color of dead cells. If @option{mold} is set, this is the first color
4116 used to represent a dead cell.
4119 Set mold color, for definitely dead and moldy cells.
4122 @subsection Examples
4126 Read a grid from @file{pattern}, and center it on a grid of size
4129 life=f=pattern:s=300x300
4133 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4135 life=ratio=2/3:s=200x200
4139 Specify a custom rule for evolving a randomly generated grid:
4145 Full example with slow death effect (mold) using @command{ffplay}:
4147 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4151 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4153 The @code{color} source provides an uniformly colored input.
4155 The @code{nullsrc} source returns unprocessed video frames. It is
4156 mainly useful to be employed in analysis / debugging tools, or as the
4157 source for filters which ignore the input data.
4159 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4160 detecting RGB vs BGR issues. You should see a red, green and blue
4161 stripe from top to bottom.
4163 The @code{smptebars} source generates a color bars pattern, based on
4164 the SMPTE Engineering Guideline EG 1-1990.
4166 The @code{testsrc} source generates a test video pattern, showing a
4167 color pattern, a scrolling gradient and a timestamp. This is mainly
4168 intended for testing purposes.
4170 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4171 separated by ":". The description of the accepted options follows.
4176 Specify the color of the source, only used in the @code{color}
4177 source. It can be the name of a color (case insensitive match) or a
4178 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4179 default value is "black".
4182 Specify the size of the sourced video, it may be a string of the form
4183 @var{width}x@var{height}, or the name of a size abbreviation. The
4184 default value is "320x240".
4187 Specify the frame rate of the sourced video, as the number of frames
4188 generated per second. It has to be a string in the format
4189 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4190 number or a valid video frame rate abbreviation. The default value is
4194 Set the sample aspect ratio of the sourced video.
4197 Set the video duration of the sourced video. The accepted syntax is:
4199 [-]HH[:MM[:SS[.m...]]]
4202 See also the function @code{av_parse_time()}.
4204 If not specified, or the expressed duration is negative, the video is
4205 supposed to be generated forever.
4208 Set the number of decimals to show in the timestamp, only used in the
4209 @code{testsrc} source.
4211 The displayed timestamp value will correspond to the original
4212 timestamp value multiplied by the power of 10 of the specified
4213 value. Default value is 0.
4216 For example the following:
4218 testsrc=duration=5.3:size=qcif:rate=10
4221 will generate a video with a duration of 5.3 seconds, with size
4222 176x144 and a frame rate of 10 frames per second.
4224 The following graph description will generate a red source
4225 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4228 color=c=red@@0.2:s=qcif:r=10
4231 If the input content is to be ignored, @code{nullsrc} can be used. The
4232 following command generates noise in the luminance plane by employing
4233 the @code{mp=geq} filter:
4235 nullsrc=s=256x256, mp=geq=random(1)*255:128:128
4238 @c man end VIDEO SOURCES
4240 @chapter Video Sinks
4241 @c man begin VIDEO SINKS
4243 Below is a description of the currently available video sinks.
4247 Buffer video frames, and make them available to the end of the filter
4250 This sink is mainly intended for a programmatic use, in particular
4251 through the interface defined in @file{libavfilter/buffersink.h}.
4253 It does not require a string parameter in input, but you need to
4254 specify a pointer to a list of supported pixel formats terminated by
4255 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4256 when initializing this sink.
4260 Null video sink, do absolutely nothing with the input video. It is
4261 mainly useful as a template and to be employed in analysis / debugging
4264 @c man end VIDEO SINKS
4266 @chapter Multimedia Filters
4267 @c man begin MULTIMEDIA FILTERS
4269 Below is a description of the currently available multimedia filters.
4271 @section asendcmd, sendcmd
4273 Send commands to filters in the filtergraph.
4275 These filters read commands to be sent to other filters in the
4278 @code{asendcmd} must be inserted between two audio filters,
4279 @code{sendcmd} must be inserted between two video filters, but apart
4280 from that they act the same way.
4282 The specification of commands can be provided in the filter arguments
4283 with the @var{commands} option, or in a file specified by the
4284 @var{filename} option.
4286 These filters accept the following options:
4289 Set the commands to be read and sent to the other filters.
4291 Set the filename of the commands to be read and sent to the other
4295 @subsection Commands syntax
4297 A commands description consists of a sequence of interval
4298 specifications, comprising a list of commands to be executed when a
4299 particular event related to that interval occurs. The occurring event
4300 is typically the current frame time entering or leaving a given time
4303 An interval is specified by the following syntax:
4305 @var{START}[-@var{END}] @var{COMMANDS};
4308 The time interval is specified by the @var{START} and @var{END} times.
4309 @var{END} is optional and defaults to the maximum time.
4311 The current frame time is considered within the specified interval if
4312 it is included in the interval [@var{START}, @var{END}), that is when
4313 the time is greater or equal to @var{START} and is lesser than
4316 @var{COMMANDS} consists of a sequence of one or more command
4317 specifications, separated by ",", relating to that interval. The
4318 syntax of a command specification is given by:
4320 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4323 @var{FLAGS} is optional and specifies the type of events relating to
4324 the time interval which enable sending the specified command, and must
4325 be a non-null sequence of identifier flags separated by "+" or "|" and
4326 enclosed between "[" and "]".
4328 The following flags are recognized:
4331 The command is sent when the current frame timestamp enters the
4332 specified interval. In other words, the command is sent when the
4333 previous frame timestamp was not in the given interval, and the
4337 The command is sent when the current frame timestamp leaves the
4338 specified interval. In other words, the command is sent when the
4339 previous frame timestamp was in the given interval, and the
4343 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4346 @var{TARGET} specifies the target of the command, usually the name of
4347 the filter class or a specific filter instance name.
4349 @var{COMMAND} specifies the name of the command for the target filter.
4351 @var{ARG} is optional and specifies the optional list of argument for
4352 the given @var{COMMAND}.
4354 Between one interval specification and another, whitespaces, or
4355 sequences of characters starting with @code{#} until the end of line,
4356 are ignored and can be used to annotate comments.
4358 A simplified BNF description of the commands specification syntax
4361 @var{COMMAND_FLAG} ::= "enter" | "leave"
4362 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4363 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4364 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4365 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4366 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4369 @subsection Examples
4373 Specify audio tempo change at second 4:
4375 asendcmd=c='4.0 atempo tempo 1.5',atempo
4379 Specify a list of drawtext and hue commands in a file.
4381 # show text in the interval 5-10
4382 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4383 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4385 # desaturate the image in the interval 15-20
4386 15.0-20.0 [enter] hue reinit s=0,
4387 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4388 [leave] hue reinit s=1,
4389 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4391 # apply an exponential saturation fade-out effect, starting from time 25
4392 25 [enter] hue s=exp(t-25)
4395 A filtergraph allowing to read and process the above command list
4396 stored in a file @file{test.cmd}, can be specified with:
4398 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4402 @section asetpts, setpts
4404 Change the PTS (presentation timestamp) of the input frames.
4406 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4408 Accept in input an expression evaluated through the eval API, which
4409 can contain the following constants:
4413 frame rate, only defined for constant frame-rate video
4416 the presentation timestamp in input
4419 the count of the input frame, starting from 0.
4421 @item NB_CONSUMED_SAMPLES
4422 the number of consumed samples, not including the current frame (only
4426 the number of samples in the current frame (only audio)
4432 the PTS of the first frame
4435 the time in seconds of the first frame
4438 tell if the current frame is interlaced
4441 the time in seconds of the current frame
4447 original position in the file of the frame, or undefined if undefined
4448 for the current frame
4454 previous input time in seconds
4460 previous output time in seconds
4463 @subsection Examples
4467 Start counting PTS from zero
4473 Apply fast motion effect:
4479 Apply slow motion effect:
4485 Set fixed rate of 25 frames per second:
4491 Set fixed rate 25 fps with some jitter:
4493 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
4497 Apply an offset of 10 seconds to the input PTS:
4505 EBU R128 scanner filter. This filter takes an audio stream as input and outputs
4506 it unchanged. By default, it logs a message at a frequency of 10Hz with the
4507 Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
4508 Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
4510 The filter also has a video output (see the @var{video} option) with a real
4511 time graph to observe the loudness evolution. The graphic contains the logged
4512 message mentioned above, so it is not printed anymore when this option is set,
4513 unless the verbose logging is set. The main graphing area contains the
4514 short-term loudness (3 seconds of analysis), and the gauge on the right is for
4515 the momentary loudness (400 milliseconds).
4517 More information about the Loudness Recommendation EBU R128 on
4518 @url{http://tech.ebu.ch/loudness}.
4520 The filter accepts the following named parameters:
4525 Activate the video output. The audio stream is passed unchanged whether this
4526 option is set or no. The video stream will be the first output stream if
4527 activated. Default is @code{0}.
4530 Set the video size. This option is for video only. Default and minimum
4531 resolution is @code{640x480}.
4534 Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
4535 @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
4536 other integer value between this range is allowed.
4540 Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
4542 ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
4545 Run an analysis with @command{ffmpeg}:
4547 ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
4550 @section settb, asettb
4552 Set the timebase to use for the output frames timestamps.
4553 It is mainly useful for testing timebase configuration.
4555 It accepts in input an arithmetic expression representing a rational.
4556 The expression can contain the constants "AVTB" (the
4557 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
4560 The default value for the input is "intb".
4562 @subsection Examples
4566 Set the timebase to 1/25:
4572 Set the timebase to 1/10:
4578 Set the timebase to 1001/1000:
4584 Set the timebase to 2*intb:
4590 Set the default timebase value:
4598 Concatenate audio and video streams, joining them together one after the
4601 The filter works on segments of synchronized video and audio streams. All
4602 segments must have the same number of streams of each type, and that will
4603 also be the number of streams at output.
4605 The filter accepts the following named parameters:
4609 Set the number of segments. Default is 2.
4612 Set the number of output video streams, that is also the number of video
4613 streams in each segment. Default is 1.
4616 Set the number of output audio streams, that is also the number of video
4617 streams in each segment. Default is 0.
4621 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
4622 @var{a} audio outputs.
4624 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
4625 segment, in the same order as the outputs, then the inputs for the second
4628 Related streams do not always have exactly the same duration, for various
4629 reasons including codec frame size or sloppy authoring. For that reason,
4630 related synchronized streams (e.g. a video and its audio track) should be
4631 concatenated at once. The concat filter will use the duration of the longest
4632 stream in each segment (except the last one), and if necessary pad shorter
4633 audio streams with silence.
4635 For this filter to work correctly, all segments must start at timestamp 0.
4637 All corresponding streams must have the same parameters in all segments; the
4638 filtering system will automatically select a common pixel format for video
4639 streams, and a common sample format, sample rate and channel layout for
4640 audio streams, but other settings, such as resolution, must be converted
4641 explicitly by the user.
4643 Different frame rates are acceptable but will result in variable frame rate
4644 at output; be sure to configure the output file to handle it.
4649 Concatenate an opening, an episode and an ending, all in bilingual version
4650 (video in stream 0, audio in streams 1 and 2):
4652 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
4653 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
4654 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
4655 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
4659 Concatenate two parts, handling audio and video separately, using the
4660 (a)movie sources, and adjusting the resolution:
4662 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
4663 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
4664 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
4666 Note that a desync will happen at the stitch if the audio and video streams
4667 do not have exactly the same duration in the first file.
4671 @section showspectrum
4673 Convert input audio to a video output, representing the audio frequency
4676 The filter accepts the following named parameters:
4679 Specify the video size for the output. Default value is @code{640x480}.
4682 The usage is very similar to the showwaves filter; see the examples in that
4687 Convert input audio to a video output, representing the samples waves.
4689 The filter accepts the following named parameters:
4693 Set the number of samples which are printed on the same column. A
4694 larger value will decrease the frame rate. Must be a positive
4695 integer. This option can be set only if the value for @var{rate}
4696 is not explicitly specified.
4699 Set the (approximate) output frame rate. This is done by setting the
4700 option @var{n}. Default value is "25".
4703 Specify the video size for the output. Default value is "600x240".
4706 Some examples follow.
4709 Output the input file audio and the corresponding video representation
4712 amovie=a.mp3,asplit[out0],showwaves[out1]
4716 Create a synthetic signal and show it with showwaves, forcing a
4717 framerate of 30 frames per second:
4719 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
4723 @c man end MULTIMEDIA FILTERS
4725 @chapter Multimedia Sources
4726 @c man begin MULTIMEDIA SOURCES
4728 Below is a description of the currently available multimedia sources.
4732 This is the same as @ref{src_movie} source, except it selects an audio
4738 Read audio and/or video stream(s) from a movie container.
4740 It accepts the syntax: @var{movie_name}[:@var{options}] where
4741 @var{movie_name} is the name of the resource to read (not necessarily
4742 a file but also a device or a stream accessed through some protocol),
4743 and @var{options} is an optional sequence of @var{key}=@var{value}
4744 pairs, separated by ":".
4746 The description of the accepted options follows.
4750 @item format_name, f
4751 Specifies the format assumed for the movie to read, and can be either
4752 the name of a container or an input device. If not specified the
4753 format is guessed from @var{movie_name} or by probing.
4755 @item seek_point, sp
4756 Specifies the seek point in seconds, the frames will be output
4757 starting from this seek point, the parameter is evaluated with
4758 @code{av_strtod} so the numerical value may be suffixed by an IS
4759 postfix. Default value is "0".
4762 Specifies the streams to read. Several streams can be specified, separated
4763 by "+". The source will then have as many outputs, in the same order. The
4764 syntax is explained in the @ref{Stream specifiers} chapter. Two special
4765 names, "dv" and "da" specify respectively the default (best suited) video
4766 and audio stream. Default is "dv", or "da" if the filter is called as
4769 @item stream_index, si
4770 Specifies the index of the video stream to read. If the value is -1,
4771 the best suited video stream will be automatically selected. Default
4772 value is "-1". Deprecated. If the filter is called "amovie", it will select
4773 audio instead of video.
4776 Specifies how many times to read the stream in sequence.
4777 If the value is less than 1, the stream will be read again and again.
4778 Default value is "1".
4780 Note that when the movie is looped the source timestamps are not
4781 changed, so it will generate non monotonically increasing timestamps.
4784 This filter allows to overlay a second video on top of main input of
4785 a filtergraph as shown in this graph:
4787 input -----------> deltapts0 --> overlay --> output
4790 movie --> scale--> deltapts1 -------+
4793 Some examples follow.
4797 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
4798 on top of the input labelled as "in":
4800 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
4801 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
4805 Read from a video4linux2 device, and overlay it on top of the input
4808 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
4809 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
4813 Read the first video stream and the audio stream with id 0x81 from
4814 dvd.vob; the video is connected to the pad named "video" and the audio is
4815 connected to the pad named "audio":
4817 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
4821 @c man end MULTIMEDIA SOURCES