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 Make @file{ffplay} speech the specified text, using @code{flite} and
1142 the @code{lavfi} device:
1144 ffplay -f lavfi flite='No more be grieved for which that thou hast done.'
1148 For more information about libflite, check:
1149 @url{http://www.speech.cs.cmu.edu/flite/}
1151 @c man end AUDIO SOURCES
1153 @chapter Audio Sinks
1154 @c man begin AUDIO SINKS
1156 Below is a description of the currently available audio sinks.
1158 @section abuffersink
1160 Buffer audio frames, and make them available to the end of filter chain.
1162 This sink is mainly intended for programmatic use, in particular
1163 through the interface defined in @file{libavfilter/buffersink.h}.
1165 It requires a pointer to an AVABufferSinkContext structure, which
1166 defines the incoming buffers' formats, to be passed as the opaque
1167 parameter to @code{avfilter_init_filter} for initialization.
1171 Null audio sink, do absolutely nothing with the input audio. It is
1172 mainly useful as a template and to be employed in analysis / debugging
1175 @section abuffersink
1176 This sink is intended for programmatic use. Frames that arrive on this sink can
1177 be retrieved by the calling program using the interface defined in
1178 @file{libavfilter/buffersink.h}.
1180 This filter accepts no parameters.
1182 @c man end AUDIO SINKS
1184 @chapter Video Filters
1185 @c man begin VIDEO FILTERS
1187 When you configure your FFmpeg build, you can disable any of the
1188 existing filters using @code{--disable-filters}.
1189 The configure output will show the video filters included in your
1192 Below is a description of the currently available video filters.
1194 @section alphaextract
1196 Extract the alpha component from the input as a grayscale video. This
1197 is especially useful with the @var{alphamerge} filter.
1201 Add or replace the alpha component of the primary input with the
1202 grayscale value of a second input. This is intended for use with
1203 @var{alphaextract} to allow the transmission or storage of frame
1204 sequences that have alpha in a format that doesn't support an alpha
1207 For example, to reconstruct full frames from a normal YUV-encoded video
1208 and a separate video created with @var{alphaextract}, you might use:
1210 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
1213 Since this filter is designed for reconstruction, it operates on frame
1214 sequences without considering timestamps, and terminates when either
1215 input reaches end of stream. This will cause problems if your encoding
1216 pipeline drops frames. If you're trying to apply an image as an
1217 overlay to a video stream, consider the @var{overlay} filter instead.
1221 Draw ASS (Advanced Substation Alpha) subtitles on top of input video
1222 using the libass library.
1224 To enable compilation of this filter you need to configure FFmpeg with
1225 @code{--enable-libass}.
1227 This filter accepts the syntax: @var{ass_filename}[:@var{options}],
1228 where @var{ass_filename} is the filename of the ASS file to read, and
1229 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
1232 A description of the accepted options follows.
1236 Specifies the size of the original video, the video for which the ASS file
1237 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
1238 necessary to correctly scale the fonts if the aspect ratio has been changed.
1241 For example, to render the file @file{sub.ass} on top of the input
1242 video, use the command:
1249 Compute the bounding box for the non-black pixels in the input frame
1252 This filter computes the bounding box containing all the pixels with a
1253 luminance value greater than the minimum allowed value.
1254 The parameters describing the bounding box are printed on the filter
1257 @section blackdetect
1259 Detect video intervals that are (almost) completely black. Can be
1260 useful to detect chapter transitions, commercials, or invalid
1261 recordings. Output lines contains the time for the start, end and
1262 duration of the detected black interval expressed in seconds.
1264 In order to display the output lines, you need to set the loglevel at
1265 least to the AV_LOG_INFO value.
1267 This filter accepts a list of options in the form of
1268 @var{key}=@var{value} pairs separated by ":". A description of the
1269 accepted options follows.
1272 @item black_min_duration, d
1273 Set the minimum detected black duration expressed in seconds. It must
1274 be a non-negative floating point number.
1276 Default value is 2.0.
1278 @item picture_black_ratio_th, pic_th
1279 Set the threshold for considering a picture "black".
1280 Express the minimum value for the ratio:
1282 @var{nb_black_pixels} / @var{nb_pixels}
1285 for which a picture is considered black.
1286 Default value is 0.98.
1288 @item pixel_black_th, pix_th
1289 Set the threshold for considering a pixel "black".
1291 The threshold expresses the maximum pixel luminance value for which a
1292 pixel is considered "black". The provided value is scaled according to
1293 the following equation:
1295 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
1298 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
1299 the input video format, the range is [0-255] for YUV full-range
1300 formats and [16-235] for YUV non full-range formats.
1302 Default value is 0.10.
1305 The following example sets the maximum pixel threshold to the minimum
1306 value, and detects only black intervals of 2 or more seconds:
1308 blackdetect=d=2:pix_th=0.00
1313 Detect frames that are (almost) completely black. Can be useful to
1314 detect chapter transitions or commercials. Output lines consist of
1315 the frame number of the detected frame, the percentage of blackness,
1316 the position in the file if known or -1 and the timestamp in seconds.
1318 In order to display the output lines, you need to set the loglevel at
1319 least to the AV_LOG_INFO value.
1321 The filter accepts the syntax:
1323 blackframe[=@var{amount}:[@var{threshold}]]
1326 @var{amount} is the percentage of the pixels that have to be below the
1327 threshold, and defaults to 98.
1329 @var{threshold} is the threshold below which a pixel value is
1330 considered black, and defaults to 32.
1334 Apply boxblur algorithm to the input video.
1336 This filter accepts the parameters:
1337 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
1339 Chroma and alpha parameters are optional, if not specified they default
1340 to the corresponding values set for @var{luma_radius} and
1343 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
1344 the radius in pixels of the box used for blurring the corresponding
1345 input plane. They are expressions, and can contain the following
1349 the input width and height in pixels
1352 the input chroma image width and height in pixels
1355 horizontal and vertical chroma subsample values. For example for the
1356 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1359 The radius must be a non-negative number, and must not be greater than
1360 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
1361 and of @code{min(cw,ch)/2} for the chroma planes.
1363 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
1364 how many times the boxblur filter is applied to the corresponding
1367 Some examples follow:
1372 Apply a boxblur filter with luma, chroma, and alpha radius
1379 Set luma radius to 2, alpha and chroma radius to 0
1385 Set luma and chroma radius to a fraction of the video dimension
1387 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
1392 @section colormatrix
1394 The colormatrix filter allows conversion between any of the following color
1395 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
1396 and FCC (@var{fcc}).
1398 The syntax of the parameters is @var{source}:@var{destination}:
1401 colormatrix=bt601:smpte240m
1406 Copy the input source unchanged to the output. Mainly useful for
1411 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
1413 The @var{keep_aspect} parameter is optional, if specified and set to a
1414 non-zero value will force the output display aspect ratio to be the
1415 same of the input, by changing the output sample aspect ratio.
1417 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1418 expressions containing the following constants:
1422 the computed values for @var{x} and @var{y}. They are evaluated for
1426 the input width and height
1429 same as @var{in_w} and @var{in_h}
1432 the output (cropped) width and height
1435 same as @var{out_w} and @var{out_h}
1438 same as @var{iw} / @var{ih}
1441 input sample aspect ratio
1444 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1447 horizontal and vertical chroma subsample values. For example for the
1448 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1451 the number of input frame, starting from 0
1454 the position in the file of the input frame, NAN if unknown
1457 timestamp expressed in seconds, NAN if the input timestamp is unknown
1461 The @var{out_w} and @var{out_h} parameters specify the expressions for
1462 the width and height of the output (cropped) video. They are
1463 evaluated just at the configuration of the filter.
1465 The default value of @var{out_w} is "in_w", and the default value of
1466 @var{out_h} is "in_h".
1468 The expression for @var{out_w} may depend on the value of @var{out_h},
1469 and the expression for @var{out_h} may depend on @var{out_w}, but they
1470 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1471 evaluated after @var{out_w} and @var{out_h}.
1473 The @var{x} and @var{y} parameters specify the expressions for the
1474 position of the top-left corner of the output (non-cropped) area. They
1475 are evaluated for each frame. If the evaluated value is not valid, it
1476 is approximated to the nearest valid value.
1478 The default value of @var{x} is "(in_w-out_w)/2", and the default
1479 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
1480 the center of the input image.
1482 The expression for @var{x} may depend on @var{y}, and the expression
1483 for @var{y} may depend on @var{x}.
1485 Follow some examples:
1487 # crop the central input area with size 100x100
1490 # crop the central input area with size 2/3 of the input video
1491 "crop=2/3*in_w:2/3*in_h"
1493 # crop the input video central square
1496 # delimit the rectangle with the top-left corner placed at position
1497 # 100:100 and the right-bottom corner corresponding to the right-bottom
1498 # corner of the input image.
1499 crop=in_w-100:in_h-100:100:100
1501 # crop 10 pixels from the left and right borders, and 20 pixels from
1502 # the top and bottom borders
1503 "crop=in_w-2*10:in_h-2*20"
1505 # keep only the bottom right quarter of the input image
1506 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1508 # crop height for getting Greek harmony
1509 "crop=in_w:1/PHI*in_w"
1512 "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)"
1514 # erratic camera effect depending on timestamp
1515 "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)"
1517 # set x depending on the value of y
1518 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1523 Auto-detect crop size.
1525 Calculate necessary cropping parameters and prints the recommended
1526 parameters through the logging system. The detected dimensions
1527 correspond to the non-black area of the input video.
1529 It accepts the syntax:
1531 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1537 Threshold, which can be optionally specified from nothing (0) to
1538 everything (255), defaults to 24.
1541 Value which the width/height should be divisible by, defaults to
1542 16. The offset is automatically adjusted to center the video. Use 2 to
1543 get only even dimensions (needed for 4:2:2 video). 16 is best when
1544 encoding to most video codecs.
1547 Counter that determines after how many frames cropdetect will reset
1548 the previously detected largest video area and start over to detect
1549 the current optimal crop area. Defaults to 0.
1551 This can be useful when channel logos distort the video area. 0
1552 indicates never reset and return the largest area encountered during
1558 This filter drops frames that do not differ greatly from the previous
1559 frame in order to reduce framerate. The main use of this filter is
1560 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1561 it could in theory be used for fixing movies that were
1562 inverse-telecined incorrectly.
1564 It accepts the following parameters:
1565 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1570 Set the maximum number of consecutive frames which can be dropped (if
1571 positive), or the minimum interval between dropped frames (if
1572 negative). If the value is 0, the frame is dropped unregarding the
1573 number of previous sequentially dropped frames.
1578 Set the dropping threshold values.
1580 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1581 represent actual pixel value differences, so a threshold of 64
1582 corresponds to 1 unit of difference for each pixel, or the same spread
1583 out differently over the block.
1585 A frame is a candidate for dropping if no 8x8 blocks differ by more
1586 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1587 meaning the whole image) differ by more than a threshold of @var{lo}.
1589 Default value for @var{hi} is 64*12, default value for @var{lo} is
1590 64*5, and default value for @var{frac} is 0.33.
1595 Suppress a TV station logo by a simple interpolation of the surrounding
1596 pixels. Just set a rectangle covering the logo and watch it disappear
1597 (and sometimes something even uglier appear - your mileage may vary).
1599 The filter accepts parameters as a string of the form
1600 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1601 @var{key}=@var{value} pairs, separated by ":".
1603 The description of the accepted parameters follows.
1608 Specify the top left corner coordinates of the logo. They must be
1612 Specify the width and height of the logo to clear. They must be
1616 Specify the thickness of the fuzzy edge of the rectangle (added to
1617 @var{w} and @var{h}). The default value is 4.
1620 When set to 1, a green rectangle is drawn on the screen to simplify
1621 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1622 @var{band} is set to 4. The default value is 0.
1626 Some examples follow.
1631 Set a rectangle covering the area with top left corner coordinates 0,0
1632 and size 100x77, setting a band of size 10:
1634 delogo=0:0:100:77:10
1638 As the previous example, but use named options:
1640 delogo=x=0:y=0:w=100:h=77:band=10
1647 Attempt to fix small changes in horizontal and/or vertical shift. This
1648 filter helps remove camera shake from hand-holding a camera, bumping a
1649 tripod, moving on a vehicle, etc.
1651 The filter accepts parameters as a string of the form
1652 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1654 A description of the accepted parameters follows.
1659 Specify a rectangular area where to limit the search for motion
1661 If desired the search for motion vectors can be limited to a
1662 rectangular area of the frame defined by its top left corner, width
1663 and height. These parameters have the same meaning as the drawbox
1664 filter which can be used to visualise the position of the bounding
1667 This is useful when simultaneous movement of subjects within the frame
1668 might be confused for camera motion by the motion vector search.
1670 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1671 then the full frame is used. This allows later options to be set
1672 without specifying the bounding box for the motion vector search.
1674 Default - search the whole frame.
1677 Specify the maximum extent of movement in x and y directions in the
1678 range 0-64 pixels. Default 16.
1681 Specify how to generate pixels to fill blanks at the edge of the
1682 frame. An integer from 0 to 3 as follows:
1685 Fill zeroes at blank locations
1687 Original image at blank locations
1689 Extruded edge value at blank locations
1691 Mirrored edge at blank locations
1694 The default setting is mirror edge at blank locations.
1697 Specify the blocksize to use for motion search. Range 4-128 pixels,
1701 Specify the contrast threshold for blocks. Only blocks with more than
1702 the specified contrast (difference between darkest and lightest
1703 pixels) will be considered. Range 1-255, default 125.
1706 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1707 search. Default - exhaustive search.
1710 If set then a detailed log of the motion search is written to the
1717 Draw a colored box on the input image.
1719 It accepts the syntax:
1721 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}
1727 Specify the top left corner coordinates of the box. Default to 0.
1730 Specify the width and height of the box, if 0 they are interpreted as
1731 the input width and height. Default to 0.
1734 Specify the color of the box to write, it can be the name of a color
1735 (case insensitive match) or a 0xRRGGBB[AA] sequence.
1738 Follow some examples:
1740 # draw a black box around the edge of the input image
1743 # draw a box with color red and an opacity of 50%
1744 drawbox=10:20:200:60:red@@0.5"
1749 Draw text string or text from specified file on top of video using the
1750 libfreetype library.
1752 To enable compilation of this filter you need to configure FFmpeg with
1753 @code{--enable-libfreetype}.
1755 The filter also recognizes strftime() sequences in the provided text
1756 and expands them accordingly. Check the documentation of strftime().
1758 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1761 The description of the accepted parameters follows.
1766 Used to draw a box around text using background color.
1767 Value should be either 1 (enable) or 0 (disable).
1768 The default value of @var{box} is 0.
1771 The color to be used for drawing box around text.
1772 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1773 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1774 The default value of @var{boxcolor} is "white".
1777 Set an expression which specifies if the text should be drawn. If the
1778 expression evaluates to 0, the text is not drawn. This is useful for
1779 specifying that the text should be drawn only when specific conditions
1782 Default value is "1".
1784 See below for the list of accepted constants and functions.
1787 If true, check and fix text coords to avoid clipping.
1790 The color to be used for drawing fonts.
1791 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1792 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1793 The default value of @var{fontcolor} is "black".
1796 The font file to be used for drawing text. Path must be included.
1797 This parameter is mandatory.
1800 The font size to be used for drawing text.
1801 The default value of @var{fontsize} is 16.
1804 Flags to be used for loading the fonts.
1806 The flags map the corresponding flags supported by libfreetype, and are
1807 a combination of the following values:
1814 @item vertical_layout
1815 @item force_autohint
1818 @item ignore_global_advance_width
1820 @item ignore_transform
1827 Default value is "render".
1829 For more information consult the documentation for the FT_LOAD_*
1833 The color to be used for drawing a shadow behind the drawn text. It
1834 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1835 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1836 The default value of @var{shadowcolor} is "black".
1838 @item shadowx, shadowy
1839 The x and y offsets for the text shadow position with respect to the
1840 position of the text. They can be either positive or negative
1841 values. Default value for both is "0".
1844 The size in number of spaces to use for rendering the tab.
1848 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
1849 format. It can be used with or without text parameter. @var{timecode_rate}
1850 option must be specified.
1852 @item timecode_rate, rate, r
1853 Set the timecode frame rate (timecode only).
1856 The text string to be drawn. The text must be a sequence of UTF-8
1858 This parameter is mandatory if no file is specified with the parameter
1862 A text file containing text to be drawn. The text must be a sequence
1863 of UTF-8 encoded characters.
1865 This parameter is mandatory if no text string is specified with the
1866 parameter @var{text}.
1868 If both @var{text} and @var{textfile} are specified, an error is thrown.
1871 The expressions which specify the offsets where text will be drawn
1872 within the video frame. They are relative to the top/left border of the
1875 The default value of @var{x} and @var{y} is "0".
1877 See below for the list of accepted constants and functions.
1880 The parameters for @var{x} and @var{y} are expressions containing the
1881 following constants and functions:
1885 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
1888 horizontal and vertical chroma subsample values. For example for the
1889 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1892 the height of each text line
1900 @item max_glyph_a, ascent
1901 the maximum distance from the baseline to the highest/upper grid
1902 coordinate used to place a glyph outline point, for all the rendered
1904 It is a positive value, due to the grid's orientation with the Y axis
1907 @item max_glyph_d, descent
1908 the maximum distance from the baseline to the lowest grid coordinate
1909 used to place a glyph outline point, for all the rendered glyphs.
1910 This is a negative value, due to the grid's orientation, with the Y axis
1914 maximum glyph height, that is the maximum height for all the glyphs
1915 contained in the rendered text, it is equivalent to @var{ascent} -
1919 maximum glyph width, that is the maximum width for all the glyphs
1920 contained in the rendered text
1923 the number of input frame, starting from 0
1925 @item rand(min, max)
1926 return a random number included between @var{min} and @var{max}
1929 input sample aspect ratio
1932 timestamp expressed in seconds, NAN if the input timestamp is unknown
1935 the height of the rendered text
1938 the width of the rendered text
1941 the x and y offset coordinates where the text is drawn.
1943 These parameters allow the @var{x} and @var{y} expressions to refer
1944 each other, so you can for example specify @code{y=x/dar}.
1947 If libavfilter was built with @code{--enable-fontconfig}, then
1948 @option{fontfile} can be a fontconfig pattern or omitted.
1950 Some examples follow.
1955 Draw "Test Text" with font FreeSerif, using the default values for the
1956 optional parameters.
1959 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
1963 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
1964 and y=50 (counting from the top-left corner of the screen), text is
1965 yellow with a red box around it. Both the text and the box have an
1969 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
1970 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
1973 Note that the double quotes are not necessary if spaces are not used
1974 within the parameter list.
1977 Show the text at the center of the video frame:
1979 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
1983 Show a text line sliding from right to left in the last row of the video
1984 frame. The file @file{LONG_LINE} is assumed to contain a single line
1987 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
1991 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
1993 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
1997 Draw a single green letter "g", at the center of the input video.
1998 The glyph baseline is placed at half screen height.
2000 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2004 Show text for 1 second every 3 seconds:
2006 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\\,3)\\,1):text='blink'"
2010 Use fontconfig to set the font. Note that the colons need to be escaped.
2012 drawtext='fontfile=Linux Libertine O-40\\:style=Semibold:text=FFmpeg'
2017 For more information about libfreetype, check:
2018 @url{http://www.freetype.org/}.
2020 For more information about fontconfig, check:
2021 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2025 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2027 This filter accepts the following optional named parameters:
2031 Set low and high threshold values used by the Canny thresholding
2034 The high threshold selects the "strong" edge pixels, which are then
2035 connected through 8-connectivity with the "weak" edge pixels selected
2036 by the low threshold.
2038 @var{low} and @var{high} threshold values must be choosen in the range
2039 [0,1], and @var{low} should be lesser or equal to @var{high}.
2041 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2047 edgedetect=low=0.1:high=0.4
2052 Apply fade-in/out effect to input video.
2054 It accepts the parameters:
2055 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2057 @var{type} specifies if the effect type, can be either "in" for
2058 fade-in, or "out" for a fade-out effect.
2060 @var{start_frame} specifies the number of the start frame for starting
2061 to apply the fade effect.
2063 @var{nb_frames} specifies the number of frames for which the fade
2064 effect has to last. At the end of the fade-in effect the output video
2065 will have the same intensity as the input video, at the end of the
2066 fade-out transition the output video will be completely black.
2068 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2069 separated by ":". The description of the accepted options follows.
2076 @item start_frame, s
2077 See @var{start_frame}.
2080 See @var{nb_frames}.
2083 If set to 1, fade only alpha channel, if one exists on the input.
2087 A few usage examples follow, usable too as test scenarios.
2089 # fade in first 30 frames of video
2092 # fade out last 45 frames of a 200-frame video
2095 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2096 fade=in:0:25, fade=out:975:25
2098 # make first 5 frames black, then fade in from frame 5-24
2101 # fade in alpha over first 25 frames of video
2102 fade=in:0:25:alpha=1
2107 Transform the field order of the input video.
2109 It accepts one parameter which specifies the required field order that
2110 the input interlaced video will be transformed to. The parameter can
2111 assume one of the following values:
2115 output bottom field first
2117 output top field first
2120 Default value is "tff".
2122 Transformation is achieved by shifting the picture content up or down
2123 by one line, and filling the remaining line with appropriate picture content.
2124 This method is consistent with most broadcast field order converters.
2126 If the input video is not flagged as being interlaced, or it is already
2127 flagged as being of the required output field order then this filter does
2128 not alter the incoming video.
2130 This filter is very useful when converting to or from PAL DV material,
2131 which is bottom field first.
2135 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2140 Buffer input images and send them when they are requested.
2142 This filter is mainly useful when auto-inserted by the libavfilter
2145 The filter does not take parameters.
2149 Convert the input video to one of the specified pixel formats.
2150 Libavfilter will try to pick one that is supported for the input to
2153 The filter accepts a list of pixel format names, separated by ":",
2154 for example "yuv420p:monow:rgb24".
2156 Some examples follow:
2158 # convert the input video to the format "yuv420p"
2161 # convert the input video to any of the formats in the list
2162 format=yuv420p:yuv444p:yuv410p
2167 Convert the video to specified constant framerate by duplicating or dropping
2168 frames as necessary.
2170 This filter accepts the following named parameters:
2174 Desired output framerate.
2180 Select one frame every N.
2182 This filter accepts in input a string representing a positive
2183 integer. Default argument is @code{1}.
2188 Apply a frei0r effect to the input video.
2190 To enable compilation of this filter you need to install the frei0r
2191 header and configure FFmpeg with @code{--enable-frei0r}.
2193 The filter supports the syntax:
2195 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2198 @var{filter_name} is the name to the frei0r effect to load. If the
2199 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2200 is searched in each one of the directories specified by the colon
2201 separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r
2202 paths, which are in this order: @file{HOME/.frei0r-1/lib/},
2203 @file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}.
2205 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2206 for the frei0r effect.
2208 A frei0r effect parameter can be a boolean (whose values are specified
2209 with "y" and "n"), a double, a color (specified by the syntax
2210 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2211 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2212 description), a position (specified by the syntax @var{X}/@var{Y},
2213 @var{X} and @var{Y} being float numbers) and a string.
2215 The number and kind of parameters depend on the loaded effect. If an
2216 effect parameter is not specified the default value is set.
2218 Some examples follow:
2222 Apply the distort0r effect, set the first two double parameters:
2224 frei0r=distort0r:0.5:0.01
2228 Apply the colordistance effect, takes a color as first parameter:
2230 frei0r=colordistance:0.2/0.3/0.4
2231 frei0r=colordistance:violet
2232 frei0r=colordistance:0x112233
2236 Apply the perspective effect, specify the top left and top right image
2239 frei0r=perspective:0.2/0.2:0.8/0.2
2243 For more information see:
2244 @url{http://frei0r.dyne.org}
2248 Fix the banding artifacts that are sometimes introduced into nearly flat
2249 regions by truncation to 8bit color depth.
2250 Interpolate the gradients that should go where the bands are, and
2253 This filter is designed for playback only. Do not use it prior to
2254 lossy compression, because compression tends to lose the dither and
2255 bring back the bands.
2257 The filter takes two optional parameters, separated by ':':
2258 @var{strength}:@var{radius}
2260 @var{strength} is the maximum amount by which the filter will change
2261 any one pixel. Also the threshold for detecting nearly flat
2262 regions. Acceptable values range from .51 to 255, default value is
2263 1.2, out-of-range values will be clipped to the valid range.
2265 @var{radius} is the neighborhood to fit the gradient to. A larger
2266 radius makes for smoother gradients, but also prevents the filter from
2267 modifying the pixels near detailed regions. Acceptable values are
2268 8-32, default value is 16, out-of-range values will be clipped to the
2272 # default parameters
2281 Flip the input video horizontally.
2283 For example to horizontally flip the input video with @command{ffmpeg}:
2285 ffmpeg -i in.avi -vf "hflip" out.avi
2290 High precision/quality 3d denoise filter. This filter aims to reduce
2291 image noise producing smooth images and making still images really
2292 still. It should enhance compressibility.
2294 It accepts the following optional parameters:
2295 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2299 a non-negative float number which specifies spatial luma strength,
2302 @item chroma_spatial
2303 a non-negative float number which specifies spatial chroma strength,
2304 defaults to 3.0*@var{luma_spatial}/4.0
2307 a float number which specifies luma temporal strength, defaults to
2308 6.0*@var{luma_spatial}/4.0
2311 a float number which specifies chroma temporal strength, defaults to
2312 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2317 Modify the hue and/or the saturation of the input.
2319 This filter accepts the following optional named options:
2323 Specify the hue angle as a number of degrees. It accepts a float
2324 number or an expression, and defaults to 0.0.
2327 Specify the hue angle as a number of degrees. It accepts a float
2328 number or an expression, and defaults to 0.0.
2331 Specify the saturation in the [-10,10] range. It accepts a float number and
2335 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2336 following constants:
2340 frame count of the input frame starting from 0
2343 presentation timestamp of the input frame expressed in time base units
2346 frame rate of the input video, NAN if the input frame rate is unknown
2349 timestamp expressed in seconds, NAN if the input timestamp is unknown
2352 time base of the input video
2355 The options can also be set using the syntax: @var{hue}:@var{saturation}
2357 In this case @var{hue} is expressed in degrees.
2359 Some examples follow:
2362 Set the hue to 90 degrees and the saturation to 1.0:
2368 Same command but expressing the hue in radians:
2374 Same command without named options, hue must be expressed in degrees:
2380 Note that "h:s" syntax does not support expressions for the values of
2381 h and s, so the following example will issue an error:
2387 Rotate hue and make the saturation swing between 0
2388 and 2 over a period of 1 second:
2390 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2394 Apply a 3 seconds saturation fade-in effect starting at 0:
2399 The general fade-in expression can be written as:
2401 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2405 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2407 hue="s=max(0\, min(1\, (8-t)/3))"
2410 The general fade-out expression can be written as:
2412 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2417 @subsection Commands
2419 This filter supports the following command:
2422 Modify the hue and/or the saturation of the input video.
2423 The command accepts the same named options and syntax than when calling the
2424 filter from the command-line.
2426 If a parameter is omitted, it is kept at its current value.
2431 Interlaceing detect filter. This filter tries to detect if the input is
2432 interlaced or progressive. Top or bottom field first.
2434 @section lut, lutrgb, lutyuv
2436 Compute a look-up table for binding each pixel component input value
2437 to an output value, and apply it to input video.
2439 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2440 to an RGB input video.
2442 These filters accept in input a ":"-separated list of options, which
2443 specify the expressions used for computing the lookup table for the
2444 corresponding pixel component values.
2446 The @var{lut} filter requires either YUV or RGB pixel formats in
2447 input, and accepts the options:
2450 first pixel component
2452 second pixel component
2454 third pixel component
2456 fourth pixel component, corresponds to the alpha component
2459 The exact component associated to each option depends on the format in
2462 The @var{lutrgb} filter requires RGB pixel formats in input, and
2463 accepts the options:
2475 The @var{lutyuv} filter requires YUV pixel formats in input, and
2476 accepts the options:
2479 Y/luminance component
2488 The expressions can contain the following constants and functions:
2492 the input width and height
2495 input value for the pixel component
2498 the input value clipped in the @var{minval}-@var{maxval} range
2501 maximum value for the pixel component
2504 minimum value for the pixel component
2507 the negated value for the pixel component value clipped in the
2508 @var{minval}-@var{maxval} range , it corresponds to the expression
2509 "maxval-clipval+minval"
2512 the computed value in @var{val} clipped in the
2513 @var{minval}-@var{maxval} range
2515 @item gammaval(gamma)
2516 the computed gamma correction value of the pixel component value
2517 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2519 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2523 All expressions default to "val".
2525 Some examples follow:
2527 # negate input video
2528 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2529 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2531 # the above is the same as
2532 lutrgb="r=negval:g=negval:b=negval"
2533 lutyuv="y=negval:u=negval:v=negval"
2538 # remove chroma components, turns the video into a graytone image
2539 lutyuv="u=128:v=128"
2541 # apply a luma burning effect
2544 # remove green and blue components
2547 # set a constant alpha channel value on input
2548 format=rgba,lutrgb=a="maxval-minval/2"
2550 # correct luminance gamma by a 0.5 factor
2551 lutyuv=y=gammaval(0.5)
2556 Apply an MPlayer filter to the input video.
2558 This filter provides a wrapper around most of the filters of
2561 This wrapper is considered experimental. Some of the wrapped filters
2562 may not work properly and we may drop support for them, as they will
2563 be implemented natively into FFmpeg. Thus you should avoid
2564 depending on them when writing portable scripts.
2566 The filters accepts the parameters:
2567 @var{filter_name}[:=]@var{filter_params}
2569 @var{filter_name} is the name of a supported MPlayer filter,
2570 @var{filter_params} is a string containing the parameters accepted by
2573 The list of the currently supported filters follows:
2617 The parameter syntax and behavior for the listed filters are the same
2618 of the corresponding MPlayer filters. For detailed instructions check
2619 the "VIDEO FILTERS" section in the MPlayer manual.
2621 Some examples follow:
2624 Adjust gamma, brightness, contrast:
2630 Add temporal noise to input video:
2636 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2642 This filter accepts an integer in input, if non-zero it negates the
2643 alpha component (if available). The default value in input is 0.
2647 Force libavfilter not to use any of the specified pixel formats for the
2648 input to the next filter.
2650 The filter accepts a list of pixel format names, separated by ":",
2651 for example "yuv420p:monow:rgb24".
2653 Some examples follow:
2655 # force libavfilter to use a format different from "yuv420p" for the
2656 # input to the vflip filter
2657 noformat=yuv420p,vflip
2659 # convert the input video to any of the formats not contained in the list
2660 noformat=yuv420p:yuv444p:yuv410p
2665 Pass the video source unchanged to the output.
2669 Apply video transform using libopencv.
2671 To enable this filter install libopencv library and headers and
2672 configure FFmpeg with @code{--enable-libopencv}.
2674 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
2676 @var{filter_name} is the name of the libopencv filter to apply.
2678 @var{filter_params} specifies the parameters to pass to the libopencv
2679 filter. If not specified the default values are assumed.
2681 Refer to the official libopencv documentation for more precise
2683 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
2685 Follows the list of supported libopencv filters.
2690 Dilate an image by using a specific structuring element.
2691 This filter corresponds to the libopencv function @code{cvDilate}.
2693 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
2695 @var{struct_el} represents a structuring element, and has the syntax:
2696 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
2698 @var{cols} and @var{rows} represent the number of columns and rows of
2699 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
2700 point, and @var{shape} the shape for the structuring element, and
2701 can be one of the values "rect", "cross", "ellipse", "custom".
2703 If the value for @var{shape} is "custom", it must be followed by a
2704 string of the form "=@var{filename}". The file with name
2705 @var{filename} is assumed to represent a binary image, with each
2706 printable character corresponding to a bright pixel. When a custom
2707 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
2708 or columns and rows of the read file are assumed instead.
2710 The default value for @var{struct_el} is "3x3+0x0/rect".
2712 @var{nb_iterations} specifies the number of times the transform is
2713 applied to the image, and defaults to 1.
2715 Follow some example:
2717 # use the default values
2720 # dilate using a structuring element with a 5x5 cross, iterate two times
2721 ocv=dilate=5x5+2x2/cross:2
2723 # read the shape from the file diamond.shape, iterate two times
2724 # the file diamond.shape may contain a pattern of characters like this:
2730 # the specified cols and rows are ignored (but not the anchor point coordinates)
2731 ocv=0x0+2x2/custom=diamond.shape:2
2736 Erode an image by using a specific structuring element.
2737 This filter corresponds to the libopencv function @code{cvErode}.
2739 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
2740 with the same syntax and semantics as the @ref{dilate} filter.
2744 Smooth the input video.
2746 The filter takes the following parameters:
2747 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
2749 @var{type} is the type of smooth filter to apply, and can be one of
2750 the following values: "blur", "blur_no_scale", "median", "gaussian",
2751 "bilateral". The default value is "gaussian".
2753 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
2754 parameters whose meanings depend on smooth type. @var{param1} and
2755 @var{param2} accept integer positive values or 0, @var{param3} and
2756 @var{param4} accept float values.
2758 The default value for @var{param1} is 3, the default value for the
2759 other parameters is 0.
2761 These parameters correspond to the parameters assigned to the
2762 libopencv function @code{cvSmooth}.
2767 Overlay one video on top of another.
2769 It takes two inputs and one output, the first input is the "main"
2770 video on which the second input is overlayed.
2772 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
2774 @var{x} is the x coordinate of the overlayed video on the main video,
2775 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
2776 the following parameters:
2779 @item main_w, main_h
2780 main input width and height
2783 same as @var{main_w} and @var{main_h}
2785 @item overlay_w, overlay_h
2786 overlay input width and height
2789 same as @var{overlay_w} and @var{overlay_h}
2792 @var{options} is an optional list of @var{key}=@var{value} pairs,
2795 The description of the accepted options follows.
2799 If set to 1, force the filter to accept inputs in the RGB
2800 color space. Default value is 0.
2803 Be aware that frames are taken from each input video in timestamp
2804 order, hence, if their initial timestamps differ, it is a a good idea
2805 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
2806 have them begin in the same zero timestamp, as it does the example for
2807 the @var{movie} filter.
2809 Follow some examples:
2811 # draw the overlay at 10 pixels from the bottom right
2812 # corner of the main video.
2813 overlay=main_w-overlay_w-10:main_h-overlay_h-10
2815 # insert a transparent PNG logo in the bottom left corner of the input
2816 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
2818 # insert 2 different transparent PNG logos (second logo on bottom
2820 ffmpeg -i input -i logo1 -i logo2 -filter_complex
2821 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
2823 # add a transparent color layer on top of the main video,
2824 # WxH specifies the size of the main input to the overlay filter
2825 color=red@.3:WxH [over]; [in][over] overlay [out]
2827 # play an original video and a filtered version (here with the deshake filter)
2829 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
2831 # the previous example is the same as:
2832 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
2835 You can chain together more overlays but the efficiency of such
2836 approach is yet to be tested.
2840 Add paddings to the input image, and places the original input at the
2841 given coordinates @var{x}, @var{y}.
2843 It accepts the following parameters:
2844 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
2846 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
2847 expressions containing the following constants:
2851 the input video width and height
2854 same as @var{in_w} and @var{in_h}
2857 the output width and height, that is the size of the padded area as
2858 specified by the @var{width} and @var{height} expressions
2861 same as @var{out_w} and @var{out_h}
2864 x and y offsets as specified by the @var{x} and @var{y}
2865 expressions, or NAN if not yet specified
2868 same as @var{iw} / @var{ih}
2871 input sample aspect ratio
2874 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
2877 horizontal and vertical chroma subsample values. For example for the
2878 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2881 Follows the description of the accepted parameters.
2886 Specify the size of the output image with the paddings added. If the
2887 value for @var{width} or @var{height} is 0, the corresponding input size
2888 is used for the output.
2890 The @var{width} expression can reference the value set by the
2891 @var{height} expression, and vice versa.
2893 The default value of @var{width} and @var{height} is 0.
2897 Specify the offsets where to place the input image in the padded area
2898 with respect to the top/left border of the output image.
2900 The @var{x} expression can reference the value set by the @var{y}
2901 expression, and vice versa.
2903 The default value of @var{x} and @var{y} is 0.
2907 Specify the color of the padded area, it can be the name of a color
2908 (case insensitive match) or a 0xRRGGBB[AA] sequence.
2910 The default value of @var{color} is "black".
2918 Add paddings with color "violet" to the input video. Output video
2919 size is 640x480, the top-left corner of the input video is placed at
2922 pad=640:480:0:40:violet
2926 Pad the input to get an output with dimensions increased by 3/2,
2927 and put the input video at the center of the padded area:
2929 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
2933 Pad the input to get a squared output with size equal to the maximum
2934 value between the input width and height, and put the input video at
2935 the center of the padded area:
2937 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
2941 Pad the input to get a final w/h ratio of 16:9:
2943 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
2947 In case of anamorphic video, in order to set the output display aspect
2948 correctly, it is necessary to use @var{sar} in the expression,
2949 according to the relation:
2951 (ih * X / ih) * sar = output_dar
2952 X = output_dar / sar
2955 Thus the previous example needs to be modified to:
2957 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
2961 Double output size and put the input video in the bottom-right
2962 corner of the output padded area:
2964 pad="2*iw:2*ih:ow-iw:oh-ih"
2968 @section pixdesctest
2970 Pixel format descriptor test filter, mainly useful for internal
2971 testing. The output video should be equal to the input video.
2975 format=monow, pixdesctest
2978 can be used to test the monowhite pixel format descriptor definition.
2982 Suppress a TV station logo, using an image file to determine which
2983 pixels comprise the logo. It works by filling in the pixels that
2984 comprise the logo with neighboring pixels.
2986 This filter requires one argument which specifies the filter bitmap
2987 file, which can be any image format supported by libavformat. The
2988 width and height of the image file must match those of the video
2989 stream being processed.
2991 Pixels in the provided bitmap image with a value of zero are not
2992 considered part of the logo, non-zero pixels are considered part of
2993 the logo. If you use white (255) for the logo and black (0) for the
2994 rest, you will be safe. For making the filter bitmap, it is
2995 recommended to take a screen capture of a black frame with the logo
2996 visible, and then using a threshold filter followed by the erode
2997 filter once or twice.
2999 If needed, little splotches can be fixed manually. Remember that if
3000 logo pixels are not covered, the filter quality will be much
3001 reduced. Marking too many pixels as part of the logo does not hurt as
3002 much, but it will increase the amount of blurring needed to cover over
3003 the image and will destroy more information than necessary, and extra
3004 pixels will slow things down on a large logo.
3008 Scale the input video to @var{width}:@var{height}[:@var{interl}=@{1|-1@}] and/or convert the image format.
3010 The scale filter forces the output display aspect ratio to be the same
3011 of the input, by changing the output sample aspect ratio.
3013 The parameters @var{width} and @var{height} are expressions containing
3014 the following constants:
3018 the input width and height
3021 same as @var{in_w} and @var{in_h}
3024 the output (cropped) width and height
3027 same as @var{out_w} and @var{out_h}
3030 same as @var{iw} / @var{ih}
3033 input sample aspect ratio
3036 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3039 horizontal and vertical chroma subsample values. For example for the
3040 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3043 If the input image format is different from the format requested by
3044 the next filter, the scale filter will convert the input to the
3047 If the value for @var{width} or @var{height} is 0, the respective input
3048 size is used for the output.
3050 If the value for @var{width} or @var{height} is -1, the scale filter will
3051 use, for the respective output size, a value that maintains the aspect
3052 ratio of the input image.
3054 The default value of @var{width} and @var{height} is 0.
3056 Valid values for the optional parameter @var{interl} are:
3060 force interlaced aware scaling
3063 select interlaced aware scaling depending on whether the source frames
3064 are flagged as interlaced or not
3067 Unless @var{interl} is set to one of the above options, interlaced scaling will not be used.
3069 Some examples follow:
3071 # scale the input video to a size of 200x100.
3074 # scale the input to 2x
3076 # the above is the same as
3079 # scale the input to 2x with forced interlaced scaling
3080 scale=2*iw:2*ih:interl=1
3082 # scale the input to half size
3085 # increase the width, and set the height to the same size
3088 # seek for Greek harmony
3092 # increase the height, and set the width to 3/2 of the height
3095 # increase the size, but make the size a multiple of the chroma
3096 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3098 # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
3099 scale='min(500\, iw*3/2):-1'
3103 Select frames to pass in output.
3105 It accepts in input an expression, which is evaluated for each input
3106 frame. If the expression is evaluated to a non-zero value, the frame
3107 is selected and passed to the output, otherwise it is discarded.
3109 The expression can contain the following constants:
3113 the sequential number of the filtered frame, starting from 0
3116 the sequential number of the selected frame, starting from 0
3118 @item prev_selected_n
3119 the sequential number of the last selected frame, NAN if undefined
3122 timebase of the input timestamps
3125 the PTS (Presentation TimeStamp) of the filtered video frame,
3126 expressed in @var{TB} units, NAN if undefined
3129 the PTS (Presentation TimeStamp) of the filtered video frame,
3130 expressed in seconds, NAN if undefined
3133 the PTS of the previously filtered video frame, NAN if undefined
3135 @item prev_selected_pts
3136 the PTS of the last previously filtered video frame, NAN if undefined
3138 @item prev_selected_t
3139 the PTS of the last previously selected video frame, NAN if undefined
3142 the PTS of the first video frame in the video, NAN if undefined
3145 the time of the first video frame in the video, NAN if undefined
3148 the type of the filtered frame, can assume one of the following
3160 @item interlace_type
3161 the frame interlace type, can assume one of the following values:
3164 the frame is progressive (not interlaced)
3166 the frame is top-field-first
3168 the frame is bottom-field-first
3172 1 if the filtered frame is a key-frame, 0 otherwise
3175 the position in the file of the filtered frame, -1 if the information
3176 is not available (e.g. for synthetic video)
3179 value between 0 and 1 to indicate a new scene; a low value reflects a low
3180 probability for the current frame to introduce a new scene, while a higher
3181 value means the current frame is more likely to be one (see the example below)
3185 The default value of the select expression is "1".
3187 Some examples follow:
3190 # select all frames in input
3193 # the above is the same as:
3199 # select only I-frames
3200 select='eq(pict_type\,I)'
3202 # select one frame every 100
3203 select='not(mod(n\,100))'
3205 # select only frames contained in the 10-20 time interval
3206 select='gte(t\,10)*lte(t\,20)'
3208 # select only I frames contained in the 10-20 time interval
3209 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
3211 # select frames with a minimum distance of 10 seconds
3212 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
3215 Complete example to create a mosaic of the first scenes:
3218 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
3221 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
3224 @section setdar, setsar
3226 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3229 This is done by changing the specified Sample (aka Pixel) Aspect
3230 Ratio, according to the following equation:
3232 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3235 Keep in mind that the @code{setdar} filter does not modify the pixel
3236 dimensions of the video frame. Also the display aspect ratio set by
3237 this filter may be changed by later filters in the filterchain,
3238 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3241 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3242 the filter output video.
3244 Note that as a consequence of the application of this filter, the
3245 output display aspect ratio will change according to the equation
3248 Keep in mind that the sample aspect ratio set by the @code{setsar}
3249 filter may be changed by later filters in the filterchain, e.g. if
3250 another "setsar" or a "setdar" filter is applied.
3252 The @code{setdar} and @code{setsar} filters accept a parameter string
3253 which represents the wanted aspect ratio. The parameter can
3254 be a floating point number string, an expression, or a string of the form
3255 @var{num}:@var{den}, where @var{num} and @var{den} are the numerator
3256 and denominator of the aspect ratio. If the parameter is not
3257 specified, it is assumed the value "0:1".
3259 For example to change the display aspect ratio to 16:9, specify:
3264 The example above is equivalent to:
3269 To change the sample aspect ratio to 10:11, specify:
3276 Force field for the output video frame.
3278 The @code{setfield} filter marks the interlace type field for the
3279 output frames. It does not change the input frame, but only sets the
3280 corresponding property, which affects how the frame is treated by
3281 following filters (e.g. @code{fieldorder} or @code{yadif}).
3283 It accepts a string parameter, which can assume the following values:
3286 Keep the same field property.
3289 Mark the frame as bottom-field-first.
3292 Mark the frame as top-field-first.
3295 Mark the frame as progressive.
3300 Show a line containing various information for each input video frame.
3301 The input video is not modified.
3303 The shown line contains a sequence of key/value pairs of the form
3304 @var{key}:@var{value}.
3306 A description of each shown parameter follows:
3310 sequential number of the input frame, starting from 0
3313 Presentation TimeStamp of the input frame, expressed as a number of
3314 time base units. The time base unit depends on the filter input pad.
3317 Presentation TimeStamp of the input frame, expressed as a number of
3321 position of the frame in the input stream, -1 if this information in
3322 unavailable and/or meaningless (for example in case of synthetic video)
3328 sample aspect ratio of the input frame, expressed in the form
3332 size of the input frame, expressed in the form
3333 @var{width}x@var{height}
3336 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3337 for bottom field first)
3340 1 if the frame is a key frame, 0 otherwise
3343 picture type of the input frame ("I" for an I-frame, "P" for a
3344 P-frame, "B" for a B-frame, "?" for unknown type).
3345 Check also the documentation of the @code{AVPictureType} enum and of
3346 the @code{av_get_picture_type_char} function defined in
3347 @file{libavutil/avutil.h}.
3350 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3352 @item plane_checksum
3353 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3354 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3359 Pass the images of input video on to next video filter as multiple
3363 ffmpeg -i in.avi -vf "slicify=32" out.avi
3366 The filter accepts the slice height as parameter. If the parameter is
3367 not specified it will use the default value of 16.
3369 Adding this in the beginning of filter chains should make filtering
3370 faster due to better use of the memory cache.
3374 Blur the input video without impacting the outlines.
3376 The filter accepts the following parameters:
3377 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3379 Parameters prefixed by @var{luma} indicate that they work on the
3380 luminance of the pixels whereas parameters prefixed by @var{chroma}
3381 refer to the chrominance of the pixels.
3383 If the chroma parameters are not set, the luma parameters are used for
3384 either the luminance and the chrominance of the pixels.
3386 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3387 range [0.1,5.0] that specifies the variance of the gaussian filter
3388 used to blur the image (slower if larger).
3390 @var{luma_strength} or @var{chroma_strength} must be a float number in
3391 the range [-1.0,1.0] that configures the blurring. A value included in
3392 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3393 will sharpen the image.
3395 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3396 the range [-30,30] that is used as a coefficient to determine whether
3397 a pixel should be blurred or not. A value of 0 will filter all the
3398 image, a value included in [0,30] will filter flat areas and a value
3399 included in [-30,0] will filter edges.
3403 Split input video into several identical outputs.
3405 The filter accepts a single parameter which specifies the number of outputs. If
3406 unspecified, it defaults to 2.
3410 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3412 will create 5 copies of the input video.
3416 [in] split [splitout1][splitout2];
3417 [splitout1] crop=100:100:0:0 [cropout];
3418 [splitout2] pad=200:200:100:100 [padout];
3421 will create two separate outputs from the same input, one cropped and
3426 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3427 Interpolate) pixel art scaling algorithm.
3429 Useful for enlarging pixel art images without reducing sharpness.
3435 Select the most representative frame in a given sequence of consecutive frames.
3437 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3438 in a set of @var{N} frames, the filter will pick one of them, and then handle
3439 the next batch of @var{N} frames until the end.
3441 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3442 value will result in a higher memory usage, so a high value is not recommended.
3444 The following example extract one picture each 50 frames:
3449 Complete example of a thumbnail creation with @command{ffmpeg}:
3451 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3456 Tile several successive frames together.
3458 It accepts as argument the tile size (i.e. the number of lines and columns)
3459 in the form "@var{w}x@var{h}".
3461 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3464 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3466 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3467 duplicating each output frame to accomodate the originally detected frame
3472 Perform various types of temporal field interlacing.
3474 Frames are counted starting from 1, so the first input frame is
3477 This filter accepts a single parameter specifying the mode. Available
3482 Move odd frames into the upper field, even into the lower field,
3483 generating a double height frame at half framerate.
3486 Only output even frames, odd frames are dropped, generating a frame with
3487 unchanged height at half framerate.
3490 Only output odd frames, even frames are dropped, generating a frame with
3491 unchanged height at half framerate.
3494 Expand each frame to full height, but pad alternate lines with black,
3495 generating a frame with double height at the same input framerate.
3497 @item interleave_top, 4
3498 Interleave the upper field from odd frames with the lower field from
3499 even frames, generating a frame with unchanged height at half framerate.
3501 @item interleave_bottom, 5
3502 Interleave the lower field from odd frames with the upper field from
3503 even frames, generating a frame with unchanged height at half framerate.
3505 @item interlacex2, 6
3506 Double frame rate with unchanged height. Frames are inserted each
3507 containing the second temporal field from the previous input frame and
3508 the first temporal field from the next input frame. This mode relies on
3509 the top_field_first flag. Useful for interlaced video displays with no
3510 field synchronisation.
3513 Numeric values are deprecated but are accepted for backward
3514 compatibility reasons.
3516 Default mode is @code{merge}.
3520 Transpose rows with columns in the input video and optionally flip it.
3522 It accepts a parameter representing an integer, which can assume the
3527 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3535 Rotate by 90 degrees clockwise, that is:
3543 Rotate by 90 degrees counterclockwise, that is:
3551 Rotate by 90 degrees clockwise and vertically flip, that is:
3559 For values between 4-7 transposition is only done if the input video
3560 geometry is portrait and not landscape.
3564 Sharpen or blur the input video.
3566 It accepts the following parameters:
3567 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3569 Negative values for the amount will blur the input video, while positive
3570 values will sharpen. All parameters are optional and default to the
3571 equivalent of the string '5:5:1.0:5:5:0.0'.
3576 Set the luma matrix horizontal size. It can be an integer between 3
3577 and 13, default value is 5.
3580 Set the luma matrix vertical size. It can be an integer between 3
3581 and 13, default value is 5.
3584 Set the luma effect strength. It can be a float number between -2.0
3585 and 5.0, default value is 1.0.
3587 @item chroma_msize_x
3588 Set the chroma matrix horizontal size. It can be an integer between 3
3589 and 13, default value is 5.
3591 @item chroma_msize_y
3592 Set the chroma matrix vertical size. It can be an integer between 3
3593 and 13, default value is 5.
3596 Set the chroma effect strength. It can be a float number between -2.0
3597 and 5.0, default value is 0.0.
3602 # Strong luma sharpen effect parameters
3605 # Strong blur of both luma and chroma parameters
3606 unsharp=7:7:-2:7:7:-2
3608 # Use the default values with @command{ffmpeg}
3609 ffmpeg -i in.avi -vf "unsharp" out.mp4
3614 Flip the input video vertically.
3617 ffmpeg -i in.avi -vf "vflip" out.avi
3622 Deinterlace the input video ("yadif" means "yet another deinterlacing
3625 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
3627 @var{mode} specifies the interlacing mode to adopt, accepts one of the
3632 output 1 frame for each frame
3634 output 1 frame for each field
3636 like 0 but skips spatial interlacing check
3638 like 1 but skips spatial interlacing check
3643 @var{parity} specifies the picture field parity assumed for the input
3644 interlaced video, accepts one of the following values:
3648 assume top field first
3650 assume bottom field first
3652 enable automatic detection
3655 Default value is -1.
3656 If interlacing is unknown or decoder does not export this information,
3657 top field first will be assumed.
3659 @var{auto} specifies if deinterlacer should trust the interlaced flag
3660 and only deinterlace frames marked as interlaced
3664 deinterlace all frames
3666 only deinterlace frames marked as interlaced
3671 @c man end VIDEO FILTERS
3673 @chapter Video Sources
3674 @c man begin VIDEO SOURCES
3676 Below is a description of the currently available video sources.
3680 Buffer video frames, and make them available to the filter chain.
3682 This source is mainly intended for a programmatic use, in particular
3683 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
3685 It accepts a list of options in the form of @var{key}=@var{value} pairs
3686 separated by ":". A descroption of the accepted options follows.
3691 Specify the size (width and height) of the buffered video frames.
3694 A string representing the pixel format of the buffered video frames.
3695 It may be a number corresponding to a pixel format, or a pixel format
3699 Specify the timebase assumed by the timestamps of the buffered frames.
3702 Specify the frame rate expected for the video stream.
3705 Specify the sample aspect ratio assumed by the video frames.
3708 Specify the optional parameters to be used for the scale filter which
3709 is automatically inserted when an input change is detected in the
3710 input size or format.
3715 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
3718 will instruct the source to accept video frames with size 320x240 and
3719 with format "yuv410p", assuming 1/24 as the timestamps timebase and
3720 square pixels (1:1 sample aspect ratio).
3721 Since the pixel format with name "yuv410p" corresponds to the number 6
3722 (check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),
3723 this example corresponds to:
3725 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
3728 Alternatively, the options can be specified as a flat string, but this
3729 syntax is deprecated:
3731 @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}]
3735 Create a pattern generated by an elementary cellular automaton.
3737 The initial state of the cellular automaton can be defined through the
3738 @option{filename}, and @option{pattern} options. If such options are
3739 not specified an initial state is created randomly.
3741 At each new frame a new row in the video is filled with the result of
3742 the cellular automaton next generation. The behavior when the whole
3743 frame is filled is defined by the @option{scroll} option.
3745 This source accepts a list of options in the form of
3746 @var{key}=@var{value} pairs separated by ":". A description of the
3747 accepted options follows.
3751 Read the initial cellular automaton state, i.e. the starting row, from
3753 In the file, each non-whitespace character is considered an alive
3754 cell, a newline will terminate the row, and further characters in the
3755 file will be ignored.
3758 Read the initial cellular automaton state, i.e. the starting row, from
3759 the specified string.
3761 Each non-whitespace character in the string is considered an alive
3762 cell, a newline will terminate the row, and further characters in the
3763 string will be ignored.
3766 Set the video rate, that is the number of frames generated per second.
3769 @item random_fill_ratio, ratio
3770 Set the random fill ratio for the initial cellular automaton row. It
3771 is a floating point number value ranging from 0 to 1, defaults to
3774 This option is ignored when a file or a pattern is specified.
3776 @item random_seed, seed
3777 Set the seed for filling randomly the initial row, must be an integer
3778 included between 0 and UINT32_MAX. If not specified, or if explicitly
3779 set to -1, the filter will try to use a good random seed on a best
3783 Set the cellular automaton rule, it is a number ranging from 0 to 255.
3784 Default value is 110.
3787 Set the size of the output video.
3789 If @option{filename} or @option{pattern} is specified, the size is set
3790 by default to the width of the specified initial state row, and the
3791 height is set to @var{width} * PHI.
3793 If @option{size} is set, it must contain the width of the specified
3794 pattern string, and the specified pattern will be centered in the
3797 If a filename or a pattern string is not specified, the size value
3798 defaults to "320x518" (used for a randomly generated initial state).
3801 If set to 1, scroll the output upward when all the rows in the output
3802 have been already filled. If set to 0, the new generated row will be
3803 written over the top row just after the bottom row is filled.
3806 @item start_full, full
3807 If set to 1, completely fill the output with generated rows before
3808 outputting the first frame.
3809 This is the default behavior, for disabling set the value to 0.
3812 If set to 1, stitch the left and right row edges together.
3813 This is the default behavior, for disabling set the value to 0.
3816 @subsection Examples
3820 Read the initial state from @file{pattern}, and specify an output of
3823 cellauto=f=pattern:s=200x400
3827 Generate a random initial row with a width of 200 cells, with a fill
3830 cellauto=ratio=2/3:s=200x200
3834 Create a pattern generated by rule 18 starting by a single alive cell
3835 centered on an initial row with width 100:
3837 cellauto=p=@@:s=100x400:full=0:rule=18
3841 Specify a more elaborated initial pattern:
3843 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
3850 Generate a Mandelbrot set fractal, and progressively zoom towards the
3851 point specified with @var{start_x} and @var{start_y}.
3853 This source accepts a list of options in the form of
3854 @var{key}=@var{value} pairs separated by ":". A description of the
3855 accepted options follows.
3860 Set the terminal pts value. Default value is 400.
3863 Set the terminal scale value.
3864 Must be a floating point value. Default value is 0.3.
3867 Set the inner coloring mode, that is the algorithm used to draw the
3868 Mandelbrot fractal internal region.
3870 It shall assume one of the following values:
3875 Show time until convergence.
3877 Set color based on point closest to the origin of the iterations.
3882 Default value is @var{mincol}.
3885 Set the bailout value. Default value is 10.0.
3888 Set the maximum of iterations performed by the rendering
3889 algorithm. Default value is 7189.
3892 Set outer coloring mode.
3893 It shall assume one of following values:
3895 @item iteration_count
3896 Set iteration cound mode.
3897 @item normalized_iteration_count
3898 set normalized iteration count mode.
3900 Default value is @var{normalized_iteration_count}.
3903 Set frame rate, expressed as number of frames per second. Default
3907 Set frame size. Default value is "640x480".
3910 Set the initial scale value. Default value is 3.0.
3913 Set the initial x position. Must be a floating point value between
3914 -100 and 100. Default value is -0.743643887037158704752191506114774.
3917 Set the initial y position. Must be a floating point value between
3918 -100 and 100. Default value is -0.131825904205311970493132056385139.
3923 Generate various test patterns, as generated by the MPlayer test filter.
3925 The size of the generated video is fixed, and is 256x256.
3926 This source is useful in particular for testing encoding features.
3928 This source accepts an optional sequence of @var{key}=@var{value} pairs,
3929 separated by ":". The description of the accepted options follows.
3934 Specify the frame rate of the sourced video, as the number of frames
3935 generated per second. It has to be a string in the format
3936 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
3937 number or a valid video frame rate abbreviation. The default value is
3941 Set the video duration of the sourced video. The accepted syntax is:
3946 See also the function @code{av_parse_time()}.
3948 If not specified, or the expressed duration is negative, the video is
3949 supposed to be generated forever.
3953 Set the number or the name of the test to perform. Supported tests are:
3968 Default value is "all", which will cycle through the list of all tests.
3971 For example the following:
3976 will generate a "dc_luma" test pattern.
3980 Provide a frei0r source.
3982 To enable compilation of this filter you need to install the frei0r
3983 header and configure FFmpeg with @code{--enable-frei0r}.
3985 The source supports the syntax:
3987 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
3990 @var{size} is the size of the video to generate, may be a string of the
3991 form @var{width}x@var{height} or a frame size abbreviation.
3992 @var{rate} is the rate of the video to generate, may be a string of
3993 the form @var{num}/@var{den} or a frame rate abbreviation.
3994 @var{src_name} is the name to the frei0r source to load. For more
3995 information regarding frei0r and how to set the parameters read the
3996 section @ref{frei0r} in the description of the video filters.
3998 For example, to generate a frei0r partik0l source with size 200x200
3999 and frame rate 10 which is overlayed on the overlay filter main input:
4001 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4006 Generate a life pattern.
4008 This source is based on a generalization of John Conway's life game.
4010 The sourced input represents a life grid, each pixel represents a cell
4011 which can be in one of two possible states, alive or dead. Every cell
4012 interacts with its eight neighbours, which are the cells that are
4013 horizontally, vertically, or diagonally adjacent.
4015 At each interaction the grid evolves according to the adopted rule,
4016 which specifies the number of neighbor alive cells which will make a
4017 cell stay alive or born. The @option{rule} option allows to specify
4020 This source accepts a list of options in the form of
4021 @var{key}=@var{value} pairs separated by ":". A description of the
4022 accepted options follows.
4026 Set the file from which to read the initial grid state. In the file,
4027 each non-whitespace character is considered an alive cell, and newline
4028 is used to delimit the end of each row.
4030 If this option is not specified, the initial grid is generated
4034 Set the video rate, that is the number of frames generated per second.
4037 @item random_fill_ratio, ratio
4038 Set the random fill ratio for the initial random grid. It is a
4039 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4040 It is ignored when a file is specified.
4042 @item random_seed, seed
4043 Set the seed for filling the initial random grid, must be an integer
4044 included between 0 and UINT32_MAX. If not specified, or if explicitly
4045 set to -1, the filter will try to use a good random seed on a best
4051 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4052 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4053 @var{NS} specifies the number of alive neighbor cells which make a
4054 live cell stay alive, and @var{NB} the number of alive neighbor cells
4055 which make a dead cell to become alive (i.e. to "born").
4056 "s" and "b" can be used in place of "S" and "B", respectively.
4058 Alternatively a rule can be specified by an 18-bits integer. The 9
4059 high order bits are used to encode the next cell state if it is alive
4060 for each number of neighbor alive cells, the low order bits specify
4061 the rule for "borning" new cells. Higher order bits encode for an
4062 higher number of neighbor cells.
4063 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4064 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4066 Default value is "S23/B3", which is the original Conway's game of life
4067 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4068 cells, and will born a new cell if there are three alive cells around
4072 Set the size of the output video.
4074 If @option{filename} is specified, the size is set by default to the
4075 same size of the input file. If @option{size} is set, it must contain
4076 the size specified in the input file, and the initial grid defined in
4077 that file is centered in the larger resulting area.
4079 If a filename is not specified, the size value defaults to "320x240"
4080 (used for a randomly generated initial grid).
4083 If set to 1, stitch the left and right grid edges together, and the
4084 top and bottom edges also. Defaults to 1.
4087 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4088 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4089 value from 0 to 255.
4092 Set the color of living (or new born) cells.
4095 Set the color of dead cells. If @option{mold} is set, this is the first color
4096 used to represent a dead cell.
4099 Set mold color, for definitely dead and moldy cells.
4102 @subsection Examples
4106 Read a grid from @file{pattern}, and center it on a grid of size
4109 life=f=pattern:s=300x300
4113 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4115 life=ratio=2/3:s=200x200
4119 Specify a custom rule for evolving a randomly generated grid:
4125 Full example with slow death effect (mold) using @command{ffplay}:
4127 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4131 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4133 The @code{color} source provides an uniformly colored input.
4135 The @code{nullsrc} source returns unprocessed video frames. It is
4136 mainly useful to be employed in analysis / debugging tools, or as the
4137 source for filters which ignore the input data.
4139 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4140 detecting RGB vs BGR issues. You should see a red, green and blue
4141 stripe from top to bottom.
4143 The @code{smptebars} source generates a color bars pattern, based on
4144 the SMPTE Engineering Guideline EG 1-1990.
4146 The @code{testsrc} source generates a test video pattern, showing a
4147 color pattern, a scrolling gradient and a timestamp. This is mainly
4148 intended for testing purposes.
4150 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4151 separated by ":". The description of the accepted options follows.
4156 Specify the color of the source, only used in the @code{color}
4157 source. It can be the name of a color (case insensitive match) or a
4158 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4159 default value is "black".
4162 Specify the size of the sourced video, it may be a string of the form
4163 @var{width}x@var{height}, or the name of a size abbreviation. The
4164 default value is "320x240".
4167 Specify the frame rate of the sourced video, as the number of frames
4168 generated per second. It has to be a string in the format
4169 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4170 number or a valid video frame rate abbreviation. The default value is
4174 Set the sample aspect ratio of the sourced video.
4177 Set the video duration of the sourced video. The accepted syntax is:
4179 [-]HH[:MM[:SS[.m...]]]
4182 See also the function @code{av_parse_time()}.
4184 If not specified, or the expressed duration is negative, the video is
4185 supposed to be generated forever.
4188 Set the number of decimals to show in the timestamp, only used in the
4189 @code{testsrc} source.
4191 The displayed timestamp value will correspond to the original
4192 timestamp value multiplied by the power of 10 of the specified
4193 value. Default value is 0.
4196 For example the following:
4198 testsrc=duration=5.3:size=qcif:rate=10
4201 will generate a video with a duration of 5.3 seconds, with size
4202 176x144 and a frame rate of 10 frames per second.
4204 The following graph description will generate a red source
4205 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4208 color=c=red@@0.2:s=qcif:r=10
4211 If the input content is to be ignored, @code{nullsrc} can be used. The
4212 following command generates noise in the luminance plane by employing
4213 the @code{mp=geq} filter:
4215 nullsrc=s=256x256, mp=geq=random(1)*255:128:128
4218 @c man end VIDEO SOURCES
4220 @chapter Video Sinks
4221 @c man begin VIDEO SINKS
4223 Below is a description of the currently available video sinks.
4227 Buffer video frames, and make them available to the end of the filter
4230 This sink is mainly intended for a programmatic use, in particular
4231 through the interface defined in @file{libavfilter/buffersink.h}.
4233 It does not require a string parameter in input, but you need to
4234 specify a pointer to a list of supported pixel formats terminated by
4235 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4236 when initializing this sink.
4240 Null video sink, do absolutely nothing with the input video. It is
4241 mainly useful as a template and to be employed in analysis / debugging
4244 @c man end VIDEO SINKS
4246 @chapter Multimedia Filters
4247 @c man begin MULTIMEDIA FILTERS
4249 Below is a description of the currently available multimedia filters.
4251 @section asendcmd, sendcmd
4253 Send commands to filters in the filtergraph.
4255 These filters read commands to be sent to other filters in the
4258 @code{asendcmd} must be inserted between two audio filters,
4259 @code{sendcmd} must be inserted between two video filters, but apart
4260 from that they act the same way.
4262 The specification of commands can be provided in the filter arguments
4263 with the @var{commands} option, or in a file specified by the
4264 @var{filename} option.
4266 These filters accept the following options:
4269 Set the commands to be read and sent to the other filters.
4271 Set the filename of the commands to be read and sent to the other
4275 @subsection Commands syntax
4277 A commands description consists of a sequence of interval
4278 specifications, comprising a list of commands to be executed when a
4279 particular event related to that interval occurs. The occurring event
4280 is typically the current frame time entering or leaving a given time
4283 An interval is specified by the following syntax:
4285 @var{START}[-@var{END}] @var{COMMANDS};
4288 The time interval is specified by the @var{START} and @var{END} times.
4289 @var{END} is optional and defaults to the maximum time.
4291 The current frame time is considered within the specified interval if
4292 it is included in the interval [@var{START}, @var{END}), that is when
4293 the time is greater or equal to @var{START} and is lesser than
4296 @var{COMMANDS} consists of a sequence of one or more command
4297 specifications, separated by ",", relating to that interval. The
4298 syntax of a command specification is given by:
4300 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4303 @var{FLAGS} is optional and specifies the type of events relating to
4304 the time interval which enable sending the specified command, and must
4305 be a non-null sequence of identifier flags separated by "+" or "|" and
4306 enclosed between "[" and "]".
4308 The following flags are recognized:
4311 The command is sent when the current frame timestamp enters the
4312 specified interval. In other words, the command is sent when the
4313 previous frame timestamp was not in the given interval, and the
4317 The command is sent when the current frame timestamp leaves the
4318 specified interval. In other words, the command is sent when the
4319 previous frame timestamp was in the given interval, and the
4323 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4326 @var{TARGET} specifies the target of the command, usually the name of
4327 the filter class or a specific filter instance name.
4329 @var{COMMAND} specifies the name of the command for the target filter.
4331 @var{ARG} is optional and specifies the optional list of argument for
4332 the given @var{COMMAND}.
4334 Between one interval specification and another, whitespaces, or
4335 sequences of characters starting with @code{#} until the end of line,
4336 are ignored and can be used to annotate comments.
4338 A simplified BNF description of the commands specification syntax
4341 @var{COMMAND_FLAG} ::= "enter" | "leave"
4342 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4343 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4344 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4345 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4346 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4349 @subsection Examples
4353 Specify audio tempo change at second 4:
4355 asendcmd=c='4.0 atempo tempo 1.5',atempo
4359 Specify a list of drawtext and hue commands in a file.
4361 # show text in the interval 5-10
4362 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4363 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4365 # desaturate the image in the interval 15-20
4366 15.0-20.0 [enter] hue reinit s=0,
4367 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4368 [leave] hue reinit s=1,
4369 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4371 # apply an exponential saturation fade-out effect, starting from time 25
4372 25 [enter] hue s=exp(t-25)
4375 A filtergraph allowing to read and process the above command list
4376 stored in a file @file{test.cmd}, can be specified with:
4378 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4382 @section asetpts, setpts
4384 Change the PTS (presentation timestamp) of the input frames.
4386 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4388 Accept in input an expression evaluated through the eval API, which
4389 can contain the following constants:
4393 frame rate, only defined for constant frame-rate video
4396 the presentation timestamp in input
4399 the count of the input frame, starting from 0.
4401 @item NB_CONSUMED_SAMPLES
4402 the number of consumed samples, not including the current frame (only
4406 the number of samples in the current frame (only audio)
4412 the PTS of the first frame
4415 the time in seconds of the first frame
4418 tell if the current frame is interlaced
4421 the time in seconds of the current frame
4427 original position in the file of the frame, or undefined if undefined
4428 for the current frame
4434 previous input time in seconds
4440 previous output time in seconds
4443 @subsection Examples
4447 Start counting PTS from zero
4453 Apply fast motion effect:
4459 Apply slow motion effect:
4465 Set fixed rate of 25 frames per second:
4471 Set fixed rate 25 fps with some jitter:
4473 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
4477 Apply an offset of 10 seconds to the input PTS:
4483 @section settb, asettb
4485 Set the timebase to use for the output frames timestamps.
4486 It is mainly useful for testing timebase configuration.
4488 It accepts in input an arithmetic expression representing a rational.
4489 The expression can contain the constants "AVTB" (the
4490 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
4493 The default value for the input is "intb".
4495 @subsection Examples
4499 Set the timebase to 1/25:
4505 Set the timebase to 1/10:
4511 Set the timebase to 1001/1000:
4517 Set the timebase to 2*intb:
4523 Set the default timebase value:
4531 Concatenate audio and video streams, joining them together one after the
4534 The filter works on segments of synchronized video and audio streams. All
4535 segments must have the same number of streams of each type, and that will
4536 also be the number of streams at output.
4538 The filter accepts the following named parameters:
4542 Set the number of segments. Default is 2.
4545 Set the number of output video streams, that is also the number of video
4546 streams in each segment. Default is 1.
4549 Set the number of output audio streams, that is also the number of video
4550 streams in each segment. Default is 0.
4554 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
4555 @var{a} audio outputs.
4557 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
4558 segment, in the same order as the outputs, then the inputs for the second
4561 Related streams do not always have exactly the same duration, for various
4562 reasons including codec frame size or sloppy authoring. For that reason,
4563 related synchronized streams (e.g. a video and its audio track) should be
4564 concatenated at once. The concat filter will use the duration of the longest
4565 stream in each segment (except the last one), and if necessary pad shorter
4566 audio streams with silence.
4568 For this filter to work correctly, all segments must start at timestamp 0.
4570 All corresponding streams must have the same parameters in all segments; the
4571 filtering system will automatically select a common pixel format for video
4572 streams, and a common sample format, sample rate and channel layout for
4573 audio streams, but other settings, such as resolution, must be converted
4574 explicitly by the user.
4576 Different frame rates are acceptable but will result in variable frame rate
4577 at output; be sure to configure the output file to handle it.
4582 Concatenate an opening, an episode and an ending, all in bilingual version
4583 (video in stream 0, audio in streams 1 and 2):
4585 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
4586 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
4587 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
4588 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
4592 Concatenate two parts, handling audio and video separately, using the
4593 (a)movie sources, and adjusting the resolution:
4595 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
4596 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
4597 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
4599 Note that a desync will happen at the stitch if the audio and video streams
4600 do not have exactly the same duration in the first file.
4604 @section showspectrum
4606 Convert input audio to a video output, representing the audio frequency
4609 The filter accepts the following named parameters:
4612 Specify the video size for the output. Default value is @code{640x480}.
4615 The usage is very similar to the showwaves filter; see the examples in that
4620 Convert input audio to a video output, representing the samples waves.
4622 The filter accepts the following named parameters:
4626 Set the number of samples which are printed on the same column. A
4627 larger value will decrease the frame rate. Must be a positive
4628 integer. This option can be set only if the value for @var{rate}
4629 is not explicitly specified.
4632 Set the (approximate) output frame rate. This is done by setting the
4633 option @var{n}. Default value is "25".
4636 Specify the video size for the output. Default value is "600x240".
4639 Some examples follow.
4642 Output the input file audio and the corresponding video representation
4645 amovie=a.mp3,asplit[out0],showwaves[out1]
4649 Create a synthetic signal and show it with showwaves, forcing a
4650 framerate of 30 frames per second:
4652 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
4656 @c man end MULTIMEDIA FILTERS
4658 @chapter Multimedia Sources
4659 @c man begin MULTIMEDIA SOURCES
4661 Below is a description of the currently available multimedia sources.
4665 This is the same as @ref{src_movie} source, except it selects an audio
4671 Read audio and/or video stream(s) from a movie container.
4673 It accepts the syntax: @var{movie_name}[:@var{options}] where
4674 @var{movie_name} is the name of the resource to read (not necessarily
4675 a file but also a device or a stream accessed through some protocol),
4676 and @var{options} is an optional sequence of @var{key}=@var{value}
4677 pairs, separated by ":".
4679 The description of the accepted options follows.
4683 @item format_name, f
4684 Specifies the format assumed for the movie to read, and can be either
4685 the name of a container or an input device. If not specified the
4686 format is guessed from @var{movie_name} or by probing.
4688 @item seek_point, sp
4689 Specifies the seek point in seconds, the frames will be output
4690 starting from this seek point, the parameter is evaluated with
4691 @code{av_strtod} so the numerical value may be suffixed by an IS
4692 postfix. Default value is "0".
4695 Specifies the streams to read. Several streams can be specified, separated
4696 by "+". The source will then have as many outputs, in the same order. The
4697 syntax is explained in the @ref{Stream specifiers} chapter. Two special
4698 names, "dv" and "da" specify respectively the default (best suited) video
4699 and audio stream. Default is "dv", or "da" if the filter is called as
4702 @item stream_index, si
4703 Specifies the index of the video stream to read. If the value is -1,
4704 the best suited video stream will be automatically selected. Default
4705 value is "-1". Deprecated. If the filter is called "amovie", it will select
4706 audio instead of video.
4709 Specifies how many times to read the stream in sequence.
4710 If the value is less than 1, the stream will be read again and again.
4711 Default value is "1".
4713 Note that when the movie is looped the source timestamps are not
4714 changed, so it will generate non monotonically increasing timestamps.
4717 This filter allows to overlay a second video on top of main input of
4718 a filtergraph as shown in this graph:
4720 input -----------> deltapts0 --> overlay --> output
4723 movie --> scale--> deltapts1 -------+
4726 Some examples follow.
4730 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
4731 on top of the input labelled as "in":
4733 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
4734 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
4738 Read from a video4linux2 device, and overlay it on top of the input
4741 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
4742 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
4746 Read the first video stream and the audio stream with id 0x81 from
4747 dvd.vob; the video is connected to the pad named "video" and the audio is
4748 connected to the pad named "audio":
4750 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
4754 @c man end MULTIMEDIA SOURCES