1 @chapter Filtering Introduction
2 @c man begin FILTERING INTRODUCTION
4 Filtering in FFmpeg is enabled through the libavfilter library.
6 Libavfilter is the filtering API of FFmpeg. It is the substitute of
7 the now deprecated 'vhooks' and started as a Google Summer of Code
10 Audio filtering integration into the main FFmpeg repository is a work in
11 progress, so audio API and ABI should not be considered stable yet.
13 In libavfilter, it is possible for filters to have multiple inputs and
15 To illustrate the sorts of things that are possible, we can
16 use a complex filter graph. For example, the following one:
19 input --> split --> fifo -----------------------> overlay --> output
22 +------> fifo --> crop --> vflip --------+
25 splits the stream in two streams, sends one stream through the crop filter
26 and the vflip filter before merging it back with the other stream by
27 overlaying it on top. You can use the following command to achieve this:
30 ffmpeg -i input -vf "[in] split [T1], fifo, [T2] overlay=0:H/2 [out]; [T1] fifo, crop=iw:ih/2:0:ih/2, vflip [T2]" output
33 The result will be that in output the top half of the video is mirrored
36 Filters are loaded using the @var{-vf} or @var{-af} option passed to
37 @command{ffmpeg} or to @command{ffplay}. Filters in the same linear
38 chain are separated by commas. In our example, @var{split, fifo,
39 overlay} are in one linear chain, and @var{fifo, crop, vflip} are in
40 another. The points where the linear chains join are labeled by names
41 enclosed in square brackets. In our example, that is @var{[T1]} and
42 @var{[T2]}. The special labels @var{[in]} and @var{[out]} are the points
43 where video is input and output.
45 Some filters take in input a list of parameters: they are specified
46 after the filter name and an equal sign, and are separated from each other
49 There exist so-called @var{source filters} that do not have an
50 audio/video input, and @var{sink filters} that will not have audio/video
53 @c man end FILTERING INTRODUCTION
56 @c man begin GRAPH2DOT
58 The @file{graph2dot} program included in the FFmpeg @file{tools}
59 directory can be used to parse a filter graph description and issue a
60 corresponding textual representation in the dot language.
67 to see how to use @file{graph2dot}.
69 You can then pass the dot description to the @file{dot} program (from
70 the graphviz suite of programs) and obtain a graphical representation
73 For example the sequence of commands:
75 echo @var{GRAPH_DESCRIPTION} | \
76 tools/graph2dot -o graph.tmp && \
77 dot -Tpng graph.tmp -o graph.png && \
81 can be used to create and display an image representing the graph
82 described by the @var{GRAPH_DESCRIPTION} string. Note that this string must be
83 a complete self-contained graph, with its inputs and outputs explicitly defined.
84 For example if your command line is of the form:
86 ffmpeg -i infile -vf scale=640:360 outfile
88 your @var{GRAPH_DESCRIPTION} string will need to be of the form:
90 nullsrc,scale=640:360,nullsink
92 you may also need to set the @var{nullsrc} parameters and add a @var{format}
93 filter in order to simulate a specific input file.
97 @chapter Filtergraph description
98 @c man begin FILTERGRAPH DESCRIPTION
100 A filtergraph is a directed graph of connected filters. It can contain
101 cycles, and there can be multiple links between a pair of
102 filters. Each link has one input pad on one side connecting it to one
103 filter from which it takes its input, and one output pad on the other
104 side connecting it to the one filter accepting its output.
106 Each filter in a filtergraph is an instance of a filter class
107 registered in the application, which defines the features and the
108 number of input and output pads of the filter.
110 A filter with no input pads is called a "source", a filter with no
111 output pads is called a "sink".
113 @anchor{Filtergraph syntax}
114 @section Filtergraph syntax
116 A filtergraph can be represented using a textual representation, which is
117 recognized by the @option{-filter}/@option{-vf} and @option{-filter_complex}
118 options in @command{ffmpeg} and @option{-vf} in @command{ffplay}, and by the
119 @code{avfilter_graph_parse()}/@code{avfilter_graph_parse2()} function defined in
120 @file{libavfilter/avfiltergraph.h}.
122 A filterchain consists of a sequence of connected filters, each one
123 connected to the previous one in the sequence. A filterchain is
124 represented by a list of ","-separated filter descriptions.
126 A filtergraph consists of a sequence of filterchains. A sequence of
127 filterchains is represented by a list of ";"-separated filterchain
130 A filter is represented by a string of the form:
131 [@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]
133 @var{filter_name} is the name of the filter class of which the
134 described filter is an instance of, and has to be the name of one of
135 the filter classes registered in the program.
136 The name of the filter class is optionally followed by a string
139 @var{arguments} is a string which contains the parameters used to
140 initialize the filter instance, and are described in the filter
143 The list of arguments can be quoted using the character "'" as initial
144 and ending mark, and the character '\' for escaping the characters
145 within the quoted text; otherwise the argument string is considered
146 terminated when the next special character (belonging to the set
147 "[]=;,") is encountered.
149 The name and arguments of the filter are optionally preceded and
150 followed by a list of link labels.
151 A link label allows to name a link and associate it to a filter output
152 or input pad. The preceding labels @var{in_link_1}
153 ... @var{in_link_N}, are associated to the filter input pads,
154 the following labels @var{out_link_1} ... @var{out_link_M}, are
155 associated to the output pads.
157 When two link labels with the same name are found in the
158 filtergraph, a link between the corresponding input and output pad is
161 If an output pad is not labelled, it is linked by default to the first
162 unlabelled input pad of the next filter in the filterchain.
163 For example in the filterchain:
165 nullsrc, split[L1], [L2]overlay, nullsink
167 the split filter instance has two output pads, and the overlay filter
168 instance two input pads. The first output pad of split is labelled
169 "L1", the first input pad of overlay is labelled "L2", and the second
170 output pad of split is linked to the second input pad of overlay,
171 which are both unlabelled.
173 In a complete filterchain all the unlabelled filter input and output
174 pads must be connected. A filtergraph is considered valid if all the
175 filter input and output pads of all the filterchains are connected.
177 Libavfilter will automatically insert scale filters where format
178 conversion is required. It is possible to specify swscale flags
179 for those automatically inserted scalers by prepending
180 @code{sws_flags=@var{flags};}
181 to the filtergraph description.
183 Follows a BNF description for the filtergraph syntax:
185 @var{NAME} ::= sequence of alphanumeric characters and '_'
186 @var{LINKLABEL} ::= "[" @var{NAME} "]"
187 @var{LINKLABELS} ::= @var{LINKLABEL} [@var{LINKLABELS}]
188 @var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)
189 @var{FILTER} ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]
190 @var{FILTERCHAIN} ::= @var{FILTER} [,@var{FILTERCHAIN}]
191 @var{FILTERGRAPH} ::= [sws_flags=@var{flags};] @var{FILTERCHAIN} [;@var{FILTERGRAPH}]
194 @section Notes on filtergraph escaping
196 Some filter arguments require the use of special characters, typically
197 @code{:} to separate key=value pairs in a named options list. In this
198 case the user should perform a first level escaping when specifying
199 the filter arguments. For example, consider the following literal
200 string to be embedded in the @ref{drawtext} filter arguments:
202 this is a 'string': may contain one, or more, special characters
205 Since @code{:} is special for the filter arguments syntax, it needs to
206 be escaped, so you get:
208 text=this is a \'string\'\: may contain one, or more, special characters
211 A second level of escaping is required when embedding the filter
212 arguments in a filtergraph description, in order to escape all the
213 filtergraph special characters. Thus the example above becomes:
215 drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
218 Finally an additional level of escaping may be needed when writing the
219 filtergraph description in a shell command, which depends on the
220 escaping rules of the adopted shell. For example, assuming that
221 @code{\} is special and needs to be escaped with another @code{\}, the
222 previous string will finally result in:
224 -vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
227 Sometimes, it might be more convenient to employ quoting in place of
228 escaping. For example the string:
230 Caesar: tu quoque, Brute, fili mi
233 Can be quoted in the filter arguments as:
235 text='Caesar: tu quoque, Brute, fili mi'
238 And finally inserted in a filtergraph like:
240 drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
243 See the @ref{quoting_and_escaping, Quoting and escaping} section for
244 more information about the escaping and quoting rules adopted by
247 @c man end FILTERGRAPH DESCRIPTION
249 @chapter Audio Filters
250 @c man begin AUDIO FILTERS
252 When you configure your FFmpeg build, you can disable any of the
253 existing filters using @code{--disable-filters}.
254 The configure output will show the audio filters included in your
257 Below is a description of the currently available audio filters.
261 Convert the input audio format to the specified formats.
263 The filter accepts a string of the form:
264 "@var{sample_format}:@var{channel_layout}".
266 @var{sample_format} specifies the sample format, and can be a string or the
267 corresponding numeric value defined in @file{libavutil/samplefmt.h}. Use 'p'
268 suffix for a planar sample format.
270 @var{channel_layout} specifies the channel layout, and can be a string
271 or the corresponding number value defined in @file{libavutil/audioconvert.h}.
273 The special parameter "auto", signifies that the filter will
274 automatically select the output format depending on the output filter.
276 Some examples follow.
280 Convert input to float, planar, stereo:
286 Convert input to unsigned 8-bit, automatically select out channel layout:
294 Convert the input audio to one of the specified formats. The framework will
295 negotiate the most appropriate format to minimize conversions.
297 The filter accepts the following named parameters:
301 A comma-separated list of requested sample formats.
304 A comma-separated list of requested sample rates.
306 @item channel_layouts
307 A comma-separated list of requested channel layouts.
311 If a parameter is omitted, all values are allowed.
313 For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
315 aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo
320 Merge two or more audio streams into a single multi-channel stream.
322 The filter accepts the following named options:
327 Set the number of inputs. Default is 2.
331 If the channel layouts of the inputs are disjoint, and therefore compatible,
332 the channel layout of the output will be set accordingly and the channels
333 will be reordered as necessary. If the channel layouts of the inputs are not
334 disjoint, the output will have all the channels of the first input then all
335 the channels of the second input, in that order, and the channel layout of
336 the output will be the default value corresponding to the total number of
339 For example, if the first input is in 2.1 (FL+FR+LF) and the second input
340 is FC+BL+BR, then the output will be in 5.1, with the channels in the
341 following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
342 first input, b1 is the first channel of the second input).
344 On the other hand, if both input are in stereo, the output channels will be
345 in the default order: a1, a2, b1, b2, and the channel layout will be
346 arbitrarily set to 4.0, which may or may not be the expected value.
348 All inputs must have the same sample rate, and format.
350 If inputs do not have the same duration, the output will stop with the
353 Example: merge two mono files into a stereo stream:
355 amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
358 Example: multiple merges:
361 amovie=input.mkv:si=0 [a0];
362 amovie=input.mkv:si=1 [a1];
363 amovie=input.mkv:si=2 [a2];
364 amovie=input.mkv:si=3 [a3];
365 amovie=input.mkv:si=4 [a4];
366 amovie=input.mkv:si=5 [a5];
367 [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
372 Mixes multiple audio inputs into a single output.
376 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
378 will mix 3 input audio streams to a single output with the same duration as the
379 first input and a dropout transition time of 3 seconds.
381 The filter accepts the following named parameters:
385 Number of inputs. If unspecified, it defaults to 2.
388 How to determine the end-of-stream.
392 Duration of longest input. (default)
395 Duration of shortest input.
398 Duration of first input.
402 @item dropout_transition
403 Transition time, in seconds, for volume renormalization when an input
404 stream ends. The default value is 2 seconds.
410 Pass the audio source unchanged to the output.
414 Resample the input audio to the specified sample rate.
416 The filter accepts exactly one parameter, the output sample rate. If not
417 specified then the filter will automatically convert between its input
418 and output sample rates.
420 For example, to resample the input audio to 44100Hz:
425 @section asetnsamples
427 Set the number of samples per each output audio frame.
429 The last output packet may contain a different number of samples, as
430 the filter will flush all the remaining samples when the input audio
433 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
438 @item nb_out_samples, n
439 Set the number of frames per each output audio frame. The number is
440 intended as the number of samples @emph{per each channel}.
441 Default value is 1024.
444 If set to 1, the filter will pad the last audio frame with zeroes, so
445 that the last frame will contain the same number of samples as the
446 previous ones. Default value is 1.
449 For example, to set the number of per-frame samples to 1234 and
450 disable padding for the last frame, use:
452 asetnsamples=n=1234:p=0
457 Show a line containing various information for each input audio frame.
458 The input audio is not modified.
460 The shown line contains a sequence of key/value pairs of the form
461 @var{key}:@var{value}.
463 A description of each shown parameter follows:
467 sequential number of the input frame, starting from 0
470 Presentation timestamp of the input frame, in time base units; the time base
471 depends on the filter input pad, and is usually 1/@var{sample_rate}.
474 presentation timestamp of the input frame in seconds
477 position of the frame in the input stream, -1 if this information in
478 unavailable and/or meaningless (for example in case of synthetic audio)
487 sample rate for the audio frame
490 number of samples (per channel) in the frame
493 Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
494 the data is treated as if all the planes were concatenated.
496 @item plane_checksums
497 A list of Adler-32 checksums for each data plane.
502 Split input audio into several identical outputs.
504 The filter accepts a single parameter which specifies the number of outputs. If
505 unspecified, it defaults to 2.
509 [in] asplit [out0][out1]
512 will create two separate outputs from the same input.
514 To create 3 or more outputs, you need to specify the number of
517 [in] asplit=3 [out0][out1][out2]
521 ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
523 will create 5 copies of the input audio.
528 Forward two audio streams and control the order the buffers are forwarded.
530 The argument to the filter is an expression deciding which stream should be
531 forwarded next: if the result is negative, the first stream is forwarded; if
532 the result is positive or zero, the second stream is forwarded. It can use
533 the following variables:
537 number of buffers forwarded so far on each stream
539 number of samples forwarded so far on each stream
541 current timestamp of each stream
544 The default value is @code{t1-t2}, which means to always forward the stream
545 that has a smaller timestamp.
547 Example: stress-test @code{amerge} by randomly sending buffers on the wrong
548 input, while avoiding too much of a desynchronization:
550 amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
551 [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
559 The filter accepts exactly one parameter, the audio tempo. If not
560 specified then the filter will assume nominal 1.0 tempo. Tempo must
561 be in the [0.5, 2.0] range.
563 For example, to slow down audio to 80% tempo:
568 For example, to speed up audio to 125% tempo:
575 Make audio easier to listen to on headphones.
577 This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio
578 so that when listened to on headphones the stereo image is moved from
579 inside your head (standard for headphones) to outside and in front of
580 the listener (standard for speakers).
586 Mix channels with specific gain levels. The filter accepts the output
587 channel layout followed by a set of channels definitions.
589 This filter is also designed to remap efficiently the channels of an audio
592 The filter accepts parameters of the form:
593 "@var{l}:@var{outdef}:@var{outdef}:..."
597 output channel layout or number of channels
600 output channel specification, of the form:
601 "@var{out_name}=[@var{gain}*]@var{in_name}[+[@var{gain}*]@var{in_name}...]"
604 output channel to define, either a channel name (FL, FR, etc.) or a channel
605 number (c0, c1, etc.)
608 multiplicative coefficient for the channel, 1 leaving the volume unchanged
611 input channel to use, see out_name for details; it is not possible to mix
612 named and numbered input channels
615 If the `=' in a channel specification is replaced by `<', then the gains for
616 that specification will be renormalized so that the total is 1, thus
617 avoiding clipping noise.
619 @subsection Mixing examples
621 For example, if you want to down-mix from stereo to mono, but with a bigger
622 factor for the left channel:
624 pan=1:c0=0.9*c0+0.1*c1
627 A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
630 pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
633 Note that @command{ffmpeg} integrates a default down-mix (and up-mix) system
634 that should be preferred (see "-ac" option) unless you have very specific
637 @subsection Remapping examples
639 The channel remapping will be effective if, and only if:
642 @item gain coefficients are zeroes or ones,
643 @item only one input per channel output,
646 If all these conditions are satisfied, the filter will notify the user ("Pure
647 channel mapping detected"), and use an optimized and lossless method to do the
650 For example, if you have a 5.1 source and want a stereo audio stream by
651 dropping the extra channels:
653 pan="stereo: c0=FL : c1=FR"
656 Given the same source, you can also switch front left and front right channels
657 and keep the input channel layout:
659 pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
662 If the input is a stereo audio stream, you can mute the front left channel (and
663 still keep the stereo channel layout) with:
668 Still with a stereo audio stream input, you can copy the right channel in both
669 front left and right:
671 pan="stereo: c0=FR : c1=FR"
674 @section silencedetect
676 Detect silence in an audio stream.
678 This filter logs a message when it detects that the input audio volume is less
679 or equal to a noise tolerance value for a duration greater or equal to the
680 minimum detected noise duration.
682 The printed times and duration are expressed in seconds.
686 Set silence duration until notification (default is 2 seconds).
689 Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
690 specified value) or amplitude ratio. Default is -60dB, or 0.001.
693 Detect 5 seconds of silence with -50dB noise tolerance:
695 silencedetect=n=-50dB:d=5
698 Complete example with @command{ffmpeg} to detect silence with 0.0001 noise
699 tolerance in @file{silence.mp3}:
701 ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
706 Adjust the input audio volume.
708 The filter accepts exactly one parameter @var{vol}, which expresses
709 how the audio volume will be increased or decreased.
711 Output values are clipped to the maximum value.
713 If @var{vol} is expressed as a decimal number, the output audio
714 volume is given by the relation:
716 @var{output_volume} = @var{vol} * @var{input_volume}
719 If @var{vol} is expressed as a decimal number followed by the string
720 "dB", the value represents the requested change in decibels of the
721 input audio power, and the output audio volume is given by the
724 @var{output_volume} = 10^(@var{vol}/20) * @var{input_volume}
727 Otherwise @var{vol} is considered an expression and its evaluated
728 value is used for computing the output audio volume according to the
731 Default value for @var{vol} is 1.0.
737 Half the input audio volume:
742 The above example is equivalent to:
748 Decrease input audio power by 12 decibels:
754 @section volumedetect
756 Detect the volume of the input video.
758 The filter has no parameters. The input is not modified. Statistics about
759 the volume will be printed in the log when the input stream end is reached.
761 In particular it will show the mean volume (root mean square), maximum
762 volume (on a per-sample basis), and the beginning of an histogram of the
763 registered volume values (from the maximum value to a cumulated 1/1000 of
766 All volumes are in decibels relative to the maximum PCM value.
768 Here is an excerpt of the output:
770 [Parsed_volumedetect_0 @ 0xa23120] mean_volume: -27 dB
771 [Parsed_volumedetect_0 @ 0xa23120] max_volume: -4 dB
772 [Parsed_volumedetect_0 @ 0xa23120] histogram_4db: 6
773 [Parsed_volumedetect_0 @ 0xa23120] histogram_5db: 62
774 [Parsed_volumedetect_0 @ 0xa23120] histogram_6db: 286
775 [Parsed_volumedetect_0 @ 0xa23120] histogram_7db: 1042
776 [Parsed_volumedetect_0 @ 0xa23120] histogram_8db: 2551
777 [Parsed_volumedetect_0 @ 0xa23120] histogram_9db: 4609
778 [Parsed_volumedetect_0 @ 0xa23120] histogram_10db: 8409
784 The mean square energy is approximately -27 dB, or 10^-2.7.
786 The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
788 There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
791 In other words, raising the volume by +4 dB does not cause any clipping,
792 raising it by +5 dB causes clipping for 6 samples, etc.
795 Synchronize audio data with timestamps by squeezing/stretching it and/or
796 dropping samples/adding silence when needed.
798 The filter accepts the following named parameters:
802 Enable stretching/squeezing the data to make it match the timestamps. Disabled
803 by default. When disabled, time gaps are covered with silence.
806 Minimum difference between timestamps and audio data (in seconds) to trigger
807 adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
808 this filter, try setting this parameter to 0.
811 Maximum compensation in samples per second. Relevant only with compensate=1.
815 Assume the first pts should be this value.
816 This allows for padding/trimming at the start of stream. By default, no
817 assumption is made about the first frame's expected pts, so no padding or
818 trimming is done. For example, this could be set to 0 to pad the beginning with
819 silence if an audio stream starts after the video stream.
823 @section channelsplit
824 Split each channel in input audio stream into a separate output stream.
826 This filter accepts the following named parameters:
829 Channel layout of the input stream. Default is "stereo".
832 For example, assuming a stereo input MP3 file
834 ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
836 will create an output Matroska file with two audio streams, one containing only
837 the left channel and the other the right channel.
839 To split a 5.1 WAV file into per-channel files
841 ffmpeg -i in.wav -filter_complex
842 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
843 -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
844 front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
849 Remap input channels to new locations.
851 This filter accepts the following named parameters:
854 Channel layout of the output stream.
857 Map channels from input to output. The argument is a comma-separated list of
858 mappings, each in the @code{@var{in_channel}-@var{out_channel}} or
859 @var{in_channel} form. @var{in_channel} can be either the name of the input
860 channel (e.g. FL for front left) or its index in the input channel layout.
861 @var{out_channel} is the name of the output channel or its index in the output
862 channel layout. If @var{out_channel} is not given then it is implicitly an
863 index, starting with zero and increasing by one for each mapping.
866 If no mapping is present, the filter will implicitly map input channels to
867 output channels preserving index.
869 For example, assuming a 5.1+downmix input MOV file
871 ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
873 will create an output WAV file tagged as stereo from the downmix channels of
876 To fix a 5.1 WAV improperly encoded in AAC's native channel order
878 ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
882 Join multiple input streams into one multi-channel stream.
884 The filter accepts the following named parameters:
888 Number of input streams. Defaults to 2.
891 Desired output channel layout. Defaults to stereo.
894 Map channels from inputs to output. The argument is a comma-separated list of
895 mappings, each in the @code{@var{input_idx}.@var{in_channel}-@var{out_channel}}
896 form. @var{input_idx} is the 0-based index of the input stream. @var{in_channel}
897 can be either the name of the input channel (e.g. FL for front left) or its
898 index in the specified input stream. @var{out_channel} is the name of the output
902 The filter will attempt to guess the mappings when those are not specified
903 explicitly. It does so by first trying to find an unused matching input channel
904 and if that fails it picks the first unused input channel.
906 E.g. to join 3 inputs (with properly set channel layouts)
908 ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
911 To build a 5.1 output from 6 single-channel streams:
913 ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
914 'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE'
919 Convert the audio sample format, sample rate and channel layout. This filter is
920 not meant to be used directly.
922 @c man end AUDIO FILTERS
924 @chapter Audio Sources
925 @c man begin AUDIO SOURCES
927 Below is a description of the currently available audio sources.
931 Buffer audio frames, and make them available to the filter chain.
933 This source is mainly intended for a programmatic use, in particular
934 through the interface defined in @file{libavfilter/asrc_abuffer.h}.
936 It accepts the following mandatory parameters:
937 @var{sample_rate}:@var{sample_fmt}:@var{channel_layout}
942 The sample rate of the incoming audio buffers.
945 The sample format of the incoming audio buffers.
946 Either a sample format name or its corresponging integer representation from
947 the enum AVSampleFormat in @file{libavutil/samplefmt.h}
950 The channel layout of the incoming audio buffers.
951 Either a channel layout name from channel_layout_map in
952 @file{libavutil/audioconvert.c} or its corresponding integer representation
953 from the AV_CH_LAYOUT_* macros in @file{libavutil/audioconvert.h}
959 abuffer=44100:s16p:stereo
962 will instruct the source to accept planar 16bit signed stereo at 44100Hz.
963 Since the sample format with name "s16p" corresponds to the number
964 6 and the "stereo" channel layout corresponds to the value 0x3, this is
972 Generate an audio signal specified by an expression.
974 This source accepts in input one or more expressions (one for each
975 channel), which are evaluated and used to generate a corresponding
978 It accepts the syntax: @var{exprs}[::@var{options}].
979 @var{exprs} is a list of expressions separated by ":", one for each
980 separate channel. In case the @var{channel_layout} is not
981 specified, the selected channel layout depends on the number of
982 provided expressions.
984 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
987 The description of the accepted options follows.
991 @item channel_layout, c
992 Set the channel layout. The number of channels in the specified layout
993 must be equal to the number of specified expressions.
996 Set the minimum duration of the sourced audio. See the function
997 @code{av_parse_time()} for the accepted format.
998 Note that the resulting duration may be greater than the specified
999 duration, as the generated audio is always cut at the end of a
1002 If not specified, or the expressed duration is negative, the audio is
1003 supposed to be generated forever.
1006 Set the number of samples per channel per each output frame,
1009 @item sample_rate, s
1010 Specify the sample rate, default to 44100.
1013 Each expression in @var{exprs} can contain the following constants:
1017 number of the evaluated sample, starting from 0
1020 time of the evaluated sample expressed in seconds, starting from 0
1027 @subsection Examples
1039 Generate a sin signal with frequency of 440 Hz, set sample rate to
1042 aevalsrc="sin(440*2*PI*t)::s=8000"
1046 Generate a two channels signal, specify the channel layout (Front
1047 Center + Back Center) explicitly:
1049 aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
1053 Generate white noise:
1055 aevalsrc="-2+random(0)"
1059 Generate an amplitude modulated signal:
1061 aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
1065 Generate 2.5 Hz binaural beats on a 360 Hz carrier:
1067 aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
1074 Null audio source, return unprocessed audio frames. It is mainly useful
1075 as a template and to be employed in analysis / debugging tools, or as
1076 the source for filters which ignore the input data (for example the sox
1079 It accepts an optional sequence of @var{key}=@var{value} pairs,
1082 The description of the accepted options follows.
1086 @item sample_rate, s
1087 Specify the sample rate, and defaults to 44100.
1089 @item channel_layout, cl
1091 Specify the channel layout, and can be either an integer or a string
1092 representing a channel layout. The default value of @var{channel_layout}
1095 Check the channel_layout_map definition in
1096 @file{libavcodec/audioconvert.c} for the mapping between strings and
1097 channel layout values.
1100 Set the number of samples per requested frames.
1104 Follow some examples:
1106 # set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
1107 anullsrc=r=48000:cl=4
1110 anullsrc=r=48000:cl=mono
1114 Buffer audio frames, and make them available to the filter chain.
1116 This source is not intended to be part of user-supplied graph descriptions but
1117 for insertion by calling programs through the interface defined in
1118 @file{libavfilter/buffersrc.h}.
1120 It accepts the following named parameters:
1124 Timebase which will be used for timestamps of submitted frames. It must be
1125 either a floating-point number or in @var{numerator}/@var{denominator} form.
1131 Name of the sample format, as returned by @code{av_get_sample_fmt_name()}.
1133 @item channel_layout
1134 Channel layout of the audio data, in the form that can be accepted by
1135 @code{av_get_channel_layout()}.
1138 All the parameters need to be explicitly defined.
1142 Synthesize a voice utterance using the libflite library.
1144 To enable compilation of this filter you need to configure FFmpeg with
1145 @code{--enable-libflite}.
1147 Note that the flite library is not thread-safe.
1149 The source accepts parameters as a list of @var{key}=@var{value} pairs,
1152 The description of the accepted parameters follows.
1157 If set to 1, list the names of the available voices and exit
1158 immediately. Default value is 0.
1161 Set the maximum number of samples per frame. Default value is 512.
1164 Set the filename containing the text to speak.
1167 Set the text to speak.
1170 Set the voice to use for the speech synthesis. Default value is
1171 @code{kal}. See also the @var{list_voices} option.
1174 @subsection Examples
1178 Read from file @file{speech.txt}, and synthetize the text using the
1179 standard flite voice:
1181 flite=textfile=speech.txt
1185 Read the specified text selecting the @code{slt} voice:
1187 flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1191 Input text to ffmpeg:
1193 ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
1197 Make @file{ffplay} speak the specified text, using @code{flite} and
1198 the @code{lavfi} device:
1200 ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
1204 For more information about libflite, check:
1205 @url{http://www.speech.cs.cmu.edu/flite/}
1207 @c man end AUDIO SOURCES
1209 @chapter Audio Sinks
1210 @c man begin AUDIO SINKS
1212 Below is a description of the currently available audio sinks.
1214 @section abuffersink
1216 Buffer audio frames, and make them available to the end of filter chain.
1218 This sink is mainly intended for programmatic use, in particular
1219 through the interface defined in @file{libavfilter/buffersink.h}.
1221 It requires a pointer to an AVABufferSinkContext structure, which
1222 defines the incoming buffers' formats, to be passed as the opaque
1223 parameter to @code{avfilter_init_filter} for initialization.
1227 Null audio sink, do absolutely nothing with the input audio. It is
1228 mainly useful as a template and to be employed in analysis / debugging
1231 @section abuffersink
1232 This sink is intended for programmatic use. Frames that arrive on this sink can
1233 be retrieved by the calling program using the interface defined in
1234 @file{libavfilter/buffersink.h}.
1236 This filter accepts no parameters.
1238 @c man end AUDIO SINKS
1240 @chapter Video Filters
1241 @c man begin VIDEO FILTERS
1243 When you configure your FFmpeg build, you can disable any of the
1244 existing filters using @code{--disable-filters}.
1245 The configure output will show the video filters included in your
1248 Below is a description of the currently available video filters.
1250 @section alphaextract
1252 Extract the alpha component from the input as a grayscale video. This
1253 is especially useful with the @var{alphamerge} filter.
1257 Add or replace the alpha component of the primary input with the
1258 grayscale value of a second input. This is intended for use with
1259 @var{alphaextract} to allow the transmission or storage of frame
1260 sequences that have alpha in a format that doesn't support an alpha
1263 For example, to reconstruct full frames from a normal YUV-encoded video
1264 and a separate video created with @var{alphaextract}, you might use:
1266 movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
1269 Since this filter is designed for reconstruction, it operates on frame
1270 sequences without considering timestamps, and terminates when either
1271 input reaches end of stream. This will cause problems if your encoding
1272 pipeline drops frames. If you're trying to apply an image as an
1273 overlay to a video stream, consider the @var{overlay} filter instead.
1277 Draw ASS (Advanced Substation Alpha) subtitles on top of input video
1278 using the libass library.
1280 To enable compilation of this filter you need to configure FFmpeg with
1281 @code{--enable-libass}.
1283 This filter accepts the following named options, expressed as a
1284 sequence of @var{key}=@var{value} pairs, separated by ":".
1288 Set the filename of the ASS file to read. It must be specified.
1291 Specify the size of the original video, the video for which the ASS file
1292 was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
1293 necessary to correctly scale the fonts if the aspect ratio has been changed.
1296 If the first key is not specified, it is assumed that the first value
1297 specifies the @option{filename}.
1299 For example, to render the file @file{sub.ass} on top of the input
1300 video, use the command:
1305 which is equivalent to:
1307 ass=filename=sub.ass
1312 Compute the bounding box for the non-black pixels in the input frame
1315 This filter computes the bounding box containing all the pixels with a
1316 luminance value greater than the minimum allowed value.
1317 The parameters describing the bounding box are printed on the filter
1320 @section blackdetect
1322 Detect video intervals that are (almost) completely black. Can be
1323 useful to detect chapter transitions, commercials, or invalid
1324 recordings. Output lines contains the time for the start, end and
1325 duration of the detected black interval expressed in seconds.
1327 In order to display the output lines, you need to set the loglevel at
1328 least to the AV_LOG_INFO value.
1330 This filter accepts a list of options in the form of
1331 @var{key}=@var{value} pairs separated by ":". A description of the
1332 accepted options follows.
1335 @item black_min_duration, d
1336 Set the minimum detected black duration expressed in seconds. It must
1337 be a non-negative floating point number.
1339 Default value is 2.0.
1341 @item picture_black_ratio_th, pic_th
1342 Set the threshold for considering a picture "black".
1343 Express the minimum value for the ratio:
1345 @var{nb_black_pixels} / @var{nb_pixels}
1348 for which a picture is considered black.
1349 Default value is 0.98.
1351 @item pixel_black_th, pix_th
1352 Set the threshold for considering a pixel "black".
1354 The threshold expresses the maximum pixel luminance value for which a
1355 pixel is considered "black". The provided value is scaled according to
1356 the following equation:
1358 @var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
1361 @var{luminance_range_size} and @var{luminance_minimum_value} depend on
1362 the input video format, the range is [0-255] for YUV full-range
1363 formats and [16-235] for YUV non full-range formats.
1365 Default value is 0.10.
1368 The following example sets the maximum pixel threshold to the minimum
1369 value, and detects only black intervals of 2 or more seconds:
1371 blackdetect=d=2:pix_th=0.00
1376 Detect frames that are (almost) completely black. Can be useful to
1377 detect chapter transitions or commercials. Output lines consist of
1378 the frame number of the detected frame, the percentage of blackness,
1379 the position in the file if known or -1 and the timestamp in seconds.
1381 In order to display the output lines, you need to set the loglevel at
1382 least to the AV_LOG_INFO value.
1384 The filter accepts the syntax:
1386 blackframe[=@var{amount}:[@var{threshold}]]
1389 @var{amount} is the percentage of the pixels that have to be below the
1390 threshold, and defaults to 98.
1392 @var{threshold} is the threshold below which a pixel value is
1393 considered black, and defaults to 32.
1397 Apply boxblur algorithm to the input video.
1399 This filter accepts the parameters:
1400 @var{luma_radius}:@var{luma_power}:@var{chroma_radius}:@var{chroma_power}:@var{alpha_radius}:@var{alpha_power}
1402 Chroma and alpha parameters are optional, if not specified they default
1403 to the corresponding values set for @var{luma_radius} and
1406 @var{luma_radius}, @var{chroma_radius}, and @var{alpha_radius} represent
1407 the radius in pixels of the box used for blurring the corresponding
1408 input plane. They are expressions, and can contain the following
1412 the input width and height in pixels
1415 the input chroma image width and height in pixels
1418 horizontal and vertical chroma subsample values. For example for the
1419 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1422 The radius must be a non-negative number, and must not be greater than
1423 the value of the expression @code{min(w,h)/2} for the luma and alpha planes,
1424 and of @code{min(cw,ch)/2} for the chroma planes.
1426 @var{luma_power}, @var{chroma_power}, and @var{alpha_power} represent
1427 how many times the boxblur filter is applied to the corresponding
1430 Some examples follow:
1435 Apply a boxblur filter with luma, chroma, and alpha radius
1442 Set luma radius to 2, alpha and chroma radius to 0
1448 Set luma and chroma radius to a fraction of the video dimension
1450 boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
1455 @section colormatrix
1457 The colormatrix filter allows conversion between any of the following color
1458 space: BT.709 (@var{bt709}), BT.601 (@var{bt601}), SMPTE-240M (@var{smpte240m})
1459 and FCC (@var{fcc}).
1461 The syntax of the parameters is @var{source}:@var{destination}:
1464 colormatrix=bt601:smpte240m
1469 Copy the input source unchanged to the output. Mainly useful for
1474 Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}:@var{keep_aspect}
1476 The @var{keep_aspect} parameter is optional, if specified and set to a
1477 non-zero value will force the output display aspect ratio to be the
1478 same of the input, by changing the output sample aspect ratio.
1480 The @var{out_w}, @var{out_h}, @var{x}, @var{y} parameters are
1481 expressions containing the following constants:
1485 the computed values for @var{x} and @var{y}. They are evaluated for
1489 the input width and height
1492 same as @var{in_w} and @var{in_h}
1495 the output (cropped) width and height
1498 same as @var{out_w} and @var{out_h}
1501 same as @var{iw} / @var{ih}
1504 input sample aspect ratio
1507 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
1510 horizontal and vertical chroma subsample values. For example for the
1511 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1514 the number of input frame, starting from 0
1517 the position in the file of the input frame, NAN if unknown
1520 timestamp expressed in seconds, NAN if the input timestamp is unknown
1524 The @var{out_w} and @var{out_h} parameters specify the expressions for
1525 the width and height of the output (cropped) video. They are
1526 evaluated just at the configuration of the filter.
1528 The default value of @var{out_w} is "in_w", and the default value of
1529 @var{out_h} is "in_h".
1531 The expression for @var{out_w} may depend on the value of @var{out_h},
1532 and the expression for @var{out_h} may depend on @var{out_w}, but they
1533 cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are
1534 evaluated after @var{out_w} and @var{out_h}.
1536 The @var{x} and @var{y} parameters specify the expressions for the
1537 position of the top-left corner of the output (non-cropped) area. They
1538 are evaluated for each frame. If the evaluated value is not valid, it
1539 is approximated to the nearest valid value.
1541 The default value of @var{x} is "(in_w-out_w)/2", and the default
1542 value for @var{y} is "(in_h-out_h)/2", which set the cropped area at
1543 the center of the input image.
1545 The expression for @var{x} may depend on @var{y}, and the expression
1546 for @var{y} may depend on @var{x}.
1548 Follow some examples:
1550 # crop the central input area with size 100x100
1553 # crop the central input area with size 2/3 of the input video
1554 "crop=2/3*in_w:2/3*in_h"
1556 # crop the input video central square
1559 # delimit the rectangle with the top-left corner placed at position
1560 # 100:100 and the right-bottom corner corresponding to the right-bottom
1561 # corner of the input image.
1562 crop=in_w-100:in_h-100:100:100
1564 # crop 10 pixels from the left and right borders, and 20 pixels from
1565 # the top and bottom borders
1566 "crop=in_w-2*10:in_h-2*20"
1568 # keep only the bottom right quarter of the input image
1569 "crop=in_w/2:in_h/2:in_w/2:in_h/2"
1571 # crop height for getting Greek harmony
1572 "crop=in_w:1/PHI*in_w"
1575 "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)"
1577 # erratic camera effect depending on timestamp
1578 "crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
1580 # set x depending on the value of y
1581 "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"
1586 Auto-detect crop size.
1588 Calculate necessary cropping parameters and prints the recommended
1589 parameters through the logging system. The detected dimensions
1590 correspond to the non-black area of the input video.
1592 It accepts the syntax:
1594 cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]
1600 Threshold, which can be optionally specified from nothing (0) to
1601 everything (255), defaults to 24.
1604 Value which the width/height should be divisible by, defaults to
1605 16. The offset is automatically adjusted to center the video. Use 2 to
1606 get only even dimensions (needed for 4:2:2 video). 16 is best when
1607 encoding to most video codecs.
1610 Counter that determines after how many frames cropdetect will reset
1611 the previously detected largest video area and start over to detect
1612 the current optimal crop area. Defaults to 0.
1614 This can be useful when channel logos distort the video area. 0
1615 indicates never reset and return the largest area encountered during
1621 This filter drops frames that do not differ greatly from the previous
1622 frame in order to reduce framerate. The main use of this filter is
1623 for very-low-bitrate encoding (e.g. streaming over dialup modem), but
1624 it could in theory be used for fixing movies that were
1625 inverse-telecined incorrectly.
1627 It accepts the following parameters:
1628 @var{max}:@var{hi}:@var{lo}:@var{frac}.
1633 Set the maximum number of consecutive frames which can be dropped (if
1634 positive), or the minimum interval between dropped frames (if
1635 negative). If the value is 0, the frame is dropped unregarding the
1636 number of previous sequentially dropped frames.
1641 Set the dropping threshold values.
1643 Values for @var{hi} and @var{lo} are for 8x8 pixel blocks and
1644 represent actual pixel value differences, so a threshold of 64
1645 corresponds to 1 unit of difference for each pixel, or the same spread
1646 out differently over the block.
1648 A frame is a candidate for dropping if no 8x8 blocks differ by more
1649 than a threshold of @var{hi}, and if no more than @var{frac} blocks (1
1650 meaning the whole image) differ by more than a threshold of @var{lo}.
1652 Default value for @var{hi} is 64*12, default value for @var{lo} is
1653 64*5, and default value for @var{frac} is 0.33.
1658 Suppress a TV station logo by a simple interpolation of the surrounding
1659 pixels. Just set a rectangle covering the logo and watch it disappear
1660 (and sometimes something even uglier appear - your mileage may vary).
1662 The filter accepts parameters as a string of the form
1663 "@var{x}:@var{y}:@var{w}:@var{h}:@var{band}", or as a list of
1664 @var{key}=@var{value} pairs, separated by ":".
1666 The description of the accepted parameters follows.
1671 Specify the top left corner coordinates of the logo. They must be
1675 Specify the width and height of the logo to clear. They must be
1679 Specify the thickness of the fuzzy edge of the rectangle (added to
1680 @var{w} and @var{h}). The default value is 4.
1683 When set to 1, a green rectangle is drawn on the screen to simplify
1684 finding the right @var{x}, @var{y}, @var{w}, @var{h} parameters, and
1685 @var{band} is set to 4. The default value is 0.
1689 Some examples follow.
1694 Set a rectangle covering the area with top left corner coordinates 0,0
1695 and size 100x77, setting a band of size 10:
1697 delogo=0:0:100:77:10
1701 As the previous example, but use named options:
1703 delogo=x=0:y=0:w=100:h=77:band=10
1710 Attempt to fix small changes in horizontal and/or vertical shift. This
1711 filter helps remove camera shake from hand-holding a camera, bumping a
1712 tripod, moving on a vehicle, etc.
1714 The filter accepts parameters as a string of the form
1715 "@var{x}:@var{y}:@var{w}:@var{h}:@var{rx}:@var{ry}:@var{edge}:@var{blocksize}:@var{contrast}:@var{search}:@var{filename}"
1717 A description of the accepted parameters follows.
1722 Specify a rectangular area where to limit the search for motion
1724 If desired the search for motion vectors can be limited to a
1725 rectangular area of the frame defined by its top left corner, width
1726 and height. These parameters have the same meaning as the drawbox
1727 filter which can be used to visualise the position of the bounding
1730 This is useful when simultaneous movement of subjects within the frame
1731 might be confused for camera motion by the motion vector search.
1733 If any or all of @var{x}, @var{y}, @var{w} and @var{h} are set to -1
1734 then the full frame is used. This allows later options to be set
1735 without specifying the bounding box for the motion vector search.
1737 Default - search the whole frame.
1740 Specify the maximum extent of movement in x and y directions in the
1741 range 0-64 pixels. Default 16.
1744 Specify how to generate pixels to fill blanks at the edge of the
1745 frame. An integer from 0 to 3 as follows:
1748 Fill zeroes at blank locations
1750 Original image at blank locations
1752 Extruded edge value at blank locations
1754 Mirrored edge at blank locations
1757 The default setting is mirror edge at blank locations.
1760 Specify the blocksize to use for motion search. Range 4-128 pixels,
1764 Specify the contrast threshold for blocks. Only blocks with more than
1765 the specified contrast (difference between darkest and lightest
1766 pixels) will be considered. Range 1-255, default 125.
1769 Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
1770 search. Default - exhaustive search.
1773 If set then a detailed log of the motion search is written to the
1780 Draw a colored box on the input image.
1782 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1785 The description of the accepted parameters follows.
1789 Specify the top left corner coordinates of the box. Default to 0.
1793 Specify the width and height of the box, if 0 they are interpreted as
1794 the input width and height. Default to 0.
1797 Specify the color of the box to write, it can be the name of a color
1798 (case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
1799 value @code{invert} is used, the box edge color is the same as the
1800 video with inverted luma.
1803 Set the thickness of the box edge. Default value is @code{4}.
1806 If the key of the first options is omitted, the arguments are
1807 interpreted according to the following syntax:
1809 drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}:@var{thickness}
1812 Some examples follow:
1815 Draw a black box around the edge of the input image:
1821 Draw a box with color red and an opacity of 50%:
1823 drawbox=10:20:200:60:red@@0.5
1826 The previous example can be specified as:
1828 drawbox=x=10:y=20:w=200:h=60:color=red@@0.5
1832 Fill the box with pink color:
1834 drawbox=x=10:y=10:w=100:h=100:color=pink@@0.5:t=max
1841 Draw text string or text from specified file on top of video using the
1842 libfreetype library.
1844 To enable compilation of this filter you need to configure FFmpeg with
1845 @code{--enable-libfreetype}.
1847 The filter also recognizes strftime() sequences in the provided text
1848 and expands them accordingly. Check the documentation of strftime().
1850 The filter accepts parameters as a list of @var{key}=@var{value} pairs,
1853 The description of the accepted parameters follows.
1858 Used to draw a box around text using background color.
1859 Value should be either 1 (enable) or 0 (disable).
1860 The default value of @var{box} is 0.
1863 The color to be used for drawing box around text.
1864 Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
1865 (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1866 The default value of @var{boxcolor} is "white".
1869 Set an expression which specifies if the text should be drawn. If the
1870 expression evaluates to 0, the text is not drawn. This is useful for
1871 specifying that the text should be drawn only when specific conditions
1874 Default value is "1".
1876 See below for the list of accepted constants and functions.
1879 If true, check and fix text coords to avoid clipping.
1882 The color to be used for drawing fonts.
1883 Either a string (e.g. "red") or in 0xRRGGBB[AA] format
1884 (e.g. "0xff000033"), possibly followed by an alpha specifier.
1885 The default value of @var{fontcolor} is "black".
1888 The font file to be used for drawing text. Path must be included.
1889 This parameter is mandatory.
1892 The font size to be used for drawing text.
1893 The default value of @var{fontsize} is 16.
1896 Flags to be used for loading the fonts.
1898 The flags map the corresponding flags supported by libfreetype, and are
1899 a combination of the following values:
1906 @item vertical_layout
1907 @item force_autohint
1910 @item ignore_global_advance_width
1912 @item ignore_transform
1919 Default value is "render".
1921 For more information consult the documentation for the FT_LOAD_*
1925 The color to be used for drawing a shadow behind the drawn text. It
1926 can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
1927 form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
1928 The default value of @var{shadowcolor} is "black".
1930 @item shadowx, shadowy
1931 The x and y offsets for the text shadow position with respect to the
1932 position of the text. They can be either positive or negative
1933 values. Default value for both is "0".
1936 The size in number of spaces to use for rendering the tab.
1940 Set the initial timecode representation in "hh:mm:ss[:;.]ff"
1941 format. It can be used with or without text parameter. @var{timecode_rate}
1942 option must be specified.
1944 @item timecode_rate, rate, r
1945 Set the timecode frame rate (timecode only).
1948 The text string to be drawn. The text must be a sequence of UTF-8
1950 This parameter is mandatory if no file is specified with the parameter
1954 A text file containing text to be drawn. The text must be a sequence
1955 of UTF-8 encoded characters.
1957 This parameter is mandatory if no text string is specified with the
1958 parameter @var{text}.
1960 If both @var{text} and @var{textfile} are specified, an error is thrown.
1963 The expressions which specify the offsets where text will be drawn
1964 within the video frame. They are relative to the top/left border of the
1967 The default value of @var{x} and @var{y} is "0".
1969 See below for the list of accepted constants and functions.
1972 The parameters for @var{x} and @var{y} are expressions containing the
1973 following constants and functions:
1977 input display aspect ratio, it is the same as (@var{w} / @var{h}) * @var{sar}
1980 horizontal and vertical chroma subsample values. For example for the
1981 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
1984 the height of each text line
1992 @item max_glyph_a, ascent
1993 the maximum distance from the baseline to the highest/upper grid
1994 coordinate used to place a glyph outline point, for all the rendered
1996 It is a positive value, due to the grid's orientation with the Y axis
1999 @item max_glyph_d, descent
2000 the maximum distance from the baseline to the lowest grid coordinate
2001 used to place a glyph outline point, for all the rendered glyphs.
2002 This is a negative value, due to the grid's orientation, with the Y axis
2006 maximum glyph height, that is the maximum height for all the glyphs
2007 contained in the rendered text, it is equivalent to @var{ascent} -
2011 maximum glyph width, that is the maximum width for all the glyphs
2012 contained in the rendered text
2015 the number of input frame, starting from 0
2017 @item rand(min, max)
2018 return a random number included between @var{min} and @var{max}
2021 input sample aspect ratio
2024 timestamp expressed in seconds, NAN if the input timestamp is unknown
2027 the height of the rendered text
2030 the width of the rendered text
2033 the x and y offset coordinates where the text is drawn.
2035 These parameters allow the @var{x} and @var{y} expressions to refer
2036 each other, so you can for example specify @code{y=x/dar}.
2039 If libavfilter was built with @code{--enable-fontconfig}, then
2040 @option{fontfile} can be a fontconfig pattern or omitted.
2042 Some examples follow.
2047 Draw "Test Text" with font FreeSerif, using the default values for the
2048 optional parameters.
2051 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
2055 Draw 'Test Text' with font FreeSerif of size 24 at position x=100
2056 and y=50 (counting from the top-left corner of the screen), text is
2057 yellow with a red box around it. Both the text and the box have an
2061 drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
2062 x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: box=1: boxcolor=red@@0.2"
2065 Note that the double quotes are not necessary if spaces are not used
2066 within the parameter list.
2069 Show the text at the center of the video frame:
2071 drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
2075 Show a text line sliding from right to left in the last row of the video
2076 frame. The file @file{LONG_LINE} is assumed to contain a single line
2079 drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
2083 Show the content of file @file{CREDITS} off the bottom of the frame and scroll up.
2085 drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
2089 Draw a single green letter "g", at the center of the input video.
2090 The glyph baseline is placed at half screen height.
2092 drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
2096 Show text for 1 second every 3 seconds:
2098 drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
2102 Use fontconfig to set the font. Note that the colons need to be escaped.
2104 drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
2109 For more information about libfreetype, check:
2110 @url{http://www.freetype.org/}.
2112 For more information about fontconfig, check:
2113 @url{http://freedesktop.org/software/fontconfig/fontconfig-user.html}.
2117 Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
2119 This filter accepts the following optional named parameters:
2123 Set low and high threshold values used by the Canny thresholding
2126 The high threshold selects the "strong" edge pixels, which are then
2127 connected through 8-connectivity with the "weak" edge pixels selected
2128 by the low threshold.
2130 @var{low} and @var{high} threshold values must be choosen in the range
2131 [0,1], and @var{low} should be lesser or equal to @var{high}.
2133 Default value for @var{low} is @code{20/255}, and default value for @var{high}
2139 edgedetect=low=0.1:high=0.4
2144 Apply fade-in/out effect to input video.
2146 It accepts the parameters:
2147 @var{type}:@var{start_frame}:@var{nb_frames}[:@var{options}]
2149 @var{type} specifies if the effect type, can be either "in" for
2150 fade-in, or "out" for a fade-out effect.
2152 @var{start_frame} specifies the number of the start frame for starting
2153 to apply the fade effect.
2155 @var{nb_frames} specifies the number of frames for which the fade
2156 effect has to last. At the end of the fade-in effect the output video
2157 will have the same intensity as the input video, at the end of the
2158 fade-out transition the output video will be completely black.
2160 @var{options} is an optional sequence of @var{key}=@var{value} pairs,
2161 separated by ":". The description of the accepted options follows.
2168 @item start_frame, s
2169 See @var{start_frame}.
2172 See @var{nb_frames}.
2175 If set to 1, fade only alpha channel, if one exists on the input.
2179 A few usage examples follow, usable too as test scenarios.
2181 # fade in first 30 frames of video
2184 # fade out last 45 frames of a 200-frame video
2187 # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
2188 fade=in:0:25, fade=out:975:25
2190 # make first 5 frames black, then fade in from frame 5-24
2193 # fade in alpha over first 25 frames of video
2194 fade=in:0:25:alpha=1
2199 Extract a single field from an interlaced image using stride
2200 arithmetic to avoid wasting CPU time. The output frames are marked as
2203 This filter accepts the following named options:
2206 Specify whether to extract the top (if the value is @code{0} or
2207 @code{top}) or the bottom field (if the value is @code{1} or
2211 If the option key is not specified, the first value sets the @var{type}
2212 option. For example:
2224 Transform the field order of the input video.
2226 It accepts one parameter which specifies the required field order that
2227 the input interlaced video will be transformed to. The parameter can
2228 assume one of the following values:
2232 output bottom field first
2234 output top field first
2237 Default value is "tff".
2239 Transformation is achieved by shifting the picture content up or down
2240 by one line, and filling the remaining line with appropriate picture content.
2241 This method is consistent with most broadcast field order converters.
2243 If the input video is not flagged as being interlaced, or it is already
2244 flagged as being of the required output field order then this filter does
2245 not alter the incoming video.
2247 This filter is very useful when converting to or from PAL DV material,
2248 which is bottom field first.
2252 ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
2257 Buffer input images and send them when they are requested.
2259 This filter is mainly useful when auto-inserted by the libavfilter
2262 The filter does not take parameters.
2266 Convert the input video to one of the specified pixel formats.
2267 Libavfilter will try to pick one that is supported for the input to
2270 The filter accepts a list of pixel format names, separated by ":",
2271 for example "yuv420p:monow:rgb24".
2273 Some examples follow:
2275 # convert the input video to the format "yuv420p"
2278 # convert the input video to any of the formats in the list
2279 format=yuv420p:yuv444p:yuv410p
2284 Convert the video to specified constant framerate by duplicating or dropping
2285 frames as necessary.
2287 This filter accepts the following named parameters:
2291 Desired output framerate.
2294 Rounding method. The default is @code{near}.
2300 Select one frame every N.
2302 This filter accepts in input a string representing a positive
2303 integer. Default argument is @code{1}.
2308 Apply a frei0r effect to the input video.
2310 To enable compilation of this filter you need to install the frei0r
2311 header and configure FFmpeg with @code{--enable-frei0r}.
2313 The filter supports the syntax:
2315 @var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]
2318 @var{filter_name} is the name to the frei0r effect to load. If the
2319 environment variable @env{FREI0R_PATH} is defined, the frei0r effect
2320 is searched in each one of the directories specified by the colon (or
2321 semicolon on Windows platforms) separated list in @env{FREIOR_PATH},
2322 otherwise in the standard frei0r paths, which are in this order:
2323 @file{HOME/.frei0r-1/lib/}, @file{/usr/local/lib/frei0r-1/},
2324 @file{/usr/lib/frei0r-1/}.
2326 @var{param1}, @var{param2}, ... , @var{paramN} specify the parameters
2327 for the frei0r effect.
2329 A frei0r effect parameter can be a boolean (whose values are specified
2330 with "y" and "n"), a double, a color (specified by the syntax
2331 @var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float
2332 numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color
2333 description), a position (specified by the syntax @var{X}/@var{Y},
2334 @var{X} and @var{Y} being float numbers) and a string.
2336 The number and kind of parameters depend on the loaded effect. If an
2337 effect parameter is not specified the default value is set.
2339 Some examples follow:
2343 Apply the distort0r effect, set the first two double parameters:
2345 frei0r=distort0r:0.5:0.01
2349 Apply the colordistance effect, takes a color as first parameter:
2351 frei0r=colordistance:0.2/0.3/0.4
2352 frei0r=colordistance:violet
2353 frei0r=colordistance:0x112233
2357 Apply the perspective effect, specify the top left and top right image
2360 frei0r=perspective:0.2/0.2:0.8/0.2
2364 For more information see:
2365 @url{http://frei0r.dyne.org}
2369 Fix the banding artifacts that are sometimes introduced into nearly flat
2370 regions by truncation to 8bit color depth.
2371 Interpolate the gradients that should go where the bands are, and
2374 This filter is designed for playback only. Do not use it prior to
2375 lossy compression, because compression tends to lose the dither and
2376 bring back the bands.
2378 The filter takes two optional parameters, separated by ':':
2379 @var{strength}:@var{radius}
2381 @var{strength} is the maximum amount by which the filter will change
2382 any one pixel. Also the threshold for detecting nearly flat
2383 regions. Acceptable values range from .51 to 255, default value is
2384 1.2, out-of-range values will be clipped to the valid range.
2386 @var{radius} is the neighborhood to fit the gradient to. A larger
2387 radius makes for smoother gradients, but also prevents the filter from
2388 modifying the pixels near detailed regions. Acceptable values are
2389 8-32, default value is 16, out-of-range values will be clipped to the
2393 # default parameters
2402 Flip the input video horizontally.
2404 For example to horizontally flip the input video with @command{ffmpeg}:
2406 ffmpeg -i in.avi -vf "hflip" out.avi
2411 High precision/quality 3d denoise filter. This filter aims to reduce
2412 image noise producing smooth images and making still images really
2413 still. It should enhance compressibility.
2415 It accepts the following optional parameters:
2416 @var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}
2420 a non-negative float number which specifies spatial luma strength,
2423 @item chroma_spatial
2424 a non-negative float number which specifies spatial chroma strength,
2425 defaults to 3.0*@var{luma_spatial}/4.0
2428 a float number which specifies luma temporal strength, defaults to
2429 6.0*@var{luma_spatial}/4.0
2432 a float number which specifies chroma temporal strength, defaults to
2433 @var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}
2438 Modify the hue and/or the saturation of the input.
2440 This filter accepts the following optional named options:
2444 Specify the hue angle as a number of degrees. It accepts a float
2445 number or an expression, and defaults to 0.0.
2448 Specify the hue angle as a number of degrees. It accepts a float
2449 number or an expression, and defaults to 0.0.
2452 Specify the saturation in the [-10,10] range. It accepts a float number and
2456 The @var{h}, @var{H} and @var{s} parameters are expressions containing the
2457 following constants:
2461 frame count of the input frame starting from 0
2464 presentation timestamp of the input frame expressed in time base units
2467 frame rate of the input video, NAN if the input frame rate is unknown
2470 timestamp expressed in seconds, NAN if the input timestamp is unknown
2473 time base of the input video
2476 The options can also be set using the syntax: @var{hue}:@var{saturation}
2478 In this case @var{hue} is expressed in degrees.
2480 Some examples follow:
2483 Set the hue to 90 degrees and the saturation to 1.0:
2489 Same command but expressing the hue in radians:
2495 Same command without named options, hue must be expressed in degrees:
2501 Note that "h:s" syntax does not support expressions for the values of
2502 h and s, so the following example will issue an error:
2508 Rotate hue and make the saturation swing between 0
2509 and 2 over a period of 1 second:
2511 hue="H=2*PI*t: s=sin(2*PI*t)+1"
2515 Apply a 3 seconds saturation fade-in effect starting at 0:
2520 The general fade-in expression can be written as:
2522 hue="s=min(0\, max((t-START)/DURATION\, 1))"
2526 Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
2528 hue="s=max(0\, min(1\, (8-t)/3))"
2531 The general fade-out expression can be written as:
2533 hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
2538 @subsection Commands
2540 This filter supports the following command:
2543 Modify the hue and/or the saturation of the input video.
2544 The command accepts the same named options and syntax than when calling the
2545 filter from the command-line.
2547 If a parameter is omitted, it is kept at its current value.
2552 Interlaceing detect filter. This filter tries to detect if the input is
2553 interlaced or progressive. Top or bottom field first.
2555 @section lut, lutrgb, lutyuv
2557 Compute a look-up table for binding each pixel component input value
2558 to an output value, and apply it to input video.
2560 @var{lutyuv} applies a lookup table to a YUV input video, @var{lutrgb}
2561 to an RGB input video.
2563 These filters accept in input a ":"-separated list of options, which
2564 specify the expressions used for computing the lookup table for the
2565 corresponding pixel component values.
2567 The @var{lut} filter requires either YUV or RGB pixel formats in
2568 input, and accepts the options:
2570 @item @var{c0} (first pixel component)
2571 @item @var{c1} (second pixel component)
2572 @item @var{c2} (third pixel component)
2573 @item @var{c3} (fourth pixel component, corresponds to the alpha component)
2576 The exact component associated to each option depends on the format in
2579 The @var{lutrgb} filter requires RGB pixel formats in input, and
2580 accepts the options:
2582 @item @var{r} (red component)
2583 @item @var{g} (green component)
2584 @item @var{b} (blue component)
2585 @item @var{a} (alpha component)
2588 The @var{lutyuv} filter requires YUV pixel formats in input, and
2589 accepts the options:
2591 @item @var{y} (Y/luminance component)
2592 @item @var{u} (U/Cb component)
2593 @item @var{v} (V/Cr component)
2594 @item @var{a} (alpha component)
2597 The expressions can contain the following constants and functions:
2601 the input width and height
2604 input value for the pixel component
2607 the input value clipped in the @var{minval}-@var{maxval} range
2610 maximum value for the pixel component
2613 minimum value for the pixel component
2616 the negated value for the pixel component value clipped in the
2617 @var{minval}-@var{maxval} range , it corresponds to the expression
2618 "maxval-clipval+minval"
2621 the computed value in @var{val} clipped in the
2622 @var{minval}-@var{maxval} range
2624 @item gammaval(gamma)
2625 the computed gamma correction value of the pixel component value
2626 clipped in the @var{minval}-@var{maxval} range, corresponds to the
2628 "pow((clipval-minval)/(maxval-minval)\,@var{gamma})*(maxval-minval)+minval"
2632 All expressions default to "val".
2634 Some examples follow:
2636 # negate input video
2637 lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
2638 lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
2640 # the above is the same as
2641 lutrgb="r=negval:g=negval:b=negval"
2642 lutyuv="y=negval:u=negval:v=negval"
2647 # remove chroma components, turns the video into a graytone image
2648 lutyuv="u=128:v=128"
2650 # apply a luma burning effect
2653 # remove green and blue components
2656 # set a constant alpha channel value on input
2657 format=rgba,lutrgb=a="maxval-minval/2"
2659 # correct luminance gamma by a 0.5 factor
2660 lutyuv=y=gammaval(0.5)
2665 Apply an MPlayer filter to the input video.
2667 This filter provides a wrapper around most of the filters of
2670 This wrapper is considered experimental. Some of the wrapped filters
2671 may not work properly and we may drop support for them, as they will
2672 be implemented natively into FFmpeg. Thus you should avoid
2673 depending on them when writing portable scripts.
2675 The filters accepts the parameters:
2676 @var{filter_name}[:=]@var{filter_params}
2678 @var{filter_name} is the name of a supported MPlayer filter,
2679 @var{filter_params} is a string containing the parameters accepted by
2682 The list of the currently supported filters follows:
2720 The parameter syntax and behavior for the listed filters are the same
2721 of the corresponding MPlayer filters. For detailed instructions check
2722 the "VIDEO FILTERS" section in the MPlayer manual.
2724 Some examples follow:
2727 Adjust gamma, brightness, contrast:
2733 Add temporal noise to input video:
2739 See also mplayer(1), @url{http://www.mplayerhq.hu/}.
2745 This filter accepts an integer in input, if non-zero it negates the
2746 alpha component (if available). The default value in input is 0.
2750 Force libavfilter not to use any of the specified pixel formats for the
2751 input to the next filter.
2753 The filter accepts a list of pixel format names, separated by ":",
2754 for example "yuv420p:monow:rgb24".
2756 Some examples follow:
2758 # force libavfilter to use a format different from "yuv420p" for the
2759 # input to the vflip filter
2760 noformat=yuv420p,vflip
2762 # convert the input video to any of the formats not contained in the list
2763 noformat=yuv420p:yuv444p:yuv410p
2768 Pass the video source unchanged to the output.
2772 Apply video transform using libopencv.
2774 To enable this filter install libopencv library and headers and
2775 configure FFmpeg with @code{--enable-libopencv}.
2777 The filter takes the parameters: @var{filter_name}@{:=@}@var{filter_params}.
2779 @var{filter_name} is the name of the libopencv filter to apply.
2781 @var{filter_params} specifies the parameters to pass to the libopencv
2782 filter. If not specified the default values are assumed.
2784 Refer to the official libopencv documentation for more precise
2786 @url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}
2788 Follows the list of supported libopencv filters.
2793 Dilate an image by using a specific structuring element.
2794 This filter corresponds to the libopencv function @code{cvDilate}.
2796 It accepts the parameters: @var{struct_el}:@var{nb_iterations}.
2798 @var{struct_el} represents a structuring element, and has the syntax:
2799 @var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}
2801 @var{cols} and @var{rows} represent the number of columns and rows of
2802 the structuring element, @var{anchor_x} and @var{anchor_y} the anchor
2803 point, and @var{shape} the shape for the structuring element, and
2804 can be one of the values "rect", "cross", "ellipse", "custom".
2806 If the value for @var{shape} is "custom", it must be followed by a
2807 string of the form "=@var{filename}". The file with name
2808 @var{filename} is assumed to represent a binary image, with each
2809 printable character corresponding to a bright pixel. When a custom
2810 @var{shape} is used, @var{cols} and @var{rows} are ignored, the number
2811 or columns and rows of the read file are assumed instead.
2813 The default value for @var{struct_el} is "3x3+0x0/rect".
2815 @var{nb_iterations} specifies the number of times the transform is
2816 applied to the image, and defaults to 1.
2818 Follow some example:
2820 # use the default values
2823 # dilate using a structuring element with a 5x5 cross, iterate two times
2824 ocv=dilate=5x5+2x2/cross:2
2826 # read the shape from the file diamond.shape, iterate two times
2827 # the file diamond.shape may contain a pattern of characters like this:
2833 # the specified cols and rows are ignored (but not the anchor point coordinates)
2834 ocv=0x0+2x2/custom=diamond.shape:2
2839 Erode an image by using a specific structuring element.
2840 This filter corresponds to the libopencv function @code{cvErode}.
2842 The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},
2843 with the same syntax and semantics as the @ref{dilate} filter.
2847 Smooth the input video.
2849 The filter takes the following parameters:
2850 @var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.
2852 @var{type} is the type of smooth filter to apply, and can be one of
2853 the following values: "blur", "blur_no_scale", "median", "gaussian",
2854 "bilateral". The default value is "gaussian".
2856 @var{param1}, @var{param2}, @var{param3}, and @var{param4} are
2857 parameters whose meanings depend on smooth type. @var{param1} and
2858 @var{param2} accept integer positive values or 0, @var{param3} and
2859 @var{param4} accept float values.
2861 The default value for @var{param1} is 3, the default value for the
2862 other parameters is 0.
2864 These parameters correspond to the parameters assigned to the
2865 libopencv function @code{cvSmooth}.
2870 Overlay one video on top of another.
2872 It takes two inputs and one output, the first input is the "main"
2873 video on which the second input is overlayed.
2875 It accepts the parameters: @var{x}:@var{y}[:@var{options}].
2877 @var{x} is the x coordinate of the overlayed video on the main video,
2878 @var{y} is the y coordinate. @var{x} and @var{y} are expressions containing
2879 the following parameters:
2882 @item main_w, main_h
2883 main input width and height
2886 same as @var{main_w} and @var{main_h}
2888 @item overlay_w, overlay_h
2889 overlay input width and height
2892 same as @var{overlay_w} and @var{overlay_h}
2895 @var{options} is an optional list of @var{key}=@var{value} pairs,
2898 The description of the accepted options follows.
2902 If set to 1, force the filter to accept inputs in the RGB
2903 color space. Default value is 0.
2906 Be aware that frames are taken from each input video in timestamp
2907 order, hence, if their initial timestamps differ, it is a a good idea
2908 to pass the two inputs through a @var{setpts=PTS-STARTPTS} filter to
2909 have them begin in the same zero timestamp, as it does the example for
2910 the @var{movie} filter.
2912 Follow some examples:
2914 # draw the overlay at 10 pixels from the bottom right
2915 # corner of the main video.
2916 overlay=main_w-overlay_w-10:main_h-overlay_h-10
2918 # insert a transparent PNG logo in the bottom left corner of the input
2919 ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
2921 # insert 2 different transparent PNG logos (second logo on bottom
2923 ffmpeg -i input -i logo1 -i logo2 -filter_complex
2924 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
2926 # add a transparent color layer on top of the main video,
2927 # WxH specifies the size of the main input to the overlay filter
2928 color=red@@.3:WxH [over]; [in][over] overlay [out]
2930 # play an original video and a filtered version (here with the deshake filter)
2932 ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
2934 # the previous example is the same as:
2935 ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
2938 You can chain together more overlays but the efficiency of such
2939 approach is yet to be tested.
2943 Add paddings to the input image, and places the original input at the
2944 given coordinates @var{x}, @var{y}.
2946 It accepts the following parameters:
2947 @var{width}:@var{height}:@var{x}:@var{y}:@var{color}.
2949 The parameters @var{width}, @var{height}, @var{x}, and @var{y} are
2950 expressions containing the following constants:
2954 the input video width and height
2957 same as @var{in_w} and @var{in_h}
2960 the output width and height, that is the size of the padded area as
2961 specified by the @var{width} and @var{height} expressions
2964 same as @var{out_w} and @var{out_h}
2967 x and y offsets as specified by the @var{x} and @var{y}
2968 expressions, or NAN if not yet specified
2971 same as @var{iw} / @var{ih}
2974 input sample aspect ratio
2977 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
2980 horizontal and vertical chroma subsample values. For example for the
2981 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
2984 Follows the description of the accepted parameters.
2989 Specify the size of the output image with the paddings added. If the
2990 value for @var{width} or @var{height} is 0, the corresponding input size
2991 is used for the output.
2993 The @var{width} expression can reference the value set by the
2994 @var{height} expression, and vice versa.
2996 The default value of @var{width} and @var{height} is 0.
3000 Specify the offsets where to place the input image in the padded area
3001 with respect to the top/left border of the output image.
3003 The @var{x} expression can reference the value set by the @var{y}
3004 expression, and vice versa.
3006 The default value of @var{x} and @var{y} is 0.
3010 Specify the color of the padded area, it can be the name of a color
3011 (case insensitive match) or a 0xRRGGBB[AA] sequence.
3013 The default value of @var{color} is "black".
3017 @subsection Examples
3021 Add paddings with color "violet" to the input video. Output video
3022 size is 640x480, the top-left corner of the input video is placed at
3025 pad=640:480:0:40:violet
3029 Pad the input to get an output with dimensions increased by 3/2,
3030 and put the input video at the center of the padded area:
3032 pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
3036 Pad the input to get a squared output with size equal to the maximum
3037 value between the input width and height, and put the input video at
3038 the center of the padded area:
3040 pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
3044 Pad the input to get a final w/h ratio of 16:9:
3046 pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
3050 In case of anamorphic video, in order to set the output display aspect
3051 correctly, it is necessary to use @var{sar} in the expression,
3052 according to the relation:
3054 (ih * X / ih) * sar = output_dar
3055 X = output_dar / sar
3058 Thus the previous example needs to be modified to:
3060 pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
3064 Double output size and put the input video in the bottom-right
3065 corner of the output padded area:
3067 pad="2*iw:2*ih:ow-iw:oh-ih"
3071 @section pixdesctest
3073 Pixel format descriptor test filter, mainly useful for internal
3074 testing. The output video should be equal to the input video.
3078 format=monow, pixdesctest
3081 can be used to test the monowhite pixel format descriptor definition.
3085 Suppress a TV station logo, using an image file to determine which
3086 pixels comprise the logo. It works by filling in the pixels that
3087 comprise the logo with neighboring pixels.
3089 This filter requires one argument which specifies the filter bitmap
3090 file, which can be any image format supported by libavformat. The
3091 width and height of the image file must match those of the video
3092 stream being processed.
3094 Pixels in the provided bitmap image with a value of zero are not
3095 considered part of the logo, non-zero pixels are considered part of
3096 the logo. If you use white (255) for the logo and black (0) for the
3097 rest, you will be safe. For making the filter bitmap, it is
3098 recommended to take a screen capture of a black frame with the logo
3099 visible, and then using a threshold filter followed by the erode
3100 filter once or twice.
3102 If needed, little splotches can be fixed manually. Remember that if
3103 logo pixels are not covered, the filter quality will be much
3104 reduced. Marking too many pixels as part of the logo does not hurt as
3105 much, but it will increase the amount of blurring needed to cover over
3106 the image and will destroy more information than necessary, and extra
3107 pixels will slow things down on a large logo.
3111 Scale (resize) the input video, using the libswscale library.
3113 The scale filter forces the output display aspect ratio to be the same
3114 of the input, by changing the output sample aspect ratio.
3116 This filter accepts a list of named options in the form of
3117 @var{key}=@var{value} pairs separated by ":". If the key for the first
3118 two options is not specified, the assumed keys for the first two
3119 values are @code{w} and @code{h}. If the first option has no key and
3120 can be interpreted like a video size specification, it will be used
3121 to set the video size.
3123 A description of the accepted options follows.
3127 Set the video width expression, default value is @code{iw}. See below
3128 for the list of accepted constants.
3131 Set the video heiht expression, default value is @code{ih}.
3132 See below for the list of accepted constants.
3135 Set the interlacing. It accepts the following values:
3139 force interlaced aware scaling
3142 do not apply interlaced scaling
3145 select interlaced aware scaling depending on whether the source frames
3146 are flagged as interlaced or not
3149 Default value is @code{0}.
3152 Set libswscale scaling flags. If not explictly specified the filter
3153 applies a bilinear scaling algorithm.
3156 Set the video size, the value must be a valid abbreviation or in the
3157 form @var{width}x@var{height}.
3160 The values of the @var{w} and @var{h} options are expressions
3161 containing the following constants:
3165 the input width and height
3168 same as @var{in_w} and @var{in_h}
3171 the output (cropped) width and height
3174 same as @var{out_w} and @var{out_h}
3177 same as @var{iw} / @var{ih}
3180 input sample aspect ratio
3183 input display aspect ratio, it is the same as (@var{iw} / @var{ih}) * @var{sar}
3186 horizontal and vertical chroma subsample values. For example for the
3187 pixel format "yuv422p" @var{hsub} is 2 and @var{vsub} is 1.
3190 If the input image format is different from the format requested by
3191 the next filter, the scale filter will convert the input to the
3194 If the value for @var{width} or @var{height} is 0, the respective input
3195 size is used for the output.
3197 If the value for @var{width} or @var{height} is -1, the scale filter will
3198 use, for the respective output size, a value that maintains the aspect
3199 ratio of the input image.
3201 @subsection Examples
3205 Scale the input video to a size of 200x100:
3210 This is equivalent to:
3221 Specify a size abbreviation for the output size:
3226 which can also be written as:
3232 Scale the input to 2x:
3238 The above is the same as:
3244 Scale the input to 2x with forced interlaced scaling:
3246 scale=2*iw:2*ih:interl=1
3250 Scale the input to half size:
3256 Increase the width, and set the height to the same size:
3262 Seek for Greek harmony:
3269 Increase the height, and set the width to 3/2 of the height:
3275 Increase the size, but make the size a multiple of the chroma:
3277 scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
3281 Increase the width to a maximum of 500 pixels, keep the same input
3284 scale='min(500\, iw*3/2):-1'
3289 Select frames to pass in output.
3291 It accepts in input an expression, which is evaluated for each input
3292 frame. If the expression is evaluated to a non-zero value, the frame
3293 is selected and passed to the output, otherwise it is discarded.
3295 The expression can contain the following constants:
3299 the sequential number of the filtered frame, starting from 0
3302 the sequential number of the selected frame, starting from 0
3304 @item prev_selected_n
3305 the sequential number of the last selected frame, NAN if undefined
3308 timebase of the input timestamps
3311 the PTS (Presentation TimeStamp) of the filtered video frame,
3312 expressed in @var{TB} units, NAN if undefined
3315 the PTS (Presentation TimeStamp) of the filtered video frame,
3316 expressed in seconds, NAN if undefined
3319 the PTS of the previously filtered video frame, NAN if undefined
3321 @item prev_selected_pts
3322 the PTS of the last previously filtered video frame, NAN if undefined
3324 @item prev_selected_t
3325 the PTS of the last previously selected video frame, NAN if undefined
3328 the PTS of the first video frame in the video, NAN if undefined
3331 the time of the first video frame in the video, NAN if undefined
3334 the type of the filtered frame, can assume one of the following
3346 @item interlace_type
3347 the frame interlace type, can assume one of the following values:
3350 the frame is progressive (not interlaced)
3352 the frame is top-field-first
3354 the frame is bottom-field-first
3358 1 if the filtered frame is a key-frame, 0 otherwise
3361 the position in the file of the filtered frame, -1 if the information
3362 is not available (e.g. for synthetic video)
3365 value between 0 and 1 to indicate a new scene; a low value reflects a low
3366 probability for the current frame to introduce a new scene, while a higher
3367 value means the current frame is more likely to be one (see the example below)
3371 The default value of the select expression is "1".
3373 Some examples follow:
3376 # select all frames in input
3379 # the above is the same as:
3385 # select only I-frames
3386 select='eq(pict_type\,I)'
3388 # select one frame every 100
3389 select='not(mod(n\,100))'
3391 # select only frames contained in the 10-20 time interval
3392 select='gte(t\,10)*lte(t\,20)'
3394 # select only I frames contained in the 10-20 time interval
3395 select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
3397 # select frames with a minimum distance of 10 seconds
3398 select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
3401 Complete example to create a mosaic of the first scenes:
3404 ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
3407 Comparing @var{scene} against a value between 0.3 and 0.5 is generally a sane
3410 @section setdar, setsar
3412 The @code{setdar} filter sets the Display Aspect Ratio for the filter
3415 This is done by changing the specified Sample (aka Pixel) Aspect
3416 Ratio, according to the following equation:
3418 @var{DAR} = @var{HORIZONTAL_RESOLUTION} / @var{VERTICAL_RESOLUTION} * @var{SAR}
3421 Keep in mind that the @code{setdar} filter does not modify the pixel
3422 dimensions of the video frame. Also the display aspect ratio set by
3423 this filter may be changed by later filters in the filterchain,
3424 e.g. in case of scaling or if another "setdar" or a "setsar" filter is
3427 The @code{setsar} filter sets the Sample (aka Pixel) Aspect Ratio for
3428 the filter output video.
3430 Note that as a consequence of the application of this filter, the
3431 output display aspect ratio will change according to the equation
3434 Keep in mind that the sample aspect ratio set by the @code{setsar}
3435 filter may be changed by later filters in the filterchain, e.g. if
3436 another "setsar" or a "setdar" filter is applied.
3438 The @code{setdar} and @code{setsar} filters accept a string in the
3439 form @var{num}:@var{den} expressing an aspect ratio, or the following
3440 named options, expressed as a sequence of @var{key}=@var{value} pairs,
3445 Set the maximum integer value to use for expressing numerator and
3446 denominator when reducing the expressed aspect ratio to a rational.
3447 Default value is @code{100}.
3450 Set the aspect ratio used by the filter.
3452 The parameter can be a floating point number string, an expression, or
3453 a string of the form @var{num}:@var{den}, where @var{num} and
3454 @var{den} are the numerator and denominator of the aspect ratio. If
3455 the parameter is not specified, it is assumed the value "0".
3456 In case the form "@var{num}:@var{den}" the @code{:} character should
3460 If the keys are omitted in the named options list, the specifed values
3461 are assumed to be @var{ratio} and @var{max} in that order.
3463 For example to change the display aspect ratio to 16:9, specify:
3468 The example above is equivalent to:
3473 To change the sample aspect ratio to 10:11, specify:
3478 To set a display aspect ratio of 16:9, and specify a maximum integer value of
3479 1000 in the aspect ratio reduction, use the command:
3481 setdar=ratio='16:9':max=1000
3486 Force field for the output video frame.
3488 The @code{setfield} filter marks the interlace type field for the
3489 output frames. It does not change the input frame, but only sets the
3490 corresponding property, which affects how the frame is treated by
3491 following filters (e.g. @code{fieldorder} or @code{yadif}).
3493 It accepts a string parameter, which can assume the following values:
3496 Keep the same field property.
3499 Mark the frame as bottom-field-first.
3502 Mark the frame as top-field-first.
3505 Mark the frame as progressive.
3510 Show a line containing various information for each input video frame.
3511 The input video is not modified.
3513 The shown line contains a sequence of key/value pairs of the form
3514 @var{key}:@var{value}.
3516 A description of each shown parameter follows:
3520 sequential number of the input frame, starting from 0
3523 Presentation TimeStamp of the input frame, expressed as a number of
3524 time base units. The time base unit depends on the filter input pad.
3527 Presentation TimeStamp of the input frame, expressed as a number of
3531 position of the frame in the input stream, -1 if this information in
3532 unavailable and/or meaningless (for example in case of synthetic video)
3538 sample aspect ratio of the input frame, expressed in the form
3542 size of the input frame, expressed in the form
3543 @var{width}x@var{height}
3546 interlaced mode ("P" for "progressive", "T" for top field first, "B"
3547 for bottom field first)
3550 1 if the frame is a key frame, 0 otherwise
3553 picture type of the input frame ("I" for an I-frame, "P" for a
3554 P-frame, "B" for a B-frame, "?" for unknown type).
3555 Check also the documentation of the @code{AVPictureType} enum and of
3556 the @code{av_get_picture_type_char} function defined in
3557 @file{libavutil/avutil.h}.
3560 Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
3562 @item plane_checksum
3563 Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
3564 expressed in the form "[@var{c0} @var{c1} @var{c2} @var{c3}]"
3569 Pass the images of input video on to next video filter as multiple
3573 ffmpeg -i in.avi -vf "slicify=32" out.avi
3576 The filter accepts the slice height as parameter. If the parameter is
3577 not specified it will use the default value of 16.
3579 Adding this in the beginning of filter chains should make filtering
3580 faster due to better use of the memory cache.
3584 Blur the input video without impacting the outlines.
3586 The filter accepts the following parameters:
3587 @var{luma_radius}:@var{luma_strength}:@var{luma_threshold}[:@var{chroma_radius}:@var{chroma_strength}:@var{chroma_threshold}]
3589 Parameters prefixed by @var{luma} indicate that they work on the
3590 luminance of the pixels whereas parameters prefixed by @var{chroma}
3591 refer to the chrominance of the pixels.
3593 If the chroma parameters are not set, the luma parameters are used for
3594 either the luminance and the chrominance of the pixels.
3596 @var{luma_radius} or @var{chroma_radius} must be a float number in the
3597 range [0.1,5.0] that specifies the variance of the gaussian filter
3598 used to blur the image (slower if larger).
3600 @var{luma_strength} or @var{chroma_strength} must be a float number in
3601 the range [-1.0,1.0] that configures the blurring. A value included in
3602 [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
3603 will sharpen the image.
3605 @var{luma_threshold} or @var{chroma_threshold} must be an integer in
3606 the range [-30,30] that is used as a coefficient to determine whether
3607 a pixel should be blurred or not. A value of 0 will filter all the
3608 image, a value included in [0,30] will filter flat areas and a value
3609 included in [-30,0] will filter edges.
3613 Split input video into several identical outputs.
3615 The filter accepts a single parameter which specifies the number of outputs. If
3616 unspecified, it defaults to 2.
3620 ffmpeg -i INPUT -filter_complex split=5 OUTPUT
3622 will create 5 copies of the input video.
3626 [in] split [splitout1][splitout2];
3627 [splitout1] crop=100:100:0:0 [cropout];
3628 [splitout2] pad=200:200:100:100 [padout];
3631 will create two separate outputs from the same input, one cropped and
3636 Scale the input by 2x and smooth using the Super2xSaI (Scale and
3637 Interpolate) pixel art scaling algorithm.
3639 Useful for enlarging pixel art images without reducing sharpness.
3645 Select the most representative frame in a given sequence of consecutive frames.
3647 It accepts as argument the frames batch size to analyze (default @var{N}=100);
3648 in a set of @var{N} frames, the filter will pick one of them, and then handle
3649 the next batch of @var{N} frames until the end.
3651 Since the filter keeps track of the whole frames sequence, a bigger @var{N}
3652 value will result in a higher memory usage, so a high value is not recommended.
3654 The following example extract one picture each 50 frames:
3659 Complete example of a thumbnail creation with @command{ffmpeg}:
3661 ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
3666 Tile several successive frames together.
3668 It accepts as argument the tile size (i.e. the number of lines and columns)
3669 in the form "@var{w}x@var{h}".
3671 For example, produce 8×8 PNG tiles of all keyframes (@option{-skip_frame
3674 ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
3676 The @option{-vsync 0} is necessary to prevent @command{ffmpeg} from
3677 duplicating each output frame to accomodate the originally detected frame
3682 Perform various types of temporal field interlacing.
3684 Frames are counted starting from 1, so the first input frame is
3687 This filter accepts a single parameter specifying the mode. Available
3692 Move odd frames into the upper field, even into the lower field,
3693 generating a double height frame at half framerate.
3696 Only output even frames, odd frames are dropped, generating a frame with
3697 unchanged height at half framerate.
3700 Only output odd frames, even frames are dropped, generating a frame with
3701 unchanged height at half framerate.
3704 Expand each frame to full height, but pad alternate lines with black,
3705 generating a frame with double height at the same input framerate.
3707 @item interleave_top, 4
3708 Interleave the upper field from odd frames with the lower field from
3709 even frames, generating a frame with unchanged height at half framerate.
3711 @item interleave_bottom, 5
3712 Interleave the lower field from odd frames with the upper field from
3713 even frames, generating a frame with unchanged height at half framerate.
3715 @item interlacex2, 6
3716 Double frame rate with unchanged height. Frames are inserted each
3717 containing the second temporal field from the previous input frame and
3718 the first temporal field from the next input frame. This mode relies on
3719 the top_field_first flag. Useful for interlaced video displays with no
3720 field synchronisation.
3723 Numeric values are deprecated but are accepted for backward
3724 compatibility reasons.
3726 Default mode is @code{merge}.
3730 Transpose rows with columns in the input video and optionally flip it.
3732 This filter accepts the following named parameters:
3736 Specify the transposition direction. Can assume the following values:
3740 Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
3748 Rotate by 90 degrees clockwise, that is:
3756 Rotate by 90 degrees counterclockwise, that is:
3764 Rotate by 90 degrees clockwise and vertically flip, that is:
3772 For values between 4-7, the transposition is only done if the input
3773 video geometry is portrait and not landscape. These values are
3774 deprecated, the @code{passthrough} option should be used instead.
3777 Do not apply the transposition if the input geometry matches the one
3778 specified by the specified value. It accepts the following values:
3781 Always apply transposition.
3783 Preserve portrait geometry (when @var{height} >= @var{width}).
3785 Preserve landscape geometry (when @var{width} >= @var{height}).
3788 Default value is @code{none}.
3793 Sharpen or blur the input video.
3795 It accepts the following parameters:
3796 @var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}
3798 Negative values for the amount will blur the input video, while positive
3799 values will sharpen. All parameters are optional and default to the
3800 equivalent of the string '5:5:1.0:5:5:0.0'.
3805 Set the luma matrix horizontal size. It can be an integer between 3
3806 and 13, default value is 5.
3809 Set the luma matrix vertical size. It can be an integer between 3
3810 and 13, default value is 5.
3813 Set the luma effect strength. It can be a float number between -2.0
3814 and 5.0, default value is 1.0.
3816 @item chroma_msize_x
3817 Set the chroma matrix horizontal size. It can be an integer between 3
3818 and 13, default value is 5.
3820 @item chroma_msize_y
3821 Set the chroma matrix vertical size. It can be an integer between 3
3822 and 13, default value is 5.
3825 Set the chroma effect strength. It can be a float number between -2.0
3826 and 5.0, default value is 0.0.
3831 # Strong luma sharpen effect parameters
3834 # Strong blur of both luma and chroma parameters
3835 unsharp=7:7:-2:7:7:-2
3837 # Use the default values with @command{ffmpeg}
3838 ffmpeg -i in.avi -vf "unsharp" out.mp4
3843 Flip the input video vertically.
3846 ffmpeg -i in.avi -vf "vflip" out.avi
3851 Deinterlace the input video ("yadif" means "yet another deinterlacing
3854 It accepts the optional parameters: @var{mode}:@var{parity}:@var{auto}.
3856 @var{mode} specifies the interlacing mode to adopt, accepts one of the
3861 output 1 frame for each frame
3863 output 1 frame for each field
3865 like 0 but skips spatial interlacing check
3867 like 1 but skips spatial interlacing check
3872 @var{parity} specifies the picture field parity assumed for the input
3873 interlaced video, accepts one of the following values:
3877 assume top field first
3879 assume bottom field first
3881 enable automatic detection
3884 Default value is -1.
3885 If interlacing is unknown or decoder does not export this information,
3886 top field first will be assumed.
3888 @var{auto} specifies if deinterlacer should trust the interlaced flag
3889 and only deinterlace frames marked as interlaced
3893 deinterlace all frames
3895 only deinterlace frames marked as interlaced
3900 @c man end VIDEO FILTERS
3902 @chapter Video Sources
3903 @c man begin VIDEO SOURCES
3905 Below is a description of the currently available video sources.
3909 Buffer video frames, and make them available to the filter chain.
3911 This source is mainly intended for a programmatic use, in particular
3912 through the interface defined in @file{libavfilter/vsrc_buffer.h}.
3914 It accepts a list of options in the form of @var{key}=@var{value} pairs
3915 separated by ":". A description of the accepted options follows.
3920 Specify the size (width and height) of the buffered video frames.
3923 A string representing the pixel format of the buffered video frames.
3924 It may be a number corresponding to a pixel format, or a pixel format
3928 Specify the timebase assumed by the timestamps of the buffered frames.
3931 Specify the frame rate expected for the video stream.
3934 Specify the sample aspect ratio assumed by the video frames.
3937 Specify the optional parameters to be used for the scale filter which
3938 is automatically inserted when an input change is detected in the
3939 input size or format.
3944 buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
3947 will instruct the source to accept video frames with size 320x240 and
3948 with format "yuv410p", assuming 1/24 as the timestamps timebase and
3949 square pixels (1:1 sample aspect ratio).
3950 Since the pixel format with name "yuv410p" corresponds to the number 6
3951 (check the enum AVPixelFormat definition in @file{libavutil/pixfmt.h}),
3952 this example corresponds to:
3954 buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
3957 Alternatively, the options can be specified as a flat string, but this
3958 syntax is deprecated:
3960 @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}]
3964 Create a pattern generated by an elementary cellular automaton.
3966 The initial state of the cellular automaton can be defined through the
3967 @option{filename}, and @option{pattern} options. If such options are
3968 not specified an initial state is created randomly.
3970 At each new frame a new row in the video is filled with the result of
3971 the cellular automaton next generation. The behavior when the whole
3972 frame is filled is defined by the @option{scroll} option.
3974 This source accepts a list of options in the form of
3975 @var{key}=@var{value} pairs separated by ":". A description of the
3976 accepted options follows.
3980 Read the initial cellular automaton state, i.e. the starting row, from
3982 In the file, each non-whitespace character is considered an alive
3983 cell, a newline will terminate the row, and further characters in the
3984 file will be ignored.
3987 Read the initial cellular automaton state, i.e. the starting row, from
3988 the specified string.
3990 Each non-whitespace character in the string is considered an alive
3991 cell, a newline will terminate the row, and further characters in the
3992 string will be ignored.
3995 Set the video rate, that is the number of frames generated per second.
3998 @item random_fill_ratio, ratio
3999 Set the random fill ratio for the initial cellular automaton row. It
4000 is a floating point number value ranging from 0 to 1, defaults to
4003 This option is ignored when a file or a pattern is specified.
4005 @item random_seed, seed
4006 Set the seed for filling randomly the initial row, must be an integer
4007 included between 0 and UINT32_MAX. If not specified, or if explicitly
4008 set to -1, the filter will try to use a good random seed on a best
4012 Set the cellular automaton rule, it is a number ranging from 0 to 255.
4013 Default value is 110.
4016 Set the size of the output video.
4018 If @option{filename} or @option{pattern} is specified, the size is set
4019 by default to the width of the specified initial state row, and the
4020 height is set to @var{width} * PHI.
4022 If @option{size} is set, it must contain the width of the specified
4023 pattern string, and the specified pattern will be centered in the
4026 If a filename or a pattern string is not specified, the size value
4027 defaults to "320x518" (used for a randomly generated initial state).
4030 If set to 1, scroll the output upward when all the rows in the output
4031 have been already filled. If set to 0, the new generated row will be
4032 written over the top row just after the bottom row is filled.
4035 @item start_full, full
4036 If set to 1, completely fill the output with generated rows before
4037 outputting the first frame.
4038 This is the default behavior, for disabling set the value to 0.
4041 If set to 1, stitch the left and right row edges together.
4042 This is the default behavior, for disabling set the value to 0.
4045 @subsection Examples
4049 Read the initial state from @file{pattern}, and specify an output of
4052 cellauto=f=pattern:s=200x400
4056 Generate a random initial row with a width of 200 cells, with a fill
4059 cellauto=ratio=2/3:s=200x200
4063 Create a pattern generated by rule 18 starting by a single alive cell
4064 centered on an initial row with width 100:
4066 cellauto=p=@@:s=100x400:full=0:rule=18
4070 Specify a more elaborated initial pattern:
4072 cellauto=p='@@@@ @@ @@@@':s=100x400:full=0:rule=18
4079 Generate a Mandelbrot set fractal, and progressively zoom towards the
4080 point specified with @var{start_x} and @var{start_y}.
4082 This source accepts a list of options in the form of
4083 @var{key}=@var{value} pairs separated by ":". A description of the
4084 accepted options follows.
4089 Set the terminal pts value. Default value is 400.
4092 Set the terminal scale value.
4093 Must be a floating point value. Default value is 0.3.
4096 Set the inner coloring mode, that is the algorithm used to draw the
4097 Mandelbrot fractal internal region.
4099 It shall assume one of the following values:
4104 Show time until convergence.
4106 Set color based on point closest to the origin of the iterations.
4111 Default value is @var{mincol}.
4114 Set the bailout value. Default value is 10.0.
4117 Set the maximum of iterations performed by the rendering
4118 algorithm. Default value is 7189.
4121 Set outer coloring mode.
4122 It shall assume one of following values:
4124 @item iteration_count
4125 Set iteration cound mode.
4126 @item normalized_iteration_count
4127 set normalized iteration count mode.
4129 Default value is @var{normalized_iteration_count}.
4132 Set frame rate, expressed as number of frames per second. Default
4136 Set frame size. Default value is "640x480".
4139 Set the initial scale value. Default value is 3.0.
4142 Set the initial x position. Must be a floating point value between
4143 -100 and 100. Default value is -0.743643887037158704752191506114774.
4146 Set the initial y position. Must be a floating point value between
4147 -100 and 100. Default value is -0.131825904205311970493132056385139.
4152 Generate various test patterns, as generated by the MPlayer test filter.
4154 The size of the generated video is fixed, and is 256x256.
4155 This source is useful in particular for testing encoding features.
4157 This source accepts an optional sequence of @var{key}=@var{value} pairs,
4158 separated by ":". The description of the accepted options follows.
4163 Specify the frame rate of the sourced video, as the number of frames
4164 generated per second. It has to be a string in the format
4165 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4166 number or a valid video frame rate abbreviation. The default value is
4170 Set the video duration of the sourced video. The accepted syntax is:
4175 See also the function @code{av_parse_time()}.
4177 If not specified, or the expressed duration is negative, the video is
4178 supposed to be generated forever.
4182 Set the number or the name of the test to perform. Supported tests are:
4197 Default value is "all", which will cycle through the list of all tests.
4200 For example the following:
4205 will generate a "dc_luma" test pattern.
4209 Provide a frei0r source.
4211 To enable compilation of this filter you need to install the frei0r
4212 header and configure FFmpeg with @code{--enable-frei0r}.
4214 The source supports the syntax:
4216 @var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]
4219 @var{size} is the size of the video to generate, may be a string of the
4220 form @var{width}x@var{height} or a frame size abbreviation.
4221 @var{rate} is the rate of the video to generate, may be a string of
4222 the form @var{num}/@var{den} or a frame rate abbreviation.
4223 @var{src_name} is the name to the frei0r source to load. For more
4224 information regarding frei0r and how to set the parameters read the
4225 section @ref{frei0r} in the description of the video filters.
4227 For example, to generate a frei0r partik0l source with size 200x200
4228 and frame rate 10 which is overlayed on the overlay filter main input:
4230 frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
4235 Generate a life pattern.
4237 This source is based on a generalization of John Conway's life game.
4239 The sourced input represents a life grid, each pixel represents a cell
4240 which can be in one of two possible states, alive or dead. Every cell
4241 interacts with its eight neighbours, which are the cells that are
4242 horizontally, vertically, or diagonally adjacent.
4244 At each interaction the grid evolves according to the adopted rule,
4245 which specifies the number of neighbor alive cells which will make a
4246 cell stay alive or born. The @option{rule} option allows to specify
4249 This source accepts a list of options in the form of
4250 @var{key}=@var{value} pairs separated by ":". A description of the
4251 accepted options follows.
4255 Set the file from which to read the initial grid state. In the file,
4256 each non-whitespace character is considered an alive cell, and newline
4257 is used to delimit the end of each row.
4259 If this option is not specified, the initial grid is generated
4263 Set the video rate, that is the number of frames generated per second.
4266 @item random_fill_ratio, ratio
4267 Set the random fill ratio for the initial random grid. It is a
4268 floating point number value ranging from 0 to 1, defaults to 1/PHI.
4269 It is ignored when a file is specified.
4271 @item random_seed, seed
4272 Set the seed for filling the initial random grid, must be an integer
4273 included between 0 and UINT32_MAX. If not specified, or if explicitly
4274 set to -1, the filter will try to use a good random seed on a best
4280 A rule can be specified with a code of the kind "S@var{NS}/B@var{NB}",
4281 where @var{NS} and @var{NB} are sequences of numbers in the range 0-8,
4282 @var{NS} specifies the number of alive neighbor cells which make a
4283 live cell stay alive, and @var{NB} the number of alive neighbor cells
4284 which make a dead cell to become alive (i.e. to "born").
4285 "s" and "b" can be used in place of "S" and "B", respectively.
4287 Alternatively a rule can be specified by an 18-bits integer. The 9
4288 high order bits are used to encode the next cell state if it is alive
4289 for each number of neighbor alive cells, the low order bits specify
4290 the rule for "borning" new cells. Higher order bits encode for an
4291 higher number of neighbor cells.
4292 For example the number 6153 = @code{(12<<9)+9} specifies a stay alive
4293 rule of 12 and a born rule of 9, which corresponds to "S23/B03".
4295 Default value is "S23/B3", which is the original Conway's game of life
4296 rule, and will keep a cell alive if it has 2 or 3 neighbor alive
4297 cells, and will born a new cell if there are three alive cells around
4301 Set the size of the output video.
4303 If @option{filename} is specified, the size is set by default to the
4304 same size of the input file. If @option{size} is set, it must contain
4305 the size specified in the input file, and the initial grid defined in
4306 that file is centered in the larger resulting area.
4308 If a filename is not specified, the size value defaults to "320x240"
4309 (used for a randomly generated initial grid).
4312 If set to 1, stitch the left and right grid edges together, and the
4313 top and bottom edges also. Defaults to 1.
4316 Set cell mold speed. If set, a dead cell will go from @option{death_color} to
4317 @option{mold_color} with a step of @option{mold}. @option{mold} can have a
4318 value from 0 to 255.
4321 Set the color of living (or new born) cells.
4324 Set the color of dead cells. If @option{mold} is set, this is the first color
4325 used to represent a dead cell.
4328 Set mold color, for definitely dead and moldy cells.
4331 @subsection Examples
4335 Read a grid from @file{pattern}, and center it on a grid of size
4338 life=f=pattern:s=300x300
4342 Generate a random grid of size 200x200, with a fill ratio of 2/3:
4344 life=ratio=2/3:s=200x200
4348 Specify a custom rule for evolving a randomly generated grid:
4354 Full example with slow death effect (mold) using @command{ffplay}:
4356 ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
4360 @section color, nullsrc, rgbtestsrc, smptebars, testsrc
4362 The @code{color} source provides an uniformly colored input.
4364 The @code{nullsrc} source returns unprocessed video frames. It is
4365 mainly useful to be employed in analysis / debugging tools, or as the
4366 source for filters which ignore the input data.
4368 The @code{rgbtestsrc} source generates an RGB test pattern useful for
4369 detecting RGB vs BGR issues. You should see a red, green and blue
4370 stripe from top to bottom.
4372 The @code{smptebars} source generates a color bars pattern, based on
4373 the SMPTE Engineering Guideline EG 1-1990.
4375 The @code{testsrc} source generates a test video pattern, showing a
4376 color pattern, a scrolling gradient and a timestamp. This is mainly
4377 intended for testing purposes.
4379 These sources accept an optional sequence of @var{key}=@var{value} pairs,
4380 separated by ":". The description of the accepted options follows.
4385 Specify the color of the source, only used in the @code{color}
4386 source. It can be the name of a color (case insensitive match) or a
4387 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
4388 default value is "black".
4391 Specify the size of the sourced video, it may be a string of the form
4392 @var{width}x@var{height}, or the name of a size abbreviation. The
4393 default value is "320x240".
4396 Specify the frame rate of the sourced video, as the number of frames
4397 generated per second. It has to be a string in the format
4398 @var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float
4399 number or a valid video frame rate abbreviation. The default value is
4403 Set the sample aspect ratio of the sourced video.
4406 Set the video duration of the sourced video. The accepted syntax is:
4408 [-]HH[:MM[:SS[.m...]]]
4411 See also the function @code{av_parse_time()}.
4413 If not specified, or the expressed duration is negative, the video is
4414 supposed to be generated forever.
4417 Set the number of decimals to show in the timestamp, only used in the
4418 @code{testsrc} source.
4420 The displayed timestamp value will correspond to the original
4421 timestamp value multiplied by the power of 10 of the specified
4422 value. Default value is 0.
4425 For example the following:
4427 testsrc=duration=5.3:size=qcif:rate=10
4430 will generate a video with a duration of 5.3 seconds, with size
4431 176x144 and a frame rate of 10 frames per second.
4433 The following graph description will generate a red source
4434 with an opacity of 0.2, with size "qcif" and a frame rate of 10
4437 color=c=red@@0.2:s=qcif:r=10
4440 If the input content is to be ignored, @code{nullsrc} can be used. The
4441 following command generates noise in the luminance plane by employing
4442 the @code{mp=geq} filter:
4444 nullsrc=s=256x256, mp=geq=random(1)*255:128:128
4447 @c man end VIDEO SOURCES
4449 @chapter Video Sinks
4450 @c man begin VIDEO SINKS
4452 Below is a description of the currently available video sinks.
4456 Buffer video frames, and make them available to the end of the filter
4459 This sink is mainly intended for a programmatic use, in particular
4460 through the interface defined in @file{libavfilter/buffersink.h}.
4462 It does not require a string parameter in input, but you need to
4463 specify a pointer to a list of supported pixel formats terminated by
4464 -1 in the opaque parameter provided to @code{avfilter_init_filter}
4465 when initializing this sink.
4469 Null video sink, do absolutely nothing with the input video. It is
4470 mainly useful as a template and to be employed in analysis / debugging
4473 @c man end VIDEO SINKS
4475 @chapter Multimedia Filters
4476 @c man begin MULTIMEDIA FILTERS
4478 Below is a description of the currently available multimedia filters.
4480 @section asendcmd, sendcmd
4482 Send commands to filters in the filtergraph.
4484 These filters read commands to be sent to other filters in the
4487 @code{asendcmd} must be inserted between two audio filters,
4488 @code{sendcmd} must be inserted between two video filters, but apart
4489 from that they act the same way.
4491 The specification of commands can be provided in the filter arguments
4492 with the @var{commands} option, or in a file specified by the
4493 @var{filename} option.
4495 These filters accept the following options:
4498 Set the commands to be read and sent to the other filters.
4500 Set the filename of the commands to be read and sent to the other
4504 @subsection Commands syntax
4506 A commands description consists of a sequence of interval
4507 specifications, comprising a list of commands to be executed when a
4508 particular event related to that interval occurs. The occurring event
4509 is typically the current frame time entering or leaving a given time
4512 An interval is specified by the following syntax:
4514 @var{START}[-@var{END}] @var{COMMANDS};
4517 The time interval is specified by the @var{START} and @var{END} times.
4518 @var{END} is optional and defaults to the maximum time.
4520 The current frame time is considered within the specified interval if
4521 it is included in the interval [@var{START}, @var{END}), that is when
4522 the time is greater or equal to @var{START} and is lesser than
4525 @var{COMMANDS} consists of a sequence of one or more command
4526 specifications, separated by ",", relating to that interval. The
4527 syntax of a command specification is given by:
4529 [@var{FLAGS}] @var{TARGET} @var{COMMAND} @var{ARG}
4532 @var{FLAGS} is optional and specifies the type of events relating to
4533 the time interval which enable sending the specified command, and must
4534 be a non-null sequence of identifier flags separated by "+" or "|" and
4535 enclosed between "[" and "]".
4537 The following flags are recognized:
4540 The command is sent when the current frame timestamp enters the
4541 specified interval. In other words, the command is sent when the
4542 previous frame timestamp was not in the given interval, and the
4546 The command is sent when the current frame timestamp leaves the
4547 specified interval. In other words, the command is sent when the
4548 previous frame timestamp was in the given interval, and the
4552 If @var{FLAGS} is not specified, a default value of @code{[enter]} is
4555 @var{TARGET} specifies the target of the command, usually the name of
4556 the filter class or a specific filter instance name.
4558 @var{COMMAND} specifies the name of the command for the target filter.
4560 @var{ARG} is optional and specifies the optional list of argument for
4561 the given @var{COMMAND}.
4563 Between one interval specification and another, whitespaces, or
4564 sequences of characters starting with @code{#} until the end of line,
4565 are ignored and can be used to annotate comments.
4567 A simplified BNF description of the commands specification syntax
4570 @var{COMMAND_FLAG} ::= "enter" | "leave"
4571 @var{COMMAND_FLAGS} ::= @var{COMMAND_FLAG} [(+|"|")@var{COMMAND_FLAG}]
4572 @var{COMMAND} ::= ["[" @var{COMMAND_FLAGS} "]"] @var{TARGET} @var{COMMAND} [@var{ARG}]
4573 @var{COMMANDS} ::= @var{COMMAND} [,@var{COMMANDS}]
4574 @var{INTERVAL} ::= @var{START}[-@var{END}] @var{COMMANDS}
4575 @var{INTERVALS} ::= @var{INTERVAL}[;@var{INTERVALS}]
4578 @subsection Examples
4582 Specify audio tempo change at second 4:
4584 asendcmd=c='4.0 atempo tempo 1.5',atempo
4588 Specify a list of drawtext and hue commands in a file.
4590 # show text in the interval 5-10
4591 5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
4592 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
4594 # desaturate the image in the interval 15-20
4595 15.0-20.0 [enter] hue reinit s=0,
4596 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
4597 [leave] hue reinit s=1,
4598 [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
4600 # apply an exponential saturation fade-out effect, starting from time 25
4601 25 [enter] hue s=exp(t-25)
4604 A filtergraph allowing to read and process the above command list
4605 stored in a file @file{test.cmd}, can be specified with:
4607 sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
4611 @section asetpts, setpts
4613 Change the PTS (presentation timestamp) of the input frames.
4615 @code{asetpts} works on audio frames, @code{setpts} on video frames.
4617 Accept in input an expression evaluated through the eval API, which
4618 can contain the following constants:
4622 frame rate, only defined for constant frame-rate video
4625 the presentation timestamp in input
4628 the count of the input frame, starting from 0.
4630 @item NB_CONSUMED_SAMPLES
4631 the number of consumed samples, not including the current frame (only
4635 the number of samples in the current frame (only audio)
4641 the PTS of the first frame
4644 the time in seconds of the first frame
4647 tell if the current frame is interlaced
4650 the time in seconds of the current frame
4656 original position in the file of the frame, or undefined if undefined
4657 for the current frame
4663 previous input time in seconds
4669 previous output time in seconds
4672 @subsection Examples
4676 Start counting PTS from zero
4682 Apply fast motion effect:
4688 Apply slow motion effect:
4694 Set fixed rate of 25 frames per second:
4700 Set fixed rate 25 fps with some jitter:
4702 setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
4706 Apply an offset of 10 seconds to the input PTS:
4714 EBU R128 scanner filter. This filter takes an audio stream as input and outputs
4715 it unchanged. By default, it logs a message at a frequency of 10Hz with the
4716 Momentary loudness (identified by @code{M}), Short-term loudness (@code{S}),
4717 Integrated loudness (@code{I}) and Loudness Range (@code{LRA}).
4719 The filter also has a video output (see the @var{video} option) with a real
4720 time graph to observe the loudness evolution. The graphic contains the logged
4721 message mentioned above, so it is not printed anymore when this option is set,
4722 unless the verbose logging is set. The main graphing area contains the
4723 short-term loudness (3 seconds of analysis), and the gauge on the right is for
4724 the momentary loudness (400 milliseconds).
4726 More information about the Loudness Recommendation EBU R128 on
4727 @url{http://tech.ebu.ch/loudness}.
4729 The filter accepts the following named parameters:
4734 Activate the video output. The audio stream is passed unchanged whether this
4735 option is set or no. The video stream will be the first output stream if
4736 activated. Default is @code{0}.
4739 Set the video size. This option is for video only. Default and minimum
4740 resolution is @code{640x480}.
4743 Set the EBU scale meter. Default is @code{9}. Common values are @code{9} and
4744 @code{18}, respectively for EBU scale meter +9 and EBU scale meter +18. Any
4745 other integer value between this range is allowed.
4749 Example of real-time graph using @command{ffplay}, with a EBU scale meter +18:
4751 ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
4754 Run an analysis with @command{ffmpeg}:
4756 ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
4759 @section settb, asettb
4761 Set the timebase to use for the output frames timestamps.
4762 It is mainly useful for testing timebase configuration.
4764 It accepts in input an arithmetic expression representing a rational.
4765 The expression can contain the constants "AVTB" (the
4766 default timebase), "intb" (the input timebase) and "sr" (the sample rate,
4769 The default value for the input is "intb".
4771 @subsection Examples
4775 Set the timebase to 1/25:
4781 Set the timebase to 1/10:
4787 Set the timebase to 1001/1000:
4793 Set the timebase to 2*intb:
4799 Set the default timebase value:
4807 Concatenate audio and video streams, joining them together one after the
4810 The filter works on segments of synchronized video and audio streams. All
4811 segments must have the same number of streams of each type, and that will
4812 also be the number of streams at output.
4814 The filter accepts the following named parameters:
4818 Set the number of segments. Default is 2.
4821 Set the number of output video streams, that is also the number of video
4822 streams in each segment. Default is 1.
4825 Set the number of output audio streams, that is also the number of video
4826 streams in each segment. Default is 0.
4829 Activate unsafe mode: do not fail if segments have a different format.
4833 The filter has @var{v}+@var{a} outputs: first @var{v} video outputs, then
4834 @var{a} audio outputs.
4836 There are @var{n}×(@var{v}+@var{a}) inputs: first the inputs for the first
4837 segment, in the same order as the outputs, then the inputs for the second
4840 Related streams do not always have exactly the same duration, for various
4841 reasons including codec frame size or sloppy authoring. For that reason,
4842 related synchronized streams (e.g. a video and its audio track) should be
4843 concatenated at once. The concat filter will use the duration of the longest
4844 stream in each segment (except the last one), and if necessary pad shorter
4845 audio streams with silence.
4847 For this filter to work correctly, all segments must start at timestamp 0.
4849 All corresponding streams must have the same parameters in all segments; the
4850 filtering system will automatically select a common pixel format for video
4851 streams, and a common sample format, sample rate and channel layout for
4852 audio streams, but other settings, such as resolution, must be converted
4853 explicitly by the user.
4855 Different frame rates are acceptable but will result in variable frame rate
4856 at output; be sure to configure the output file to handle it.
4861 Concatenate an opening, an episode and an ending, all in bilingual version
4862 (video in stream 0, audio in streams 1 and 2):
4864 ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
4865 '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
4866 concat=n=3:v=1:a=2 [v] [a1] [a2]' \
4867 -map '[v]' -map '[a1]' -map '[a2]' output.mkv
4871 Concatenate two parts, handling audio and video separately, using the
4872 (a)movie sources, and adjusting the resolution:
4874 movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
4875 movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
4876 [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
4878 Note that a desync will happen at the stitch if the audio and video streams
4879 do not have exactly the same duration in the first file.
4883 @section showspectrum
4885 Convert input audio to a video output, representing the audio frequency
4888 The filter accepts the following named parameters:
4891 Specify the video size for the output. Default value is @code{640x480}.
4893 Specify if the spectrum should slide along the window. Default value is
4897 The usage is very similar to the showwaves filter; see the examples in that
4902 Convert input audio to a video output, representing the samples waves.
4904 The filter accepts the following named parameters:
4908 Set the number of samples which are printed on the same column. A
4909 larger value will decrease the frame rate. Must be a positive
4910 integer. This option can be set only if the value for @var{rate}
4911 is not explicitly specified.
4914 Set the (approximate) output frame rate. This is done by setting the
4915 option @var{n}. Default value is "25".
4918 Specify the video size for the output. Default value is "600x240".
4921 Some examples follow.
4924 Output the input file audio and the corresponding video representation
4927 amovie=a.mp3,asplit[out0],showwaves[out1]
4931 Create a synthetic signal and show it with showwaves, forcing a
4932 framerate of 30 frames per second:
4934 aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
4938 @c man end MULTIMEDIA FILTERS
4940 @chapter Multimedia Sources
4941 @c man begin MULTIMEDIA SOURCES
4943 Below is a description of the currently available multimedia sources.
4947 This is the same as @ref{src_movie} source, except it selects an audio
4953 Read audio and/or video stream(s) from a movie container.
4955 It accepts the syntax: @var{movie_name}[:@var{options}] where
4956 @var{movie_name} is the name of the resource to read (not necessarily
4957 a file but also a device or a stream accessed through some protocol),
4958 and @var{options} is an optional sequence of @var{key}=@var{value}
4959 pairs, separated by ":".
4961 The description of the accepted options follows.
4965 @item format_name, f
4966 Specifies the format assumed for the movie to read, and can be either
4967 the name of a container or an input device. If not specified the
4968 format is guessed from @var{movie_name} or by probing.
4970 @item seek_point, sp
4971 Specifies the seek point in seconds, the frames will be output
4972 starting from this seek point, the parameter is evaluated with
4973 @code{av_strtod} so the numerical value may be suffixed by an IS
4974 postfix. Default value is "0".
4977 Specifies the streams to read. Several streams can be specified, separated
4978 by "+". The source will then have as many outputs, in the same order. The
4979 syntax is explained in the @ref{Stream specifiers} chapter. Two special
4980 names, "dv" and "da" specify respectively the default (best suited) video
4981 and audio stream. Default is "dv", or "da" if the filter is called as
4984 @item stream_index, si
4985 Specifies the index of the video stream to read. If the value is -1,
4986 the best suited video stream will be automatically selected. Default
4987 value is "-1". Deprecated. If the filter is called "amovie", it will select
4988 audio instead of video.
4991 Specifies how many times to read the stream in sequence.
4992 If the value is less than 1, the stream will be read again and again.
4993 Default value is "1".
4995 Note that when the movie is looped the source timestamps are not
4996 changed, so it will generate non monotonically increasing timestamps.
4999 This filter allows to overlay a second video on top of main input of
5000 a filtergraph as shown in this graph:
5002 input -----------> deltapts0 --> overlay --> output
5005 movie --> scale--> deltapts1 -------+
5008 Some examples follow.
5012 Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
5013 on top of the input labelled as "in":
5015 movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5016 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5020 Read from a video4linux2 device, and overlay it on top of the input
5023 movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
5024 [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
5028 Read the first video stream and the audio stream with id 0x81 from
5029 dvd.vob; the video is connected to the pad named "video" and the audio is
5030 connected to the pad named "audio":
5032 movie=dvd.vob:s=v:0+#0x81 [video] [audio]
5036 @c man end MULTIMEDIA SOURCES