@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{dash} @section dash Dynamic Adaptive Streaming over HTTP (DASH) muxer that creates segments and manifest files according to the MPEG-DASH standard ISO/IEC 23009-1:2014. For more information see: @itemize @bullet @item ISO DASH Specification: @url{http://standards.iso.org/ittf/PubliclyAvailableStandards/c065274_ISO_IEC_23009-1_2014.zip} @item WebM DASH Specification: @url{https://sites.google.com/a/webmproject.org/wiki/adaptive-streaming/webm-dash-specification} @end itemize It creates a MPD manifest file and segment files for each stream. The segment filename might contain pre-defined identifiers used with SegmentTemplate as defined in section 5.3.9.4.4 of the standard. Available identifiers are "$RepresentationID$", "$Number$", "$Bandwidth$" and "$Time$". @example ffmpeg -re -i -map 0 -map 0 -c:a libfdk_aac -c:v libx264 -b:v:0 800k -b:v:1 300k -s:v:1 320x170 -profile:v:1 baseline -profile:v:0 main -bf 1 -keyint_min 120 -g 120 -sc_threshold 0 -b_strategy 0 -ar:a:1 22050 -use_timeline 1 -use_template 1 -window_size 5 -adaptation_sets "id=0,streams=v id=1,streams=a" -f dash /path/to/out.mpd @end example @table @option @item -min_seg_duration @var{microseconds} This is a deprecated option to set the segment length in microseconds, use @var{seg_duration} instead. @item -seg_duration @var{duration} Set the segment length in seconds (fractional value can be set). The value is treated as average segment duration when @var{use_template} is enabled and @var{use_timeline} is disabled and as minimum segment duration for all the other use cases. @item -window_size @var{size} Set the maximum number of segments kept in the manifest. @item -extra_window_size @var{size} Set the maximum number of segments kept outside of the manifest before removing from disk. @item -remove_at_exit @var{remove} Enable (1) or disable (0) removal of all segments when finished. @item -use_template @var{template} Enable (1) or disable (0) use of SegmentTemplate instead of SegmentList. @item -use_timeline @var{timeline} Enable (1) or disable (0) use of SegmentTimeline in SegmentTemplate. @item -single_file @var{single_file} Enable (1) or disable (0) storing all segments in one file, accessed using byte ranges. @item -single_file_name @var{file_name} DASH-templated name to be used for baseURL. Implies @var{single_file} set to "1". @item -init_seg_name @var{init_name} DASH-templated name to used for the initialization segment. Default is "init-stream$RepresentationID$.m4s" @item -media_seg_name @var{segment_name} DASH-templated name to used for the media segments. Default is "chunk-stream$RepresentationID$-$Number%05d$.m4s" @item -utc_timing_url @var{utc_url} URL of the page that will return the UTC timestamp in ISO format. Example: "https://time.akamai.com/?iso" @item method @var{method} Use the given HTTP method to create output files. Generally set to PUT or POST. @item -http_user_agent @var{user_agent} Override User-Agent field in HTTP header. Applicable only for HTTP output. @item -http_persistent @var{http_persistent} Use persistent HTTP connections. Applicable only for HTTP output. @item -hls_playlist @var{hls_playlist} Generate HLS playlist files as well. The master playlist is generated with the filename master.m3u8. One media playlist file is generated for each stream with filenames media_0.m3u8, media_1.m3u8, etc. @item -streaming @var{streaming} Enable (1) or disable (0) chunk streaming mode of output. In chunk streaming mode, each frame will be a moof fragment which forms a chunk. @item -adaptation_sets @var{adaptation_sets} Assign streams to AdaptationSets. Syntax is "id=x,streams=a,b,c id=y,streams=d,e" with x and y being the IDs of the adaptation sets and a,b,c,d and e are the indices of the mapped streams. To map all video (or audio) streams to an AdaptationSet, "v" (or "a") can be used as stream identifier instead of IDs. When no assignment is defined, this defaults to an AdaptationSet for each stream. @item -timeout @var{timeout} Set timeout for socket I/O operations. Applicable only for HTTP output. @item -index_correction @var{index_correction} Enable (1) or Disable (0) segment index correction logic. Applicable only when @var{use_template} is enabled and @var{use_timeline} is disabled. When enabled, the logic monitors the flow of segment indexes. If a streams's segment index value is not at the expected real time position, then the logic corrects that index value. Typically this logic is needed in live streaming use cases. The network bandwidth fluctuations are common during long run streaming. Each fluctuation can cause the segment indexes fall behind the expected real time position. @item -format_options @var{options_list} Set container format (mp4/webm) options using a @code{:} separated list of key=value parameters. Values containing @code{:} special characters must be escaped. @item dash_segment_type @var{dash_segment_type} Possible values: @item mp4 If this flag is set, the dash segment files will be in in ISOBMFF format. This is the default format. @item webm If this flag is set, the dash segment files will be in in WebM format. @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. Make sure to require a closed GOP when encoding and to set the GOP size to fit your segment time constraint. For example, to convert an input file with @command{ffmpeg}: @example ffmpeg -i in.mkv -c:v h264 -flags +cgop -g 30 -hls_time 1 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_delete_threshold @var{size} Set the number of unreferenced segments to keep on disk before @code{hls_flags delete_segments} deletes them. Increase this to allow continue clients to download segments which were recently referenced in the playlist. Default value is 1, meaning segments older than @code{hls_list_size+1} will be deleted. @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 strftime_mkdir is set, the whole expanded value of @var{filename} will be written into the m3u8 segment list. When @code{var_stream_map} is set with two or more variant streams, the @var{filename} pattern must contain the string "%v", this string specifies the position of variant stream index in the generated segment file names. @example ffmpeg -i in.ts -b:v:0 1000k -b:v:1 256k -b:a:0 64k -b:a:1 32k \ -map 0:v -map 0:a -map 0:v -map 0:a -f hls -var_stream_map "v:0,a:0 v:1,a:1" \ -hls_segment_filename 'file_%v_%03d.ts' out_%v.m3u8 @end example This example will produce the playlists segment file sets: @file{file_0_000.ts}, @file{file_0_001.ts}, @file{file_0_002.ts}, etc. and @file{file_1_000.ts}, @file{file_1_001.ts}, @file{file_1_002.ts}, etc. The string "%v" may be present in the filename or in the last directory name containing the file. If the string is present in the directory name, then sub-directories are created after expanding the directory name pattern. This enables creation of segments corresponding to different variant streams in subdirectories. @example ffmpeg -i in.ts -b:v:0 1000k -b:v:1 256k -b:a:0 64k -b:a:1 32k \ -map 0:v -map 0:a -map 0:v -map 0:a -f hls -var_stream_map "v:0,a:0 v:1,a:1" \ -hls_segment_filename 'vs%v/file_%03d.ts' vs%v/out.m3u8 @end example This example will produce the playlists segment file sets: @file{vs0/file_000.ts}, @file{vs0/file_001.ts}, @file{vs0/file_002.ts}, etc. and @file{vs1/file_000.ts}, @file{vs1/file_001.ts}, @file{vs1/file_002.ts}, etc. @item use_localtime Same as strftime option, will be deprecated. @item strftime 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 -strftime 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 -strftime 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 Same as strftime_mkdir option, will be deprecated . @item strftime_mkdir Used together with -strftime_mkdir, it will create all subdirectories which is expanded in @var{filename}. @example ffmpeg -i in.nut -strftime 1 -strftime_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 -strftime 1 -strftime_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}. When @code{var_stream_map} is set with two or more variant streams, the @var{filename} pattern must contain the string "%v", this string specifies the position of variant stream index in the generated init file names. The string "%v" may be present in the filename or in the last directory name containing the file. If the string is present in the directory name, then sub-directories are created after expanding the directory name pattern. This enables creation of init files corresponding to different variant streams in subdirectories. @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 independent_segments Add the @code{#EXT-X-INDEPENDENT-SEGMENTS} to playlists that has video segments and when all the segments of that playlist are guaranteed to start with a Key frame. @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 strftime 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 strftime 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 strftime 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 \ -strftime 1 -strftime_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. @item http_user_agent Override User-Agent field in HTTP header. Applicable only for HTTP output. @item var_stream_map Map string which specifies how to group the audio, video and subtitle streams into different variant streams. The variant stream groups are separated by space. Expected string format is like this "a:0,v:0 a:1,v:1 ....". Here a:, v:, s: are the keys to specify audio, video and subtitle streams respectively. Allowed values are 0 to 9 (limited just based on practical usage). When there are two or more variant streams, the output filename pattern must contain the string "%v", this string specifies the position of variant stream index in the output media playlist filenames. The string "%v" may be present in the filename or in the last directory name containing the file. If the string is present in the directory name, then sub-directories are created after expanding the directory name pattern. This enables creation of variant streams in subdirectories. @example ffmpeg -re -i in.ts -b:v:0 1000k -b:v:1 256k -b:a:0 64k -b:a:1 32k \ -map 0:v -map 0:a -map 0:v -map 0:a -f hls -var_stream_map "v:0,a:0 v:1,a:1" \ http://example.com/live/out_%v.m3u8 @end example This example creates two hls variant streams. The first variant stream will contain video stream of bitrate 1000k and audio stream of bitrate 64k and the second variant stream will contain video stream of bitrate 256k and audio stream of bitrate 32k. Here, two media playlist with file names out_0.m3u8 and out_1.m3u8 will be created. @example ffmpeg -re -i in.ts -b:v:0 1000k -b:v:1 256k -b:a:0 64k \ -map 0:v -map 0:a -map 0:v -f hls -var_stream_map "v:0 a:0 v:1" \ http://example.com/live/out_%v.m3u8 @end example This example creates three hls variant streams. The first variant stream will be a video only stream with video bitrate 1000k, the second variant stream will be an audio only stream with bitrate 64k and the third variant stream will be a video only stream with bitrate 256k. Here, three media playlist with file names out_0.m3u8, out_1.m3u8 and out_2.m3u8 will be created. @example ffmpeg -re -i in.ts -b:v:0 1000k -b:v:1 256k -b:a:0 64k -b:a:1 32k \ -map 0:v -map 0:a -map 0:v -map 0:a -f hls -var_stream_map "v:0,a:0 v:1,a:1" \ http://example.com/live/vs_%v/out.m3u8 @end example This example creates the variant streams in subdirectories. Here, the first media playlist is created at @file{http://example.com/live/vs_0/out.m3u8} and the second one at @file{http://example.com/live/vs_1/out.m3u8}. @example ffmpeg -re -i in.ts -b:a:0 32k -b:a:1 64k -b:v:0 1000k -b:v:1 3000k \ -map 0:a -map 0:a -map 0:v -map 0:v -f hls \ -var_stream_map "a:0,agroup:aud_low a:1,agroup:aud_high v:0,agroup:aud_low v:1,agroup:aud_high" \ -master_pl_name master.m3u8 \ http://example.com/live/out_%v.m3u8 @end example This example creates two audio only and two video only variant streams. In addition to the #EXT-X-STREAM-INF tag for each variant stream in the master playlist, #EXT-X-MEDIA tag is also added for the two audio only variant streams and they are mapped to the two video only variant streams with audio group names 'aud_low' and 'aud_high'. By default, a single hls variant containing all the encoded streams is created. @item cc_stream_map Map string which specifies different closed captions groups and their attributes. The closed captions stream groups are separated by space. Expected string format is like this "ccgroup:,instreamid:,language: ....". 'ccgroup' and 'instreamid' are mandatory attributes. 'language' is an optional attribute. The closed captions groups configured using this option are mapped to different variant streams by providing the same 'ccgroup' name in the @code{var_stream_map} string. If @code{var_stream_map} is not set, then the first available ccgroup in @code{cc_stream_map} is mapped to the output variant stream. The examples for these two use cases are given below. @example ffmpeg -re -i in.ts -b:v 1000k -b:a 64k -a53cc 1 -f hls \ -cc_stream_map "ccgroup:cc,instreamid:CC1,language:en" \ -master_pl_name master.m3u8 \ http://example.com/live/out.m3u8 @end example This example adds @code{#EXT-X-MEDIA} tag with @code{TYPE=CLOSED-CAPTIONS} in the master playlist with group name 'cc', langauge 'en' (english) and INSTREAM-ID 'CC1'. Also, it adds @code{CLOSED-CAPTIONS} attribute with group name 'cc' for the output variant stream. @example ffmpeg -re -i in.ts -b:v:0 1000k -b:v:1 256k -b:a:0 64k -b:a:1 32k \ -a53cc:0 1 -a53cc:1 1\ -map 0:v -map 0:a -map 0:v -map 0:a -f hls \ -cc_stream_map "ccgroup:cc,instreamid:CC1,language:en ccgroup:cc,instreamid:CC2,language:sp" \ -var_stream_map "v:0,a:0,ccgroup:cc v:1,a:1,ccgroup:cc" \ -master_pl_name master.m3u8 \ http://example.com/live/out_%v.m3u8 @end example This example adds two @code{#EXT-X-MEDIA} tags with @code{TYPE=CLOSED-CAPTIONS} in the master playlist for the INSTREAM-IDs 'CC1' and 'CC2'. Also, it adds @code{CLOSED-CAPTIONS} attribute with group name 'cc' for the two output variant streams. @item master_pl_name Create HLS master playlist with the given name. @example ffmpeg -re -i in.ts -f hls -master_pl_name master.m3u8 http://example.com/live/out.m3u8 @end example This example creates HLS master playlist with name master.m3u8 and it is published at http://example.com/live/ @item master_pl_publish_rate Publish master play list repeatedly every after specified number of segment intervals. @example ffmpeg -re -i in.ts -f hls -master_pl_name master.m3u8 \ -hls_time 2 -master_pl_publish_rate 30 http://example.com/live/out.m3u8 @end example This example creates HLS master playlist with name master.m3u8 and keep publishing it repeatedly every after 30 segments i.e. every after 60s. @item http_persistent Use persistent HTTP connections. Applicable only for HTTP output. @item timeout Set timeout for socket I/O operations. Applicable only for HTTP output. @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 You can set the file name with current frame's PTS: @example ffmpeg -f v4l2 -r 1 -i /dev/video0 -copyts -f image2 -frame_pts true %d.jpg" @end example @subsection Options @table @option @item frame_pts If set to 1, expand the filename with pts from pkt->pts. Default value is 0. @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). @item -movflags negative_cts_offsets Enables utilization of version 1 of the CTTS box, in which the CTS offsets can be negative. This enables the initial sample to have DTS/CTS of zero, and reduces the need for edit lists for some cases such as video tracks with B-frames. Additionally, eases conformance with the DASH-IF interoperability guidelines. This option is implicitly set when writing ismv (Smooth Streaming) files. @item -write_prft Write producer time reference box (PRFT) with a specified time source for the NTP field in the PRFT box. Set value as @samp{wallclock} to specify timesource as wallclock time and @samp{pts} to specify timesource as input packets' PTS values. Setting value to @samp{pts} is applicable only for a live encoding use case, where PTS values are set as as wallclock time at the source. For example, an encoding use case with decklink capture source where @option{video_pts} and @option{audio_pts} are set to @samp{abs_wallclock}. @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{} -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 beginning 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 Make sure to require a closed GOP when encoding and to set the GOP size to fit your segment time constraint. @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 hevc -flags +cgop -g 60 -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 outputs, such as files or streams. It can be used, for example, to stream a video over a network and save it to disk at the same time. It is different from specifying several outputs to the @command{ffmpeg} command-line tool. With the tee muxer, the audio and video data will be encoded only once. With conventional multiple outputs, multiple encoding operations in parallel are initiated, which can be a very expensive process. The tee muxer is not useful when using the libavformat API directly because it is then possible to feed the same packets to several muxers directly. Since the tee muxer does not represent any particular output format, ffmpeg cannot auto-select output streams. So all streams intended for output must be specified using @code{-map}. See the examples below. Some encoders may need different options depending on the output format; the auto-detection of this can not work with the tee muxer, so they need to be explicitly specified. The main example is the @option{global_header} flag. 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, those must be escaped (see @ref{quoting_and_escaping,,the "Quoting and escaping" section in the ffmpeg-utils(1) manual,ffmpeg-utils}). @subsection Options @table @option @item use_fifo @var{bool} If set to 1, slave outputs will be processed in separate threads using the @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 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. Required if it cannot be guessed from the output URL. @item bsfs[/@var{spec}] Specify a list of bitstream filters to apply to the specified output. 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. This will cause that output operation to fail if the output contains streams to which the bitstream filter cannot be applied e.g. @code{h264_mp4toannexb} being applied to an output containing an audio stream. Options for a bitstream filter must be specified in the form of @code{opt=value}. Several bitstream filters can be specified, separated by ",". @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}. @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 mapped streams. This will cause that output operation to fail if the output format does not accept all mapped 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: @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=freq=keyframe]out.ts|[movflags=+faststart]out.mp4|[select=a]out.aac" @end example @item As above, 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=freq=keyframe]out.ts|[movflags=+faststart]out.mp4|[select=\'a:1\']out.aac" @end example @end itemize @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