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@chapter Muxers
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@c man begin MUXERS
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Muxers are configured elements in FFmpeg which allow writing
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multimedia streams to a particular type of file.
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When you configure your FFmpeg build, all the supported muxers
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are enabled by default. You can list all available muxers using the
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configure option @code{--list-muxers}.
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You can disable all the muxers with the configure option
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@code{--disable-muxers} and selectively enable / disable single muxers
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with the options @code{--enable-muxer=@var{MUXER}} /
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@code{--disable-muxer=@var{MUXER}}.
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The option @code{-formats} of the ff* tools will display the list of
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enabled muxers.
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A description of some of the currently available muxers follows.
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@section crc
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CRC (Cyclic Redundancy Check) testing format.
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This muxer computes and prints the Adler-32 CRC of all the input audio
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and video frames. By default audio frames are converted to signed
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16-bit raw audio and video frames to raw video before computing the
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CRC.
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The output of the muxer consists of a single line of the form:
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CRC=0x@var{CRC}, where @var{CRC} is a hexadecimal number 0-padded to
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8 digits containing the CRC for all the decoded input frames.
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For example to compute the CRC of the input, and store it in the file
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@file{out.crc}:
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@example
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ffmpeg -i INPUT -f crc out.crc
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@end example
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You can print the CRC to stdout with the command:
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@example
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ffmpeg -i INPUT -f crc -
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@end example
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You can select the output format of each frame with @file{ffmpeg} by
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specifying the audio and video codec and format. For example to
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compute the CRC of the input audio converted to PCM unsigned 8-bit
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and the input video converted to MPEG-2 video, use the command:
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@example
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ffmpeg -i INPUT -acodec pcm_u8 -vcodec mpeg2video -f crc -
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@end example
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@section image2
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Image file muxer.
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This muxer writes video frames to multiple image files specified by a
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pattern.
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The pattern may contain the string "%d" or "%0@var{N}d", which
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specifies the position of the characters representing a numbering in
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the filenames. If the form "%d0@var{N}d" is used, the string
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representing the number in each filename is 0-padded to @var{N}
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digits. The literal character '%' can be specified in the pattern with
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the string "%%".
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If the pattern contains "%d" or "%0@var{N}d", the first filename of
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the file list specified will contain the number 1, all the following
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numbers will be sequential.
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The pattern may contain a suffix which is used to automatically
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determine the format of the image files to write.
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For example the pattern "img-%03d.bmp" will specify a sequence of
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filenames of the form @file{img-001.bmp}, @file{img-002.bmp}, ...,
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@file{img-010.bmp}, etc.
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The pattern "img%%-%d.jpg" will specify a sequence of filenames of the
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form @file{img%-1.jpg}, @file{img%-2.jpg}, ..., @file{img%-10.jpg},
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etc.
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The following example shows how to use @file{ffmpeg} for creating a
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sequence of files @file{img-001.jpeg}, @file{img-002.jpeg}, ...,
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taking one image every second from the input video:
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@example
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ffmpeg -i in.avi -r 1 -f image2 'img-%03d.jpeg'
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@end example
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Note that with @file{ffmpeg}, if the format is not specified with the
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@code{-f} option and the output filename specifies an image file
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format, the image2 muxer is automatically selected, so the previous
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command can be written as:
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@example
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ffmpeg -i in.avi -r 1 'img-%03d.jpeg'
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@end example
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Note also that the pattern must not necessarily contain "%d" or
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"%0@var{N}d", for example to create a single image file
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@file{img.jpeg} from the input video you can employ the command:
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@example
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ffmpeg -i in.avi -f image2 -vframes 1 img.jpeg
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@end example
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@section mpegts
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MPEG transport stream muxer.
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This muxer implements ISO 13818-1 and part of ETSI EN 300 468.
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The muxer options are:
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@table @option
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@item -mpegts_original_network_id @var{number}
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Set the original_network_id (default 0x0001). This is unique identifier
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of a network in DVB. Its main use is in the unique identification of a
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service through the path Original_Network_ID, Transport_Stream_ID.
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@item -mpegts_transport_stream_id @var{number}
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Set the transport_stream_id (default 0x0001). This identifies a
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transponder in DVB.
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@item -mpegts_service_id @var{number}
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Set the service_id (default 0x0001) also known as program in DVB.
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@item -mpegts_pmt_start_pid @var{number}
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Set the first PID for PMT (default 0x1000, max 0x1f00).
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@item -mpegts_start_pid @var{number}
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Set the first PID for data packets (default 0x0100, max 0x0f00).
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@end table
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The recognized metadata settings in mpegts muxer are @code{service_provider}
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and @code{service_name}. If they are not set the default for
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@code{service_provider} is "FFmpeg" and the default for
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@code{service_name} is "Service01".
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@example
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ffmpeg -i file.mpg -acodec copy -vcodec copy \
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     -mpegts_original_network_id 0x1122 \
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     -mpegts_transport_stream_id 0x3344 \
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     -mpegts_service_id 0x5566 \
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     -mpegts_pmt_start_pid 0x1500 \
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     -mpegts_start_pid 0x150 \
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     -metadata service_provider="Some provider" \
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     -metadata service_name="Some Channel" \
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     -y out.ts
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@end example
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@section null
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Null muxer.
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This muxer does not generate any output file, it is mainly useful for
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testing or benchmarking purposes.
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For example to benchmark decoding with @file{ffmpeg} you can use the
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command:
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@example
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ffmpeg -benchmark -i INPUT -f null out.null
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@end example
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Note that the above command does not read or write the @file{out.null}
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file, but specifying the output file is required by the @file{ffmpeg}
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syntax.
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Alternatively you can write the command as:
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@example
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ffmpeg -benchmark -i INPUT -f null -
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@end example
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@c man end MUXERS