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 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.

@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 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.

@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 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 Libav 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 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 Libav 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

# column 0, row 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

equation:

@math{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.

The filter accepts a parameter string which represents the wanted

sample 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 sample aspect ratio to 10:11, specify:

@example

setsar=10:11

@end example

@section settb

Set the timebase to use for the output frames timestamps.

It is mainly useful for testing timebase configuration.

It accepts in input an arithmetic expression representing a rational.

The expression can contain the constants "PI", "E", "PHI", "AVTB" (the

default timebase), and "intb" (the input timebase).

The default value for the input is "intb".

Follow some examples.

@example

# set the timebase to 1/25

settb=1/25

# set the timebase to 1/10

settb=0.1

#set the timebase to 1001/1000

settb=1+0.001

#set the timebase to 2*intb

settb=2*intb

#set the default timebase value

settb=AVTB

@end example

@section slicify

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

slices.

@example

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

@end example

The filter accepts the slice height as parameter. If the parameter is

not specified it will use the default value of 16.

Adding this in the beginning of filter chains should make filtering

faster due to better use of the memory cache.

@section transpose

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

It accepts a parameter representing an integer, which can assume the

values:

@table @samp

@item 0

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

@example

L.R     L.l

. . ->  . .

l.r     R.r

@end example

@item 1

Rotate by 90 degrees clockwise, that is:

@example

L.R     l.L

. . ->  . .

l.r     r.R

@end example

@item 2

Rotate by 90 degrees counterclockwise, that is:

@example

L.R     R.r

. . ->  . .

l.r     L.l

@end example

@item 3

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

@example

L.R     r.R

. . ->  . .

l.r     l.L

@end example

@end table

@section unsharp

Sharpen or blur the input video.

It accepts the following parameters:

@var{luma_msize_x}:@var{luma_msize_y}:@var{luma_amount}:@var{chroma_msize_x}:@var{chroma_msize_y}:@var{chroma_amount}

Negative values for the amount will blur the input video, while positive

values will sharpen. All parameters are optional and default to the

equivalent of the string '5:5:1.0:0:0:0.0'.

@table @option

@item luma_msize_x

Set the luma matrix horizontal size. It can be an integer between 3

and 13, default value is 5.

@item luma_msize_y

Set the luma matrix vertical size. It can be an integer between 3

and 13, default value is 5.

@item luma_amount

Set the luma effect strength. It can be a float number between -2.0

and 5.0, default value is 1.0.

@item chroma_msize_x

Set the chroma matrix horizontal size. It can be an integer between 3

and 13, default value is 0.

@item chroma_msize_y

Set the chroma matrix vertical size. It can be an integer between 3

and 13, default value is 0.

@item luma_amount

Set the chroma effect strength. It can be a float number between -2.0

and 5.0, default value is 0.0.

@end table

@example

# Strong luma sharpen effect parameters

unsharp=7:7:2.5

# Strong blur of both luma and chroma parameters

unsharp=7:7:-2:7:7:-2

# Use the default values with @command{ffmpeg}

./ffmpeg -i in.avi -vf "unsharp" out.mp4

@end example

@section vflip

Flip the input video vertically.

@example

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

@end example

@section yadif

Deinterlace the input video ("yadif" means "yet another deinterlacing

filter").

It accepts the optional parameters: @var{mode}:@var{parity}.

@var{mode} specifies the interlacing mode to adopt, accepts one of the

following values:

@table @option

@item 0

output 1 frame for each frame

@item 1

output 1 frame for each field

@item 2

like 0 but skips spatial interlacing check

@item 3

like 1 but skips spatial interlacing check

@end table

Default value is 0.

@var{parity} specifies the picture field parity assumed for the input

interlaced video, accepts one of the following values:

@table @option

@item 0

assume bottom field first

@item 1

assume top field first

@item -1

enable automatic detection

@end table

Default value is -1.

If interlacing is unknown or decoder does not export this information,

top field first will be assumed.

@c man end VIDEO FILTERS

@chapter Video Sources

@c man begin VIDEO SOURCES

Below is a description of the currently available video sources.

@section 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 @file{libavfilter/vsrc_buffer.h}.

It accepts the following parameters:

@var{width}:@var{height}:@var{pix_fmt_string}:@var{timebase_num}:@var{timebase_den}

All the parameters need to be explicitely defined.

Follows the list of the accepted parameters.

@table @option

@item width, height

Specify the width and height of the buffered video frames.

@item pix_fmt_string

A string representing the pixel format of the buffered video frames.

It may be a number corresponding to a pixel format, or a pixel format

name.

@item timebase_num, timebase_den

Specify numerator and denomitor of the timebase assumed by the

timestamps of the buffered frames.

@end table

For example:

@example

buffer=320:240:yuv410p:1:24

@end example

will instruct the source to accept video frames with size 320x240 and

with format "yuv410p" and assuming 1/24 as the timestamps timebase.

Since the pixel format with name "yuv410p" corresponds to the number 6

(check the enum PixelFormat definition in @file{libavutil/pixfmt.h}),

this example corresponds to:

@example

buffer=320:240:6:1:24

@end example

@section color

Provide an uniformly colored input.

It accepts the following parameters:

@var{color}:@var{frame_size}:@var{frame_rate}

Follows the description of the accepted parameters.

@table @option

@item 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".

@item frame_size

Specify the size of the sourced video, it may be a string of the form

@var{width}x@var{heigth}, or the name of a size abbreviation. The

default value is "320x240".

@item frame_rate

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

@var{frame_rate_num}/@var{frame_rate_den}, an integer number, a float

number or a valid video frame rate abbreviation. The default value is

"25".

@end table

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".

@example

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

@end example

@section movie

Read a video stream from a movie container.

It accepts the syntax: @var{movie_name}[:@var{options}] where

@var{movie_name} is the name of the resource to read (not necessarily

a file but also a device or a stream accessed through some protocol),

and @var{options} is an optional sequence of @var{key}=@var{value}

pairs, separated by ":".

The description of the accepted options follows.

@table @option

@item 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 @var{movie_name} or by probing.

@item seek_point, sp

Specifies the seek point in seconds, the frames will be output

starting from this seek point, the parameter is evaluated with

@code{av_strtod} so the numerical value may be suffixed by an IS

postfix. Default value is "0".

@item 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".

@end table

This filter allows to overlay a second video on top of main input of

a filtergraph as shown in this graph:

@example

input -----------> deltapts0 --> overlay --> output

                                    ^

                                    |

movie --> scale--> deltapts1 -------+

@end example

Some examples follow:

@example

# 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]

@end example

@section 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

@var{width}:@var{height}:@var{timebase}.

@var{width} and @var{height} specify the size of the configured

source. The default values of @var{width} and @var{height} are

respectively 352 and 288 (corresponding to the CIF size format).

@var{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".

@section 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.

The source supports the syntax:

@example

@var{size}:@var{rate}:@var{src_name}[@{=|:@}@var{param1}:@var{param2}:...:@var{paramN}]

@end example

@var{size} is the size of the video to generate, may be a string of the

form @var{width}x@var{height} or a frame size abbreviation.

@var{rate} is the rate of the video to generate, may be a string of

the form @var{num}/@var{den} or a frame rate abbreviation.

@var{src_name} is the name to the frei0r source to load. For more

information regarding frei0r and how to set the parameters read the

section "frei0r" (@pxref{frei0r}) in the description of the video

filters.

Some examples follow:

@example

# generate a frei0r partik0l source with size 200x200 and framerate 10

# which is overlayed on the overlay filter main input

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

@end example

@c man end VIDEO SOURCES

@chapter Video Sinks

@c man begin VIDEO SINKS

Below is a description of the currently available video sinks.

@section 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.

@c man end VIDEO SINKS