PeerStreamer

@chapter Filtergraph description

@c man begin 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".

@section Filtergraph syntax

A filtergraph can be represented using a textual representation, which

is recognized by the @code{-vf} and @code{-af} options of the ff*

tools, and by the @code{av_parse_graph()} function defined in

@file{libavfilter/avfiltergraph}.

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:

[@var{in_link_1}]...[@var{in_link_N}]@var{filter_name}=@var{arguments}[@var{out_link_1}]...[@var{out_link_M}]

@var{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

"=@var{arguments}".

@var{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 @var{in_link_1}

... @var{in_link_N}, are associated to the filter input pads,

the following labels @var{out_link_1} ... @var{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:

@example

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

@end example

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.

Follows a BNF description for the filtergraph syntax:

@example

@var{NAME}             ::= sequence of alphanumeric characters and '_'

@var{LINKLABEL}        ::= "[" @var{NAME} "]"

@var{LINKLABELS}       ::= @var{LINKLABEL} [@var{LINKLABELS}]

@var{FILTER_ARGUMENTS} ::= sequence of chars (eventually quoted)

@var{FILTER}           ::= [@var{LINKNAMES}] @var{NAME} ["=" @var{ARGUMENTS}] [@var{LINKNAMES}]

@var{FILTERCHAIN}      ::= @var{FILTER} [,@var{FILTERCHAIN}]

@var{FILTERGRAPH}      ::= @var{FILTERCHAIN} [;@var{FILTERGRAPH}]

@end example

@c man end FILTERGRAPH DESCRIPTION

@chapter Audio Filters

@c man begin 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.

@section anull

Pass the audio source unchanged to the output.

@c man end AUDIO FILTERS

@chapter Audio Sources

@c man begin AUDIO SOURCES

Below is a description of the currently available audio sources.

@section 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

@var{sample_rate}:@var{channel_layout}.

@var{sample_rate} specify the sample rate, and defaults to 44100.

@var{channel_layout} specify the channel layout, and can be either an

integer or a string representing a channel layout. The default value

of @var{channel_layout} is 3, which corresponds to CH_LAYOUT_STEREO.

Check the channel_layout_map definition in

@file{libavcodec/audioconvert.c} for the mapping between strings and

channel layout values.

Follow some examples:

@example

#  set the sample rate to 48000 Hz and the channel layout to CH_LAYOUT_MONO.

anullsrc=48000:4

# same as

anullsrc=48000:mono

@end example

@c man end AUDIO SOURCES

@chapter Audio Sinks

@c man begin AUDIO SINKS

Below is a description of the currently available audio sinks.

@section 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.

@c man end AUDIO SINKS

@chapter Video Filters

@c man begin 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.

@section 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:

@example

blackframe[=@var{amount}:[@var{threshold}]]

@end example

@var{amount} is the percentage of the pixels that have to be below the

threshold, and defaults to 98.

@var{threshold} is the threshold below which a pixel value is

considered black, and defaults to 32.

@section copy

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

testing purposes.

@section crop

Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}.

The parameters are expressions containing the following constants:

@table @option

@item E, PI, PHI

the corresponding mathematical approximated values for e

(euler number), pi (greek PI), PHI (golden ratio)

@item x, y

the computed values for @var{x} and @var{y}. They are evaluated for

each new frame.

@item in_w, in_h

the input width and heigth

@item iw, ih

same as @var{in_w} and @var{in_h}

@item out_w, out_h

the output (cropped) width and heigth

@item ow, oh

same as @var{out_w} and @var{out_h}

@item n

the number of input frame, starting from 0

@item pos

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

@item t

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

@end table

The @var{out_w} and @var{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 @var{out_w} is "in_w", and the default value of

@var{out_h} is "in_h".

The expression for @var{out_w} may depend on the value of @var{out_h},

and the expression for @var{out_h} may depend on @var{out_w}, but they

cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are

evaluated after @var{out_w} and @var{out_h}.

The @var{x} and @var{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 @var{x} is "(in_w-out_w)/2", and the default

value for @var{y} is "(in_h-out_h)/2", which set the cropped area at

the center of the input image.

The expression for @var{x} may depend on @var{y}, and the expression

for @var{y} may depend on @var{x}.

Follow some examples:

@example

# 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)"

@end example

@section 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:

@example

cropdetect[=@var{limit}[:@var{round}[:@var{reset}]]]

@end example

@table @option

@item limit

Threshold, which can be optionally specified from nothing (0) to

everything (255), defaults to 24.

@item 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.

@item 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.

@end table

@section drawbox

Draw a colored box on the input image.

It accepts the syntax:

@example

drawbox=@var{x}:@var{y}:@var{width}:@var{height}:@var{color}

@end example

@table @option

@item x, y

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

@item width, height

Specify the width and height of the box, if 0 they are interpreted as

the input width and height. Default to 0.

@item 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.

@end table

Follow some examples:

@example

# 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"

@end example

@section 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

@code{--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 @var{key}=@var{value} pairs,

separated by ":".

The description of the accepted parameters follows.

@table @option

@item fontfile

The font file to be used for drawing text. Path must be included.

This parameter is mandatory.

@item 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

@var{textfile}.

@item 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 @var{text}.

If both text and textfile are specified, an error is thrown.

@item x, y

The offsets where text will be drawn within the video frame.

Relative to the top/left border of the output image.

The default value of @var{x} and @var{y} is 0.

@item fontsize

The font size to be used for drawing text.

The default value of @var{fontsize} is 16.

@item 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 @var{fontcolor} is "black".

@item 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 @var{boxcolor} is "white".

@item box

Used to draw a box around text using background color.

Value should be either 1 (enable) or 0 (disable).

The default value of @var{box} is 0.

@item 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".

@item 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 @var{shadowcolor} is "black".

@item 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:

@table @var

@item default

@item no_scale

@item no_hinting

@item render

@item no_bitmap

@item vertical_layout

@item force_autohint

@item crop_bitmap

@item pedantic

@item ignore_global_advance_width

@item no_recurse

@item ignore_transform

@item monochrome

@item linear_design

@item no_autohint

@item end table

@end table

Default value is "render".

For more information consult the documentation for the FT_LOAD_*

libfreetype flags.

@item tabsize

The size in number of spaces to use for rendering the tab.

Default value is 4.

@end table

For example the command:

@example

drawtext="fontfile=FreeSerif.ttf: text='Test Text': x=100: y=50: fontsize=24: fontcolor=yellow@@0.2: boxcolor=red@@0.2: box=1"

@end example

will draw 'Test Text' with font FreeSerif of size 24 at position

(100,50), text color is yellow, and draw a red box around text. 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:

@url{http://www.freetype.org/}.

@section fade

Apply fade-in/out effect to input video.

It accepts the parameters:

@var{type}:@var{start_frame}:@var{nb_frames}

@var{type} specifies if the effect type, can be either "in" for

fade-in, or "out" for a fade-out effect.

@var{start_frame} specifies the number of the start frame for starting

to apply the fade effect.

@var{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.

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

@example

# 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

@end example

@section 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.

@section 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:

@example

# 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

@end example

@anchor{frei0r}

@section 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:

@example

@var{filter_name}[@{:|=@}@var{param1}:@var{param2}:...:@var{paramN}]

@end example

@var{filter_name} is the name to the frei0r effect to load. If the

environment variable @env{FREI0R_PATH} is defined, the frei0r effect

is searched in each one of the directories specified by the colon

separated list in @env{FREIOR_PATH}, otherwise in the standard frei0r

paths, which are in this order: @file{HOME/.frei0r-1/lib/},

@file{/usr/local/lib/frei0r-1/}, @file{/usr/lib/frei0r-1/}.

@var{param1}, @var{param2}, ... , @var{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

@var{R}/@var{G}/@var{B}, @var{R}, @var{G}, and @var{B} being float

numbers from 0.0 to 1.0) or by an @code{av_parse_color()} color

description), a position (specified by the syntax @var{X}/@var{Y},

@var{X} and @var{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:

@example

# 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

@end example

For more information see:

@url{http://piksel.org/frei0r}

@section 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.

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

@var{strength}:@var{radius}

@var{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.

@var{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.

@example

# default parameters

gradfun=1.2:16

# omitting radius

gradfun=1.2

@end example

@section hflip

Flip the input video horizontally.

For example to horizontally flip the video in input with

@file{ffmpeg}:

@example

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

@end example

@section 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:

@var{luma_spatial}:@var{chroma_spatial}:@var{luma_tmp}:@var{chroma_tmp}

@table @option

@item luma_spatial

a non-negative float number which specifies spatial luma strength,

defaults to 4.0

@item chroma_spatial

a non-negative float number which specifies spatial chroma strength,

defaults to 3.0*@var{luma_spatial}/4.0

@item luma_tmp

a float number which specifies luma temporal strength, defaults to

6.0*@var{luma_spatial}/4.0

@item chroma_tmp

a float number which specifies chroma temporal strength, defaults to

@var{luma_tmp}*@var{chroma_spatial}/@var{luma_spatial}

@end table

@section 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:

@var{filter_name}[:=]@var{filter_params}

@var{filter_name} is the name of a supported MPlayer filter,

@var{filter_params} is a string containing the parameters accepted by

the named filter.

The list of the currently supported filters follows:

@table @var

@item 2xsai

@item blackframe

@item boxblur

@item cropdetect

@item decimate

@item delogo

@item denoise3d

@item detc

@item dint

@item divtc

@item down3dright

@item dsize

@item eq2

@item eq

@item field

@item fil

@item fixpts

@item framestep

@item fspp

@item geq

@item gradfun

@item harddup

@item hqdn3d

@item hue

@item il

@item ilpack

@item ivtc

@item kerndeint

@item mcdeint

@item mirror

@item noise

@item ow

@item palette

@item perspective

@item phase

@item pp7

@item pullup

@item qp

@item rectangle

@item remove_logo

@item rgbtest

@item rotate

@item sab

@item screenshot

@item smartblur

@item softpulldown

@item softskip

@item spp

@item swapuv

@item telecine

@item test

@item tile

@item tinterlace

@item unsharp

@item uspp

@item yuvcsp

@item yvu9

@end table

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:

@example

# remove a logo by interpolating the surrounding pixels

mp=delogo=200:200:80:20:1

# adjust gamma, brightness, contrast

mp=eq2=1.0:2:0.5

# tweak hue and saturation

mp=hue=100:-10

@end example

See also mplayer(1), @url{http://www.mplayerhq.hu/}.

@section 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:

@example

# 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

@end example

@section null

Pass the video source unchanged to the output.

@section 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: @var{filter_name}@{:=@}@var{filter_params}.

@var{filter_name} is the name of the libopencv filter to apply.

@var{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

informations:

@url{http://opencv.willowgarage.com/documentation/c/image_filtering.html}

Follows the list of supported libopencv filters.

@anchor{dilate}

@subsection dilate

Dilate an image by using a specific structuring element.

This filter corresponds to the libopencv function @code{cvDilate}.

It accepts the parameters: @var{struct_el}:@var{nb_iterations}.

@var{struct_el} represents a structuring element, and has the syntax:

@var{cols}x@var{rows}+@var{anchor_x}x@var{anchor_y}/@var{shape}

@var{cols} and @var{rows} represent the number of colums and rows of

the structuring element, @var{anchor_x} and @var{anchor_y} the anchor

point, and @var{shape} the shape for the structuring element, and

can be one of the values "rect", "cross", "ellipse", "custom".

If the value for @var{shape} is "custom", it must be followed by a

string of the form "=@var{filename}". The file with name

@var{filename} is assumed to represent a binary image, with each

printable character corresponding to a bright pixel. When a custom

@var{shape} is used, @var{cols} and @var{rows} are ignored, the number

or columns and rows of the read file are assumed instead.

The default value for @var{struct_el} is "3x3+0x0/rect".

@var{nb_iterations} specifies the number of times the transform is

applied to the image, and defaults to 1.

Follow some example:

@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

@end example

@subsection erode

Erode an image by using a specific structuring element.

This filter corresponds to the libopencv function @code{cvErode}.

The filter accepts the parameters: @var{struct_el}:@var{nb_iterations},

with the same meaning and use of those of the dilate filter

(@pxref{dilate}).

@subsection smooth

Smooth the input video.

The filter takes the following parameters:

@var{type}:@var{param1}:@var{param2}:@var{param3}:@var{param4}.

@var{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".

@var{param1}, @var{param2}, @var{param3}, and @var{param4} are

parameters whose meanings depend on smooth type. @var{param1} and

@var{param2} accept integer positive values or 0, @var{param3} and

@var{param4} accept float values.

The default value for @var{param1} is 3, the default value for the

other parameters is 0.

These parameters correspond to the parameters assigned to the

libopencv function @code{cvSmooth}.

@section 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: @var{x}:@var{y}.

@var{x} is the x coordinate of the overlayed video on the main video,

@var{y} is the y coordinate. The parameters are expressions containing

the following parameters:

@table @option

@item main_w, main_h

main input width and height

@item W, H

same as @var{main_w} and @var{main_h}

@item overlay_w, overlay_h

overlay input width and height

@item w, h

same as @var{overlay_w} and @var{overlay_h}

@end table

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 @var{setpts=PTS-STARTPTS} filter to

have them begin in the same zero timestamp, as it does the example for

the @var{movie} filter.

Follow some examples:

@example

# 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

movie=logo.png [logo];

[in][logo] overlay=10:main_h-overlay_h-10 [out]

# insert 2 different transparent PNG logos (second logo on bottom

# right corner):

movie=logo1.png [logo1];

movie=logo2.png [logo2];

[in][logo1]       overlay=10:H-h-10 [in+logo1];

[in+logo1][logo2] overlay=W-w-10:H-h-10 [out]

# 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]

@end example

You can chain togheter more overlays but the efficiency of such

approach is yet to be tested.

@section pad

Add paddings to the input image, and places the original input at the

given coordinates @var{x}, @var{y}.

It accepts the following parameters:

@var{width}:@var{height}:@var{x}:@var{y}:@var{color}.

Follows the description of the accepted parameters.

@table @option

@item width, height

Specify the size of the output image with the paddings added. If the

value for @var{width} or @var{height} is 0, the corresponding input size

is used for the output.

The default value of @var{width} and @var{height} is 0.

@item 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 default value of @var{x} and @var{y} is 0.

@item 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 @var{color} is "black".

@end table

For example:

@example

# 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

# row 0, column 40.

pad=640:480:0:40:violet

@end example

@section pixdesctest

Pixel format descriptor test filter, mainly useful for internal

testing. The output video should be equal to the input video.

For example:

@example

format=monow, pixdesctest

@end example

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

@section scale

Scale the input video to @var{width}:@var{height} and/or convert the image format.

For example the command:

@example

./ffmpeg -i in.avi -vf "scale=200:100" out.avi

@end example

will scale the input video to a size of 200x100.

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 @var{width} or @var{height} is 0, the respective input

size is used for the output.

If the value for @var{width} or @var{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 @var{width} and @var{height} is 0.

@anchor{setdar}

@section 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:

@math{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.

The filter accepts a parameter string which represents the wanted

display aspect ratio.

The parameter can be a floating point number string, or an expression

of the form @var{num}:@var{den}, where @var{num} and @var{den} are the

numerator and denominator of the aspect ratio.

If the parameter is not specified, it is assumed the value "0:1".

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

@example

setdar=16:9

# the above is equivalent to

setdar=1.77777

@end example

See also the "setsar" filter documentation (@pxref{setsar}).

@section setpts

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

Accept in input an expression evaluated through the eval API, which

can contain the following constants:

@table @option

@item PTS

the presentation timestamp in input

@item PI

Greek PI

@item PHI

golden ratio

@item E

Euler number

@item N

the count of the input frame, starting from 0.

@item STARTPTS

the PTS of the first video frame

@item INTERLACED

tell if the current frame is interlaced

@item POS

original position in the file of the frame, or undefined if undefined

for the current frame

@item PREV_INPTS

previous input PTS

@item PREV_OUTPTS

previous output PTS

@end table

Some examples follow:

@example

# start counting PTS from zero

setpts=PTS-STARTPTS

# fast motion

setpts=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))'

@end example

@anchor{setsar}

@section 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