1@chapter Muxers 2@c man begin MUXERS 3 4Muxers are configured elements in Libav which allow writing 5multimedia streams to a particular type of file. 6 7When you configure your Libav build, all the supported muxers 8are enabled by default. You can list all available muxers using the 9configure option @code{--list-muxers}. 10 11You can disable all the muxers with the configure option 12@code{--disable-muxers} and selectively enable / disable single muxers 13with the options @code{--enable-muxer=@var{MUXER}} / 14@code{--disable-muxer=@var{MUXER}}. 15 16The option @code{-formats} of the av* tools will display the list of 17enabled muxers. 18 19A description of some of the currently available muxers follows. 20 21@anchor{crc} 22@section crc 23 24CRC (Cyclic Redundancy Check) testing format. 25 26This muxer computes and prints the Adler-32 CRC of all the input audio 27and video frames. By default audio frames are converted to signed 2816-bit raw audio and video frames to raw video before computing the 29CRC. 30 31The output of the muxer consists of a single line of the form: 32CRC=0x@var{CRC}, where @var{CRC} is a hexadecimal number 0-padded to 338 digits containing the CRC for all the decoded input frames. 34 35For example to compute the CRC of the input, and store it in the file 36@file{out.crc}: 37@example 38avconv -i INPUT -f crc out.crc 39@end example 40 41You can print the CRC to stdout with the command: 42@example 43avconv -i INPUT -f crc - 44@end example 45 46You can select the output format of each frame with @command{avconv} by 47specifying the audio and video codec and format. For example to 48compute the CRC of the input audio converted to PCM unsigned 8-bit 49and the input video converted to MPEG-2 video, use the command: 50@example 51avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f crc - 52@end example 53 54See also the @ref{framecrc} muxer. 55 56@anchor{framecrc} 57@section framecrc 58 59Per-frame CRC (Cyclic Redundancy Check) testing format. 60 61This muxer computes and prints the Adler-32 CRC for each decoded audio 62and video frame. By default audio frames are converted to signed 6316-bit raw audio and video frames to raw video before computing the 64CRC. 65 66The output of the muxer consists of a line for each audio and video 67frame of the form: @var{stream_index}, @var{frame_dts}, 68@var{frame_size}, 0x@var{CRC}, where @var{CRC} is a hexadecimal 69number 0-padded to 8 digits containing the CRC of the decoded frame. 70 71For example to compute the CRC of each decoded frame in the input, and 72store it in the file @file{out.crc}: 73@example 74avconv -i INPUT -f framecrc out.crc 75@end example 76 77You can print the CRC of each decoded frame to stdout with the command: 78@example 79avconv -i INPUT -f framecrc - 80@end example 81 82You can select the output format of each frame with @command{avconv} by 83specifying the audio and video codec and format. For example, to 84compute the CRC of each decoded input audio frame converted to PCM 85unsigned 8-bit and of each decoded input video frame converted to 86MPEG-2 video, use the command: 87@example 88avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f framecrc - 89@end example 90 91See also the @ref{crc} muxer. 92 93@anchor{image2} 94@section image2 95 96Image file muxer. 97 98The image file muxer writes video frames to image files. 99 100The output filenames are specified by a pattern, which can be used to 101produce sequentially numbered series of files. 102The pattern may contain the string "%d" or "%0@var{N}d", this string 103specifies the position of the characters representing a numbering in 104the filenames. If the form "%0@var{N}d" is used, the string 105representing the number in each filename is 0-padded to @var{N} 106digits. The literal character '%' can be specified in the pattern with 107the string "%%". 108 109If the pattern contains "%d" or "%0@var{N}d", the first filename of 110the file list specified will contain the number 1, all the following 111numbers will be sequential. 112 113The pattern may contain a suffix which is used to automatically 114determine the format of the image files to write. 115 116For example the pattern "img-%03d.bmp" will specify a sequence of 117filenames of the form @file{img-001.bmp}, @file{img-002.bmp}, ..., 118@file{img-010.bmp}, etc. 119The pattern "img%%-%d.jpg" will specify a sequence of filenames of the 120form @file{img%-1.jpg}, @file{img%-2.jpg}, ..., @file{img%-10.jpg}, 121etc. 122 123The following example shows how to use @command{avconv} for creating a 124sequence of files @file{img-001.jpeg}, @file{img-002.jpeg}, ..., 125taking one image every second from the input video: 126@example 127avconv -i in.avi -vsync 1 -r 1 -f image2 'img-%03d.jpeg' 128@end example 129 130Note that with @command{avconv}, if the format is not specified with the 131@code{-f} option and the output filename specifies an image file 132format, the image2 muxer is automatically selected, so the previous 133command can be written as: 134@example 135avconv -i in.avi -vsync 1 -r 1 'img-%03d.jpeg' 136@end example 137 138Note also that the pattern must not necessarily contain "%d" or 139"%0@var{N}d", for example to create a single image file 140@file{img.jpeg} from the input video you can employ the command: 141@example 142avconv -i in.avi -f image2 -frames:v 1 img.jpeg 143@end example 144 145@section mpegts 146 147MPEG transport stream muxer. 148 149This muxer implements ISO 13818-1 and part of ETSI EN 300 468. 150 151The muxer options are: 152 153@table @option 154@item -mpegts_original_network_id @var{number} 155Set the original_network_id (default 0x0001). This is unique identifier 156of a network in DVB. Its main use is in the unique identification of a 157service through the path Original_Network_ID, Transport_Stream_ID. 158@item -mpegts_transport_stream_id @var{number} 159Set the transport_stream_id (default 0x0001). This identifies a 160transponder in DVB. 161@item -mpegts_service_id @var{number} 162Set the service_id (default 0x0001) also known as program in DVB. 163@item -mpegts_pmt_start_pid @var{number} 164Set the first PID for PMT (default 0x1000, max 0x1f00). 165@item -mpegts_start_pid @var{number} 166Set the first PID for data packets (default 0x0100, max 0x0f00). 167@end table 168 169The recognized metadata settings in mpegts muxer are @code{service_provider} 170and @code{service_name}. If they are not set the default for 171@code{service_provider} is "Libav" and the default for 172@code{service_name} is "Service01". 173 174@example 175avconv -i file.mpg -c copy \ 176 -mpegts_original_network_id 0x1122 \ 177 -mpegts_transport_stream_id 0x3344 \ 178 -mpegts_service_id 0x5566 \ 179 -mpegts_pmt_start_pid 0x1500 \ 180 -mpegts_start_pid 0x150 \ 181 -metadata service_provider="Some provider" \ 182 -metadata service_name="Some Channel" \ 183 -y out.ts 184@end example 185 186@section null 187 188Null muxer. 189 190This muxer does not generate any output file, it is mainly useful for 191testing or benchmarking purposes. 192 193For example to benchmark decoding with @command{avconv} you can use the 194command: 195@example 196avconv -benchmark -i INPUT -f null out.null 197@end example 198 199Note that the above command does not read or write the @file{out.null} 200file, but specifying the output file is required by the @command{avconv} 201syntax. 202 203Alternatively you can write the command as: 204@example 205avconv -benchmark -i INPUT -f null - 206@end example 207 208@section matroska 209 210Matroska container muxer. 211 212This muxer implements the matroska and webm container specs. 213 214The recognized metadata settings in this muxer are: 215 216@table @option 217 218@item title=@var{title name} 219Name provided to a single track 220@end table 221 222@table @option 223 224@item language=@var{language name} 225Specifies the language of the track in the Matroska languages form 226@end table 227 228@table @option 229 230@item STEREO_MODE=@var{mode} 231Stereo 3D video layout of two views in a single video track 232@table @option 233@item mono 234video is not stereo 235@item left_right 236Both views are arranged side by side, Left-eye view is on the left 237@item bottom_top 238Both views are arranged in top-bottom orientation, Left-eye view is at bottom 239@item top_bottom 240Both views are arranged in top-bottom orientation, Left-eye view is on top 241@item checkerboard_rl 242Each view is arranged in a checkerboard interleaved pattern, Left-eye view being first 243@item checkerboard_lr 244Each view is arranged in a checkerboard interleaved pattern, Right-eye view being first 245@item row_interleaved_rl 246Each view is constituted by a row based interleaving, Right-eye view is first row 247@item row_interleaved_lr 248Each view is constituted by a row based interleaving, Left-eye view is first row 249@item col_interleaved_rl 250Both views are arranged in a column based interleaving manner, Right-eye view is first column 251@item col_interleaved_lr 252Both views are arranged in a column based interleaving manner, Left-eye view is first column 253@item anaglyph_cyan_red 254All frames are in anaglyph format viewable through red-cyan filters 255@item right_left 256Both views are arranged side by side, Right-eye view is on the left 257@item anaglyph_green_magenta 258All frames are in anaglyph format viewable through green-magenta filters 259@item block_lr 260Both eyes laced in one Block, Left-eye view is first 261@item block_rl 262Both eyes laced in one Block, Right-eye view is first 263@end table 264@end table 265 266For example a 3D WebM clip can be created using the following command line: 267@example 268avconv -i sample_left_right_clip.mpg -an -c:v libvpx -metadata STEREO_MODE=left_right -y stereo_clip.webm 269@end example 270 271@section segment 272 273Basic stream segmenter. 274 275The segmenter muxer outputs streams to a number of separate files of nearly 276fixed duration. Output filename pattern can be set in a fashion similar to 277@ref{image2}. 278 279Every segment starts with a video keyframe, if a video stream is present. 280The segment muxer works best with a single constant frame rate video. 281 282Optionally it can generate a flat list of the created segments, one segment 283per line. 284 285@table @option 286@item segment_format @var{format} 287Override the inner container format, by default it is guessed by the filename 288extension. 289@item segment_time @var{t} 290Set segment duration to @var{t} seconds. 291@item segment_list @var{name} 292Generate also a listfile named @var{name}. 293@item segment_list_size @var{size} 294Overwrite the listfile once it reaches @var{size} entries. 295@end table 296 297@example 298avconv -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut 299@end example 300 301 302@c man end MUXERS 303