PeerStreamer

@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 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 lefth 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 and position

"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 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".

The following command:

@example

./ffmpeg -i in.avi -vf "format=yuv420p" out.avi

@end example

will convert the input video to the format "yuv420p".

@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 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 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".

The following command:

@example

./ffmpeg -i in.avi -vf "noformat=yuv420p, vflip" out.avi

@end example

will make libavfilter use a format different from "yuv420p" for the

input to the vflip filter.

@section null

Pass the video source unchanged to the output.

@section ocv_smooth

Apply smooth transform using libopencv.

To enable this filter install libopencv library and headers and

configure FFmpeg with --enable-libopencv.

The filter accepts 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}. Refer to the official libopencv

documentation for the exact meaning of the parameters:

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

@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

@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.

@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 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

yadif is "yet another deinterlacing filter".

It accepts the syntax:

@example

yadif=[@var{mode}[:@var{parity}]]

@end example

@table @option

@item mode

Specify 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.

@item parity

0 if is bottom field first, 1 if the interlaced video is top field

first, -1 to enable automatic detection.

@end table

@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 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".

@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