@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{-muxers} of the ff* tools will display the list of
enabled muxers. Use @code{-formats} to view a combined list of
enabled demuxers and muxers.

A description of some of the currently available muxers follows.

@anchor{aiff}
@section aiff

Audio Interchange File Format muxer.

@subsection Options

It accepts the following options:

@table @option
@item write_id3v2
Enable ID3v2 tags writing when set to 1. Default is 0 (disabled).

@item id3v2_version
Select ID3v2 version to write. Currently only version 3 and 4 (aka.
ID3v2.3 and ID3v2.4) are supported. The default is version 4.

@end table

@anchor{asf}
@section asf

Advanced Systems Format muxer.

Note that Windows Media Audio (wma) and Windows Media Video (wmv) use this
muxer too.

@subsection Options

It accepts the following options:

@table @option
@item packet_size
Set the muxer packet size. By tuning this setting you may reduce data
fragmentation or muxer overhead depending on your source. Default value is
3200, minimum is 100, maximum is 64k.

@end table

@anchor{avi}
@section avi

Audio Video Interleaved muxer.

@subsection Options

It accepts the following options:

@table @option
@item reserve_index_space
Reserve the specified amount of bytes for the OpenDML master index of each
stream within the file header. By default additional master indexes are
embedded within the data packets if there is no space left in the first master
index and are linked together as a chain of indexes. This index structure can
cause problems for some use cases, e.g. third-party software strictly relying
on the OpenDML index specification or when file seeking is slow. Reserving
enough index space in the file header avoids these problems.

The required index space depends on the output file size and should be about 16
bytes per gigabyte. When this option is omitted or set to zero the necessary
index space is guessed.

@item write_channel_mask
Write the channel layout mask into the audio stream header.

This option is enabled by default. Disabling the channel mask can be useful in
specific scenarios, e.g. when merging multiple audio streams into one for
compatibility with software that only supports a single audio stream in AVI
(see @ref{amerge,,the "amerge" section in the ffmpeg-filters manual,ffmpeg-filters}).

@end table

@anchor{chromaprint}
@section chromaprint

Chromaprint fingerprinter

This muxer feeds audio data to the Chromaprint library, which generates
a fingerprint for the provided audio data. It takes a single signed
native-endian 16-bit raw audio stream.

@subsection Options

@table @option
@item silence_threshold
Threshold for detecting silence, ranges from 0 to 32767. -1 for default
(required for use with the AcoustID service).

@item algorithm
Algorithm index to fingerprint with.

@item fp_format
Format to output the fingerprint as. Accepts the following options:
@table @samp
@item raw
Binary raw fingerprint

@item compressed
Binary compressed fingerprint

@item base64
Base64 compressed fingerprint

@end table

@end table

@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.

See also the @ref{framecrc} muxer.

@subsection Examples

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 @command{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 -c:a pcm_u8 -c:v mpeg2video -f crc -
@end example

@section flv

Adobe Flash Video Format muxer.

This muxer accepts the following options:

@table @option

@item flvflags @var{flags}
Possible values:

@table @samp

@item aac_seq_header_detect
Place AAC sequence header based on audio stream data.

@item no_sequence_end
Disable sequence end tag.

@item no_metadata
Disable metadata tag.

@item no_duration_filesize
Disable duration and filesize in metadata when they are equal to zero
at the end of stream. (Be used to non-seekable living stream).

@item add_keyframe_index
Used to facilitate seeking; particularly for HTTP pseudo streaming.
@end table
@end table

@anchor{framecrc}
@section framecrc

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

This muxer computes and prints the Adler-32 CRC for each audio
and video packet. 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
packet of the form:
@example
@var{stream_index}, @var{packet_dts}, @var{packet_pts}, @var{packet_duration}, @var{packet_size}, 0x@var{CRC}
@end example

@var{CRC} is a hexadecimal number 0-padded to 8 digits containing the
CRC of the packet.

@subsection Examples

For example to compute the CRC of the audio and video frames in
@file{INPUT}, converted to raw audio and video packets, and store it
in the file @file{out.crc}:
@example
ffmpeg -i INPUT -f framecrc out.crc
@end example

To print the information to stdout, use the command:
@example
ffmpeg -i INPUT -f framecrc -
@end example

With @command{ffmpeg}, you can select the output format to which the
audio and video frames are encoded before computing the CRC for each
packet by specifying the audio and video codec. 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 -c:a pcm_u8 -c:v mpeg2video -f framecrc -
@end example

See also the @ref{crc} muxer.

@anchor{framehash}
@section framehash

Per-packet hash testing format.

This muxer computes and prints a cryptographic hash for each audio
and video packet. This can be used for packet-by-packet equality
checks without having to individually do a binary comparison on each.

By default audio frames are converted to signed 16-bit raw audio and
video frames to raw video before computing the hash, but the output
of explicit conversions to other codecs can also be used. It uses the
SHA-256 cryptographic hash function by default, but supports several
other algorithms.

The output of the muxer consists of a line for each audio and video
packet of the form:
@example
@var{stream_index}, @var{packet_dts}, @var{packet_pts}, @var{packet_duration}, @var{packet_size}, @var{hash}
@end example

@var{hash} is a hexadecimal number representing the computed hash
for the packet.

@table @option
@item hash @var{algorithm}
Use the cryptographic hash function specified by the string @var{algorithm}.
Supported values include @code{MD5}, @code{murmur3}, @code{RIPEMD128},
@code{RIPEMD160}, @code{RIPEMD256}, @code{RIPEMD320}, @code{SHA160},
@code{SHA224}, @code{SHA256} (default), @code{SHA512/224}, @code{SHA512/256},
@code{SHA384}, @code{SHA512}, @code{CRC32} and @code{adler32}.

@end table

@subsection Examples

To compute the SHA-256 hash of the audio and video frames in @file{INPUT},
converted to raw audio and video packets, and store it in the file
@file{out.sha256}:
@example
ffmpeg -i INPUT -f framehash out.sha256
@end example

To print the information to stdout, using the MD5 hash function, use
the command:
@example
ffmpeg -i INPUT -f framehash -hash md5 -
@end example

See also the @ref{hash} muxer.

@anchor{framemd5}
@section framemd5

Per-packet MD5 testing format.

This is a variant of the @ref{framehash} muxer. Unlike that muxer,
it defaults to using the MD5 hash function.

@subsection Examples

To compute the MD5 hash of the audio and video frames in @file{INPUT},
converted to raw audio and video packets, and store it in the file
@file{out.md5}:
@example
ffmpeg -i INPUT -f framemd5 out.md5
@end example

To print the information to stdout, use the command:
@example
ffmpeg -i INPUT -f framemd5 -
@end example

See also the @ref{framehash} and @ref{md5} muxers.

@anchor{gif}
@section gif

Animated GIF muxer.

It accepts the following options:

@table @option
@item loop
Set the number of times to loop the output. Use @code{-1} for no loop, @code{0}
for looping indefinitely (default).

@item final_delay
Force the delay (expressed in centiseconds) after the last frame. Each frame
ends with a delay until the next frame. The default is @code{-1}, which is a
special value to tell the muxer to re-use the previous delay. In case of a
loop, you might want to customize this value to mark a pause for instance.
@end table

For example, to encode a gif looping 10 times, with a 5 seconds delay between
the loops:
@example
ffmpeg -i INPUT -loop 10 -final_delay 500 out.gif
@end example

Note 1: if you wish to extract the frames into separate GIF files, you need to
force the @ref{image2} muxer:
@example
ffmpeg -i INPUT -c:v gif -f image2 "out%d.gif"
@end example

Note 2: the GIF format has a very large time base: the delay between two frames
can therefore not be smaller than one centi second.

@anchor{hash}
@section hash

Hash testing format.

This muxer computes and prints a cryptographic hash of all the input
audio and video frames. This can be used for equality checks without
having to do a complete binary comparison.

By default audio frames are converted to signed 16-bit raw audio and
video frames to raw video before computing the hash, but the output
of explicit conversions to other codecs can also be used. Timestamps
are ignored. It uses the SHA-256 cryptographic hash function by default,
but supports several other algorithms.

The output of the muxer consists of a single line of the form:
@var{algo}=@var{hash}, where @var{algo} is a short string representing
the hash function used, and @var{hash} is a hexadecimal number
representing the computed hash.

@table @option
@item hash @var{algorithm}
Use the cryptographic hash function specified by the string @var{algorithm}.
Supported values include @code{MD5}, @code{murmur3}, @code{RIPEMD128},
@code{RIPEMD160}, @code{RIPEMD256}, @code{RIPEMD320}, @code{SHA160},
@code{SHA224}, @code{SHA256} (default), @code{SHA512/224}, @code{SHA512/256},
@code{SHA384}, @code{SHA512}, @code{CRC32} and @code{adler32}.

@end table

@subsection Examples

To compute the SHA-256 hash of the input converted to raw audio and
video, and store it in the file @file{out.sha256}:
@example
ffmpeg -i INPUT -f hash out.sha256
@end example

To print an MD5 hash to stdout use the command:
@example
ffmpeg -i INPUT -f hash -hash md5 -
@end example

See also the @ref{framehash} muxer.

@anchor{hls}
@section hls

Apple HTTP Live Streaming muxer that segments MPEG-TS according to
the HTTP Live Streaming (HLS) specification.

It creates a playlist file, and one or more segment files. The output filename
specifies the playlist filename.

By default, the muxer creates a file for each segment produced. These files
have the same name as the playlist, followed by a sequential number and a
.ts extension.

For example, to convert an input file with @command{ffmpeg}:
@example
ffmpeg -i in.nut out.m3u8
@end example
This example will produce the playlist, @file{out.m3u8}, and segment files:
@file{out0.ts}, @file{out1.ts}, @file{out2.ts}, etc.

See also the @ref{segment} muxer, which provides a more generic and
flexible implementation of a segmenter, and can be used to perform HLS
segmentation.

@subsection Options

This muxer supports the following options:

@table @option
@item hls_init_time @var{seconds}
Set the initial target segment length in seconds. Default value is @var{0}.
Segment will be cut on the next key frame after this time has passed on the first m3u8 list.
After the initial playlist is filled @command{ffmpeg} will cut segments
at duration equal to @code{hls_time}

@item hls_time @var{seconds}
Set the target segment length in seconds. Default value is 2.
Segment will be cut on the next key frame after this time has passed.

@item hls_list_size @var{size}
Set the maximum number of playlist entries. If set to 0 the list file
will contain all the segments. Default value is 5.

@item hls_ts_options @var{options_list}
Set output format options using a :-separated list of key=value
parameters. Values containing @code{:} special characters must be
escaped.

@item hls_wrap @var{wrap}
This is a deprecated option, you can use @code{hls_list_size}
and @code{hls_flags delete_segments} instead it

This option is useful to avoid to fill the disk with many segment
files, and limits the maximum number of segment files written to disk
to @var{wrap}.


@item hls_start_number_source
Start the playlist sequence number (@code{#EXT-X-MEDIA-SEQUENCE}) according to the specified source.
Unless @code{hls_flags single_file} is set, it also specifies source of starting sequence numbers of
segment and subtitle filenames. In any case, if @code{hls_flags append_list}
is set and read playlist sequence number is greater than the specified start sequence number,
then that value will be used as start value.

It accepts the following values:

@table @option

@item generic (default)
Set the starting sequence numbers according to @var{start_number} option value.

@item epoch
The start number will be the seconds since epoch (1970-01-01 00:00:00)

@item datetime
The start number will be based on the current date/time as YYYYmmddHHMMSS. e.g. 20161231235759.

@end table

@item start_number @var{number}
Start the playlist sequence number (@code{#EXT-X-MEDIA-SEQUENCE}) from the specified @var{number}
when @var{hls_start_number_source} value is @var{generic}. (This is the default case.)
Unless @code{hls_flags single_file} is set, it also specifies starting sequence numbers of segment and subtitle filenames.
Default value is 0.

@item hls_allow_cache @var{allowcache}
Explicitly set whether the client MAY (1) or MUST NOT (0) cache media segments.

@item hls_base_url @var{baseurl}
Append @var{baseurl} to every entry in the playlist.
Useful to generate playlists with absolute paths.

Note that the playlist sequence number must be unique for each segment
and it is not to be confused with the segment filename sequence number
which can be cyclic, for example if the @option{wrap} option is
specified.

@item hls_segment_filename @var{filename}
Set the segment filename. Unless @code{hls_flags single_file} is set,
@var{filename} is used as a string format with the segment number:
@example
ffmpeg -i in.nut -hls_segment_filename 'file%03d.ts' out.m3u8
@end example
This example will produce the playlist, @file{out.m3u8}, and segment files:
@file{file000.ts}, @file{file001.ts}, @file{file002.ts}, etc.

@var{filename} may contain full path or relative path specification,
but only the file name part without any path info will be contained in the m3u8 segment list.
Should a relative path be specified, the path of the created segment
files will be relative to the current working directory.
When use_localtime_mkdir is set, the whole expanded value of @var{filename} will be written into the m3u8 segment list.


@item use_localtime
Use strftime() on @var{filename} to expand the segment filename with localtime.
The segment number is also available in this mode, but to use it, you need to specify second_level_segment_index
hls_flag and %%d will be the specifier.
@example
ffmpeg -i in.nut -use_localtime 1 -hls_segment_filename 'file-%Y%m%d-%s.ts' out.m3u8
@end example
This example will produce the playlist, @file{out.m3u8}, and segment files:
@file{file-20160215-1455569023.ts}, @file{file-20160215-1455569024.ts}, etc.
Note: On some systems/environments, the @code{%s} specifier is not available. See
  @code{strftime()} documentation.
@example
ffmpeg -i in.nut -use_localtime 1 -hls_flags second_level_segment_index -hls_segment_filename 'file-%Y%m%d-%%04d.ts' out.m3u8
@end example
This example will produce the playlist, @file{out.m3u8}, and segment files:
@file{file-20160215-0001.ts}, @file{file-20160215-0002.ts}, etc.

@item use_localtime_mkdir
Used together with -use_localtime, it will create all subdirectories which
is expanded in @var{filename}.
@example
ffmpeg -i in.nut -use_localtime 1 -use_localtime_mkdir 1 -hls_segment_filename '%Y%m%d/file-%Y%m%d-%s.ts' out.m3u8
@end example
This example will create a directory 201560215 (if it does not exist), and then
produce the playlist, @file{out.m3u8}, and segment files:
@file{20160215/file-20160215-1455569023.ts}, @file{20160215/file-20160215-1455569024.ts}, etc.

@example
ffmpeg -i in.nut -use_localtime 1 -use_localtime_mkdir 1 -hls_segment_filename '%Y/%m/%d/file-%Y%m%d-%s.ts' out.m3u8
@end example
This example will create a directory hierarchy 2016/02/15 (if any of them do not exist), and then
produce the playlist, @file{out.m3u8}, and segment files:
@file{2016/02/15/file-20160215-1455569023.ts}, @file{2016/02/15/file-20160215-1455569024.ts}, etc.


@item hls_key_info_file @var{key_info_file}
Use the information in @var{key_info_file} for segment encryption. The first
line of @var{key_info_file} specifies the key URI written to the playlist. The
key URL is used to access the encryption key during playback. The second line
specifies the path to the key file used to obtain the key during the encryption
process. The key file is read as a single packed array of 16 octets in binary
format. The optional third line specifies the initialization vector (IV) as a
hexadecimal string to be used instead of the segment sequence number (default)
for encryption. Changes to @var{key_info_file} will result in segment
encryption with the new key/IV and an entry in the playlist for the new key
URI/IV if @code{hls_flags periodic_rekey} is enabled.

Key info file format:
@example
@var{key URI}
@var{key file path}
@var{IV} (optional)
@end example

Example key URIs:
@example
http://server/file.key
/path/to/file.key
file.key
@end example

Example key file paths:
@example
file.key
/path/to/file.key
@end example

Example IV:
@example
0123456789ABCDEF0123456789ABCDEF
@end example

Key info file example:
@example
http://server/file.key
/path/to/file.key
0123456789ABCDEF0123456789ABCDEF
@end example

Example shell script:
@example
#!/bin/sh
BASE_URL=$@{1:-'.'@}
openssl rand 16 > file.key
echo $BASE_URL/file.key > file.keyinfo
echo file.key >> file.keyinfo
echo $(openssl rand -hex 16) >> file.keyinfo
ffmpeg -f lavfi -re -i testsrc -c:v h264 -hls_flags delete_segments \
  -hls_key_info_file file.keyinfo out.m3u8
@end example

@item -hls_enc @var{enc}
Enable (1) or disable (0) the AES128 encryption.
When enabled every segment generated is encrypted and the encryption key
is saved as @var{playlist name}.key.

@item -hls_enc_key @var{key}
Hex-coded 16byte key to encrypt the segments, by default it
is randomly generated.

@item -hls_enc_key_url @var{keyurl}
If set, @var{keyurl} is prepended instead of @var{baseurl} to the key filename
in the playlist.

@item -hls_enc_iv @var{iv}
Hex-coded 16byte initialization vector for every segment instead
of the autogenerated ones.

@item hls_segment_type @var{flags}
Possible values:

@table @samp
@item mpegts
If this flag is set, the hls segment files will format to mpegts.
the mpegts files is used in all hls versions.

@item fmp4
If this flag is set, the hls segment files will format to fragment mp4 looks like dash.
the fmp4 files is used in hls after version 7.

@end table

@item hls_fmp4_init_filename @var{filename}
set filename to the fragment files header file, default filename is @file{init.mp4}.

@item hls_flags @var{flags}
Possible values:

@table @samp
@item single_file
If this flag is set, the muxer will store all segments in a single MPEG-TS
file, and will use byte ranges in the playlist. HLS playlists generated with
this way will have the version number 4.
For example:
@example
ffmpeg -i in.nut -hls_flags single_file out.m3u8
@end example
Will produce the playlist, @file{out.m3u8}, and a single segment file,
@file{out.ts}.

@item delete_segments
Segment files removed from the playlist are deleted after a period of time
equal to the duration of the segment plus the duration of the playlist.

@item append_list
Append new segments into the end of old segment list,
and remove the @code{#EXT-X-ENDLIST} from the old segment list.

@item round_durations
Round the duration info in the playlist file segment info to integer
values, instead of using floating point.

@item discont_start
Add the @code{#EXT-X-DISCONTINUITY} tag to the playlist, before the
first segment's information.

@item omit_endlist
Do not append the @code{EXT-X-ENDLIST} tag at the end of the playlist.

@item periodic_rekey
The file specified by @code{hls_key_info_file} will be checked periodically and
detect updates to the encryption info. Be sure to replace this file atomically,
including the file containing the AES encryption key.

@item split_by_time
Allow segments to start on frames other than keyframes. This improves
behavior on some players when the time between keyframes is inconsistent,
but may make things worse on others, and can cause some oddities during
seeking. This flag should be used with the @code{hls_time} option.

@item program_date_time
Generate @code{EXT-X-PROGRAM-DATE-TIME} tags.

@item second_level_segment_index
Makes it possible to use segment indexes as %%d in hls_segment_filename expression
besides date/time values when use_localtime is on.
To get fixed width numbers with trailing zeroes, %%0xd format is available where x is the required width.

@item second_level_segment_size
Makes it possible to use segment sizes (counted in bytes) as %%s in hls_segment_filename
expression besides date/time values when use_localtime is on.
To get fixed width numbers with trailing zeroes, %%0xs format is available where x is the required width.

@item second_level_segment_duration
Makes it possible to use segment duration (calculated  in microseconds) as %%t in hls_segment_filename
expression besides date/time values when use_localtime is on.
To get fixed width numbers with trailing zeroes, %%0xt format is available where x is the required width.

@example
ffmpeg -i sample.mpeg \
   -f hls -hls_time 3 -hls_list_size 5 \
   -hls_flags second_level_segment_index+second_level_segment_size+second_level_segment_duration \
   -use_localtime 1 -use_localtime_mkdir 1 -hls_segment_filename "segment_%Y%m%d%H%M%S_%%04d_%%08s_%%013t.ts" stream.m3u8
@end example
This will produce segments like this:
@file{segment_20170102194334_0003_00122200_0000003000000.ts}, @file{segment_20170102194334_0004_00120072_0000003000000.ts} etc.

@item temp_file
Write segment data to filename.tmp and rename to filename only once the segment is complete. A webserver
serving up segments can be configured to reject requests to *.tmp to prevent access to in-progress segments
before they have been added to the m3u8 playlist.

@end table

@item hls_playlist_type event
Emit @code{#EXT-X-PLAYLIST-TYPE:EVENT} in the m3u8 header. Forces
@option{hls_list_size} to 0; the playlist can only be appended to.

@item hls_playlist_type vod
Emit @code{#EXT-X-PLAYLIST-TYPE:VOD} in the m3u8 header. Forces
@option{hls_list_size} to 0; the playlist must not change.

@item method
Use the given HTTP method to create the hls files.
@example
ffmpeg -re -i in.ts -f hls -method PUT http://example.com/live/out.m3u8
@end example
This example will upload all the mpegts segment files to the HTTP
server using the HTTP PUT method, and update the m3u8 files every
@code{refresh} times using the same method.
Note that the HTTP server must support the given method for uploading
files.
@end table

@anchor{ico}
@section ico

ICO file muxer.

Microsoft's icon file format (ICO) has some strict limitations that should be noted:

@itemize
@item
Size cannot exceed 256 pixels in any dimension

@item
Only BMP and PNG images can be stored

@item
If a BMP image is used, it must be one of the following pixel formats:
@example
BMP Bit Depth      FFmpeg Pixel Format
1bit               pal8
4bit               pal8
8bit               pal8
16bit              rgb555le
24bit              bgr24
32bit              bgra
@end example

@item
If a BMP image is used, it must use the BITMAPINFOHEADER DIB header

@item
If a PNG image is used, it must use the rgba pixel format
@end itemize

@anchor{image2}
@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.

@subsection Examples

The following example shows how to use @command{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 -vsync cfr -r 1 -f image2 'img-%03d.jpeg'
@end example

Note that with @command{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 -vsync cfr -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 start of the input video you can employ the command:
@example
ffmpeg -i in.avi -f image2 -frames:v 1 img.jpeg
@end example

The @option{strftime} option allows you to expand the filename with
date and time information. Check the documentation of
the @code{strftime()} function for the syntax.

For example to generate image files from the @code{strftime()}
"%Y-%m-%d_%H-%M-%S" pattern, the following @command{ffmpeg} command
can be used:
@example
ffmpeg -f v4l2 -r 1 -i /dev/video0 -f image2 -strftime 1 "%Y-%m-%d_%H-%M-%S.jpg"
@end example

@subsection Options

@table @option
@item start_number
Start the sequence from the specified number. Default value is 1.

@item update
If set to 1, the filename will always be interpreted as just a
filename, not a pattern, and the corresponding file will be continuously
overwritten with new images. Default value is 0.

@item strftime
If set to 1, expand the filename with date and time information from
@code{strftime()}. Default value is 0.
@end table

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 matroska

Matroska container muxer.

This muxer implements the matroska and webm container specs.

@subsection Metadata

The recognized metadata settings in this muxer are:

@table @option
@item title
Set title name provided to a single track.

@item language
Specify the language of the track in the Matroska languages form.

The language can be either the 3 letters bibliographic ISO-639-2 (ISO
639-2/B) form (like "fre" for French), or a language code mixed with a
country code for specialities in languages (like "fre-ca" for Canadian
French).

@item stereo_mode
Set stereo 3D video layout of two views in a single video track.

The following values are recognized:
@table @samp
@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 -c:v libvpx -metadata stereo_mode=left_right -y stereo_clip.webm
@end example

@subsection Options

This muxer supports the following options:

@table @option
@item reserve_index_space
By default, this muxer writes the index for seeking (called cues in Matroska
terms) at the end of the file, because it cannot know in advance how much space
to leave for the index at the beginning of the file. However for some use cases
-- e.g.  streaming where seeking is possible but slow -- it is useful to put the
index at the beginning of the file.

If this option is set to a non-zero value, the muxer will reserve a given amount
of space in the file header and then try to write the cues there when the muxing
finishes. If the available space does not suffice, muxing will fail. A safe size
for most use cases should be about 50kB per hour of video.

Note that cues are only written if the output is seekable and this option will
have no effect if it is not.
@end table

@anchor{md5}
@section md5

MD5 testing format.

This is a variant of the @ref{hash} muxer. Unlike that muxer, it
defaults to using the MD5 hash function.

@subsection Examples

To compute the MD5 hash of the input converted to raw
audio and video, and store it in the file @file{out.md5}:
@example
ffmpeg -i INPUT -f md5 out.md5
@end example

You can print the MD5 to stdout with the command:
@example
ffmpeg -i INPUT -f md5 -
@end example

See also the @ref{hash} and @ref{framemd5} muxers.

@section mov, mp4, ismv

MOV/MP4/ISMV (Smooth Streaming) muxer.

The mov/mp4/ismv muxer supports fragmentation. Normally, a MOV/MP4
file has all the metadata about all packets stored in one location
(written at the end of the file, it can be moved to the start for
better playback by adding @var{faststart} to the @var{movflags}, or
using the @command{qt-faststart} tool). A fragmented
file consists of a number of fragments, where packets and metadata
about these packets are stored together. Writing a fragmented
file has the advantage that the file is decodable even if the
writing is interrupted (while a normal MOV/MP4 is undecodable if
it is not properly finished), and it requires less memory when writing
very long files (since writing normal MOV/MP4 files stores info about
every single packet in memory until the file is closed). The downside
is that it is less compatible with other applications.

@subsection Options

Fragmentation is enabled by setting one of the AVOptions that define
how to cut the file into fragments:

@table @option
@item -moov_size @var{bytes}
Reserves space for the moov atom at the beginning of the file instead of placing the
moov atom at the end. If the space reserved is insufficient, muxing will fail.
@item -movflags frag_keyframe
Start a new fragment at each video keyframe.
@item -frag_duration @var{duration}
Create fragments that are @var{duration} microseconds long.
@item -frag_size @var{size}
Create fragments that contain up to @var{size} bytes of payload data.
@item -movflags frag_custom
Allow the caller to manually choose when to cut fragments, by
calling @code{av_write_frame(ctx, NULL)} to write a fragment with
the packets written so far. (This is only useful with other
applications integrating libavformat, not from @command{ffmpeg}.)
@item -min_frag_duration @var{duration}
Don't create fragments that are shorter than @var{duration} microseconds long.
@end table

If more than one condition is specified, fragments are cut when
one of the specified conditions is fulfilled. The exception to this is
@code{-min_frag_duration}, which has to be fulfilled for any of the other
conditions to apply.

Additionally, the way the output file is written can be adjusted
through a few other options:

@table @option
@item -movflags empty_moov
Write an initial moov atom directly at the start of the file, without
describing any samples in it. Generally, an mdat/moov pair is written
at the start of the file, as a normal MOV/MP4 file, containing only
a short portion of the file. With this option set, there is no initial
mdat atom, and the moov atom only describes the tracks but has
a zero duration.

This option is implicitly set when writing ismv (Smooth Streaming) files.
@item -movflags separate_moof
Write a separate moof (movie fragment) atom for each track. Normally,
packets for all tracks are written in a moof atom (which is slightly
more efficient), but with this option set, the muxer writes one moof/mdat
pair for each track, making it easier to separate tracks.

This option is implicitly set when writing ismv (Smooth Streaming) files.
@item -movflags faststart
Run a second pass moving the index (moov atom) to the beginning of the file.
This operation can take a while, and will not work in various situations such
as fragmented output, thus it is not enabled by default.
@item -movflags rtphint
Add RTP hinting tracks to the output file.
@item -movflags disable_chpl
Disable Nero chapter markers (chpl atom).  Normally, both Nero chapters
and a QuickTime chapter track are written to the file. With this option
set, only the QuickTime chapter track will be written. Nero chapters can
cause failures when the file is reprocessed with certain tagging programs, like
mp3Tag 2.61a and iTunes 11.3, most likely other versions are affected as well.
@item -movflags omit_tfhd_offset
Do not write any absolute base_data_offset in tfhd atoms. This avoids
tying fragments to absolute byte positions in the file/streams.
@item -movflags default_base_moof
Similarly to the omit_tfhd_offset, this flag avoids writing the
absolute base_data_offset field in tfhd atoms, but does so by using
the new default-base-is-moof flag instead. This flag is new from
14496-12:2012. This may make the fragments easier to parse in certain
circumstances (avoiding basing track fragment location calculations
on the implicit end of the previous track fragment).
@item -write_tmcd
Specify @code{on} to force writing a timecode track, @code{off} to disable it
and @code{auto} to write a timecode track only for mov and mp4 output (default).
@end table

@subsection Example

Smooth Streaming content can be pushed in real time to a publishing
point on IIS with this muxer. Example:
@example
ffmpeg -re @var{<normal input/transcoding options>} -movflags isml+frag_keyframe -f ismv http://server/publishingpoint.isml/Streams(Encoder1)
@end example

@subsection Audible AAX

Audible AAX files are encrypted M4B files, and they can be decrypted by specifying a 4 byte activation secret.
@example
ffmpeg -activation_bytes 1CEB00DA -i test.aax -vn -c:a copy output.mp4
@end example

@section mp3

The MP3 muxer writes a raw MP3 stream with the following optional features:
@itemize @bullet
@item
An ID3v2 metadata header at the beginning (enabled by default). Versions 2.3 and
2.4 are supported, the @code{id3v2_version} private option controls which one is
used (3 or 4). Setting @code{id3v2_version} to 0 disables the ID3v2 header
completely.

The muxer supports writing attached pictures (APIC frames) to the ID3v2 header.
The pictures are supplied to the muxer in form of a video stream with a single
packet. There can be any number of those streams, each will correspond to a
single APIC frame.  The stream metadata tags @var{title} and @var{comment} map
to APIC @var{description} and @var{picture type} respectively. See
@url{http://id3.org/id3v2.4.0-frames} for allowed picture types.

Note that the APIC frames must be written at the beginning, so the muxer will
buffer the audio frames until it gets all the pictures. It is therefore advised
to provide the pictures as soon as possible to avoid excessive buffering.

@item
A Xing/LAME frame right after the ID3v2 header (if present). It is enabled by
default, but will be written only if the output is seekable. The
@code{write_xing} private option can be used to disable it.  The frame contains
various information that may be useful to the decoder, like the audio duration
or encoder delay.

@item
A legacy ID3v1 tag at the end of the file (disabled by default). It may be
enabled with the @code{write_id3v1} private option, but as its capabilities are
very limited, its usage is not recommended.
@end itemize

Examples:

Write an mp3 with an ID3v2.3 header and an ID3v1 footer:
@example
ffmpeg -i INPUT -id3v2_version 3 -write_id3v1 1 out.mp3
@end example

To attach a picture to an mp3 file select both the audio and the picture stream
with @code{map}:
@example
ffmpeg -i input.mp3 -i cover.png -c copy -map 0 -map 1
-metadata:s:v title="Album cover" -metadata:s:v comment="Cover (Front)" out.mp3
@end example

Write a "clean" MP3 without any extra features:
@example
ffmpeg -i input.wav -write_xing 0 -id3v2_version 0 out.mp3
@end example

@section mpegts

MPEG transport stream muxer.

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

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 @samp{FFmpeg} and the default for
@code{service_name} is @samp{Service01}.

@subsection Options

The muxer options are:

@table @option
@item mpegts_transport_stream_id @var{integer}
Set the @samp{transport_stream_id}. This identifies a transponder in DVB.
Default is @code{0x0001}.

@item mpegts_original_network_id @var{integer}
Set the @samp{original_network_id}. This is unique identifier of a
network in DVB. Its main use is in the unique identification of a service
through the path @samp{Original_Network_ID, Transport_Stream_ID}. Default
is @code{0x0001}.

@item mpegts_service_id @var{integer}
Set the @samp{service_id}, also known as program in DVB. Default is
@code{0x0001}.

@item mpegts_service_type @var{integer}
Set the program @samp{service_type}. Default is @code{digital_tv}.
Accepts the following options:
@table @samp
@item hex_value
Any hexdecimal value between @code{0x01} to @code{0xff} as defined in
ETSI 300 468.
@item digital_tv
Digital TV service.
@item digital_radio
Digital Radio service.
@item teletext
Teletext service.
@item advanced_codec_digital_radio
Advanced Codec Digital Radio service.
@item mpeg2_digital_hdtv
MPEG2 Digital HDTV service.
@item advanced_codec_digital_sdtv
Advanced Codec Digital SDTV service.
@item advanced_codec_digital_hdtv
Advanced Codec Digital HDTV service.
@end table

@item mpegts_pmt_start_pid @var{integer}
Set the first PID for PMT. Default is @code{0x1000}. Max is @code{0x1f00}.

@item mpegts_start_pid @var{integer}
Set the first PID for data packets. Default is @code{0x0100}. Max is
@code{0x0f00}.

@item mpegts_m2ts_mode @var{boolean}
Enable m2ts mode if set to @code{1}. Default value is @code{-1} which
disables m2ts mode.

@item muxrate @var{integer}
Set a constant muxrate. Default is VBR.

@item pes_payload_size @var{integer}
Set minimum PES packet payload in bytes. Default is @code{2930}.

@item mpegts_flags @var{flags}
Set mpegts flags. Accepts the following options:
@table @samp
@item resend_headers
Reemit PAT/PMT before writing the next packet.
@item latm
Use LATM packetization for AAC.
@item pat_pmt_at_frames
Reemit PAT and PMT at each video frame.
@item system_b
Conform to System B (DVB) instead of System A (ATSC).
@item initial_discontinuity
Mark the initial packet of each stream as discontinuity.
@end table

@item resend_headers @var{integer}
Reemit PAT/PMT before writing the next packet. This option is deprecated:
use @option{mpegts_flags} instead.

@item mpegts_copyts @var{boolean}
Preserve original timestamps, if value is set to @code{1}. Default value
is @code{-1}, which results in shifting timestamps so that they start from 0.

@item omit_video_pes_length @var{boolean}
Omit the PES packet length for video packets. Default is @code{1} (true).

@item pcr_period @var{integer}
Override the default PCR retransmission time in milliseconds. Ignored if
variable muxrate is selected. Default is @code{20}.

@item pat_period @var{double}
Maximum time in seconds between PAT/PMT tables.

@item sdt_period @var{double}
Maximum time in seconds between SDT tables.

@item tables_version @var{integer}
Set PAT, PMT and SDT version (default @code{0}, valid values are from 0 to 31, inclusively).
This option allows updating stream structure so that standard consumer may
detect the change. To do so, reopen output @code{AVFormatContext} (in case of API
usage) or restart @command{ffmpeg} instance, cyclically changing
@option{tables_version} value:

@example
ffmpeg -i source1.ts -codec copy -f mpegts -tables_version 0 udp://1.1.1.1:1111
ffmpeg -i source2.ts -codec copy -f mpegts -tables_version 1 udp://1.1.1.1:1111
...
ffmpeg -i source3.ts -codec copy -f mpegts -tables_version 31 udp://1.1.1.1:1111
ffmpeg -i source1.ts -codec copy -f mpegts -tables_version 0 udp://1.1.1.1:1111
ffmpeg -i source2.ts -codec copy -f mpegts -tables_version 1 udp://1.1.1.1:1111
...
@end example
@end table

@subsection Example

@example
ffmpeg -i file.mpg -c 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" \
     out.ts
@end example

@section mxf, mxf_d10

MXF muxer.

@subsection Options

The muxer options are:

@table @option
@item store_user_comments @var{bool}
Set if user comments should be stored if available or never.
IRT D-10 does not allow user comments. The default is thus to write them for
mxf but not for mxf_d10
@end table

@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 @command{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 @command{ffmpeg}
syntax.

Alternatively you can write the command as:
@example
ffmpeg -benchmark -i INPUT -f null -
@end example

@section nut

@table @option
@item -syncpoints @var{flags}
Change the syncpoint usage in nut:
@table @option
@item @var{default} use the normal low-overhead seeking aids.
@item @var{none} do not use the syncpoints at all, reducing the overhead but making the stream non-seekable;
    Use of this option is not recommended, as the resulting files are very damage
    sensitive and seeking is not possible. Also in general the overhead from
    syncpoints is negligible. Note, -@code{write_index} 0 can be used to disable
    all growing data tables, allowing to mux endless streams with limited memory
    and without these disadvantages.
@item @var{timestamped} extend the syncpoint with a wallclock field.
@end table
The @var{none} and @var{timestamped} flags are experimental.
@item -write_index @var{bool}
Write index at the end, the default is to write an index.
@end table

@example
ffmpeg -i INPUT -f_strict experimental -syncpoints none - | processor
@end example

@section ogg

Ogg container muxer.

@table @option
@item -page_duration @var{duration}
Preferred page duration, in microseconds. The muxer will attempt to create
pages that are approximately @var{duration} microseconds long. This allows the
user to compromise between seek granularity and container overhead. The default
is 1 second. A value of 0 will fill all segments, making pages as large as
possible. A value of 1 will effectively use 1 packet-per-page in most
situations, giving a small seek granularity at the cost of additional container
overhead.
@item -serial_offset @var{value}
Serial value from which to set the streams serial number.
Setting it to different and sufficiently large values ensures that the produced
ogg files can be safely chained.

@end table

@anchor{segment}
@section segment, stream_segment, ssegment

Basic stream segmenter.

This muxer outputs streams to a number of separate files of nearly
fixed duration. Output filename pattern can be set in a fashion
similar to @ref{image2}, or by using a @code{strftime} template if
the @option{strftime} option is enabled.

@code{stream_segment} is a variant of the muxer used to write to
streaming output formats, i.e. which do not require global headers,
and is recommended for outputting e.g. to MPEG transport stream segments.
@code{ssegment} is a shorter alias for @code{stream_segment}.

Every segment starts with a keyframe of the selected reference stream,
which is set through the @option{reference_stream} option.

Note that if you want accurate splitting for a video file, you need to
make the input key frames correspond to the exact splitting times
expected by the segmenter, or the segment muxer will start the new
segment with the key frame found next after the specified start
time.

The segment muxer works best with a single constant frame rate video.

Optionally it can generate a list of the created segments, by setting
the option @var{segment_list}. The list type is specified by the
@var{segment_list_type} option. The entry filenames in the segment
list are set by default to the basename of the corresponding segment
files.

See also the @ref{hls} muxer, which provides a more specific
implementation for HLS segmentation.

@subsection Options

The segment muxer supports the following options:

@table @option
@item increment_tc @var{1|0}
if set to @code{1}, increment timecode between each segment
If this is selected, the input need to have
a timecode in the first video stream. Default value is
@code{0}.

@item reference_stream @var{specifier}
Set the reference stream, as specified by the string @var{specifier}.
If @var{specifier} is set to @code{auto}, the reference is chosen
automatically. Otherwise it must be a stream specifier (see the ``Stream
specifiers'' chapter in the ffmpeg manual) which specifies the
reference stream. The default value is @code{auto}.

@item segment_format @var{format}
Override the inner container format, by default it is guessed by the filename
extension.

@item segment_format_options @var{options_list}
Set output format options using a :-separated list of key=value
parameters. Values containing the @code{:} special character must be
escaped.

@item segment_list @var{name}
Generate also a listfile named @var{name}. If not specified no
listfile is generated.

@item segment_list_flags @var{flags}
Set flags affecting the segment list generation.

It currently supports the following flags:
@table @samp
@item cache
Allow caching (only affects M3U8 list files).

@item live
Allow live-friendly file generation.
@end table

@item segment_list_size @var{size}
Update the list file so that it contains at most @var{size}
segments. If 0 the list file will contain all the segments. Default
value is 0.

@item segment_list_entry_prefix @var{prefix}
Prepend @var{prefix} to each entry. Useful to generate absolute paths.
By default no prefix is applied.

@item segment_list_type @var{type}
Select the listing format.

The following values are recognized:
@table @samp
@item flat
Generate a flat list for the created segments, one segment per line.

@item csv, ext
Generate a list for the created segments, one segment per line,
each line matching the format (comma-separated values):
@example
@var{segment_filename},@var{segment_start_time},@var{segment_end_time}
@end example

@var{segment_filename} is the name of the output file generated by the
muxer according to the provided pattern. CSV escaping (according to
RFC4180) is applied if required.

@var{segment_start_time} and @var{segment_end_time} specify
the segment start and end time expressed in seconds.

A list file with the suffix @code{".csv"} or @code{".ext"} will
auto-select this format.

@samp{ext} is deprecated in favor or @samp{csv}.

@item ffconcat
Generate an ffconcat file for the created segments. The resulting file
can be read using the FFmpeg @ref{concat} demuxer.

A list file with the suffix @code{".ffcat"} or @code{".ffconcat"} will
auto-select this format.

@item m3u8
Generate an extended M3U8 file, version 3, compliant with
@url{http://tools.ietf.org/id/draft-pantos-http-live-streaming}.

A list file with the suffix @code{".m3u8"} will auto-select this format.
@end table

If not specified the type is guessed from the list file name suffix.

@item segment_time @var{time}
Set segment duration to @var{time}, the value must be a duration
specification. Default value is "2". See also the
@option{segment_times} option.

Note that splitting may not be accurate, unless you force the
reference stream key-frames at the given time. See the introductory
notice and the examples below.

@item segment_atclocktime @var{1|0}
If set to "1" split at regular clock time intervals starting from 00:00
o'clock. The @var{time} value specified in @option{segment_time} is
used for setting the length of the splitting interval.

For example with @option{segment_time} set to "900" this makes it possible
to create files at 12:00 o'clock, 12:15, 12:30, etc.

Default value is "0".

@item segment_clocktime_offset @var{duration}
Delay the segment splitting times with the specified duration when using
@option{segment_atclocktime}.

For example with @option{segment_time} set to "900" and
@option{segment_clocktime_offset} set to "300" this makes it possible to
create files at 12:05, 12:20, 12:35, etc.

Default value is "0".

@item segment_clocktime_wrap_duration @var{duration}
Force the segmenter to only start a new segment if a packet reaches the muxer
within the specified duration after the segmenting clock time. This way you
can make the segmenter more resilient to backward local time jumps, such as
leap seconds or transition to standard time from daylight savings time.

Default is the maximum possible duration which means starting a new segment
regardless of the elapsed time since the last clock time.

@item segment_time_delta @var{delta}
Specify the accuracy time when selecting the start time for a
segment, expressed as a duration specification. Default value is "0".

When delta is specified a key-frame will start a new segment if its
PTS satisfies the relation:
@example
PTS >= start_time - time_delta
@end example

This option is useful when splitting video content, which is always
split at GOP boundaries, in case a key frame is found just before the
specified split time.

In particular may be used in combination with the @file{ffmpeg} option
@var{force_key_frames}. The key frame times specified by
@var{force_key_frames} may not be set accurately because of rounding
issues, with the consequence that a key frame time may result set just
before the specified time. For constant frame rate videos a value of
1/(2*@var{frame_rate}) should address the worst case mismatch between
the specified time and the time set by @var{force_key_frames}.

@item segment_times @var{times}
Specify a list of split points. @var{times} contains a list of comma
separated duration specifications, in increasing order. See also
the @option{segment_time} option.

@item segment_frames @var{frames}
Specify a list of split video frame numbers. @var{frames} contains a
list of comma separated integer numbers, in increasing order.

This option specifies to start a new segment whenever a reference
stream key frame is found and the sequential number (starting from 0)
of the frame is greater or equal to the next value in the list.

@item segment_wrap @var{limit}
Wrap around segment index once it reaches @var{limit}.

@item segment_start_number @var{number}
Set the sequence number of the first segment. Defaults to @code{0}.

@item strftime @var{1|0}
Use the @code{strftime} function to define the name of the new
segments to write. If this is selected, the output segment name must
contain a @code{strftime} function template. Default value is
@code{0}.

@item break_non_keyframes @var{1|0}
If enabled, allow segments to start on frames other than keyframes. This
improves behavior on some players when the time between keyframes is
inconsistent, but may make things worse on others, and can cause some oddities
during seeking. Defaults to @code{0}.

@item reset_timestamps @var{1|0}
Reset timestamps at the begin of each segment, so that each segment
will start with near-zero timestamps. It is meant to ease the playback
of the generated segments. May not work with some combinations of
muxers/codecs. It is set to @code{0} by default.

@item initial_offset @var{offset}
Specify timestamp offset to apply to the output packet timestamps. The
argument must be a time duration specification, and defaults to 0.

@item write_empty_segments @var{1|0}
If enabled, write an empty segment if there are no packets during the period a
segment would usually span. Otherwise, the segment will be filled with the next
packet written. Defaults to @code{0}.
@end table

@subsection Examples

@itemize
@item
Remux the content of file @file{in.mkv} to a list of segments
@file{out-000.nut}, @file{out-001.nut}, etc., and write the list of
generated segments to @file{out.list}:
@example
ffmpeg -i in.mkv -codec copy -map 0 -f segment -segment_list out.list out%03d.nut
@end example

@item
Segment input and set output format options for the output segments:
@example
ffmpeg -i in.mkv -f segment -segment_time 10 -segment_format_options movflags=+faststart out%03d.mp4
@end example

@item
Segment the input file according to the split points specified by the
@var{segment_times} option:
@example
ffmpeg -i in.mkv -codec copy -map 0 -f segment -segment_list out.csv -segment_times 1,2,3,5,8,13,21 out%03d.nut
@end example

@item
Use the @command{ffmpeg} @option{force_key_frames}
option to force key frames in the input at the specified location, together
with the segment option @option{segment_time_delta} to account for
possible roundings operated when setting key frame times.
@example
ffmpeg -i in.mkv -force_key_frames 1,2,3,5,8,13,21 -codec:v mpeg4 -codec:a pcm_s16le -map 0 \
-f segment -segment_list out.csv -segment_times 1,2,3,5,8,13,21 -segment_time_delta 0.05 out%03d.nut
@end example
In order to force key frames on the input file, transcoding is
required.

@item
Segment the input file by splitting the input file according to the
frame numbers sequence specified with the @option{segment_frames} option:
@example
ffmpeg -i in.mkv -codec copy -map 0 -f segment -segment_list out.csv -segment_frames 100,200,300,500,800 out%03d.nut
@end example

@item
Convert the @file{in.mkv} to TS segments using the @code{libx264}
and @code{aac} encoders:
@example
ffmpeg -i in.mkv -map 0 -codec:v libx264 -codec:a aac -f ssegment -segment_list out.list out%03d.ts
@end example

@item
Segment the input file, and create an M3U8 live playlist (can be used
as live HLS source):
@example
ffmpeg -re -i in.mkv -codec copy -map 0 -f segment -segment_list playlist.m3u8 \
-segment_list_flags +live -segment_time 10 out%03d.mkv
@end example
@end itemize

@section smoothstreaming

Smooth Streaming muxer generates a set of files (Manifest, chunks) suitable for serving with conventional web server.

@table @option
@item window_size
Specify the number of fragments kept in the manifest. Default 0 (keep all).

@item extra_window_size
Specify the number of fragments kept outside of the manifest before removing from disk. Default 5.

@item lookahead_count
Specify the number of lookahead fragments. Default 2.

@item min_frag_duration
Specify the minimum fragment duration (in microseconds). Default 5000000.

@item remove_at_exit
Specify whether to remove all fragments when finished. Default 0 (do not remove).

@end table

@anchor{fifo}
@section fifo

The fifo pseudo-muxer allows the separation of encoding and muxing by using
first-in-first-out queue and running the actual muxer in a separate thread. This
is especially useful in combination with the @ref{tee} muxer and can be used to
send data to several destinations with different reliability/writing speed/latency.

API users should be aware that callback functions (interrupt_callback,
io_open and io_close) used within its AVFormatContext must be thread-safe.

The behavior of the fifo muxer if the queue fills up or if the output fails is
selectable,

@itemize @bullet

@item
output can be transparently restarted with configurable delay between retries
based on real time or time of the processed stream.

@item
encoding can be blocked during temporary failure, or continue transparently
dropping packets in case fifo queue fills up.

@end itemize

@table @option

@item fifo_format
Specify the format name. Useful if it cannot be guessed from the
output name suffix.

@item queue_size
Specify size of the queue (number of packets). Default value is 60.

@item format_opts
Specify format options for the underlying muxer. Muxer options can be specified
as a list of @var{key}=@var{value} pairs separated by ':'.

@item drop_pkts_on_overflow @var{bool}
If set to 1 (true), in case the fifo queue fills up, packets will be dropped
rather than blocking the encoder. This makes it possible to continue streaming without
delaying the input, at the cost of omitting part of the stream. By default
this option is set to 0 (false), so in such cases the encoder will be blocked
until the muxer processes some of the packets and none of them is lost.

@item attempt_recovery @var{bool}
If failure occurs, attempt to recover the output. This is especially useful
when used with network output, since it makes it possible to restart streaming transparently.
By default this option is set to 0 (false).

@item max_recovery_attempts
Sets maximum number of successive unsuccessful recovery attempts after which
the output fails permanently. By default this option is set to 0 (unlimited).

@item recovery_wait_time @var{duration}
Waiting time before the next recovery attempt after previous unsuccessful
recovery attempt. Default value is 5 seconds.

@item recovery_wait_streamtime @var{bool}
If set to 0 (false), the real time is used when waiting for the recovery
attempt (i.e. the recovery will be attempted after at least
recovery_wait_time seconds).
If set to 1 (true), the time of the processed stream is taken into account
instead (i.e. the recovery will be attempted after at least @var{recovery_wait_time}
seconds of the stream is omitted).
By default, this option is set to 0 (false).

@item recover_any_error @var{bool}
If set to 1 (true), recovery will be attempted regardless of type of the error
causing the failure. By default this option is set to 0 (false) and in case of
certain (usually permanent) errors the recovery is not attempted even when
@var{attempt_recovery} is set to 1.

@item restart_with_keyframe @var{bool}
Specify whether to wait for the keyframe after recovering from
queue overflow or failure. This option is set to 0 (false) by default.

@end table

@subsection Examples

@itemize

@item
Stream something to rtmp server, continue processing the stream at real-time
rate even in case of temporary failure (network outage) and attempt to recover
streaming every second indefinitely.
@example
ffmpeg -re -i ... -c:v libx264 -c:a aac -f fifo -fifo_format flv -map 0:v -map 0:a
  -drop_pkts_on_overflow 1 -attempt_recovery 1 -recovery_wait_time 1 rtmp://example.com/live/stream_name
@end example

@end itemize

@anchor{tee}
@section tee

The tee muxer can be used to write the same data to several files or any
other kind of muxer. It can be used, for example, to both stream a video to
the network and save it to disk at the same time.

It is different from specifying several outputs to the @command{ffmpeg}
command-line tool because the audio and video data will be encoded only once
with the tee muxer; encoding can be a very expensive process. It is not
useful when using the libavformat API directly because it is then possible
to feed the same packets to several muxers directly.

@table @option

@item use_fifo @var{bool}
If set to 1, slave outputs will be processed in separate thread using @ref{fifo}
muxer. This allows to compensate for different speed/latency/reliability of
outputs and setup transparent recovery. By default this feature is turned off.

@item fifo_options
Options to pass to fifo pseudo-muxer instances. See @ref{fifo}.

@end table

The slave outputs are specified in the file name given to the muxer,
separated by '|'. If any of the slave name contains the '|' separator,
leading or trailing spaces or any special character, it must be
escaped (see @ref{quoting_and_escaping,,the "Quoting and escaping"
section in the ffmpeg-utils(1) manual,ffmpeg-utils}).

Muxer options can be specified for each slave by prepending them as a list of
@var{key}=@var{value} pairs separated by ':', between square brackets. If
the options values contain a special character or the ':' separator, they
must be escaped; note that this is a second level escaping.

The following special options are also recognized:
@table @option
@item f
Specify the format name. Useful if it cannot be guessed from the
output name suffix.

@item bsfs[/@var{spec}]
Specify a list of bitstream filters to apply to the specified
output.

@item use_fifo @var{bool}
This allows to override tee muxer use_fifo option for individual slave muxer.

@item fifo_options
This allows to override tee muxer fifo_options for individual slave muxer.
See @ref{fifo}.

It is possible to specify to which streams a given bitstream filter
applies, by appending a stream specifier to the option separated by
@code{/}. @var{spec} must be a stream specifier (see @ref{Format
stream specifiers}).  If the stream specifier is not specified, the
bitstream filters will be applied to all streams in the output.

Several bitstream filters can be specified, separated by ",".

@item select
Select the streams that should be mapped to the slave output,
specified by a stream specifier. If not specified, this defaults to
all the input streams. You may use multiple stream specifiers
separated by commas (@code{,}) e.g.: @code{a:0,v}

@item onfail
Specify behaviour on output failure. This can be set to either @code{abort} (which is
default) or @code{ignore}. @code{abort} will cause whole process to fail in case of failure
on this slave output. @code{ignore} will ignore failure on this output, so other outputs
will continue without being affected.
@end table

@subsection Examples

@itemize
@item
Encode something and both archive it in a WebM file and stream it
as MPEG-TS over UDP (the streams need to be explicitly mapped):
@example
ffmpeg -i ... -c:v libx264 -c:a mp2 -f tee -map 0:v -map 0:a
  "archive-20121107.mkv|[f=mpegts]udp://10.0.1.255:1234/"
@end example

@item
As above, but continue streaming even if output to local file fails
(for example local drive fills up):
@example
ffmpeg -i ... -c:v libx264 -c:a mp2 -f tee -map 0:v -map 0:a
  "[onfail=ignore]archive-20121107.mkv|[f=mpegts]udp://10.0.1.255:1234/"
@end example

@item
Use @command{ffmpeg} to encode the input, and send the output
to three different destinations. The @code{dump_extra} bitstream
filter is used to add extradata information to all the output video
keyframes packets, as requested by the MPEG-TS format. The select
option is applied to @file{out.aac} in order to make it contain only
audio packets.
@example
ffmpeg -i ... -map 0 -flags +global_header -c:v libx264 -c:a aac
       -f tee "[bsfs/v=dump_extra]out.ts|[movflags=+faststart]out.mp4|[select=a]out.aac"
@end example

@item
As below, but select only stream @code{a:1} for the audio output. Note
that a second level escaping must be performed, as ":" is a special
character used to separate options.
@example
ffmpeg -i ... -map 0 -flags +global_header -c:v libx264 -c:a aac
       -f tee "[bsfs/v=dump_extra]out.ts|[movflags=+faststart]out.mp4|[select=\'a:1\']out.aac"
@end example
@end itemize

Note: some codecs may need different options depending on the output format;
the auto-detection of this can not work with the tee muxer. The main example
is the @option{global_header} flag.

@section webm_dash_manifest

WebM DASH Manifest muxer.

This muxer implements the WebM DASH Manifest specification to generate the DASH
manifest XML. It also supports manifest generation for DASH live streams.

For more information see:

@itemize @bullet
@item
WebM DASH Specification: @url{https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/webm-dash-specification}
@item
ISO DASH Specification: @url{http://standards.iso.org/ittf/PubliclyAvailableStandards/c065274_ISO_IEC_23009-1_2014.zip}
@end itemize

@subsection Options

This muxer supports the following options:

@table @option
@item adaptation_sets
This option has the following syntax: "id=x,streams=a,b,c id=y,streams=d,e" where x and y are the
unique identifiers of the adaptation sets and a,b,c,d and e are the indices of the corresponding
audio and video streams. Any number of adaptation sets can be added using this option.

@item live
Set this to 1 to create a live stream DASH Manifest. Default: 0.

@item chunk_start_index
Start index of the first chunk. This will go in the @samp{startNumber} attribute
of the @samp{SegmentTemplate} element in the manifest. Default: 0.

@item chunk_duration_ms
Duration of each chunk in milliseconds. This will go in the @samp{duration}
attribute of the @samp{SegmentTemplate} element in the manifest. Default: 1000.

@item utc_timing_url
URL of the page that will return the UTC timestamp in ISO format. This will go
in the @samp{value} attribute of the @samp{UTCTiming} element in the manifest.
Default: None.

@item time_shift_buffer_depth
Smallest time (in seconds) shifting buffer for which any Representation is
guaranteed to be available. This will go in the @samp{timeShiftBufferDepth}
attribute of the @samp{MPD} element. Default: 60.

@item minimum_update_period
Minimum update period (in seconds) of the manifest. This will go in the
@samp{minimumUpdatePeriod} attribute of the @samp{MPD} element. Default: 0.

@end table

@subsection Example
@example
ffmpeg -f webm_dash_manifest -i video1.webm \
       -f webm_dash_manifest -i video2.webm \
       -f webm_dash_manifest -i audio1.webm \
       -f webm_dash_manifest -i audio2.webm \
       -map 0 -map 1 -map 2 -map 3 \
       -c copy \
       -f webm_dash_manifest \
       -adaptation_sets "id=0,streams=0,1 id=1,streams=2,3" \
       manifest.xml
@end example

@section webm_chunk

WebM Live Chunk Muxer.

This muxer writes out WebM headers and chunks as separate files which can be
consumed by clients that support WebM Live streams via DASH.

@subsection Options

This muxer supports the following options:

@table @option
@item chunk_start_index
Index of the first chunk (defaults to 0).

@item header
Filename of the header where the initialization data will be written.

@item audio_chunk_duration
Duration of each audio chunk in milliseconds (defaults to 5000).
@end table

@subsection Example
@example
ffmpeg -f v4l2 -i /dev/video0 \
       -f alsa -i hw:0 \
       -map 0:0 \
       -c:v libvpx-vp9 \
       -s 640x360 -keyint_min 30 -g 30 \
       -f webm_chunk \
       -header webm_live_video_360.hdr \
       -chunk_start_index 1 \
       webm_live_video_360_%d.chk \
       -map 1:0 \
       -c:a libvorbis \
       -b:a 128k \
       -f webm_chunk \
       -header webm_live_audio_128.hdr \
       -chunk_start_index 1 \
       -audio_chunk_duration 1000 \
       webm_live_audio_128_%d.chk
@end example

@c man end MUXERS