Filtering Introduction
**********************

Filtering in FFmpeg is enabled through the libavfilter library.

Libavfilter is the filtering API of FFmpeg. It is the substitute of the now deprecated 'vhooks' and started as a Google Summer of Code project.

Audio filtering integration into the main FFmpeg repository is a work in progress, so audio API and ABI should not be considered stable yet.

In libavfilter, it is possible for filters to have multiple inputs and multiple outputs. To illustrate the sorts of things that are possible, we can use a complex filter graph. For example, the following one:

     input --> split --> fifo -----------------------> overlay --> output
                 |                                        ^
                 |                                        |
                 +------> fifo --> crop --> vflip --------+

splits the stream in two streams, sends one stream through the crop filter and the vflip filter before merging it back with the other stream by overlaying it on top. You can use the following command to achieve this:

     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

The result will be that in output the top half of the video is mirrored onto the bottom half.

Filters are loaded using the -VF or -AF option passed to ffmpeg or to ffplay. Filters in the same linear chain are separated by commas. In our example, SPLIT, FIFO, OVERLAY are in one linear chain, and FIFO, CROP, VFLIP are in another. The points where the linear chains join are labeled by names enclosed in square brackets. In our example, that is [T1] and [T2]. The special labels [IN] and [OUT] are the points where video is input and output.

Some filters take in input a list of parameters: they are specified after the filter name and an equal sign, and are separated from each other by a colon.

There exist so-called SOURCE FILTERS that do not have an audio/video input, and SINK FILTERS that will not have audio/video output.

graph2dot
*********

The graph2dot program included in the FFmpeg tools directory can be used to parse a filter graph description and issue a corresponding textual representation in the dot language.

Invoke the command:

     graph2dot -h

to see how to use graph2dot.

You can then pass the dot description to the dot program (from the graphviz suite of programs) and obtain a graphical representation of the filter graph.

For example the sequence of commands:

     echo GRAPH_DESCRIPTION | \
     tools/graph2dot -o graph.tmp && \
     dot -Tpng graph.tmp -o graph.png && \
     display graph.png

can be used to create and display an image representing the graph described by the GRAPH_DESCRIPTION string. Note that this string must be a complete self-contained graph, with its inputs and outputs explicitly defined. For example if your command line is of the form:

     ffmpeg -i infile -vf scale=640:360 outfile

your GRAPH_DESCRIPTION string will need to be of the form:

     nullsrc,scale=640:360,nullsink

you may also need to set the NULLSRC parameters and add a FORMAT filter in order to simulate a specific input file.

Filtergraph description
***********************

A filtergraph is a directed graph of connected filters. It can contain cycles, and there can be multiple links between a pair of filters. Each link has one input pad on one side connecting it to one filter from which it takes its input, and one output pad on the other side connecting it to the one filter accepting its output.

Each filter in a filtergraph is an instance of a filter class registered in the application, which defines the features and the number of input and output pads of the filter.

A filter with no input pads is called a "source", a filter with no output pads is called a "sink".

Filtergraph syntax
==================

A filtergraph can be represented using a textual representation, which is recognized by the -filter/-vf and -filter_complex options in ffmpeg and -vf in ffplay, and by the avfilter_graph_parse()/avfilter_graph_parse2() function defined in libavfilter/avfiltergraph.h.

A filterchain consists of a sequence of connected filters, each one connected to the previous one in the sequence. A filterchain is represented by a list of ","-separated filter descriptions.

A filtergraph consists of a sequence of filterchains. A sequence of filterchains is represented by a list of ";"-separated filterchain descriptions.

A filter is represented by a string of the form: [IN_LINK_1]...[IN_LINK_N]FILTER_NAME=ARGUMENTS[OUT_LINK_1]...[OUT_LINK_M]

FILTER_NAME is the name of the filter class of which the described filter is an instance of, and has to be the name of one of the filter classes registered in the program. The name of the filter class is optionally followed by a string "=ARGUMENTS".

ARGUMENTS is a string which contains the parameters used to initialize the filter instance, and are described in the filter descriptions below.

The list of arguments can be quoted using the character "'" as initial and ending mark, and the character '\' for escaping the characters within the quoted text; otherwise the argument string is considered terminated when the next special character (belonging to the set "[]=;,") is encountered.

The name and arguments of the filter are optionally preceded and followed by a list of link labels. A link label allows to name a link and associate it to a filter output or input pad. The preceding labels IN_LINK_1 ... IN_LINK_N, are associated to the filter input pads, the following labels OUT_LINK_1 ... OUT_LINK_M, are associated to the output pads.

When two link labels with the same name are found in the filtergraph, a link between the corresponding input and output pad is created.

If an output pad is not labelled, it is linked by default to the first unlabelled input pad of the next filter in the filterchain. For example in the filterchain:

     nullsrc, split[L1], [L2]overlay, nullsink

the split filter instance has two output pads, and the overlay filter instance two input pads. The first output pad of split is labelled "L1", the first input pad of overlay is labelled "L2", and the second output pad of split is linked to the second input pad of overlay, which are both unlabelled.

In a complete filterchain all the unlabelled filter input and output pads must be connected. A filtergraph is considered valid if all the filter input and output pads of all the filterchains are connected.

Libavfilter will automatically insert scale filters where format conversion is required. It is possible to specify swscale flags for those automatically inserted scalers by prepending sws_flags=FLAGS; to the filtergraph description.

Follows a BNF description for the filtergraph syntax:

     NAME             ::= sequence of alphanumeric characters and '_'
     LINKLABEL        ::= "[" NAME "]"
     LINKLABELS       ::= LINKLABEL [LINKLABELS]
     FILTER_ARGUMENTS ::= sequence of chars (eventually quoted)
     FILTER           ::= [LINKNAMES] NAME ["=" ARGUMENTS] [LINKNAMES]
     FILTERCHAIN      ::= FILTER [,FILTERCHAIN]
     FILTERGRAPH      ::= [sws_flags=FLAGS;] FILTERCHAIN [;FILTERGRAPH]

Audio Filters
*************

When you configure your FFmpeg build, you can disable any of the existing filters using --disable-filters. The configure output will show the audio filters included in your build.

Below is a description of the currently available audio filters.

aconvert
========

Convert the input audio format to the specified formats.

The filter accepts a string of the form: "SAMPLE_FORMAT:CHANNEL_LAYOUT".

SAMPLE_FORMAT specifies the sample format, and can be a string or the corresponding numeric value defined in libavutil/samplefmt.h. Use 'p' suffix for a planar sample format.

CHANNEL_LAYOUT specifies the channel layout, and can be a string or the corresponding number value defined in libavutil/audioconvert.h.

The special parameter "auto", signifies that the filter will automatically select the output format depending on the output filter.

Some examples follow.

  * Convert input to float, planar, stereo:

          aconvert=fltp:stereo

  * Convert input to unsigned 8-bit, automatically select out channel layout:

          aconvert=u8:auto

aformat
=======

Convert the input audio to one of the specified formats. The framework will negotiate the most appropriate format to minimize conversions.

The filter accepts the following named parameters:

sample_fmts
     A comma-separated list of requested sample formats.

sample_rates
     A comma-separated list of requested sample rates.

channel_layouts
     A comma-separated list of requested channel layouts.

If a parameter is omitted, all values are allowed.

For example to force the output to either unsigned 8-bit or signed 16-bit stereo:

     aformat=sample_fmts\=u8\,s16:channel_layouts\=stereo

amerge
======

Merge two or more audio streams into a single multi-channel stream.

The filter accepts the following named options:

inputs
     Set the number of inputs. Default is 2.

If the channel layouts of the inputs are disjoint, and therefore compatible, the channel layout of the output will be set accordingly and the channels will be reordered as necessary. If the channel layouts of the inputs are not disjoint, the output will have all the channels of the first input then all the channels of the second input, in that order, and the channel layout of the output will be the default value corresponding to the total number of channels.

For example, if the first input is in 2.1 (FL+FR+LF) and the second input is FC+BL+BR, then the output will be in 5.1, with the channels in the following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the first input, b1 is the first channel of the second input).

On the other hand, if both input are in stereo, the output channels will be in the default order: a1, a2, b1, b2, and the channel layout will be arbitrarily set to 4.0, which may or may not be the expected value.

All inputs must have the same sample rate, and format.

If inputs do not have the same duration, the output will stop with the shortest.

Example: merge two mono files into a stereo stream:

     amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge

Example: multiple merges:

     ffmpeg -f lavfi -i "
     amovie=input.mkv:si=0 [a0];
     amovie=input.mkv:si=1 [a1];
     amovie=input.mkv:si=2 [a2];
     amovie=input.mkv:si=3 [a3];
     amovie=input.mkv:si=4 [a4];
     amovie=input.mkv:si=5 [a5];
     [a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv

amix
====

Mixes multiple audio inputs into a single output.

For example

     ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT

will mix 3 input audio streams to a single output with the same duration as the first input and a dropout transition time of 3 seconds.

The filter accepts the following named parameters:

inputs
     Number of inputs. If unspecified, it defaults to 2.

duration
     How to determine the end-of-stream.

     longest
          Duration of longest input. (default)

     shortest
          Duration of shortest input.

     first
          Duration of first input.

dropout_transition
     Transition time, in seconds, for volume renormalization when an input stream ends. The default value is 2 seconds.

anull
=====

Pass the audio source unchanged to the output.

aresample
=========

Resample the input audio to the specified sample rate.

The filter accepts exactly one parameter, the output sample rate. If not specified then the filter will automatically convert between its input and output sample rates.

For example, to resample the input audio to 44100Hz:

     aresample=44100

asetnsamples
============

Set the number of samples per each output audio frame.

The last output packet may contain a different number of samples, as the filter will flush all the remaining samples when the input audio signal its end.

The filter accepts parameters as a list of KEY=VALUE pairs, separated by ":".

nb_out_samples, n
     Set the number of frames per each output audio frame. The number is intended as the number of samples per each channel. Default value is 1024.

pad, p
     If set to 1, the filter will pad the last audio frame with zeroes, so that the last frame will contain the same number of samples as the previous ones. Default value is 1.

For example, to set the number of per-frame samples to 1234 and disable padding for the last frame, use:

     asetnsamples=n=1234:p=0

ashowinfo
=========

Show a line containing various information for each input audio frame. The input audio is not modified.

The shown line contains a sequence of key/value pairs of the form KEY:VALUE.

A description of each shown parameter follows:

n
     sequential number of the input frame, starting from 0

pts
     presentation TimeStamp of the input frame, expressed as a number of time base units. The time base unit depends on the filter input pad, and is usually 1/SAMPLE_RATE.

pts_time
     presentation TimeStamp of the input frame, expressed as a number of seconds

pos
     position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic audio)

fmt
     sample format name

chlayout
     channel layout description

nb_samples
     number of samples (per each channel) contained in the filtered frame

rate
     sample rate for the audio frame

checksum
     Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame

plane_checksum
     Adler-32 checksum (printed in hexadecimal) for each input frame plane, expressed in the form "[C0 C1 C2 C3 C4 C5 C6 C7]"

asplit
======

Split input audio into several identical outputs.

The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults to 2.

For example:

     [in] asplit [out0][out1]

will create two separate outputs from the same input.

To create 3 or more outputs, you need to specify the number of outputs, like in:

     [in] asplit=3 [out0][out1][out2]

     ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT

will create 5 copies of the input audio.

astreamsync
===========

Forward two audio streams and control the order the buffers are forwarded.

The argument to the filter is an expression deciding which stream should be forwarded next: if the result is negative, the first stream is forwarded; if the result is positive or zero, the second stream is forwarded. It can use the following variables:

b1 b2
     number of buffers forwarded so far on each stream

s1 s2
     number of samples forwarded so far on each stream

t1 t2
     current timestamp of each stream

The default value is t1-t2, which means to always forward the stream that has a smaller timestamp.

Example: stress-test amerge by randomly sending buffers on the wrong input, while avoiding too much of a desynchronization:

     amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
     [a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
     [a2] [b2] amerge

atempo
======

Adjust audio tempo.

The filter accepts exactly one parameter, the audio tempo. If not specified then the filter will assume nominal 1.0 tempo. Tempo must be in the [0.5, 2.0] range.

For example, to slow down audio to 80% tempo:

     atempo=0.8

For example, to speed up audio to 125% tempo:

     atempo=1.25

earwax
======

Make audio easier to listen to on headphones.

This filter adds `cues' to 44.1kHz stereo (i.e. audio CD format) audio so that when listened to on headphones the stereo image is moved from inside your head (standard for headphones) to outside and in front of the listener (standard for speakers).

Ported from SoX.

pan
===

Mix channels with specific gain levels. The filter accepts the output channel layout followed by a set of channels definitions.

This filter is also designed to remap efficiently the channels of an audio stream.

The filter accepts parameters of the form: "L:OUTDEF:OUTDEF:..."

l
     output channel layout or number of channels

outdef
     output channel specification, of the form: "OUT_NAME=[GAIN*]IN_NAME[+[GAIN*]IN_NAME...]"

out_name
     output channel to define, either a channel name (FL, FR, etc.) or a channel number (c0, c1, etc.)

gain
     multiplicative coefficient for the channel, 1 leaving the volume unchanged

in_name
     input channel to use, see out_name for details; it is not possible to mix named and numbered input channels

If the `=' in a channel specification is replaced by `<', then the gains for that specification will be renormalized so that the total is 1, thus avoiding clipping noise.

Mixing examples
---------------

For example, if you want to down-mix from stereo to mono, but with a bigger factor for the left channel:

     pan=1:c0=0.9*c0+0.1*c1

A customized down-mix to stereo that works automatically for 3-, 4-, 5- and 7-channels surround:

     pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR

Note that ffmpeg integrates a default down-mix (and up-mix) system that should be preferred (see "-ac" option) unless you have very specific needs.

Remapping examples
------------------

The channel remapping will be effective if, and only if:

  * gain coefficients are zeroes or ones,

  * only one input per channel output,

If all these conditions are satisfied, the filter will notify the user ("Pure channel mapping detected"), and use an optimized and lossless method to do the remapping.

For example, if you have a 5.1 source and want a stereo audio stream by dropping the extra channels:

     pan="stereo: c0=FL : c1=FR"

Given the same source, you can also switch front left and front right channels and keep the input channel layout:

     pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"

If the input is a stereo audio stream, you can mute the front left channel (and still keep the stereo channel layout) with:

     pan="stereo:c1=c1"

Still with a stereo audio stream input, you can copy the right channel in both front left and right:

     pan="stereo: c0=FR : c1=FR"

silencedetect
=============

Detect silence in an audio stream.

This filter logs a message when it detects that the input audio volume is less or equal to a noise tolerance value for a duration greater or equal to the minimum detected noise duration.

The printed times and duration are expressed in seconds.

duration, d
     Set silence duration until notification (default is 2 seconds).

noise, n
     Set noise tolerance. Can be specified in dB (in case "dB" is appended to the specified value) or amplitude ratio. Default is -60dB, or 0.001.

Detect 5 seconds of silence with -50dB noise tolerance:

     silencedetect=n=-50dB:d=5

Complete example with ffmpeg to detect silence with 0.0001 noise tolerance in silence.mp3:

     ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -

volume
======

Adjust the input audio volume.

The filter accepts exactly one parameter VOL, which expresses how the audio volume will be increased or decreased.

Output values are clipped to the maximum value.

If VOL is expressed as a decimal number, the output audio volume is given by the relation:

     OUTPUT_VOLUME = VOL * INPUT_VOLUME

If VOL is expressed as a decimal number followed by the string "dB", the value represents the requested change in decibels of the input audio power, and the output audio volume is given by the relation:

     OUTPUT_VOLUME = 10^(VOL/20) * INPUT_VOLUME

Otherwise VOL is considered an expression and its evaluated value is used for computing the output audio volume according to the first relation.

Default value for VOL is 1.0.

Examples
--------

  * Half the input audio volume:

          volume=0.5

     The above example is equivalent to:

          volume=1/2

  * Decrease input audio power by 12 decibels:

          volume=-12dB

volumedetect
============

Detect the volume of the input video.

The filter has no parameters. The input is not modified. Statistics about the volume will be printed in the log when the input stream end is reached.

In particular it will show the mean volume (root mean square), maximum volume (on a per-sample basis), and the beginning of an histogram of the registered volume values (from the maximum value to a cumulated 1/1000 of the samples).

All volumes are in decibels relative to the maximum PCM value.

Here is an excerpt of the output:

     [Parsed_volumedetect_0  0xa23120] mean_volume: -27 dB
     [Parsed_volumedetect_0  0xa23120] max_volume: -4 dB
     [Parsed_volumedetect_0  0xa23120] histogram_4db: 6
     [Parsed_volumedetect_0  0xa23120] histogram_5db: 62
     [Parsed_volumedetect_0  0xa23120] histogram_6db: 286
     [Parsed_volumedetect_0  0xa23120] histogram_7db: 1042
     [Parsed_volumedetect_0  0xa23120] histogram_8db: 2551
     [Parsed_volumedetect_0  0xa23120] histogram_9db: 4609
     [Parsed_volumedetect_0  0xa23120] histogram_10db: 8409

It means that:

  * The mean square energy is approximately -27 dB, or 10^-2.7.

  * The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.

  * There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.

In other words, raising the volume by +4 dB does not cause any clipping, raising it by +5 dB causes clipping for 6 samples, etc.

asyncts
=======

Synchronize audio data with timestamps by squeezing/stretching it and/or dropping samples/adding silence when needed.

The filter accepts the following named parameters:

compensate
     Enable stretching/squeezing the data to make it match the timestamps. Disabled by default. When disabled, time gaps are covered with silence.

min_delta
     Minimum difference between timestamps and audio data (in seconds) to trigger adding/dropping samples. Default value is 0.1. If you get non-perfect sync with this filter, try setting this parameter to 0.

max_comp
     Maximum compensation in samples per second. Relevant only with compensate=1. Default value 500.

first_pts
     Assume the first pts should be this value. This allows for padding/trimming at the start of stream. By default, no assumption is made about the first frame's expected pts, so no padding or trimming is done. For example, this could be set to 0 to pad the beginning with silence if an audio stream starts after the video stream.

channelsplit
============

Split each channel in input audio stream into a separate output stream.

This filter accepts the following named parameters:

channel_layout
     Channel layout of the input stream. Default is "stereo".

For example, assuming a stereo input MP3 file

     ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv

will create an output Matroska file with two audio streams, one containing only the left channel and the other the right channel.

To split a 5.1 WAV file into per-channel files

     ffmpeg -i in.wav -filter_complex
     'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
     -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
     front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
     side_right.wav

channelmap
==========

Remap input channels to new locations.

This filter accepts the following named parameters:

channel_layout
     Channel layout of the output stream.

map
     Map channels from input to output. The argument is a comma-separated list of mappings, each in the IN_CHANNEL-OUT_CHANNEL or IN_CHANNEL form. IN_CHANNEL can be either the name of the input channel (e.g. FL for front left) or its index in the input channel layout. OUT_CHANNEL is the name of the output channel or its index in the output channel layout. If OUT_CHANNEL is not given then it is implicitly an index, starting with zero and increasing by one for each mapping.

If no mapping is present, the filter will implicitly map input channels to output channels preserving index.

For example, assuming a 5.1+downmix input MOV file

     ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav

will create an output WAV file tagged as stereo from the downmix channels of the input.

To fix a 5.1 WAV improperly encoded in AAC's native channel order

     ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav

join
====

Join multiple input streams into one multi-channel stream.

The filter accepts the following named parameters:

inputs
     Number of input streams. Defaults to 2.

channel_layout
     Desired output channel layout. Defaults to stereo.

map
     Map channels from inputs to output. The argument is a comma-separated list of mappings, each in the INPUT_IDX.IN_CHANNEL-OUT_CHANNEL form. INPUT_IDX is the 0-based index of the input stream. IN_CHANNEL can be either the name of the input channel (e.g. FL for front left) or its index in the specified input stream. OUT_CHANNEL is the name of the output channel.

The filter will attempt to guess the mappings when those are not specified explicitly. It does so by first trying to find an unused matching input channel and if that fails it picks the first unused input channel.

E.g. to join 3 inputs (with properly set channel layouts)

     ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT

To build a 5.1 output from 6 single-channel streams:

     ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
     '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'
     out

resample
========

Convert the audio sample format, sample rate and channel layout. This filter is not meant to be used directly.

Audio Sources
*************

Below is a description of the currently available audio sources.

abuffer
=======

Buffer audio frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular through the interface defined in libavfilter/asrc_abuffer.h.

It accepts the following mandatory parameters: SAMPLE_RATE:SAMPLE_FMT:CHANNEL_LAYOUT

sample_rate
     The sample rate of the incoming audio buffers.

sample_fmt
     The sample format of the incoming audio buffers. Either a sample format name or its corresponging integer representation from the enum AVSampleFormat in libavutil/samplefmt.h

channel_layout
     The channel layout of the incoming audio buffers. Either a channel layout name from channel_layout_map in libavutil/audioconvert.c or its corresponding integer representation from the AV_CH_LAYOUT_* macros in libavutil/audioconvert.h

For example:

     abuffer=44100:s16p:stereo

will instruct the source to accept planar 16bit signed stereo at 44100Hz. Since the sample format with name "s16p" corresponds to the number 6 and the "stereo" channel layout corresponds to the value 0x3, this is equivalent to:

     abuffer=44100:6:0x3

aevalsrc
========

Generate an audio signal specified by an expression.

This source accepts in input one or more expressions (one for each channel), which are evaluated and used to generate a corresponding audio signal.

It accepts the syntax: EXPRS[::OPTIONS]. EXPRS is a list of expressions separated by ":", one for each separate channel. In case the CHANNEL_LAYOUT is not specified, the selected channel layout depends on the number of provided expressions.

OPTIONS is an optional sequence of KEY=VALUE pairs, separated by ":".

The description of the accepted options follows.

channel_layout, c
     Set the channel layout. The number of channels in the specified layout must be equal to the number of specified expressions.

duration, d
     Set the minimum duration of the sourced audio. See the function av_parse_time() for the accepted format. Note that the resulting duration may be greater than the specified duration, as the generated audio is always cut at the end of a complete frame.

     If not specified, or the expressed duration is negative, the audio is supposed to be generated forever.

nb_samples, n
     Set the number of samples per channel per each output frame, default to 1024.

sample_rate, s
     Specify the sample rate, default to 44100.

Each expression in EXPRS can contain the following constants:

n
     number of the evaluated sample, starting from 0

t
     time of the evaluated sample expressed in seconds, starting from 0

s
     sample rate

Examples
--------

  * Generate silence:

          aevalsrc=0

  * Generate a sin signal with frequency of 440 Hz, set sample rate to 8000 Hz:

          aevalsrc="sin(440*2*PI*t)::s=8000"

  * Generate a two channels signal, specify the channel layout (Front Center + Back Center) explicitly:

          aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"

  * Generate white noise:

          aevalsrc="-2+random(0)"

  * Generate an amplitude modulated signal:

          aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"

  * Generate 2.5 Hz binaural beats on a 360 Hz carrier:

          aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"

anullsrc
========

Null audio source, return unprocessed audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools, or as the source for filters which ignore the input data (for example the sox synth filter).

It accepts an optional sequence of KEY=VALUE pairs, separated by ":".

The description of the accepted options follows.

sample_rate, s
     Specify the sample rate, and defaults to 44100.

channel_layout, cl

     Specify the channel layout, and can be either an integer or a string representing a channel layout. The default value of CHANNEL_LAYOUT is "stereo".

     Check the channel_layout_map definition in libavcodec/audioconvert.c for the mapping between strings and channel layout values.

nb_samples, n
     Set the number of samples per requested frames.

Follow some examples:

     #  set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
     anullsrc=r=48000:cl=4

     # same as
     anullsrc=r=48000:cl=mono

abuffer
=======

Buffer audio frames, and make them available to the filter chain.

This source is not intended to be part of user-supplied graph descriptions but for insertion by calling programs through the interface defined in libavfilter/buffersrc.h.

It accepts the following named parameters:

time_base
     Timebase which will be used for timestamps of submitted frames. It must be either a floating-point number or in NUMERATOR/DENOMINATOR form.

sample_rate
     Audio sample rate.

sample_fmt
     Name of the sample format, as returned by av_get_sample_fmt_name().

channel_layout
     Channel layout of the audio data, in the form that can be accepted by av_get_channel_layout().

All the parameters need to be explicitly defined.

flite
=====

Synthesize a voice utterance using the libflite library.

To enable compilation of this filter you need to configure FFmpeg with --enable-libflite.

Note that the flite library is not thread-safe.

The source accepts parameters as a list of KEY=VALUE pairs, separated by ":".

The description of the accepted parameters follows.

list_voices
     If set to 1, list the names of the available voices and exit immediately. Default value is 0.

nb_samples, n
     Set the maximum number of samples per frame. Default value is 512.

textfile
     Set the filename containing the text to speak.

text
     Set the text to speak.

voice, v
     Set the voice to use for the speech synthesis. Default value is kal. See also the LIST_VOICES option.

Examples
--------

  * Read from file speech.txt, and synthetize the text using the standard flite voice:

          flite=textfile=speech.txt

  * Read the specified text selecting the slt voice:

          flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt

  * Input text to ffmpeg:

          ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt

  * Make ffplay speak the specified text, using flite and the lavfi device:

          ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'

For more information about libflite, check: http://www.speech.cs.cmu.edu/flite/

Audio Sinks
***********

Below is a description of the currently available audio sinks.

abuffersink
===========

Buffer audio frames, and make them available to the end of filter chain.

This sink is mainly intended for programmatic use, in particular through the interface defined in libavfilter/buffersink.h.

It requires a pointer to an AVABufferSinkContext structure, which defines the incoming buffers' formats, to be passed as the opaque parameter to avfilter_init_filter for initialization.

anullsink
=========

Null audio sink, do absolutely nothing with the input audio. It is mainly useful as a template and to be employed in analysis / debugging tools.

abuffersink
===========

This sink is intended for programmatic use. Frames that arrive on this sink can be retrieved by the calling program using the interface defined in libavfilter/buffersink.h.

This filter accepts no parameters.

Video Filters
*************

When you configure your FFmpeg build, you can disable any of the existing filters using --disable-filters. The configure output will show the video filters included in your build.

Below is a description of the currently available video filters.

alphaextract
============

Extract the alpha component from the input as a grayscale video. This is especially useful with the ALPHAMERGE filter.

alphamerge
==========

Add or replace the alpha component of the primary input with the grayscale value of a second input. This is intended for use with ALPHAEXTRACT to allow the transmission or storage of frame sequences that have alpha in a format that doesn't support an alpha channel.

For example, to reconstruct full frames from a normal YUV-encoded video and a separate video created with ALPHAEXTRACT, you might use:

     movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]

Since this filter is designed for reconstruction, it operates on frame sequences without considering timestamps, and terminates when either input reaches end of stream. This will cause problems if your encoding pipeline drops frames. If you're trying to apply an image as an overlay to a video stream, consider the OVERLAY filter instead.

ass
===

Draw ASS (Advanced Substation Alpha) subtitles on top of input video using the libass library.

To enable compilation of this filter you need to configure FFmpeg with --enable-libass.

This filter accepts the following named options, expressed as a sequence of KEY=VALUE pairs, separated by ":".

filename, f
     Set the filename of the ASS file to read. It must be specified.

original_size
     Specify the size of the original video, the video for which the ASS file was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is necessary to correctly scale the fonts if the aspect ratio has been changed.

If the first key is not specified, it is assumed that the first value specifies the filename.

For example, to render the file sub.ass on top of the input video, use the command:

     ass=sub.ass

which is equivalent to:

     ass=filename=sub.ass

bbox
====

Compute the bounding box for the non-black pixels in the input frame luminance plane.

This filter computes the bounding box containing all the pixels with a luminance value greater than the minimum allowed value. The parameters describing the bounding box are printed on the filter log.

blackdetect
===========

Detect video intervals that are (almost) completely black. Can be useful to detect chapter transitions, commercials, or invalid recordings. Output lines contains the time for the start, end and duration of the detected black interval expressed in seconds.

In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.

This filter accepts a list of options in the form of KEY=VALUE pairs separated by ":". A description of the accepted options follows.

black_min_duration, d
     Set the minimum detected black duration expressed in seconds. It must be a non-negative floating point number.

     Default value is 2.0.

picture_black_ratio_th, pic_th
     Set the threshold for considering a picture "black". Express the minimum value for the ratio:

          NB_BLACK_PIXELS / NB_PIXELS

     for which a picture is considered black. Default value is 0.98.

pixel_black_th, pix_th
     Set the threshold for considering a pixel "black".

     The threshold expresses the maximum pixel luminance value for which a pixel is considered "black". The provided value is scaled according to the following equation:

          ABSOLUTE_THRESHOLD = LUMINANCE_MINIMUM_VALUE + PIXEL_BLACK_TH * LUMINANCE_RANGE_SIZE

     LUMINANCE_RANGE_SIZE and LUMINANCE_MINIMUM_VALUE depend on the input video format, the range is [0-255] for YUV full-range formats and [16-235] for YUV non full-range formats.

     Default value is 0.10.

The following example sets the maximum pixel threshold to the minimum value, and detects only black intervals of 2 or more seconds:

     blackdetect=d=2:pix_th=0.00

blackframe
==========

Detect frames that are (almost) completely black. Can be useful to detect chapter transitions or commercials. Output lines consist of the frame number of the detected frame, the percentage of blackness, the position in the file if known or -1 and the timestamp in seconds.

In order to display the output lines, you need to set the loglevel at least to the AV_LOG_INFO value.

The filter accepts the syntax:

     blackframe[=AMOUNT:[THRESHOLD]]

AMOUNT is the percentage of the pixels that have to be below the threshold, and defaults to 98.

THRESHOLD is the threshold below which a pixel value is considered black, and defaults to 32.

boxblur
=======

Apply boxblur algorithm to the input video.

This filter accepts the parameters: LUMA_RADIUS:LUMA_POWER:CHROMA_RADIUS:CHROMA_POWER:ALPHA_RADIUS:ALPHA_POWER

Chroma and alpha parameters are optional, if not specified they default to the corresponding values set for LUMA_RADIUS and LUMA_POWER.

LUMA_RADIUS, CHROMA_RADIUS, and ALPHA_RADIUS represent the radius in pixels of the box used for blurring the corresponding input plane. They are expressions, and can contain the following constants:

w, h
     the input width and height in pixels

cw, ch
     the input chroma image width and height in pixels

hsub, vsub
     horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" HSUB is 2 and VSUB is 1.

The radius must be a non-negative number, and must not be greater than the value of the expression min(w,h)/2 for the luma and alpha planes, and of min(cw,ch)/2 for the chroma planes.

LUMA_POWER, CHROMA_POWER, and ALPHA_POWER represent how many times the boxblur filter is applied to the corresponding plane.

Some examples follow:

  * Apply a boxblur filter with luma, chroma, and alpha radius set to 2:

          boxblur=2:1

  * Set luma radius to 2, alpha and chroma radius to 0

          boxblur=2:1:0:0:0:0

  * Set luma and chroma radius to a fraction of the video dimension

          boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1

colormatrix
===========

The colormatrix filter allows conversion between any of the following color space: BT.709 (BT709), BT.601 (BT601), SMPTE-240M (SMPTE240M) and FCC (FCC).

The syntax of the parameters is SOURCE:DESTINATION:

     colormatrix=bt601:smpte240m

copy
====

Copy the input source unchanged to the output. Mainly useful for testing purposes.

crop
====

Crop the input video to OUT_W:OUT_H:X:Y:KEEP_ASPECT

The KEEP_ASPECT parameter is optional, if specified and set to a non-zero value will force the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio.

The OUT_W, OUT_H, X, Y parameters are expressions containing the following constants:

x, y
     the computed values for X and Y. They are evaluated for each new frame.

in_w, in_h
     the input width and height

iw, ih
     same as IN_W and IN_H

out_w, out_h
     the output (cropped) width and height

ow, oh
     same as OUT_W and OUT_H

a
     same as IW / IH

sar
     input sample aspect ratio

dar
     input display aspect ratio, it is the same as (IW / IH) * SAR

hsub, vsub
     horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" HSUB is 2 and VSUB is 1.

n
     the number of input frame, starting from 0

pos
     the position in the file of the input frame, NAN if unknown

t
     timestamp expressed in seconds, NAN if the input timestamp is unknown

The OUT_W and OUT_H parameters specify the expressions for the width and height of the output (cropped) video. They are evaluated just at the configuration of the filter.

The default value of OUT_W is "in_w", and the default value of OUT_H is "in_h".

The expression for OUT_W may depend on the value of OUT_H, and the expression for OUT_H may depend on OUT_W, but they cannot depend on X and Y, as X and Y are evaluated after OUT_W and OUT_H.

The X and Y parameters specify the expressions for the position of the top-left corner of the output (non-cropped) area. They are evaluated for each frame. If the evaluated value is not valid, it is approximated to the nearest valid value.

The default value of X is "(in_w-out_w)/2", and the default value for Y is "(in_h-out_h)/2", which set the cropped area at the center of the input image.

The expression for X may depend on Y, and the expression for Y may depend on X.

Follow some examples:

     # crop the central input area with size 100x100
     crop=100:100

     # crop the central input area with size 2/3 of the input video
     "crop=2/3*in_w:2/3*in_h"

     # crop the input video central square
     crop=in_h

     # delimit the rectangle with the top-left corner placed at position
     # 100:100 and the right-bottom corner corresponding to the right-bottom
     # corner of the input image.
     crop=in_w-100:in_h-100:100:100

     # crop 10 pixels from the left and right borders, and 20 pixels from
     # the top and bottom borders
     "crop=in_w-2*10:in_h-2*20"

     # keep only the bottom right quarter of the input image
     "crop=in_w/2:in_h/2:in_w/2:in_h/2"

     # crop height for getting Greek harmony
     "crop=in_w:1/PHI*in_w"

     # trembling effect
     "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)"

     # erratic camera effect depending on timestamp
     "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)"

     # set x depending on the value of y
     "crop=in_w/2:in_h/2:y:10+10*sin(n/10)"

cropdetect
==========

Auto-detect crop size.

Calculate necessary cropping parameters and prints the recommended parameters through the logging system. The detected dimensions correspond to the non-black area of the input video.

It accepts the syntax:

     cropdetect[=LIMIT[:ROUND[:RESET]]]

limit
     Threshold, which can be optionally specified from nothing (0) to everything (255), defaults to 24.

round
     Value which the width/height should be divisible by, defaults to 16. The offset is automatically adjusted to center the video. Use 2 to get only even dimensions (needed for 4:2:2 video). 16 is best when encoding to most video codecs.

reset
     Counter that determines after how many frames cropdetect will reset the previously detected largest video area and start over to detect the current optimal crop area. Defaults to 0.

     This can be useful when channel logos distort the video area. 0 indicates never reset and return the largest area encountered during playback.

decimate
========

This filter drops frames that do not differ greatly from the previous frame in order to reduce framerate.  The main use of this filter is for very-low-bitrate encoding (e.g. streaming over dialup modem), but it could in theory be used for fixing movies that were inverse-telecined incorrectly.

It accepts the following parameters: MAX:HI:LO:FRAC.

max
     Set the maximum number of consecutive frames which can be dropped (if positive), or the minimum interval between dropped frames (if negative). If the value is 0, the frame is dropped unregarding the number of previous sequentially dropped frames.

     Default value is 0.

hi, lo, frac
     Set the dropping threshold values.

     Values for HI and LO are for 8x8 pixel blocks and represent actual pixel value differences, so a threshold of 64 corresponds to 1 unit of difference for each pixel, or the same spread out differently over the block.

     A frame is a candidate for dropping if no 8x8 blocks differ by more than a threshold of HI, and if no more than FRAC blocks (1 meaning the whole image) differ by more than a threshold of LO.

     Default value for HI is 64*12, default value for LO is 64*5, and default value for FRAC is 0.33.

delogo
======

Suppress a TV station logo by a simple interpolation of the surrounding pixels. Just set a rectangle covering the logo and watch it disappear (and sometimes something even uglier appear - your mileage may vary).

The filter accepts parameters as a string of the form "X:Y:W:H:BAND", or as a list of KEY=VALUE pairs, separated by ":".

The description of the accepted parameters follows.

x, y
     Specify the top left corner coordinates of the logo. They must be specified.

w, h
     Specify the width and height of the logo to clear. They must be specified.

band, t
     Specify the thickness of the fuzzy edge of the rectangle (added to W and H). The default value is 4.

show
     When set to 1, a green rectangle is drawn on the screen to simplify finding the right X, Y, W, H parameters, and BAND is set to 4. The default value is 0.

Some examples follow.

  * Set a rectangle covering the area with top left corner coordinates 0,0 and size 100x77, setting a band of size 10:

          delogo=0:0:100:77:10

  * As the previous example, but use named options:

          delogo=x=0:y=0:w=100:h=77:band=10

deshake
=======

Attempt to fix small changes in horizontal and/or vertical shift. This filter helps remove camera shake from hand-holding a camera, bumping a tripod, moving on a vehicle, etc.

The filter accepts parameters as a string of the form "X:Y:W:H:RX:RY:EDGE:BLOCKSIZE:CONTRAST:SEARCH:FILENAME"

A description of the accepted parameters follows.

x, y, w, h
     Specify a rectangular area where to limit the search for motion vectors. If desired the search for motion vectors can be limited to a rectangular area of the frame defined by its top left corner, width and height. These parameters have the same meaning as the drawbox filter which can be used to visualise the position of the bounding box.

     This is useful when simultaneous movement of subjects within the frame might be confused for camera motion by the motion vector search.

     If any or all of X, Y, W and H are set to -1 then the full frame is used. This allows later options to be set without specifying the bounding box for the motion vector search.

     Default - search the whole frame.

rx, ry
     Specify the maximum extent of movement in x and y directions in the range 0-64 pixels. Default 16.

edge
     Specify how to generate pixels to fill blanks at the edge of the frame. An integer from 0 to 3 as follows:

     0
          Fill zeroes at blank locations

     1
          Original image at blank locations

     2
          Extruded edge value at blank locations

     3
          Mirrored edge at blank locations

     The default setting is mirror edge at blank locations.

blocksize
     Specify the blocksize to use for motion search. Range 4-128 pixels, default 8.

contrast
     Specify the contrast threshold for blocks. Only blocks with more than the specified contrast (difference between darkest and lightest pixels) will be considered. Range 1-255, default 125.

search
     Specify the search strategy 0 = exhaustive search, 1 = less exhaustive search. Default - exhaustive search.

filename
     If set then a detailed log of the motion search is written to the specified file.

drawbox
=======

Draw a colored box on the input image.

It accepts the syntax:

     drawbox=X:Y:WIDTH:HEIGHT:COLOR

x, y
     Specify the top left corner coordinates of the box. Default to 0.

width, height
     Specify the width and height of the box, if 0 they are interpreted as the input width and height. Default to 0.

color
     Specify the color of the box to write, it can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence.

Follow some examples:

     # draw a black box around the edge of the input image
     drawbox

     # draw a box with color red and an opacity of 50%
     drawbox=10:20:200:60:red@0.5"

drawtext
========

Draw text string or text from specified file on top of video using the libfreetype library.

To enable compilation of this filter you need to configure FFmpeg with --enable-libfreetype.

The filter also recognizes strftime() sequences in the provided text and expands them accordingly. Check the documentation of strftime().

The filter accepts parameters as a list of KEY=VALUE pairs, separated by ":".

The description of the accepted parameters follows.

box
     Used to draw a box around text using background color. Value should be either 1 (enable) or 0 (disable). The default value of BOX is 0.

boxcolor
     The color to be used for drawing box around text. Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of BOXCOLOR is "white".

draw
     Set an expression which specifies if the text should be drawn. If the expression evaluates to 0, the text is not drawn. This is useful for specifying that the text should be drawn only when specific conditions are met.

     Default value is "1".

     See below for the list of accepted constants and functions.

fix_bounds
     If true, check and fix text coords to avoid clipping.

fontcolor
     The color to be used for drawing fonts. Either a string (e.g. "red") or in 0xRRGGBB[AA] format (e.g. "0xff000033"), possibly followed by an alpha specifier. The default value of FONTCOLOR is "black".

fontfile
     The font file to be used for drawing text. Path must be included. This parameter is mandatory.

fontsize
     The font size to be used for drawing text. The default value of FONTSIZE is 16.

ft_load_flags
     Flags to be used for loading the fonts.

     The flags map the corresponding flags supported by libfreetype, and are a combination of the following values:

     default

     no_scale

     no_hinting

     render

     no_bitmap

     vertical_layout

     force_autohint

     crop_bitmap

     pedantic

     ignore_global_advance_width

     no_recurse

     ignore_transform

     monochrome

     linear_design

     no_autohint

     end table

     Default value is "render".

     For more information consult the documentation for the FT_LOAD_* libfreetype flags.

shadowcolor
     The color to be used for drawing a shadow behind the drawn text.  It can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA] form (e.g. "0xff00ff"), possibly followed by an alpha specifier. The default value of SHADOWCOLOR is "black".

shadowx, shadowy
     The x and y offsets for the text shadow position with respect to the position of the text. They can be either positive or negative values. Default value for both is "0".

tabsize
     The size in number of spaces to use for rendering the tab. Default value is 4.

timecode
     Set the initial timecode representation in "hh:mm:ss[:;.]ff" format. It can be used with or without text parameter. TIMECODE_RATE option must be specified.

timecode_rate, rate, r
     Set the timecode frame rate (timecode only).

text
     The text string to be drawn. The text must be a sequence of UTF-8 encoded characters. This parameter is mandatory if no file is specified with the parameter TEXTFILE.

textfile
     A text file containing text to be drawn. The text must be a sequence of UTF-8 encoded characters.

     This parameter is mandatory if no text string is specified with the parameter TEXT.

     If both TEXT and TEXTFILE are specified, an error is thrown.

x, y
     The expressions which specify the offsets where text will be drawn within the video frame. They are relative to the top/left border of the output image.

     The default value of X and Y is "0".

     See below for the list of accepted constants and functions.

The parameters for X and Y are expressions containing the following constants and functions:

dar
     input display aspect ratio, it is the same as (W / H) * SAR

hsub, vsub
     horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" HSUB is 2 and VSUB is 1.

line_h, lh
     the height of each text line

main_h, h, H
     the input height

main_w, w, W
     the input width

max_glyph_a, ascent
     the maximum distance from the baseline to the highest/upper grid coordinate used to place a glyph outline point, for all the rendered glyphs. It is a positive value, due to the grid's orientation with the Y axis upwards.

max_glyph_d, descent
     the maximum distance from the baseline to the lowest grid coordinate used to place a glyph outline point, for all the rendered glyphs. This is a negative value, due to the grid's orientation, with the Y axis upwards.

max_glyph_h
     maximum glyph height, that is the maximum height for all the glyphs contained in the rendered text, it is equivalent to ASCENT - DESCENT.

max_glyph_w
     maximum glyph width, that is the maximum width for all the glyphs contained in the rendered text

n
     the number of input frame, starting from 0

rand(min, max)
     return a random number included between MIN and MAX

sar
     input sample aspect ratio

t
     timestamp expressed in seconds, NAN if the input timestamp is unknown

text_h, th
     the height of the rendered text

text_w, tw
     the width of the rendered text

x, y
     the x and y offset coordinates where the text is drawn.

     These parameters allow the X and Y expressions to refer each other, so you can for example specify y=x/dar.

If libavfilter was built with --enable-fontconfig, then fontfile can be a fontconfig pattern or omitted.

Some examples follow.

  * Draw "Test Text" with font FreeSerif, using the default values for the optional parameters.

          drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"

  * Draw 'Test Text' with font FreeSerif of size 24 at position x=100 and y=50 (counting from the top-left corner of the screen), text is yellow with a red box around it. Both the text and the box have an opacity of 20%.

          drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
                    x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"

     Note that the double quotes are not necessary if spaces are not used within the parameter list.

  * Show the text at the center of the video frame:

          drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"

  * Show a text line sliding from right to left in the last row of the video frame. The file LONG_LINE is assumed to contain a single line with no newlines.

          drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"

  * Show the content of file CREDITS off the bottom of the frame and scroll up.

          drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"

  * Draw a single green letter "g", at the center of the input video. The glyph baseline is placed at half screen height.

          drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"

  * Show text for 1 second every 3 seconds:

          drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\\,3)\\,1):text='blink'"

  * Use fontconfig to set the font. Note that the colons need to be escaped.

          drawtext='fontfile=Linux Libertine O-40\\:style=Semibold:text=FFmpeg'

For more information about libfreetype, check: http://www.freetype.org/.

For more information about fontconfig, check: http://freedesktop.org/software/fontconfig/fontconfig-user.html.

edgedetect
==========

Detect and draw edges. The filter uses the Canny Edge Detection algorithm.

This filter accepts the following optional named parameters:

low, high
     Set low and high threshold values used by the Canny thresholding algorithm.

     The high threshold selects the "strong" edge pixels, which are then connected through 8-connectivity with the "weak" edge pixels selected by the low threshold.

     LOW and HIGH threshold values must be choosen in the range [0,1], and LOW should be lesser or equal to HIGH.

     Default value for LOW is 20/255, and default value for HIGH is 50/255.

Example:

     edgedetect=low=0.1:high=0.4

fade
====

Apply fade-in/out effect to input video.

It accepts the parameters: TYPE:START_FRAME:NB_FRAMES[:OPTIONS]

TYPE specifies if the effect type, can be either "in" for fade-in, or "out" for a fade-out effect.

START_FRAME specifies the number of the start frame for starting to apply the fade effect.

NB_FRAMES specifies the number of frames for which the fade effect has to last. At the end of the fade-in effect the output video will have the same intensity as the input video, at the end of the fade-out transition the output video will be completely black.

OPTIONS is an optional sequence of KEY=VALUE pairs, separated by ":". The description of the accepted options follows.

type, t
     See TYPE.

start_frame, s
     See START_FRAME.

nb_frames, n
     See NB_FRAMES.

alpha
     If set to 1, fade only alpha channel, if one exists on the input. Default value is 0.

A few usage examples follow, usable too as test scenarios.

     # fade in first 30 frames of video
     fade=in:0:30

     # fade out last 45 frames of a 200-frame video
     fade=out:155:45

     # fade in first 25 frames and fade out last 25 frames of a 1000-frame video
     fade=in:0:25, fade=out:975:25

     # make first 5 frames black, then fade in from frame 5-24
     fade=in:5:20

     # fade in alpha over first 25 frames of video
     fade=in:0:25:alpha=1

fieldorder
==========

Transform the field order of the input video.

It accepts one parameter which specifies the required field order that the input interlaced video will be transformed to. The parameter can assume one of the following values:

0 or bff
     output bottom field first

1 or tff
     output top field first

Default value is "tff".

Transformation is achieved by shifting the picture content up or down by one line, and filling the remaining line with appropriate picture content. This method is consistent with most broadcast field order converters.

If the input video is not flagged as being interlaced, or it is already flagged as being of the required output field order then this filter does not alter the incoming video.

This filter is very useful when converting to or from PAL DV material, which is bottom field first.

For example:

     ffmpeg -i in.vob -vf "fieldorder=bff" out.dv

fifo
====

Buffer input images and send them when they are requested.

This filter is mainly useful when auto-inserted by the libavfilter framework.

The filter does not take parameters.

format
======

Convert the input video to one of the specified pixel formats. Libavfilter will try to pick one that is supported for the input to the next filter.

The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24".

Some examples follow:

     # convert the input video to the format "yuv420p"
     format=yuv420p

     # convert the input video to any of the formats in the list
     format=yuv420p:yuv444p:yuv410p

fps
===

Convert the video to specified constant framerate by duplicating or dropping frames as necessary.

This filter accepts the following named parameters:

fps
     Desired output framerate.

framestep
=========

Select one frame every N.

This filter accepts in input a string representing a positive integer. Default argument is 1.

frei0r
======

Apply a frei0r effect to the input video.

To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with --enable-frei0r.

The filter supports the syntax:

     FILTER_NAME[{:|=}PARAM1:PARAM2:...:PARAMN]

FILTER_NAME is the name to the frei0r effect to load. If the environment variable FREI0R_PATH is defined, the frei0r effect is searched in each one of the directories specified by the colon separated list in FREIOR_PATH, otherwise in the standard frei0r paths, which are in this order: HOME/.frei0r-1/lib/, /usr/local/lib/frei0r-1/, /usr/lib/frei0r-1/.

PARAM1, PARAM2, ... , PARAMN specify the parameters for the frei0r effect.

A frei0r effect parameter can be a boolean (whose values are specified with "y" and "n"), a double, a color (specified by the syntax R/G/B, R, G, and B being float numbers from 0.0 to 1.0) or by an av_parse_color() color description), a position (specified by the syntax X/Y, X and Y being float numbers) and a string.

The number and kind of parameters depend on the loaded effect. If an effect parameter is not specified the default value is set.

Some examples follow:

  * Apply the distort0r effect, set the first two double parameters:

          frei0r=distort0r:0.5:0.01

  * Apply the colordistance effect, takes a color as first parameter:

          frei0r=colordistance:0.2/0.3/0.4
          frei0r=colordistance:violet
          frei0r=colordistance:0x112233

  * Apply the perspective effect, specify the top left and top right image positions:

          frei0r=perspective:0.2/0.2:0.8/0.2

For more information see: http://frei0r.dyne.org

gradfun
=======

Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8bit color depth. Interpolate the gradients that should go where the bands are, and dither them.

This filter is designed for playback only.  Do not use it prior to lossy compression, because compression tends to lose the dither and bring back the bands.

The filter takes two optional parameters, separated by ':': STRENGTH:RADIUS

STRENGTH is the maximum amount by which the filter will change any one pixel. Also the threshold for detecting nearly flat regions. Acceptable values range from .51 to 255, default value is 1.2, out-of-range values will be clipped to the valid range.

RADIUS is the neighborhood to fit the gradient to. A larger radius makes for smoother gradients, but also prevents the filter from modifying the pixels near detailed regions. Acceptable values are 8-32, default value is 16, out-of-range values will be clipped to the valid range.

     # default parameters
     gradfun=1.2:16

     # omitting radius
     gradfun=1.2

hflip
=====

Flip the input video horizontally.

For example to horizontally flip the input video with ffmpeg:

     ffmpeg -i in.avi -vf "hflip" out.avi

hqdn3d
======

High precision/quality 3d denoise filter. This filter aims to reduce image noise producing smooth images and making still images really still. It should enhance compressibility.

It accepts the following optional parameters: LUMA_SPATIAL:CHROMA_SPATIAL:LUMA_TMP:CHROMA_TMP

luma_spatial
     a non-negative float number which specifies spatial luma strength, defaults to 4.0

chroma_spatial
     a non-negative float number which specifies spatial chroma strength, defaults to 3.0*LUMA_SPATIAL/4.0

luma_tmp
     a float number which specifies luma temporal strength, defaults to 6.0*LUMA_SPATIAL/4.0

chroma_tmp
     a float number which specifies chroma temporal strength, defaults to LUMA_TMP*CHROMA_SPATIAL/LUMA_SPATIAL

hue
===

Modify the hue and/or the saturation of the input.

This filter accepts the following optional named options:

h
     Specify the hue angle as a number of degrees. It accepts a float number or an expression, and defaults to 0.0.

H
     Specify the hue angle as a number of degrees. It accepts a float number or an expression, and defaults to 0.0.

s
     Specify the saturation in the [-10,10] range. It accepts a float number and defaults to 1.0.

The H, H and S parameters are expressions containing the following constants:

n
     frame count of the input frame starting from 0

pts
     presentation timestamp of the input frame expressed in time base units

r
     frame rate of the input video, NAN if the input frame rate is unknown

t
     timestamp expressed in seconds, NAN if the input timestamp is unknown

tb
     time base of the input video

The options can also be set using the syntax: HUE:SATURATION

In this case HUE is expressed in degrees.

Some examples follow:

  * Set the hue to 90 degrees and the saturation to 1.0:

          hue=h=90:s=1

  * Same command but expressing the hue in radians:

          hue=H=PI/2:s=1

  * Same command without named options, hue must be expressed in degrees:

          hue=90:1

  * Note that "h:s" syntax does not support expressions for the values of h and s, so the following example will issue an error:

          hue=PI/2:1

  * Rotate hue and make the saturation swing between 0 and 2 over a period of 1 second:

          hue="H=2*PI*t: s=sin(2*PI*t)+1"

  * Apply a 3 seconds saturation fade-in effect starting at 0:

          hue="s=min(t/3\,1)"

     The general fade-in expression can be written as:

          hue="s=min(0\, max((t-START)/DURATION\, 1))"

  * Apply a 3 seconds saturation fade-out effect starting at 5 seconds:

          hue="s=max(0\, min(1\, (8-t)/3))"

     The general fade-out expression can be written as:

          hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"

Commands
--------

This filter supports the following command:

reinit
     Modify the hue and/or the saturation of the input video. The command accepts the same named options and syntax than when calling the filter from the command-line.

     If a parameter is omitted, it is kept at its current value.

idet
====

Interlaceing detect filter. This filter tries to detect if the input is interlaced or progressive. Top or bottom field first.

lut, lutrgb, lutyuv
===================

Compute a look-up table for binding each pixel component input value to an output value, and apply it to input video.

LUTYUV applies a lookup table to a YUV input video, LUTRGB to an RGB input video.

These filters accept in input a ":"-separated list of options, which specify the expressions used for computing the lookup table for the corresponding pixel component values.

The LUT filter requires either YUV or RGB pixel formats in input, and accepts the options:

C0 (first  pixel component)

C1 (second pixel component)

C2 (third  pixel component)

C3 (fourth pixel component, corresponds to the alpha component)

The exact component associated to each option depends on the format in input.

The LUTRGB filter requires RGB pixel formats in input, and accepts the options:

R (red component)

G (green component)

B (blue component)

A (alpha component)

The LUTYUV filter requires YUV pixel formats in input, and accepts the options:

Y (Y/luminance component)

U (U/Cb component)

V (V/Cr component)

A (alpha component)

The expressions can contain the following constants and functions:

w, h
     the input width and height

val
     input value for the pixel component

clipval
     the input value clipped in the MINVAL-MAXVAL range

maxval
     maximum value for the pixel component

minval
     minimum value for the pixel component

negval
     the negated value for the pixel component value clipped in the MINVAL-MAXVAL range , it corresponds to the expression "maxval-clipval+minval"

clip(val)
     the computed value in VAL clipped in the MINVAL-MAXVAL range

gammaval(gamma)
     the computed gamma correction value of the pixel component value clipped in the MINVAL-MAXVAL range, corresponds to the expression "pow((clipval-minval)/(maxval-minval)\,GAMMA)*(maxval-minval)+minval"

All expressions default to "val".

Some examples follow:

     # negate input video
     lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
     lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"

     # the above is the same as
     lutrgb="r=negval:g=negval:b=negval"
     lutyuv="y=negval:u=negval:v=negval"

     # negate luminance
     lutyuv=y=negval

     # remove chroma components, turns the video into a graytone image
     lutyuv="u=128:v=128"

     # apply a luma burning effect
     lutyuv="y=2*val"

     # remove green and blue components
     lutrgb="g=0:b=0"

     # set a constant alpha channel value on input
     format=rgba,lutrgb=a="maxval-minval/2"

     # correct luminance gamma by a 0.5 factor
     lutyuv=y=gammaval(0.5)

mp
==

Apply an MPlayer filter to the input video.

This filter provides a wrapper around most of the filters of MPlayer/MEncoder.

This wrapper is considered experimental. Some of the wrapped filters may not work properly and we may drop support for them, as they will be implemented natively into FFmpeg. Thus you should avoid depending on them when writing portable scripts.

The filters accepts the parameters: FILTER_NAME[:=]FILTER_PARAMS

FILTER_NAME is the name of a supported MPlayer filter, FILTER_PARAMS is a string containing the parameters accepted by the named filter.

The list of the currently supported filters follows:

denoise3d

detc

dint

divtc

down3dright

dsize

eq2

eq

field

fil

fixpts

fspp

geq

harddup

hqdn3d

il

ilpack

ivtc

kerndeint

mcdeint

noise

ow

palette

perspective

phase

pp7

pullup

qp

rectangle

sab

softpulldown

softskip

spp

telecine

tile

tinterlace

unsharp

uspp

yuvcsp

yvu9

The parameter syntax and behavior for the listed filters are the same of the corresponding MPlayer filters. For detailed instructions check the "VIDEO FILTERS" section in the MPlayer manual.

Some examples follow:

  * Adjust gamma, brightness, contrast:

          mp=eq2=1.0:2:0.5

  * Add temporal noise to input video:

          mp=noise=20t

See also mplayer(1), http://www.mplayerhq.hu/.

negate
======

Negate input video.

This filter accepts an integer in input, if non-zero it negates the alpha component (if available). The default value in input is 0.

noformat
========

Force libavfilter not to use any of the specified pixel formats for the input to the next filter.

The filter accepts a list of pixel format names, separated by ":", for example "yuv420p:monow:rgb24".

Some examples follow:

     # force libavfilter to use a format different from "yuv420p" for the
     # input to the vflip filter
     noformat=yuv420p,vflip

     # convert the input video to any of the formats not contained in the list
     noformat=yuv420p:yuv444p:yuv410p

null
====

Pass the video source unchanged to the output.

ocv
===

Apply video transform using libopencv.

To enable this filter install libopencv library and headers and configure FFmpeg with --enable-libopencv.

The filter takes the parameters: FILTER_NAME{:=}FILTER_PARAMS.

FILTER_NAME is the name of the libopencv filter to apply.

FILTER_PARAMS specifies the parameters to pass to the libopencv filter. If not specified the default values are assumed.

Refer to the official libopencv documentation for more precise information: http://opencv.willowgarage.com/documentation/c/image_filtering.html

Follows the list of supported libopencv filters.

dilate
------

Dilate an image by using a specific structuring element. This filter corresponds to the libopencv function cvDilate.

It accepts the parameters: STRUCT_EL:NB_ITERATIONS.

STRUCT_EL represents a structuring element, and has the syntax: COLSxROWS+ANCHOR_XxANCHOR_Y/SHAPE

COLS and ROWS represent the number of columns and rows of the structuring element, ANCHOR_X and ANCHOR_Y the anchor point, and SHAPE the shape for the structuring element, and can be one of the values "rect", "cross", "ellipse", "custom".

If the value for SHAPE is "custom", it must be followed by a string of the form "=FILENAME". The file with name FILENAME is assumed to represent a binary image, with each printable character corresponding to a bright pixel. When a custom SHAPE is used, COLS and ROWS are ignored, the number or columns and rows of the read file are assumed instead.

The default value for STRUCT_EL is "3x3+0x0/rect".

NB_ITERATIONS specifies the number of times the transform is applied to the image, and defaults to 1.

Follow some example:

     # use the default values
     ocv=dilate

     # dilate using a structuring element with a 5x5 cross, iterate two times
     ocv=dilate=5x5+2x2/cross:2

     # read the shape from the file diamond.shape, iterate two times
     # the file diamond.shape may contain a pattern of characters like this:
     #   *
     #  ***
     # *****
     #  ***
     #   *
     # the specified cols and rows are ignored (but not the anchor point coordinates)
     ocv=0x0+2x2/custom=diamond.shape:2

erode
-----

Erode an image by using a specific structuring element. This filter corresponds to the libopencv function cvErode.

The filter accepts the parameters: STRUCT_EL:NB_ITERATIONS, with the same syntax and semantics as the dilate filter.

smooth
------

Smooth the input video.

The filter takes the following parameters: TYPE:PARAM1:PARAM2:PARAM3:PARAM4.

TYPE is the type of smooth filter to apply, and can be one of the following values: "blur", "blur_no_scale", "median", "gaussian", "bilateral". The default value is "gaussian".

PARAM1, PARAM2, PARAM3, and PARAM4 are parameters whose meanings depend on smooth type. PARAM1 and PARAM2 accept integer positive values or 0, PARAM3 and PARAM4 accept float values.

The default value for PARAM1 is 3, the default value for the other parameters is 0.

These parameters correspond to the parameters assigned to the libopencv function cvSmooth.

overlay
=======

Overlay one video on top of another.

It takes two inputs and one output, the first input is the "main" video on which the second input is overlayed.

It accepts the parameters: X:Y[:OPTIONS].

X is the x coordinate of the overlayed video on the main video, Y is the y coordinate. X and Y are expressions containing the following parameters:

main_w, main_h
     main input width and height

W, H
     same as MAIN_W and MAIN_H

overlay_w, overlay_h
     overlay input width and height

w, h
     same as OVERLAY_W and OVERLAY_H

OPTIONS is an optional list of KEY=VALUE pairs, separated by ":".

The description of the accepted options follows.

rgb
     If set to 1, force the filter to accept inputs in the RGB color space. Default value is 0.

Be aware that frames are taken from each input video in timestamp order, hence, if their initial timestamps differ, it is a a good idea to pass the two inputs through a SETPTS=PTS-STARTPTS filter to have them begin in the same zero timestamp, as it does the example for the MOVIE filter.

Follow some examples:

     # draw the overlay at 10 pixels from the bottom right
     # corner of the main video.
     overlay=main_w-overlay_w-10:main_h-overlay_h-10

     # insert a transparent PNG logo in the bottom left corner of the input
     ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output

     # insert 2 different transparent PNG logos (second logo on bottom
     # right corner):
     ffmpeg -i input -i logo1 -i logo2 -filter_complex
     'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output

     # add a transparent color layer on top of the main video,
     # WxH specifies the size of the main input to the overlay filter
     color=red.3:WxH [over]; [in][over] overlay [out]

     # play an original video and a filtered version (here with the deshake filter)
     # side by side
     ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'

     # the previous example is the same as:
     ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'

You can chain together more overlays but the efficiency of such approach is yet to be tested.

pad
===

Add paddings to the input image, and places the original input at the given coordinates X, Y.

It accepts the following parameters: WIDTH:HEIGHT:X:Y:COLOR.

The parameters WIDTH, HEIGHT, X, and Y are expressions containing the following constants:

in_w, in_h
     the input video width and height

iw, ih
     same as IN_W and IN_H

out_w, out_h
     the output width and height, that is the size of the padded area as specified by the WIDTH and HEIGHT expressions

ow, oh
     same as OUT_W and OUT_H

x, y
     x and y offsets as specified by the X and Y expressions, or NAN if not yet specified

a
     same as IW / IH

sar
     input sample aspect ratio

dar
     input display aspect ratio, it is the same as (IW / IH) * SAR

hsub, vsub
     horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" HSUB is 2 and VSUB is 1.

Follows the description of the accepted parameters.

width, height

     Specify the size of the output image with the paddings added. If the value for WIDTH or HEIGHT is 0, the corresponding input size is used for the output.

     The WIDTH expression can reference the value set by the HEIGHT expression, and vice versa.

     The default value of WIDTH and HEIGHT is 0.

x, y

     Specify the offsets where to place the input image in the padded area with respect to the top/left border of the output image.

     The X expression can reference the value set by the Y expression, and vice versa.

     The default value of X and Y is 0.

color

     Specify the color of the padded area, it can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence.

     The default value of COLOR is "black".

Examples
--------

  * Add paddings with color "violet" to the input video. Output video size is 640x480, the top-left corner of the input video is placed at column 0, row 40:

          pad=640:480:0:40:violet

  * Pad the input to get an output with dimensions increased by 3/2, and put the input video at the center of the padded area:

          pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"

  * Pad the input to get a squared output with size equal to the maximum value between the input width and height, and put the input video at the center of the padded area:

          pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"

  * Pad the input to get a final w/h ratio of 16:9:

          pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"

  * In case of anamorphic video, in order to set the output display aspect correctly, it is necessary to use SAR in the expression, according to the relation:

          (ih * X / ih) * sar = output_dar
          X = output_dar / sar

     Thus the previous example needs to be modified to:

          pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"

  * Double output size and put the input video in the bottom-right corner of the output padded area:

          pad="2*iw:2*ih:ow-iw:oh-ih"

pixdesctest
===========

Pixel format descriptor test filter, mainly useful for internal testing. The output video should be equal to the input video.

For example:

     format=monow, pixdesctest

can be used to test the monowhite pixel format descriptor definition.

removelogo
==========

Suppress a TV station logo, using an image file to determine which pixels comprise the logo. It works by filling in the pixels that comprise the logo with neighboring pixels.

This filter requires one argument which specifies the filter bitmap file, which can be any image format supported by libavformat. The width and height of the image file must match those of the video stream being processed.

Pixels in the provided bitmap image with a value of zero are not considered part of the logo, non-zero pixels are considered part of the logo. If you use white (255) for the logo and black (0) for the rest, you will be safe. For making the filter bitmap, it is recommended to take a screen capture of a black frame with the logo visible, and then using a threshold filter followed by the erode filter once or twice.

If needed, little splotches can be fixed manually. Remember that if logo pixels are not covered, the filter quality will be much reduced. Marking too many pixels as part of the logo does not hurt as much, but it will increase the amount of blurring needed to cover over the image and will destroy more information than necessary, and extra pixels will slow things down on a large logo.

scale
=====

Scale (resize) the input video to WIDTH:HEIGHT[:INTERL={1|-1}] and/or convert the image format.

The scale filter forces the output display aspect ratio to be the same of the input, by changing the output sample aspect ratio.

The parameters WIDTH and HEIGHT are expressions containing the following constants:

in_w, in_h
     the input width and height

iw, ih
     same as IN_W and IN_H

out_w, out_h
     the output (cropped) width and height

ow, oh
     same as OUT_W and OUT_H

a
     same as IW / IH

sar
     input sample aspect ratio

dar
     input display aspect ratio, it is the same as (IW / IH) * SAR

hsub, vsub
     horizontal and vertical chroma subsample values. For example for the pixel format "yuv422p" HSUB is 2 and VSUB is 1.

If the input image format is different from the format requested by the next filter, the scale filter will convert the input to the requested format.

If the value for WIDTH or HEIGHT is 0, the respective input size is used for the output.

If the value for WIDTH or HEIGHT is -1, the scale filter will use, for the respective output size, a value that maintains the aspect ratio of the input image.

The default value of WIDTH and HEIGHT is 0.

Valid values for the optional parameter INTERL are:

1
     force interlaced aware scaling

-1
     select interlaced aware scaling depending on whether the source frames are flagged as interlaced or not

Unless INTERL is set to one of the above options, interlaced scaling will not be used.

Some examples follow:

     # scale the input video to a size of 200x100.
     scale=200:100

     # scale the input to 2x
     scale=2*iw:2*ih
     # the above is the same as
     scale=2*in_w:2*in_h

     # scale the input to 2x with forced interlaced scaling
     scale=2*iw:2*ih:interl=1

     # scale the input to half size
     scale=iw/2:ih/2

     # increase the width, and set the height to the same size
     scale=3/2*iw:ow

     # seek for Greek harmony
     scale=iw:1/PHI*iw
     scale=ih*PHI:ih

     # increase the height, and set the width to 3/2 of the height
     scale=3/2*oh:3/5*ih

     # increase the size, but make the size a multiple of the chroma
     scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"

     # increase the width to a maximum of 500 pixels, keep the same input aspect ratio
     scale='min(500\, iw*3/2):-1'

select
======

Select frames to pass in output.

It accepts in input an expression, which is evaluated for each input frame. If the expression is evaluated to a non-zero value, the frame is selected and passed to the output, otherwise it is discarded.

The expression can contain the following constants:

n
     the sequential number of the filtered frame, starting from 0

selected_n
     the sequential number of the selected frame, starting from 0

prev_selected_n
     the sequential number of the last selected frame, NAN if undefined

TB
     timebase of the input timestamps

pts
     the PTS (Presentation TimeStamp) of the filtered video frame, expressed in TB units, NAN if undefined

t
     the PTS (Presentation TimeStamp) of the filtered video frame, expressed in seconds, NAN if undefined

prev_pts
     the PTS of the previously filtered video frame, NAN if undefined

prev_selected_pts
     the PTS of the last previously filtered video frame, NAN if undefined

prev_selected_t
     the PTS of the last previously selected video frame, NAN if undefined

start_pts
     the PTS of the first video frame in the video, NAN if undefined

start_t
     the time of the first video frame in the video, NAN if undefined

pict_type
     the type of the filtered frame, can assume one of the following values:

     I

     P

     B

     S

     SI

     SP

     BI

interlace_type
     the frame interlace type, can assume one of the following values:

     PROGRESSIVE
          the frame is progressive (not interlaced)

     TOPFIRST
          the frame is top-field-first

     BOTTOMFIRST
          the frame is bottom-field-first

key
     1 if the filtered frame is a key-frame, 0 otherwise

pos
     the position in the file of the filtered frame, -1 if the information is not available (e.g. for synthetic video)

scene
     value between 0 and 1 to indicate a new scene; a low value reflects a low probability for the current frame to introduce a new scene, while a higher value means the current frame is more likely to be one (see the example below)

The default value of the select expression is "1".

Some examples follow:

     # select all frames in input
     select

     # the above is the same as:
     select=1

     # skip all frames:
     select=0

     # select only I-frames
     select='eq(pict_type\,I)'

     # select one frame every 100
     select='not(mod(n\,100))'

     # select only frames contained in the 10-20 time interval
     select='gte(t\,10)*lte(t\,20)'

     # select only I frames contained in the 10-20 time interval
     select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'

     # select frames with a minimum distance of 10 seconds
     select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'

Complete example to create a mosaic of the first scenes:

     ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png

Comparing SCENE against a value between 0.3 and 0.5 is generally a sane choice.

setdar, setsar
==============

The setdar filter sets the Display Aspect Ratio for the filter output video.

This is done by changing the specified Sample (aka Pixel) Aspect Ratio, according to the following equation:

     DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR

Keep in mind that the setdar filter does not modify the pixel dimensions of the video frame. Also the display aspect ratio set by this filter may be changed by later filters in the filterchain, e.g. in case of scaling or if another "setdar" or a "setsar" filter is applied.

The setsar filter sets the Sample (aka Pixel) Aspect Ratio for the filter output video.

Note that as a consequence of the application of this filter, the output display aspect ratio will change according to the equation above.

Keep in mind that the sample aspect ratio set by the setsar filter may be changed by later filters in the filterchain, e.g. if another "setsar" or a "setdar" filter is applied.

The setdar and setsar filters accept a string in the form NUM:DEN expressing an aspect ratio, or the following named options, expressed as a sequence of KEY=VALUE pairs, separated by ":".

max
     Set the maximum integer value to use for expressing numerator and denominator when reducing the expressed aspect ratio to a rational. Default value is 100.

r, ratio:
     Set the aspect ratio used by the filter.

     The parameter can be a floating point number string, an expression, or a string of the form NUM:DEN, where NUM and DEN are the numerator and denominator of the aspect ratio. If the parameter is not specified, it is assumed the value "0". In case the form "NUM:DEN" the : character should be escaped.

If the keys are omitted in the named options list, the specifed values are assumed to be RATIO and MAX in that order.

For example to change the display aspect ratio to 16:9, specify:

     setdar='16:9'

The example above is equivalent to:

     setdar=1.77777

To change the sample aspect ratio to 10:11, specify:

     setsar='10:11'

To set a display aspect ratio of 16:9, and specify a maximum integer value of 1000 in the aspect ratio reduction, use the command:

     setdar=ratio='16:9':max=1000

setfield
========

Force field for the output video frame.

The setfield filter marks the interlace type field for the output frames. It does not change the input frame, but only sets the corresponding property, which affects how the frame is treated by following filters (e.g. fieldorder or yadif).

It accepts a string parameter, which can assume the following values:

auto
     Keep the same field property.

bff
     Mark the frame as bottom-field-first.

tff
     Mark the frame as top-field-first.

prog
     Mark the frame as progressive.

showinfo
========

Show a line containing various information for each input video frame. The input video is not modified.

The shown line contains a sequence of key/value pairs of the form KEY:VALUE.

A description of each shown parameter follows:

n
     sequential number of the input frame, starting from 0

pts
     Presentation TimeStamp of the input frame, expressed as a number of time base units. The time base unit depends on the filter input pad.

pts_time
     Presentation TimeStamp of the input frame, expressed as a number of seconds

pos
     position of the frame in the input stream, -1 if this information in unavailable and/or meaningless (for example in case of synthetic video)

fmt
     pixel format name

sar
     sample aspect ratio of the input frame, expressed in the form NUM/DEN

s
     size of the input frame, expressed in the form WIDTHxHEIGHT

i
     interlaced mode ("P" for "progressive", "T" for top field first, "B" for bottom field first)

iskey
     1 if the frame is a key frame, 0 otherwise

type
     picture type of the input frame ("I" for an I-frame, "P" for a P-frame, "B" for a B-frame, "?" for unknown type). Check also the documentation of the AVPictureType enum and of the av_get_picture_type_char function defined in libavutil/avutil.h.

checksum
     Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame

plane_checksum
     Adler-32 checksum (printed in hexadecimal) of each plane of the input frame, expressed in the form "[C0 C1 C2 C3]"

slicify
=======

Pass the images of input video on to next video filter as multiple slices.

     ffmpeg -i in.avi -vf "slicify=32" out.avi

The filter accepts the slice height as parameter. If the parameter is not specified it will use the default value of 16.

Adding this in the beginning of filter chains should make filtering faster due to better use of the memory cache.

smartblur
=========

Blur the input video without impacting the outlines.

The filter accepts the following parameters: LUMA_RADIUS:LUMA_STRENGTH:LUMA_THRESHOLD[:CHROMA_RADIUS:CHROMA_STRENGTH:CHROMA_THRESHOLD]

Parameters prefixed by LUMA indicate that they work on the luminance of the pixels whereas parameters prefixed by CHROMA refer to the chrominance of the pixels.

If the chroma parameters are not set, the luma parameters are used for either the luminance and the chrominance of the pixels.

LUMA_RADIUS or CHROMA_RADIUS must be a float number in the range [0.1,5.0] that specifies the variance of the gaussian filter used to blur the image (slower if larger).

LUMA_STRENGTH or CHROMA_STRENGTH must be a float number in the range [-1.0,1.0] that configures the blurring. A value included in [0.0,1.0] will blur the image whereas a value included in [-1.0,0.0] will sharpen the image.

LUMA_THRESHOLD or CHROMA_THRESHOLD must be an integer in the range [-30,30] that is used as a coefficient to determine whether a pixel should be blurred or not. A value of 0 will filter all the image, a value included in [0,30] will filter flat areas and a value included in [-30,0] will filter edges.

split
=====

Split input video into several identical outputs.

The filter accepts a single parameter which specifies the number of outputs. If unspecified, it defaults to 2.

For example

     ffmpeg -i INPUT -filter_complex split=5 OUTPUT

will create 5 copies of the input video.

For example:

     [in] split [splitout1][splitout2];
     [splitout1] crop=100:100:0:0    [cropout];
     [splitout2] pad=200:200:100:100 [padout];

will create two separate outputs from the same input, one cropped and one padded.

super2xsai
==========

Scale the input by 2x and smooth using the Super2xSaI (Scale and Interpolate) pixel art scaling algorithm.

Useful for enlarging pixel art images without reducing sharpness.

swapuv
======

Swap U & V plane.

thumbnail
=========

Select the most representative frame in a given sequence of consecutive frames.

It accepts as argument the frames batch size to analyze (default N=100); in a set of N frames, the filter will pick one of them, and then handle the next batch of N frames until the end.

Since the filter keeps track of the whole frames sequence, a bigger N value will result in a higher memory usage, so a high value is not recommended.

The following example extract one picture each 50 frames:

     thumbnail=50

Complete example of a thumbnail creation with ffmpeg:

     ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png

tile
====

Tile several successive frames together.

It accepts as argument the tile size (i.e. the number of lines and columns) in the form "WxH".

For example, produce 8×8 PNG tiles of all keyframes (-skip_frame nokey) in a movie:

     ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png

The -vsync 0 is necessary to prevent ffmpeg from duplicating each output frame to accomodate the originally detected frame rate.

tinterlace
==========

Perform various types of temporal field interlacing.

Frames are counted starting from 1, so the first input frame is considered odd.

This filter accepts a single parameter specifying the mode. Available modes are:

merge, 0
     Move odd frames into the upper field, even into the lower field, generating a double height frame at half framerate.

drop_odd, 1
     Only output even frames, odd frames are dropped, generating a frame with unchanged height at half framerate.

drop_even, 2
     Only output odd frames, even frames are dropped, generating a frame with unchanged height at half framerate.

pad, 3
     Expand each frame to full height, but pad alternate lines with black, generating a frame with double height at the same input framerate.

interleave_top, 4
     Interleave the upper field from odd frames with the lower field from even frames, generating a frame with unchanged height at half framerate.

interleave_bottom, 5
     Interleave the lower field from odd frames with the upper field from even frames, generating a frame with unchanged height at half framerate.

interlacex2, 6
     Double frame rate with unchanged height. Frames are inserted each containing the second temporal field from the previous input frame and the first temporal field from the next input frame. This mode relies on the top_field_first flag. Useful for interlaced video displays with no field synchronisation.

Numeric values are deprecated but are accepted for backward compatibility reasons.

Default mode is merge.

transpose
=========

Transpose rows with columns in the input video and optionally flip it.

This filter accepts the following named parameters:

dir
     Specify the transposition direction. Can assume the following values:

     0, 4
          Rotate by 90 degrees counterclockwise and vertically flip (default), that is:

               L.R     L.l
               . . ->  . .
               l.r     R.r

     1, 5
          Rotate by 90 degrees clockwise, that is:

               L.R     l.L
               . . ->  . .
               l.r     r.R

     2, 6
          Rotate by 90 degrees counterclockwise, that is:

               L.R     R.r
               . . ->  . .
               l.r     L.l

     3, 7
          Rotate by 90 degrees clockwise and vertically flip, that is:

               L.R     r.R
               . . ->  . .
               l.r     l.L

     For values between 4-7, the transposition is only done if the input video geometry is portrait and not landscape. These values are deprecated, the passthrough option should be used instead.

passthrough
     Do not apply the transposition if the input geometry matches the one specified by the specified value. It accepts the following values:

     none
          Always apply transposition.

     portrait
          Preserve portrait geometry (when HEIGHT >= WIDTH).

     landscape
          Preserve landscape geometry (when WIDTH >= HEIGHT).

     Default value is none.

unsharp
=======

Sharpen or blur the input video.

It accepts the following parameters: LUMA_MSIZE_X:LUMA_MSIZE_Y:LUMA_AMOUNT:CHROMA_MSIZE_X:CHROMA_MSIZE_Y:CHROMA_AMOUNT

Negative values for the amount will blur the input video, while positive values will sharpen. All parameters are optional and default to the equivalent of the string '5:5:1.0:5:5:0.0'.

luma_msize_x
     Set the luma matrix horizontal size. It can be an integer between 3 and 13, default value is 5.

luma_msize_y
     Set the luma matrix vertical size. It can be an integer between 3 and 13, default value is 5.

luma_amount
     Set the luma effect strength. It can be a float number between -2.0 and 5.0, default value is 1.0.

chroma_msize_x
     Set the chroma matrix horizontal size. It can be an integer between 3 and 13, default value is 5.

chroma_msize_y
     Set the chroma matrix vertical size. It can be an integer between 3 and 13, default value is 5.

chroma_amount
     Set the chroma effect strength. It can be a float number between -2.0 and 5.0, default value is 0.0.

     # Strong luma sharpen effect parameters
     unsharp=7:7:2.5

     # Strong blur of both luma and chroma parameters
     unsharp=7:7:-2:7:7:-2

     # Use the default values with ffmpeg
     ffmpeg -i in.avi -vf "unsharp" out.mp4

vflip
=====

Flip the input video vertically.

     ffmpeg -i in.avi -vf "vflip" out.avi

yadif
=====

Deinterlace the input video ("yadif" means "yet another deinterlacing filter").

It accepts the optional parameters: MODE:PARITY:AUTO.

MODE specifies the interlacing mode to adopt, accepts one of the following values:

0
     output 1 frame for each frame

1
     output 1 frame for each field

2
     like 0 but skips spatial interlacing check

3
     like 1 but skips spatial interlacing check

Default value is 0.

PARITY specifies the picture field parity assumed for the input interlaced video, accepts one of the following values:

0
     assume top field first

1
     assume bottom field first

-1
     enable automatic detection

Default value is -1. If interlacing is unknown or decoder does not export this information, top field first will be assumed.

AUTO specifies if deinterlacer should trust the interlaced flag and only deinterlace frames marked as interlaced

0
     deinterlace all frames

1
     only deinterlace frames marked as interlaced

Default value is 0.

Video Sources
*************

Below is a description of the currently available video sources.

buffer
======

Buffer video frames, and make them available to the filter chain.

This source is mainly intended for a programmatic use, in particular through the interface defined in libavfilter/vsrc_buffer.h.

It accepts a list of options in the form of KEY=VALUE pairs separated by ":". A description of the accepted options follows.

video_size
     Specify the size (width and height) of the buffered video frames.

pix_fmt
     A string representing the pixel format of the buffered video frames. It may be a number corresponding to a pixel format, or a pixel format name.

time_base
     Specify the timebase assumed by the timestamps of the buffered frames.

time_base
     Specify the frame rate expected for the video stream.

pixel_aspect
     Specify the sample aspect ratio assumed by the video frames.

sws_param
     Specify the optional parameters to be used for the scale filter which is automatically inserted when an input change is detected in the input size or format.

For example:

     buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1

will instruct the source to accept video frames with size 320x240 and with format "yuv410p", assuming 1/24 as the timestamps timebase and square pixels (1:1 sample aspect ratio). Since the pixel format with name "yuv410p" corresponds to the number 6 (check the enum AVPixelFormat definition in libavutil/pixfmt.h), this example corresponds to:

     buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1

Alternatively, the options can be specified as a flat string, but this syntax is deprecated:

WIDTH:HEIGHT:PIX_FMT:TIME_BASE.NUM:TIME_BASE.DEN:PIXEL_ASPECT.NUM:PIXEL_ASPECT.DEN[:SWS_PARAM]

cellauto
========

Create a pattern generated by an elementary cellular automaton.

The initial state of the cellular automaton can be defined through the filename, and pattern options. If such options are not specified an initial state is created randomly.

At each new frame a new row in the video is filled with the result of the cellular automaton next generation. The behavior when the whole frame is filled is defined by the scroll option.

This source accepts a list of options in the form of KEY=VALUE pairs separated by ":". A description of the accepted options follows.

filename, f
     Read the initial cellular automaton state, i.e. the starting row, from the specified file. In the file, each non-whitespace character is considered an alive cell, a newline will terminate the row, and further characters in the file will be ignored.

pattern, p
     Read the initial cellular automaton state, i.e. the starting row, from the specified string.

     Each non-whitespace character in the string is considered an alive cell, a newline will terminate the row, and further characters in the string will be ignored.

rate, r
     Set the video rate, that is the number of frames generated per second. Default is 25.

random_fill_ratio, ratio
     Set the random fill ratio for the initial cellular automaton row. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI.

     This option is ignored when a file or a pattern is specified.

random_seed, seed
     Set the seed for filling randomly the initial row, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

rule
     Set the cellular automaton rule, it is a number ranging from 0 to 255. Default value is 110.

size, s
     Set the size of the output video.

     If filename or pattern is specified, the size is set by default to the width of the specified initial state row, and the height is set to WIDTH * PHI.

     If size is set, it must contain the width of the specified pattern string, and the specified pattern will be centered in the larger row.

     If a filename or a pattern string is not specified, the size value defaults to "320x518" (used for a randomly generated initial state).

scroll
     If set to 1, scroll the output upward when all the rows in the output have been already filled. If set to 0, the new generated row will be written over the top row just after the bottom row is filled. Defaults to 1.

start_full, full
     If set to 1, completely fill the output with generated rows before outputting the first frame. This is the default behavior, for disabling set the value to 0.

stitch
     If set to 1, stitch the left and right row edges together. This is the default behavior, for disabling set the value to 0.

Examples
--------

  * Read the initial state from pattern, and specify an output of size 200x400.

          cellauto=f=pattern:s=200x400

  * Generate a random initial row with a width of 200 cells, with a fill ratio of 2/3:

          cellauto=ratio=2/3:s=200x200

  * Create a pattern generated by rule 18 starting by a single alive cell centered on an initial row with width 100:

          cellauto=p=@:s=100x400:full=0:rule=18

  * Specify a more elaborated initial pattern:

          cellauto=p='@@ @ @@':s=100x400:full=0:rule=18

mandelbrot
==========

Generate a Mandelbrot set fractal, and progressively zoom towards the point specified with START_X and START_Y.

This source accepts a list of options in the form of KEY=VALUE pairs separated by ":". A description of the accepted options follows.

end_pts
     Set the terminal pts value. Default value is 400.

end_scale
     Set the terminal scale value. Must be a floating point value. Default value is 0.3.

inner
     Set the inner coloring mode, that is the algorithm used to draw the Mandelbrot fractal internal region.

     It shall assume one of the following values:

     black
          Set black mode.

     convergence
          Show time until convergence.

     mincol
          Set color based on point closest to the origin of the iterations.

     period
          Set period mode.

     Default value is MINCOL.

bailout
     Set the bailout value. Default value is 10.0.

maxiter
     Set the maximum of iterations performed by the rendering algorithm. Default value is 7189.

outer
     Set outer coloring mode. It shall assume one of following values:

     iteration_count
          Set iteration cound mode.

     normalized_iteration_count
          set normalized iteration count mode.

     Default value is NORMALIZED_ITERATION_COUNT.

rate, r
     Set frame rate, expressed as number of frames per second. Default value is "25".

size, s
     Set frame size. Default value is "640x480".

start_scale
     Set the initial scale value. Default value is 3.0.

start_x
     Set the initial x position. Must be a floating point value between -100 and 100. Default value is -0.743643887037158704752191506114774.

start_y
     Set the initial y position. Must be a floating point value between -100 and 100. Default value is -0.131825904205311970493132056385139.

mptestsrc
=========

Generate various test patterns, as generated by the MPlayer test filter.

The size of the generated video is fixed, and is 256x256. This source is useful in particular for testing encoding features.

This source accepts an optional sequence of KEY=VALUE pairs, separated by ":". The description of the accepted options follows.

rate, r
     Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format FRAME_RATE_NUM/FRAME_RATE_DEN, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25".

duration, d
     Set the video duration of the sourced video. The accepted syntax is:

          [-]HH:MM:SS[.m...]
          [-]S+[.m...]

     See also the function av_parse_time().

     If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

test, t

     Set the number or the name of the test to perform. Supported tests are:

     dc_luma

     dc_chroma

     freq_luma

     freq_chroma

     amp_luma

     amp_chroma

     cbp

     mv

     ring1

     ring2

     all

     Default value is "all", which will cycle through the list of all tests.

For example the following:

     testsrc=t=dc_luma

will generate a "dc_luma" test pattern.

frei0r_src
==========

Provide a frei0r source.

To enable compilation of this filter you need to install the frei0r header and configure FFmpeg with --enable-frei0r.

The source supports the syntax:

     SIZE:RATE:SRC_NAME[{=|:}PARAM1:PARAM2:...:PARAMN]

SIZE is the size of the video to generate, may be a string of the form WIDTHxHEIGHT or a frame size abbreviation. RATE is the rate of the video to generate, may be a string of the form NUM/DEN or a frame rate abbreviation. SRC_NAME is the name to the frei0r source to load. For more information regarding frei0r and how to set the parameters read the section frei0r in the description of the video filters.

For example, to generate a frei0r partik0l source with size 200x200 and frame rate 10 which is overlayed on the overlay filter main input:

     frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay

life
====

Generate a life pattern.

This source is based on a generalization of John Conway's life game.

The sourced input represents a life grid, each pixel represents a cell which can be in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent.

At each interaction the grid evolves according to the adopted rule, which specifies the number of neighbor alive cells which will make a cell stay alive or born. The rule option allows to specify the rule to adopt.

This source accepts a list of options in the form of KEY=VALUE pairs separated by ":". A description of the accepted options follows.

filename, f
     Set the file from which to read the initial grid state. In the file, each non-whitespace character is considered an alive cell, and newline is used to delimit the end of each row.

     If this option is not specified, the initial grid is generated randomly.

rate, r
     Set the video rate, that is the number of frames generated per second. Default is 25.

random_fill_ratio, ratio
     Set the random fill ratio for the initial random grid. It is a floating point number value ranging from 0 to 1, defaults to 1/PHI. It is ignored when a file is specified.

random_seed, seed
     Set the seed for filling the initial random grid, must be an integer included between 0 and UINT32_MAX. If not specified, or if explicitly set to -1, the filter will try to use a good random seed on a best effort basis.

rule
     Set the life rule.

     A rule can be specified with a code of the kind "SNS/BNB", where NS and NB are sequences of numbers in the range 0-8, NS specifies the number of alive neighbor cells which make a live cell stay alive, and NB the number of alive neighbor cells which make a dead cell to become alive (i.e. to "born"). "s" and "b" can be used in place of "S" and "B", respectively.

     Alternatively a rule can be specified by an 18-bits integer. The 9 high order bits are used to encode the next cell state if it is alive for each number of neighbor alive cells, the low order bits specify the rule for "borning" new cells. Higher order bits encode for an higher number of neighbor cells. For example the number 6153 = (12<<9)+9 specifies a stay alive rule of 12 and a born rule of 9, which corresponds to "S23/B03".

     Default value is "S23/B3", which is the original Conway's game of life rule, and will keep a cell alive if it has 2 or 3 neighbor alive cells, and will born a new cell if there are three alive cells around a dead cell.

size, s
     Set the size of the output video.

     If filename is specified, the size is set by default to the same size of the input file. If size is set, it must contain the size specified in the input file, and the initial grid defined in that file is centered in the larger resulting area.

     If a filename is not specified, the size value defaults to "320x240" (used for a randomly generated initial grid).

stitch
     If set to 1, stitch the left and right grid edges together, and the top and bottom edges also. Defaults to 1.

mold
     Set cell mold speed. If set, a dead cell will go from death_color to mold_color with a step of mold. mold can have a value from 0 to 255.

life_color
     Set the color of living (or new born) cells.

death_color
     Set the color of dead cells. If mold is set, this is the first color used to represent a dead cell.

mold_color
     Set mold color, for definitely dead and moldy cells.

Examples
--------

  * Read a grid from pattern, and center it on a grid of size 300x300 pixels:

          life=f=pattern:s=300x300

  * Generate a random grid of size 200x200, with a fill ratio of 2/3:

          life=ratio=2/3:s=200x200

  * Specify a custom rule for evolving a randomly generated grid:

          life=rule=S14/B34

  * Full example with slow death effect (mold) using ffplay:

          ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16

color, nullsrc, rgbtestsrc, smptebars, testsrc
==============================================

The color source provides an uniformly colored input.

The nullsrc source returns unprocessed video frames. It is mainly useful to be employed in analysis / debugging tools, or as the source for filters which ignore the input data.

The rgbtestsrc source generates an RGB test pattern useful for detecting RGB vs BGR issues. You should see a red, green and blue stripe from top to bottom.

The smptebars source generates a color bars pattern, based on the SMPTE Engineering Guideline EG 1-1990.

The testsrc source generates a test video pattern, showing a color pattern, a scrolling gradient and a timestamp. This is mainly intended for testing purposes.

These sources accept an optional sequence of KEY=VALUE pairs, separated by ":". The description of the accepted options follows.

color, c
     Specify the color of the source, only used in the color source. It can be the name of a color (case insensitive match) or a 0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The default value is "black".

size, s
     Specify the size of the sourced video, it may be a string of the form WIDTHxHEIGHT, or the name of a size abbreviation. The default value is "320x240".

rate, r
     Specify the frame rate of the sourced video, as the number of frames generated per second. It has to be a string in the format FRAME_RATE_NUM/FRAME_RATE_DEN, an integer number, a float number or a valid video frame rate abbreviation. The default value is "25".

sar
     Set the sample aspect ratio of the sourced video.

duration, d
     Set the video duration of the sourced video. The accepted syntax is:

          [-]HH[:MM[:SS[.m...]]]
          [-]S+[.m...]

     See also the function av_parse_time().

     If not specified, or the expressed duration is negative, the video is supposed to be generated forever.

decimals, n
     Set the number of decimals to show in the timestamp, only used in the testsrc source.

     The displayed timestamp value will correspond to the original timestamp value multiplied by the power of 10 of the specified value. Default value is 0.

For example the following:

     testsrc=duration=5.3:size=qcif:rate=10

will generate a video with a duration of 5.3 seconds, with size 176x144 and a frame rate of 10 frames per second.

The following graph description will generate a red source with an opacity of 0.2, with size "qcif" and a frame rate of 10 frames per second.

     color=c=red@0.2:s=qcif:r=10

If the input content is to be ignored, nullsrc can be used. The following command generates noise in the luminance plane by employing the mp=geq filter:

     nullsrc=s=256x256, mp=geq=random(1)*255:128:128

Video Sinks
***********

Below is a description of the currently available video sinks.

buffersink
==========

Buffer video frames, and make them available to the end of the filter graph.

This sink is mainly intended for a programmatic use, in particular through the interface defined in libavfilter/buffersink.h.

It does not require a string parameter in input, but you need to specify a pointer to a list of supported pixel formats terminated by -1 in the opaque parameter provided to avfilter_init_filter when initializing this sink.

nullsink
========

Null video sink, do absolutely nothing with the input video. It is mainly useful as a template and to be employed in analysis / debugging tools.

Multimedia Filters
******************

Below is a description of the currently available multimedia filters.

asendcmd, sendcmd
=================

Send commands to filters in the filtergraph.

These filters read commands to be sent to other filters in the filtergraph.

asendcmd must be inserted between two audio filters, sendcmd must be inserted between two video filters, but apart from that they act the same way.

The specification of commands can be provided in the filter arguments with the COMMANDS option, or in a file specified by the FILENAME option.

These filters accept the following options:

commands, c
     Set the commands to be read and sent to the other filters.

filename, f
     Set the filename of the commands to be read and sent to the other filters.

Commands syntax
---------------

A commands description consists of a sequence of interval specifications, comprising a list of commands to be executed when a particular event related to that interval occurs. The occurring event is typically the current frame time entering or leaving a given time interval.

An interval is specified by the following syntax:

     START[-END] COMMANDS;

The time interval is specified by the START and END times. END is optional and defaults to the maximum time.

The current frame time is considered within the specified interval if it is included in the interval [START, END), that is when the time is greater or equal to START and is lesser than END.

COMMANDS consists of a sequence of one or more command specifications, separated by ",", relating to that interval.  The syntax of a command specification is given by:

     [FLAGS] TARGET COMMAND ARG

FLAGS is optional and specifies the type of events relating to the time interval which enable sending the specified command, and must be a non-null sequence of identifier flags separated by "+" or "|" and enclosed between "[" and "]".

The following flags are recognized:

enter
     The command is sent when the current frame timestamp enters the specified interval. In other words, the command is sent when the previous frame timestamp was not in the given interval, and the current is.

leave
     The command is sent when the current frame timestamp leaves the specified interval. In other words, the command is sent when the previous frame timestamp was in the given interval, and the current is not.

If FLAGS is not specified, a default value of [enter] is assumed.

TARGET specifies the target of the command, usually the name of the filter class or a specific filter instance name.

COMMAND specifies the name of the command for the target filter.

ARG is optional and specifies the optional list of argument for the given COMMAND.

Between one interval specification and another, whitespaces, or sequences of characters starting with # until the end of line, are ignored and can be used to annotate comments.

A simplified BNF description of the commands specification syntax follows:

     COMMAND_FLAG  ::= "enter" | "leave"
     COMMAND_FLAGS ::= COMMAND_FLAG [(+|"|")COMMAND_FLAG]
     COMMAND       ::= ["[" COMMAND_FLAGS "]"] TARGET COMMAND [ARG]
     COMMANDS      ::= COMMAND [,COMMANDS]
     INTERVAL      ::= START[-END] COMMANDS
     INTERVALS     ::= INTERVAL[;INTERVALS]

Examples
--------

  * Specify audio tempo change at second 4:

          asendcmd=c='4.0 atempo tempo 1.5',atempo

  * Specify a list of drawtext and hue commands in a file.

          # show text in the interval 5-10
          5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
                   [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';

          # desaturate the image in the interval 15-20
          15.0-20.0 [enter] hue reinit s=0,
                    [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
                    [leave] hue reinit s=1,
                    [leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';

          # apply an exponential saturation fade-out effect, starting from time 25
          25 [enter] hue s=exp(t-25)

     A filtergraph allowing to read and process the above command list stored in a file test.cmd, can be specified with:

          sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue

asetpts, setpts
===============

Change the PTS (presentation timestamp) of the input frames.

asetpts works on audio frames, setpts on video frames.

Accept in input an expression evaluated through the eval API, which can contain the following constants:

FRAME_RATE
     frame rate, only defined for constant frame-rate video

PTS
     the presentation timestamp in input

N
     the count of the input frame, starting from 0.

NB_CONSUMED_SAMPLES
     the number of consumed samples, not including the current frame (only audio)

NB_SAMPLES
     the number of samples in the current frame (only audio)

SAMPLE_RATE
     audio sample rate

STARTPTS
     the PTS of the first frame

STARTT
     the time in seconds of the first frame

INTERLACED
     tell if the current frame is interlaced

T
     the time in seconds of the current frame

TB
     the time base

POS
     original position in the file of the frame, or undefined if undefined for the current frame

PREV_INPTS
     previous input PTS

PREV_INT
     previous input time in seconds

PREV_OUTPTS
     previous output PTS

PREV_OUTT
     previous output time in seconds

Examples
--------

  * Start counting PTS from zero

          setpts=PTS-STARTPTS

  * Apply fast motion effect:

          setpts=0.5*PTS

  * Apply slow motion effect:

          setpts=2.0*PTS

  * Set fixed rate of 25 frames per second:

          setpts=N/(25*TB)

  * Set fixed rate 25 fps with some jitter:

          setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'

  * Apply an offset of 10 seconds to the input PTS:

          setpts=PTS+10/TB

ebur128
=======

EBU R128 scanner filter. This filter takes an audio stream as input and outputs it unchanged. By default, it logs a message at a frequency of 10Hz with the Momentary loudness (identified by M), Short-term loudness (S), Integrated loudness (I) and Loudness Range (LRA).

The filter also has a video output (see the VIDEO option) with a real time graph to observe the loudness evolution. The graphic contains the logged message mentioned above, so it is not printed anymore when this option is set, unless the verbose logging is set. The main graphing area contains the short-term loudness (3 seconds of analysis), and the gauge on the right is for the momentary loudness (400 milliseconds).

More information about the Loudness Recommendation EBU R128 on http://tech.ebu.ch/loudness.

The filter accepts the following named parameters:

video
     Activate the video output. The audio stream is passed unchanged whether this option is set or no. The video stream will be the first output stream if activated. Default is 0.

size
     Set the video size. This option is for video only. Default and minimum resolution is 640x480.

meter
     Set the EBU scale meter. Default is 9. Common values are 9 and 18, respectively for EBU scale meter +9 and EBU scale meter +18. Any other integer value between this range is allowed.

Example of real-time graph using ffplay, with a EBU scale meter +18:

     ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"

Run an analysis with ffmpeg:

     ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -

settb, asettb
=============

Set the timebase to use for the output frames timestamps. It is mainly useful for testing timebase configuration.

It accepts in input an arithmetic expression representing a rational. The expression can contain the constants "AVTB" (the default timebase), "intb" (the input timebase) and "sr" (the sample rate, audio only).

The default value for the input is "intb".

Examples
--------

  * Set the timebase to 1/25:

          settb=1/25

  * Set the timebase to 1/10:

          settb=0.1

  * Set the timebase to 1001/1000:

          settb=1+0.001

  * Set the timebase to 2*intb:

          settb=2*intb

  * Set the default timebase value:

          settb=AVTB

concat
======

Concatenate audio and video streams, joining them together one after the other.

The filter works on segments of synchronized video and audio streams. All segments must have the same number of streams of each type, and that will also be the number of streams at output.

The filter accepts the following named parameters:

n
     Set the number of segments. Default is 2.

v
     Set the number of output video streams, that is also the number of video streams in each segment. Default is 1.

a
     Set the number of output audio streams, that is also the number of video streams in each segment. Default is 0.

The filter has V+A outputs: first V video outputs, then A audio outputs.

There are N×(V+A) inputs: first the inputs for the first segment, in the same order as the outputs, then the inputs for the second segment, etc.

Related streams do not always have exactly the same duration, for various reasons including codec frame size or sloppy authoring. For that reason, related synchronized streams (e.g. a video and its audio track) should be concatenated at once. The concat filter will use the duration of the longest stream in each segment (except the last one), and if necessary pad shorter audio streams with silence.

For this filter to work correctly, all segments must start at timestamp 0.

All corresponding streams must have the same parameters in all segments; the filtering system will automatically select a common pixel format for video streams, and a common sample format, sample rate and channel layout for audio streams, but other settings, such as resolution, must be converted explicitly by the user.

Different frame rates are acceptable but will result in variable frame rate at output; be sure to configure the output file to handle it.

Examples:

  * Concatenate an opening, an episode and an ending, all in bilingual version (video in stream 0, audio in streams 1 and 2):

          ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
            '[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
             concat=n=3:v=1:a=2 [v] [a1] [a2]' \
            -map '[v]' -map '[a1]' -map '[a2]' output.mkv

  * Concatenate two parts, handling audio and video separately, using the (a)movie sources, and adjusting the resolution:

          movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
          movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
          [v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]

     Note that a desync will happen at the stitch if the audio and video streams do not have exactly the same duration in the first file.

showspectrum
============

Convert input audio to a video output, representing the audio frequency spectrum.

The filter accepts the following named parameters:

size, s
     Specify the video size for the output. Default value is 640x480.

The usage is very similar to the showwaves filter; see the examples in that section.

showwaves
=========

Convert input audio to a video output, representing the samples waves.

The filter accepts the following named parameters:

n
     Set the number of samples which are printed on the same column. A larger value will decrease the frame rate. Must be a positive integer. This option can be set only if the value for RATE is not explicitly specified.

rate, r
     Set the (approximate) output frame rate. This is done by setting the option N. Default value is "25".

size, s
     Specify the video size for the output. Default value is "600x240".

Some examples follow.

  * Output the input file audio and the corresponding video representation at the same time:

          amovie=a.mp3,asplit[out0],showwaves[out1]

  * Create a synthetic signal and show it with showwaves, forcing a framerate of 30 frames per second:

          aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]

Multimedia Sources
******************

Below is a description of the currently available multimedia sources.

amovie
======

This is the same as src_movie source, except it selects an audio stream by default.

movie
=====

Read audio and/or video stream(s) from a movie container.

It accepts the syntax: MOVIE_NAME[:OPTIONS] where MOVIE_NAME is the name of the resource to read (not necessarily a file but also a device or a stream accessed through some protocol), and OPTIONS is an optional sequence of KEY=VALUE pairs, separated by ":".

The description of the accepted options follows.

format_name, f
     Specifies the format assumed for the movie to read, and can be either the name of a container or an input device. If not specified the format is guessed from MOVIE_NAME or by probing.

seek_point, sp
     Specifies the seek point in seconds, the frames will be output starting from this seek point, the parameter is evaluated with av_strtod so the numerical value may be suffixed by an IS postfix. Default value is "0".

streams, s
     Specifies the streams to read. Several streams can be specified, separated by "+". The source will then have as many outputs, in the same order. The syntax is explained in the Stream specifiers chapter. Two special names, "dv" and "da" specify respectively the default (best suited) video and audio stream. Default is "dv", or "da" if the filter is called as "amovie".

stream_index, si
     Specifies the index of the video stream to read. If the value is -1, the best suited video stream will be automatically selected. Default value is "-1". Deprecated. If the filter is called "amovie", it will select audio instead of video.

loop
     Specifies how many times to read the stream in sequence. If the value is less than 1, the stream will be read again and again. Default value is "1".

     Note that when the movie is looped the source timestamps are not changed, so it will generate non monotonically increasing timestamps.

This filter allows to overlay a second video on top of main input of a filtergraph as shown in this graph:

     input -----------> deltapts0 --> overlay --> output
                                         ^
                                         |
     movie --> scale--> deltapts1 -------+

Some examples follow.

  * Skip 3.2 seconds from the start of the avi file in.avi, and overlay it on top of the input labelled as "in":

          movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
          [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]

  * Read from a video4linux2 device, and overlay it on top of the input labelled as "in":

          movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
          [in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]

  * Read the first video stream and the audio stream with id 0x81 from dvd.vob; the video is connected to the pad named "video" and the audio is connected to the pad named "audio":

          movie=dvd.vob:s=v:0+#0x81 [video] [audio]