@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.

The image file muxer writes video frames to image files.

The output filenames are specified by a pattern, which can be used to
produce sequentially numbered series of files.
The pattern may contain the string "%d" or "%0@var{N}d", this string
specifies the position of the characters representing a numbering in
the filenames. If the form "%0@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

The image muxer supports the .Y.U.V image file format. This format is
special in that that each image frame consists of three files, for
each of the YUV420P components. To read or write this image file format,
specify the name of the '.Y' file. The muxer will automatically open the
'.U' and '.V' files as required.

@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

@section matroska

Matroska container muxer.

This muxer implements the matroska and webm container specs.

The recognized metadata settings in this muxer are:

@table @option

@item title=@var{title name}
Name provided to a single track
@end table

@table @option

@item language=@var{language name}
Specifies the language of the track in the Matroska languages form
@end table

@table @option

@item stereo_mode=@var{mode}
Stereo 3D video layout of two views in a single video track
@table @option
@item mono
video is not stereo
@item left_right
Both views are arranged side by side, Left-eye view is on the left
@item bottom_top
Both views are arranged in top-bottom orientation, Left-eye view is at bottom
@item top_bottom
Both views are arranged in top-bottom orientation, Left-eye view is on top
@item checkerboard_rl
Each view is arranged in a checkerboard interleaved pattern, Left-eye view being first
@item checkerboard_lr
Each view is arranged in a checkerboard interleaved pattern, Right-eye view being first
@item row_interleaved_rl
Each view is constituted by a row based interleaving, Right-eye view is first row
@item row_interleaved_lr
Each view is constituted by a row based interleaving, Left-eye view is first row
@item col_interleaved_rl
Both views are arranged in a column based interleaving manner, Right-eye view is first column
@item col_interleaved_lr
Both views are arranged in a column based interleaving manner, Left-eye view is first column
@item anaglyph_cyan_red
All frames are in anaglyph format viewable through red-cyan filters
@item right_left
Both views are arranged side by side, Right-eye view is on the left
@item anaglyph_green_magenta
All frames are in anaglyph format viewable through green-magenta filters
@item block_lr
Both eyes laced in one Block, Left-eye view is first
@item block_rl
Both eyes laced in one Block, Right-eye view is first
@end table
@end table

For example a 3D WebM clip can be created using the following command line:
@example
ffmpeg -i sample_left_right_clip.mpg -an -vcodec libvpx -metadata stereo_mode=left_right -y stereo_clip.webm
@end example

@c man end MUXERS