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 avconv and -vf in avplay, and by the avfilter_graph_parse()/avfilter_graph_parse2() function defined in libavfilter/avfilter.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. It may have one of the two allowed forms:

  * A ':'-separated list of KEY=VALUE pairs.

  * A ':'-separated list of VALUE. In this case, the keys are assumed to be the option names in the order they are declared. E.g. the fade filter declares three options in this order -- type, start_frame and nb_frames. Then the parameter list IN:0:30 means that the value IN is assigned to the option type, 0 to start_frame and 30 to nb_frames.

If the option value itself is a list of items (e.g. the format filter takes a list of pixel formats), the items in the list are usually separated by '|'.

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           ::= [LINKLABELS] NAME ["=" FILTER_ARGUMENTS] [LINKLABELS]
     FILTERCHAIN      ::= FILTER [,FILTERCHAIN]
     FILTERGRAPH      ::= [sws_flags=FLAGS;] FILTERCHAIN [;FILTERGRAPH]

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

When you configure your Libav 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.

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 '|'-separated list of requested sample formats.

sample_rates
     A '|'-separated list of requested sample rates.

channel_layouts
     A '|'-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

amix
====

Mixes multiple audio inputs into a single output.

For example

     avconv -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.

asetpts
=======

Change the PTS (presentation timestamp) of the input audio frames.

This filter accepts the following options:

expr
     The expression which is evaluated for each frame to construct its timestamp.

The expression is evaluated through the eval API and can contain the following constants:

PTS
     the presentation timestamp in input

PI
     Greek PI

PHI
     golden ratio

E
     Euler number

N
     Number of the audio samples pass through the filter so far, starting at 0.

S
     Number of the audio samples in the current frame.

SR
     Audio sample rate.

STARTPTS
     the PTS of the first frame

PREV_INPTS
     previous input PTS

PREV_OUTPTS
     previous output PTS

RTCTIME
     wallclock (RTC) time in microseconds

RTCSTART
     wallclock (RTC) time at the start of the movie in microseconds

Some examples follow:

     # start counting PTS from zero
     asetpts=expr=PTS-STARTPTS

     #generate timestamps by counting samples
     asetpts=expr=N/SR/TB

     # generate timestamps from a "live source" and rebase onto the current timebase
     asetpts='(RTCTIME - RTCSTART) / (TB * 1000000)"

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, in time base units; the time base depends on the filter input pad, and is usually 1/SAMPLE_RATE.

pts_time
     presentation timestamp of the input frame in seconds

fmt
     sample format

chlayout
     channel layout

rate
     sample rate for the audio frame

nb_samples
     number of samples (per channel) in the frame

checksum
     Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio the data is treated as if all the planes were concatenated.

plane_checksums
     A list of Adler-32 checksums for each data plane.

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

     avconv -i INPUT -filter_complex asplit=5 OUTPUT

will create 5 copies of the input audio.

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. The time base is 1 / sample rate. 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 or to trim any samples with a negative pts due to encoder delay.

atrim
=====

Trim the input so that the output contains one continuous subpart of the input.

This filter accepts the following options:

start
     Timestamp (in seconds) of the start of the kept section. I.e. the audio sample with the timestamp START will be the first sample in the output.

end
     Timestamp (in seconds) of the first audio sample that will be dropped. I.e. the audio sample immediately preceding the one with the timestamp END will be the last sample in the output.

start_pts
     Same as START, except this option sets the start timestamp in samples instead of seconds.

end_pts
     Same as END, except this option sets the end timestamp in samples instead of seconds.

duration
     Maximum duration of the output in seconds.

start_sample
     Number of the first sample that should be passed to output.

end_sample
     Number of the first sample that should be dropped.

Note that the first two sets of the start/end options and the duration option look at the frame timestamp, while the _sample options simply count the samples that pass through the filter. So start/end_pts and start/end_sample will give different results when the timestamps are wrong, inexact or do not start at zero. Also note that this filter does not modify the timestamps. If you wish that the output timestamps start at zero, insert the asetpts filter after the atrim filter.

If multiple start or end options are set, this filter tries to be greedy and keep all samples that match at least one of the specified constraints. To keep only the part that matches all the constraints at once, chain multiple atrim filters.

The defaults are such that all the input is kept. So it is possible to set e.g. just the end values to keep everything before the specified time.

Examples:

  * drop everything except the second minute of input

          avconv -i INPUT -af atrim=60:120

  * keep only the first 1000 samples

          avconv -i INPUT -af atrim=end_sample=1000

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

     avconv -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

     avconv -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 '|'-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

     avconv -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

     avconv -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 '|'-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)

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

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

     avconv -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, it is inserted automatically by libavfilter whenever conversion is needed. Use the AFORMAT filter to force a specific conversion.

volume
======

Adjust the input audio volume.

The filter accepts the following named parameters:

volume
     Expresses how the audio volume will be increased or decreased.

     Output values are clipped to the maximum value.

     The output audio volume is given by the relation:

          OUTPUT_VOLUME = VOLUME * INPUT_VOLUME

     Default value for VOLUME is 1.0.

precision
     Mathematical precision.

     This determines which input sample formats will be allowed, which affects the precision of the volume scaling.

     fixed
          8-bit fixed-point; limits input sample format to U8, S16, and S32.

     float
          32-bit floating-point; limits input sample format to FLT. (default)

     double
          64-bit floating-point; limits input sample format to DBL.

Examples
--------

  * Halve the input audio volume:

          volume=volume=0.5
          volume=volume=1/2
          volume=volume=-6.0206dB

  * Increase input audio power by 6 decibels using fixed-point precision:

          volume=volume=6dB:precision=fixed

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

Below is a description of the currently available audio sources.

anullsrc
========

Null audio source, never return audio frames. It is mainly useful as a template and to be employed in analysis / debugging tools.

It accepts as optional parameter a string of the form SAMPLE_RATE:CHANNEL_LAYOUT.

SAMPLE_RATE specify the sample rate, and defaults to 44100.

CHANNEL_LAYOUT specify the channel layout, and can be either an integer or a string representing a channel layout. The default value of CHANNEL_LAYOUT is 3, which corresponds to CH_LAYOUT_STEREO.

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

Follow some examples:

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

     # same as
     anullsrc=48000: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.

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

Below is a description of the currently available audio sinks.

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 Libav 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.

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 following options:

amount
     The percentage of the pixels that have to be below the threshold, defaults to 98.

threshold
     Threshold below which a pixel value is considered black, defaults to 32.

boxblur
=======

Apply boxblur algorithm to the input video.

This filter accepts the following options:

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=luma_radius=2:luma_power=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=luma_radius=min(h\,w)/10:luma_power=1:chroma_radius=min(cw\,ch)/10:chroma_power=1

copy
====

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

crop
====

Crop the input video to given dimensions.

This filter accepts the following options:

out_w
     Width of the output video.

out_h
     Height of the output video.

x
     Horizontal position, in the input video, of the left edge of the output video.

y
     Vertical position, in the input video, of the top edge of the output video.

The parameters are expressions containing the following constants:

E, PI, PHI
     the corresponding mathematical approximated values for e (euler number), pi (greek PI), PHI (golden ratio)

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

n
     the number of input frame, starting from 0

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=out_w=100:out_h=100

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

     # crop the input video central square
     crop=out_w=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=out_w=in_w-100:out_h=in_h-100:x=100:y=100

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

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

     # crop height for getting Greek harmony
     "crop=out_w=in_w:out_h=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=out_w=in_w/2:out_h=in_h/2:x=(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):y=(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.

This filter accepts the following options:

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.

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).

This filter accepts the following options:

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

drawbox
=======

Draw a colored box on the input image.

This filter accepts the following options:

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=x=10:y=20:width=200:height=60:color=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 Libav with --enable-libfreetype.

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

The description of the accepted parameters follows.

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

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 offsets where text will be drawn within the video frame. Relative to the top/left border of the output image. They accept expressions similar to the overlay filter:

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

     main_w, main_h
          main input width and height

     W, H
          same as MAIN_W and MAIN_H

     text_w, text_h
          rendered text width and height

     w, h
          same as TEXT_W and TEXT_H

     n
          the number of frames processed, starting from 0

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

     The default value of X and Y is 0.

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

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".

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".

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.

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".

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".

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.

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

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

For example the command:

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

will draw "Test Text" with font FreeSerif, using the default values for the optional parameters.

The command:

     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"

will 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%.

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

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

fade
====

Apply fade-in/out effect to input video.

This filter accepts the following options:

type
     The effect type -- can be either "in" for fade-in, or "out" for a fade-out effect.

start_frame
     The number of the start frame for starting to apply the fade effect.

nb_frames
     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.

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

     # fade in first 30 frames of video
     fade=type=in:nb_frames=30

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

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

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

fieldorder
==========

Transform the field order of the input video.

This filter accepts the following options:

order
     Output field order. Valid values are TFF for top field first or BFF for bottom 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:

     ./avconv -i in.vob -vf "fieldorder=order=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.

This filter accepts the following parameters:

pix_fmts
     A '|'-separated list of pixel format names, for example "pix_fmts=yuv420p|monow|rgb24".

Some examples follow:

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

     # convert the input video to any of the formats in the list
     format=pix_fmts=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.

frei0r
======

Apply a frei0r effect to the input video.

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

This filter accepts the following options:

filter_name
     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/.

filter_params
     A '|'-separated list of parameters to pass to 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=filter_name=distort0r:filter_params=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://piksel.org/frei0r

gradfun
=======

Fix the banding artifacts that are sometimes introduced into nearly flat regions by truncation to 8bit colordepth. 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.

This filter accepts the following options:

strength
     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 64, default value is 1.2, out-of-range values will be clipped to the valid range.

radius
     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=strength=1.2:radius=16

     # omitting radius
     gradfun=1.2

hflip
=====

Flip the input video horizontally.

For example to horizontally flip the input video with avconv:

     avconv -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
     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

interlace
=========

Simple interlacing filter from progressive contents. This interleaves upper (or lower) lines from odd frames with lower (or upper) lines from even frames, halving the frame rate and preserving image height.

        Original        Original             New Frame
        Frame 'j'      Frame 'j+1'             (tff)
       ==========      ===========       ==================
         Line 0  -------------------->    Frame 'j' Line 0
         Line 1          Line 1  ---->   Frame 'j+1' Line 1
         Line 2 --------------------->    Frame 'j' Line 2
         Line 3          Line 3  ---->   Frame 'j+1' Line 3
          ...             ...                   ...
     New Frame + 1 will be generated by Frame 'j+2' and Frame 'j+3' and so on

It accepts the following optional parameters:

scan
     determines whether the interlaced frame is taken from the even (tff - default) or odd (bff) lines of the progressive frame.

lowpass
     Enable (default) or disable the vertical lowpass filter to avoid twitter interlacing and reduce moire patterns.

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 the following options:

C0 (first  pixel component)

C1 (second pixel component)

C2 (third  pixel component)

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

R (red component)

G (green component)

B (blue component)

A (alpha component)

Y (Y/luminance component)

U (U/Cb component)

V (V/Cr component)

Each of them specifies the expression to use for computing the lookup table for the corresponding pixel component values.

The exact component associated to each of the C* options depends on the format in input.

The LUT filter requires either YUV or RGB pixel formats in input, LUTRGB requires RGB pixel formats in input, and LUTYUV requires YUV.

The expressions can contain the following constants and functions:

E, PI, PHI
     the corresponding mathematical approximated values for e (euler number), pi (greek PI), PHI (golden ratio)

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=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)

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.

This filter accepts the following parameters:

pix_fmts
     A '|'-separated list of pixel format names, for example "pix_fmts=yuv420p|monow|rgb24".

Some examples follow:

     # force libavfilter to use a format different from "yuv420p" for the
     # input to the vflip filter
     noformat=pix_fmts=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 Libav with --enable-libopencv.

This filter accepts the following parameters:

filter_name
     The name of the libopencv filter to apply.

filter_params
     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=filter_name=dilate:filter_params=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=dilate: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.

This filter accepts the following parameters:

x
     The horizontal position of the left edge of the overlaid video on the main video.

y
     The vertical position of the top edge of the overlaid video on the main video.

The parameters 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

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=x=main_w-overlay_w-10:y=main_h-overlay_h-10

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

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

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.

This filter accepts the following 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".

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

E, PI, PHI
     the corresponding mathematical approximated values for e (euler number), pi (greek PI), phi (golden ratio)

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
     input display aspect ratio, same as IW / IH

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

Some examples follow:

     # 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=width=640:height=480:x=0:y=40:color=violet

     # pad the input to get an output with dimensions increased bt 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"

     # 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.

scale
=====

Scale the input video and/or convert the image format.

This filter accepts the following options:

w
     Output video width.

h
     Output video height.

The parameters W and H are expressions containing the following constants:

E, PI, PHI
     the corresponding mathematical approximated values for e (euler number), pi (greek PI), phi (golden ratio)

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

dar, a
     input display aspect ratio, same as IW / IH

sar
     input sample aspect ratio

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 W or H is 0, the respective input size is used for the output.

If the value for W or H 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 W and H is 0.

Some examples follow:

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

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

     # scale the input to half size
     scale=w=iw/2:h=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=w=3/2*oh:h=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=w='min(500\, iw*3/2):h=-1'

select
======

Select frames to pass in output.

This filter accepts the following options:

expr
     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:

PI
     Greek PI

PHI
     golden ratio

E
     Euler number

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

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=expr=1

     # skip all frames:
     select=expr=0

     # select only I-frames
     select='expr=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)'

setdar
======

Set 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 this 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.

This filter accepts the following options:

dar
     Output display aspect ratio, as a rational or a decimal number.

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

     setdar=dar=16/9
     # the above is equivalent to
     setdar=dar=1.77777

See also the setsar filter documentation.

setpts
======

Change the PTS (presentation timestamp) of the input video frames.

This filter accepts the following options:

expr
     The expression which is evaluated for each frame to construct its timestamp.

The expression is evaluated through the eval API and can contain the following constants:

PTS
     the presentation timestamp in input

PI
     Greek PI

PHI
     golden ratio

E
     Euler number

N
     the count of the input frame, starting from 0.

STARTPTS
     the PTS of the first video frame

INTERLACED
     tell if the current frame is interlaced

PREV_INPTS
     previous input PTS

PREV_OUTPTS
     previous output PTS

RTCTIME
     wallclock (RTC) time in microseconds

RTCSTART
     wallclock (RTC) time at the start of the movie in microseconds

Some examples follow:

     # start counting PTS from zero
     setpts=expr=PTS-STARTPTS

     # fast motion
     setpts=expr=0.5*PTS

     # slow motion
     setpts=2.0*PTS

     # fixed rate 25 fps
     setpts=N/(25*TB)

     # fixed rate 25 fps with some jitter
     setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'

     # generate timestamps from a "live source" and rebase onto the current timebase
     setpts='(RTCTIME - RTCSTART) / (TB * 1000000)"

setsar
======

Set 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 following equation: DAR = HORIZONTAL_RESOLUTION / VERTICAL_RESOLUTION * SAR

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

This filter accepts the following options:

sar
     Output sample aspect ratio, as a rational or decimal number.

For example to change the sample aspect ratio to 10:11, specify:

     setsar=sar=10/11

settb
=====

Set the timebase to use for the output frames timestamps. It is mainly useful for testing timebase configuration.

This filter accepts the following options:

expr
     The expression which is evaluated into the output timebase.

The expression can contain the constants "PI", "E", "PHI", "AVTB" (the default timebase), and "intb" (the input timebase).

The default value for the input is "intb".

Follow some examples.

     # set the timebase to 1/25
     settb=expr=1/25

     # set the timebase to 1/10
     settb=expr=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

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 of all the planes of the input frame

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

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

     avconv -i INPUT -filter_complex split=5 OUTPUT

will create 5 copies of the input video.

transpose
=========

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

This filter accepts the following options:

dir
     The direction of the transpose.

The direction can assume the following values:

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

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

clock
     Rotate by 90 degrees clockwise, that is:

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

cclock
     Rotate by 90 degrees counterclockwise, that is:

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

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

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

trim
====

Trim the input so that the output contains one continuous subpart of the input.

This filter accepts the following options:

start
     Timestamp (in seconds) of the start of the kept section. I.e. the frame with the timestamp START will be the first frame in the output.

end
     Timestamp (in seconds) of the first frame that will be dropped. I.e. the frame immediately preceding the one with the timestamp END will be the last frame in the output.

start_pts
     Same as START, except this option sets the start timestamp in timebase units instead of seconds.

end_pts
     Same as END, except this option sets the end timestamp in timebase units instead of seconds.

duration
     Maximum duration of the output in seconds.

start_frame
     Number of the first frame that should be passed to output.

end_frame
     Number of the first frame that should be dropped.

Note that the first two sets of the start/end options and the duration option look at the frame timestamp, while the _frame variants simply count the frames that pass through the filter. Also note that this filter does not modify the timestamps. If you wish that the output timestamps start at zero, insert a setpts filter after the trim filter.

If multiple start or end options are set, this filter tries to be greedy and keep all the frames that match at least one of the specified constraints. To keep only the part that matches all the constraints at once, chain multiple trim filters.

The defaults are such that all the input is kept. So it is possible to set e.g. just the end values to keep everything before the specified time.

Examples:

  * drop everything except the second minute of input

          avconv -i INPUT -vf trim=60:120

  * keep only the first second

          avconv -i INPUT -vf trim=duration=1

unsharp
=======

Sharpen or blur the input video.

It accepts the following parameters:

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.

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

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'.

     # Strong luma sharpen effect parameters
     unsharp=luma_msize_x=7:luma_msize_y=7:luma_amount=2.5

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

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

vflip
=====

Flip the input video vertically.

     ./avconv -i in.avi -vf "vflip" out.avi

yadif
=====

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

This filter accepts the following options:

mode
     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
     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
     Whether 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.

This filter accepts the following parameters:

width
     Input video width.

height
     Input video height.

pix_fmt
     Name of the input video pixel format.

time_base
     The time base used for input timestamps.

sar
     Sample (pixel) aspect ratio of the input video.

For example:

     buffer=width=320:height=240:pix_fmt=yuv410p:time_base=1/24:sar=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).

color
=====

Provide an uniformly colored input.

It accepts the following parameters:

color
     Specify the color of the 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
     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".

framerate
     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".

For example 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, which will be overlayed over the source connected to the pad with identifier "in".

     "color=red@0.2:qcif:10 [color]; [in][color] overlay [out]"

movie
=====

Read a video stream from a movie container.

Note that this source is a hack that bypasses the standard input path. It can be useful in applications that do not support arbitrary filter graphs, but its use is discouraged in those that do. Specifically in avconv this filter should never be used, the -filter_complex option fully replaces it.

This filter accepts the following options:

filename
     The name of the resource to read (not necessarily a file but also a device or a stream accessed through some protocol).

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".

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".

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]

nullsrc
=======

Null video source, never return images. It is mainly useful as a template and to be employed in analysis / debugging tools.

It accepts as optional parameter a string of the form WIDTH:HEIGHT:TIMEBASE.

WIDTH and HEIGHT specify the size of the configured source. The default values of WIDTH and HEIGHT are respectively 352 and 288 (corresponding to the CIF size format).

TIMEBASE specifies an arithmetic expression representing a timebase. The expression can contain the constants "PI", "E", "PHI", "AVTB" (the default timebase), and defaults to the value "AVTB".

frei0r_src
==========

Provide a frei0r source.

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

This source accepts the following options:

size
     The size of the video to generate, may be a string of the form WIDTHxHEIGHT or a frame size abbreviation.

framerate
     Framerate of the generated video, may be a string of the form NUM/DEN or a frame rate abbreviation.

filter_name
     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.

filter_params
     A '|'-separated list of parameters to pass to the frei0r source.

Some examples follow:

     # generate a frei0r partik0l source with size 200x200 and framerate 10
     # which is overlayed on the overlay filter main input
     frei0r_src=size=200x200:framerate=10:filter_name=partik0l:filter_params=1234 [overlay]; [in][overlay] overlay

rgbtestsrc, testsrc
===================

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

The sources accept the following options:

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
     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.

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 framerate of 10 frames per second.

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 intended for a programmatic use through the interface defined in libavfilter/buffersink.h.

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.