PeerStreamer

@chapter Muxers

@c man begin MUXERS

Muxers are configured elements in FFmpeg which allow writing

multimedia streams to a particular type of file.

When you configure your FFmpeg build, all the supported muxers

are enabled by default. You can list all available muxers using the

configure option @code{--list-muxers}.

You can disable all the muxers with the configure option

@code{--disable-muxers} and selectively enable / disable single muxers

with the options @code{--enable-muxer=@var{MUXER}} /

@code{--disable-muxer=@var{MUXER}}.

The option @code{-formats} of the ff* tools will display the list of

enabled muxers.

A description of some of the currently available muxers follows.

@anchor{crc}

@section crc

CRC (Cyclic Redundancy Check) testing format.

This muxer computes and prints the Adler-32 CRC of all the input audio

and video frames. By default audio frames are converted to signed

16-bit raw audio and video frames to raw video before computing the

CRC.

The output of the muxer consists of a single line of the form:

CRC=0x@var{CRC}, where @var{CRC} is a hexadecimal number 0-padded to

8 digits containing the CRC for all the decoded input frames.

For example to compute the CRC of the input, and store it in the file

@file{out.crc}:

@example

ffmpeg -i INPUT -f crc out.crc

@end example

You can print the CRC to stdout with the command:

@example

ffmpeg -i INPUT -f crc -

@end example

You can select the output format of each frame with @file{ffmpeg} by

specifying the audio and video codec and format. For example to

compute the CRC of the input audio converted to PCM unsigned 8-bit

and the input video converted to MPEG-2 video, use the command:

@example

ffmpeg -i INPUT -acodec pcm_u8 -vcodec mpeg2video -f crc -

@end example

See also the @code{framecrc} muxer (@pxref{framecrc}).

@anchor{framecrc}

@section framecrc

Per-frame CRC (Cyclic Redundancy Check) testing format.

This muxer computes and prints the Adler-32 CRC for each decoded audio

and video frame. By default audio frames are converted to signed

16-bit raw audio and video frames to raw video before computing the

CRC.

The output of the muxer consists of a line for each audio and video

frame of the form: @var{stream_index}, @var{frame_dts},

@var{frame_size}, 0x@var{CRC}, where @var{CRC} is a hexadecimal

number 0-padded to 8 digits containing the CRC of the decoded frame.

For example to compute the CRC of each decoded frame in the input, and

store it in the file @file{out.crc}:

@example

ffmpeg -i INPUT -f framecrc out.crc

@end example

You can print the CRC of each decoded frame to stdout with the command:

@example

ffmpeg -i INPUT -f framecrc -

@end example

You can select the output format of each frame with @file{ffmpeg} by

specifying the audio and video codec and format. For example, to

compute the CRC of each decoded input audio frame converted to PCM

unsigned 8-bit and of each decoded input video frame converted to

MPEG-2 video, use the command:

@example

ffmpeg -i INPUT -acodec pcm_u8 -vcodec mpeg2video -f framecrc -

@end example

See also the @code{crc} muxer (@pxref{crc}).

@section image2

Image file muxer.

This muxer writes video frames to multiple image files specified by a

pattern.

The pattern may contain the string "%d" or "%0@var{N}d", which

specifies the position of the characters representing a numbering in

the filenames. If the form "%d0@var{N}d" is used, the string

representing the number in each filename is 0-padded to @var{N}

digits. The literal character '%' can be specified in the pattern with

the string "%%".

If the pattern contains "%d" or "%0@var{N}d", the first filename of

the file list specified will contain the number 1, all the following

numbers will be sequential.

The pattern may contain a suffix which is used to automatically

determine the format of the image files to write.

For example the pattern "img-%03d.bmp" will specify a sequence of

filenames of the form @file{img-001.bmp}, @file{img-002.bmp}, ...,

@file{img-010.bmp}, etc.

The pattern "img%%-%d.jpg" will specify a sequence of filenames of the

form @file{img%-1.jpg}, @file{img%-2.jpg}, ..., @file{img%-10.jpg},

etc.

The following example shows how to use @file{ffmpeg} for creating a

sequence of files @file{img-001.jpeg}, @file{img-002.jpeg}, ...,

taking one image every second from the input video:

@example

ffmpeg -i in.avi -r 1 -f image2 'img-%03d.jpeg'

@end example

Note that with @file{ffmpeg}, if the format is not specified with the

@code{-f} option and the output filename specifies an image file

format, the image2 muxer is automatically selected, so the previous

command can be written as:

@example

ffmpeg -i in.avi -r 1 'img-%03d.jpeg'

@end example

Note also that the pattern must not necessarily contain "%d" or

"%0@var{N}d", for example to create a single image file

@file{img.jpeg} from the input video you can employ the command:

@example

ffmpeg -i in.avi -f image2 -vframes 1 img.jpeg

@end example

@section mpegts

MPEG transport stream muxer.

This muxer implements ISO 13818-1 and part of ETSI EN 300 468.

The muxer options are:

@table @option

@item -mpegts_original_network_id @var{number}

Set the original_network_id (default 0x0001). This is unique identifier

of a network in DVB. Its main use is in the unique identification of a

service through the path Original_Network_ID, Transport_Stream_ID.

@item -mpegts_transport_stream_id @var{number}

Set the transport_stream_id (default 0x0001). This identifies a

transponder in DVB.

@item -mpegts_service_id @var{number}

Set the service_id (default 0x0001) also known as program in DVB.

@item -mpegts_pmt_start_pid @var{number}

Set the first PID for PMT (default 0x1000, max 0x1f00).

@item -mpegts_start_pid @var{number}

Set the first PID for data packets (default 0x0100, max 0x0f00).

@end table

The recognized metadata settings in mpegts muxer are @code{service_provider}

and @code{service_name}. If they are not set the default for

@code{service_provider} is "FFmpeg" and the default for

@code{service_name} is "Service01".

@example

ffmpeg -i file.mpg -acodec copy -vcodec copy \

     -mpegts_original_network_id 0x1122 \

     -mpegts_transport_stream_id 0x3344 \

     -mpegts_service_id 0x5566 \

     -mpegts_pmt_start_pid 0x1500 \

     -mpegts_start_pid 0x150 \

     -metadata service_provider="Some provider" \

     -metadata service_name="Some Channel" \

     -y out.ts

@end example

@section null

Null muxer.

This muxer does not generate any output file, it is mainly useful for

testing or benchmarking purposes.

For example to benchmark decoding with @file{ffmpeg} you can use the

command:

@example

ffmpeg -benchmark -i INPUT -f null out.null

@end example

Note that the above command does not read or write the @file{out.null}

file, but specifying the output file is required by the @file{ffmpeg}

syntax.

Alternatively you can write the command as:

@example

ffmpeg -benchmark -i INPUT -f null -

@end example

@c man end MUXERS