doc: Document the omit_tfhd_offset flag to the mp4 muxer
[libav.git] / doc / muxers.texi
1 @chapter Muxers
2 @c man begin MUXERS
4 Muxers are configured elements in Libav which allow writing
5 multimedia streams to a particular type of file.
7 When you configure your Libav build, all the supported muxers
8 are enabled by default. You can list all available muxers using the
9 configure option @code{--list-muxers}.
11 You can disable all the muxers with the configure option
12 @code{--disable-muxers} and selectively enable / disable single muxers
13 with the options @code{--enable-muxer=@var{MUXER}} /
14 @code{--disable-muxer=@var{MUXER}}.
16 The option @code{-formats} of the av* tools will display the list of
17 enabled muxers.
19 A description of some of the currently available muxers follows.
21 @anchor{crc}
22 @section crc
24 CRC (Cyclic Redundancy Check) testing format.
26 This muxer computes and prints the Adler-32 CRC of all the input audio
27 and video frames. By default audio frames are converted to signed
28 16-bit raw audio and video frames to raw video before computing the
29 CRC.
31 The output of the muxer consists of a single line of the form:
32 CRC=0x@var{CRC}, where @var{CRC} is a hexadecimal number 0-padded to
33 8 digits containing the CRC for all the decoded input frames.
35 For example to compute the CRC of the input, and store it in the file
36 @file{out.crc}:
37 @example
38 avconv -i INPUT -f crc out.crc
39 @end example
41 You can print the CRC to stdout with the command:
42 @example
43 avconv -i INPUT -f crc -
44 @end example
46 You can select the output format of each frame with @command{avconv} by
47 specifying the audio and video codec and format. For example to
48 compute the CRC of the input audio converted to PCM unsigned 8-bit
49 and the input video converted to MPEG-2 video, use the command:
50 @example
51 avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f crc -
52 @end example
54 See also the @ref{framecrc} muxer.
56 @anchor{framecrc}
57 @section framecrc
59 Per-frame CRC (Cyclic Redundancy Check) testing format.
61 This muxer computes and prints the Adler-32 CRC for each decoded audio
62 and video frame. By default audio frames are converted to signed
63 16-bit raw audio and video frames to raw video before computing the
64 CRC.
66 The output of the muxer consists of a line for each audio and video
67 frame of the form: @var{stream_index}, @var{frame_dts},
68 @var{frame_size}, 0x@var{CRC}, where @var{CRC} is a hexadecimal
69 number 0-padded to 8 digits containing the CRC of the decoded frame.
71 For example to compute the CRC of each decoded frame in the input, and
72 store it in the file @file{out.crc}:
73 @example
74 avconv -i INPUT -f framecrc out.crc
75 @end example
77 You can print the CRC of each decoded frame to stdout with the command:
78 @example
79 avconv -i INPUT -f framecrc -
80 @end example
82 You can select the output format of each frame with @command{avconv} by
83 specifying the audio and video codec and format. For example, to
84 compute the CRC of each decoded input audio frame converted to PCM
85 unsigned 8-bit and of each decoded input video frame converted to
86 MPEG-2 video, use the command:
87 @example
88 avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f framecrc -
89 @end example
91 See also the @ref{crc} muxer.
93 @anchor{hls}
94 @section hls
96 Apple HTTP Live Streaming muxer that segments MPEG-TS according to
97 the HTTP Live Streaming specification.
99 It creates a playlist file and numbered segment files. The output
100 filename specifies the playlist filename; the segment filenames
101 receive the same basename as the playlist, a sequential number and
102 a .ts extension.
104 @example
105 avconv -i in.nut out.m3u8
106 @end example
108 @table @option
109 @item -hls_time @var{seconds}
110 Set the segment length in seconds.
111 @item -hls_list_size @var{size}
112 Set the maximum number of playlist entries.
113 @item -hls_wrap @var{wrap}
114 Set the number after which index wraps.
115 @item -start_number @var{number}
116 Start the sequence from @var{number}.
117 @item -hls_base_url @var{baseurl}
118 Append @var{baseurl} to every entry in the playlist.
119 Useful to generate playlists with absolute paths.
120 @item -hls_allow_cache @var{allowcache}
121 Explicitly set whether the client MAY (1) or MUST NOT (0) cache media segments
122 @end table
124 @anchor{image2}
125 @section image2
127 Image file muxer.
129 The image file muxer writes video frames to image files.
131 The output filenames are specified by a pattern, which can be used to
132 produce sequentially numbered series of files.
133 The pattern may contain the string "%d" or "%0@var{N}d", this string
134 specifies the position of the characters representing a numbering in
135 the filenames. If the form "%0@var{N}d" is used, the string
136 representing the number in each filename is 0-padded to @var{N}
137 digits. The literal character '%' can be specified in the pattern with
138 the string "%%".
140 If the pattern contains "%d" or "%0@var{N}d", the first filename of
141 the file list specified will contain the number 1, all the following
142 numbers will be sequential.
144 The pattern may contain a suffix which is used to automatically
145 determine the format of the image files to write.
147 For example the pattern "img-%03d.bmp" will specify a sequence of
148 filenames of the form @file{img-001.bmp}, @file{img-002.bmp}, ...,
149 @file{img-010.bmp}, etc.
150 The pattern "img%%-%d.jpg" will specify a sequence of filenames of the
151 form @file{img%-1.jpg}, @file{img%-2.jpg}, ..., @file{img%-10.jpg},
152 etc.
154 The following example shows how to use @command{avconv} for creating a
155 sequence of files @file{img-001.jpeg}, @file{img-002.jpeg}, ...,
156 taking one image every second from the input video:
157 @example
158 avconv -i in.avi -vsync 1 -r 1 -f image2 'img-%03d.jpeg'
159 @end example
161 Note that with @command{avconv}, if the format is not specified with the
162 @code{-f} option and the output filename specifies an image file
163 format, the image2 muxer is automatically selected, so the previous
164 command can be written as:
165 @example
166 avconv -i in.avi -vsync 1 -r 1 'img-%03d.jpeg'
167 @end example
169 Note also that the pattern must not necessarily contain "%d" or
170 "%0@var{N}d", for example to create a single image file
171 @file{img.jpeg} from the input video you can employ the command:
172 @example
173 avconv -i in.avi -f image2 -frames:v 1 img.jpeg
174 @end example
176 @table @option
177 @item -start_number @var{number}
178 Start the sequence from @var{number}.
180 @item -update @var{number}
181 If @var{number} is nonzero, the filename will always be interpreted as just a
182 filename, not a pattern, and this file will be continuously overwritten with new
183 images.
185 @end table
187 @section matroska
189 Matroska container muxer.
191 This muxer implements the matroska and webm container specs.
193 The recognized metadata settings in this muxer are:
195 @table @option
197 @item title=@var{title name}
198 Name provided to a single track
199 @end table
201 @table @option
203 @item language=@var{language name}
204 Specifies the language of the track in the Matroska languages form
205 @end table
207 @table @option
209 @item STEREO_MODE=@var{mode}
210 Stereo 3D video layout of two views in a single video track
211 @table @option
212 @item mono
213 video is not stereo
214 @item left_right
215 Both views are arranged side by side, Left-eye view is on the left
216 @item bottom_top
217 Both views are arranged in top-bottom orientation, Left-eye view is at bottom
218 @item top_bottom
219 Both views are arranged in top-bottom orientation, Left-eye view is on top
220 @item checkerboard_rl
221 Each view is arranged in a checkerboard interleaved pattern, Left-eye view being first
222 @item checkerboard_lr
223 Each view is arranged in a checkerboard interleaved pattern, Right-eye view being first
224 @item row_interleaved_rl
225 Each view is constituted by a row based interleaving, Right-eye view is first row
226 @item row_interleaved_lr
227 Each view is constituted by a row based interleaving, Left-eye view is first row
228 @item col_interleaved_rl
229 Both views are arranged in a column based interleaving manner, Right-eye view is first column
230 @item col_interleaved_lr
231 Both views are arranged in a column based interleaving manner, Left-eye view is first column
232 @item anaglyph_cyan_red
233 All frames are in anaglyph format viewable through red-cyan filters
234 @item right_left
235 Both views are arranged side by side, Right-eye view is on the left
236 @item anaglyph_green_magenta
237 All frames are in anaglyph format viewable through green-magenta filters
238 @item block_lr
239 Both eyes laced in one Block, Left-eye view is first
240 @item block_rl
241 Both eyes laced in one Block, Right-eye view is first
242 @end table
243 @end table
245 For example a 3D WebM clip can be created using the following command line:
246 @example
247 avconv -i sample_left_right_clip.mpg -an -c:v libvpx -metadata STEREO_MODE=left_right -y stereo_clip.webm
248 @end example
250 This muxer supports the following options:
252 @table @option
254 @item reserve_index_space
255 By default, this muxer writes the index for seeking (called cues in Matroska
256 terms) at the end of the file, because it cannot know in advance how much space
257 to leave for the index at the beginning of the file. However for some use cases
258 -- e.g. streaming where seeking is possible but slow -- it is useful to put the
259 index at the beginning of the file.
261 If this option is set to a non-zero value, the muxer will reserve a given amount
262 of space in the file header and then try to write the cues there when the muxing
263 finishes. If the available space does not suffice, muxing will fail. A safe size
264 for most use cases should be about 50kB per hour of video.
266 Note that cues are only written if the output is seekable and this option will
267 have no effect if it is not.
269 @end table
271 @section mov, mp4, ismv
273 The mov/mp4/ismv muxer supports fragmentation. Normally, a MOV/MP4
274 file has all the metadata about all packets stored in one location
275 (written at the end of the file, it can be moved to the start for
276 better playback using the @command{qt-faststart} tool). A fragmented
277 file consists of a number of fragments, where packets and metadata
278 about these packets are stored together. Writing a fragmented
279 file has the advantage that the file is decodable even if the
280 writing is interrupted (while a normal MOV/MP4 is undecodable if
281 it is not properly finished), and it requires less memory when writing
282 very long files (since writing normal MOV/MP4 files stores info about
283 every single packet in memory until the file is closed). The downside
284 is that it is less compatible with other applications.
286 Fragmentation is enabled by setting one of the AVOptions that define
287 how to cut the file into fragments:
289 @table @option
290 @item -movflags frag_keyframe
291 Start a new fragment at each video keyframe.
292 @item -frag_duration @var{duration}
293 Create fragments that are @var{duration} microseconds long.
294 @item -frag_size @var{size}
295 Create fragments that contain up to @var{size} bytes of payload data.
296 @item -movflags frag_custom
297 Allow the caller to manually choose when to cut fragments, by
298 calling @code{av_write_frame(ctx, NULL)} to write a fragment with
299 the packets written so far. (This is only useful with other
300 applications integrating libavformat, not from @command{avconv}.)
301 @item -min_frag_duration @var{duration}
302 Don't create fragments that are shorter than @var{duration} microseconds long.
303 @end table
305 If more than one condition is specified, fragments are cut when
306 one of the specified conditions is fulfilled. The exception to this is
307 @code{-min_frag_duration}, which has to be fulfilled for any of the other
308 conditions to apply.
310 Additionally, the way the output file is written can be adjusted
311 through a few other options:
313 @table @option
314 @item -movflags empty_moov
315 Write an initial moov atom directly at the start of the file, without
316 describing any samples in it. Generally, an mdat/moov pair is written
317 at the start of the file, as a normal MOV/MP4 file, containing only
318 a short portion of the file. With this option set, there is no initial
319 mdat atom, and the moov atom only describes the tracks but has
320 a zero duration.
322 Files written with this option set do not work in QuickTime.
323 This option is implicitly set when writing ismv (Smooth Streaming) files.
324 @item -movflags separate_moof
325 Write a separate moof (movie fragment) atom for each track. Normally,
326 packets for all tracks are written in a moof atom (which is slightly
327 more efficient), but with this option set, the muxer writes one moof/mdat
328 pair for each track, making it easier to separate tracks.
330 This option is implicitly set when writing ismv (Smooth Streaming) files.
331 @item -movflags faststart
332 Run a second pass moving the index (moov atom) to the beginning of the file.
333 This operation can take a while, and will not work in various situations such
334 as fragmented output, thus it is not enabled by default.
335 @item -movflags disable_chpl
336 Disable Nero chapter markers (chpl atom). Normally, both Nero chapters
337 and a QuickTime chapter track are written to the file. With this option
338 set, only the QuickTime chapter track will be written. Nero chapters can
339 cause failures when the file is reprocessed with certain tagging programs.
340 @item -movflags omit_tfhd_offset
341 Do not write any absolute base_data_offset in tfhd atoms. This avoids
342 tying fragments to absolute byte positions in the file/streams.
343 @end table
345 Smooth Streaming content can be pushed in real time to a publishing
346 point on IIS with this muxer. Example:
347 @example
348 avconv -re @var{<normal input/transcoding options>} -movflags isml+frag_keyframe -f ismv http://server/publishingpoint.isml/Streams(Encoder1)
349 @end example
351 @section mp3
353 The MP3 muxer writes a raw MP3 stream with the following optional features:
354 @itemize @bullet
355 @item
356 An ID3v2 metadata header at the beginning (enabled by default). Versions 2.3 and
357 2.4 are supported, the @code{id3v2_version} private option controls which one is
358 used (3 or 4). Setting @code{id3v2_version} to 0 disables the ID3v2 header
359 completely.
361 The muxer supports writing attached pictures (APIC frames) to the ID3v2 header.
362 The pictures are supplied to the muxer in form of a video stream with a single
363 packet. There can be any number of those streams, each will correspond to a
364 single APIC frame. The stream metadata tags @var{title} and @var{comment} map
365 to APIC @var{description} and @var{picture type} respectively. See
366 @url{} for allowed picture types.
368 Note that the APIC frames must be written at the beginning, so the muxer will
369 buffer the audio frames until it gets all the pictures. It is therefore advised
370 to provide the pictures as soon as possible to avoid excessive buffering.
372 @item
373 A Xing/LAME frame right after the ID3v2 header (if present). It is enabled by
374 default, but will be written only if the output is seekable. The
375 @code{write_xing} private option can be used to disable it. The frame contains
376 various information that may be useful to the decoder, like the audio duration
377 or encoder delay.
379 @item
380 A legacy ID3v1 tag at the end of the file (disabled by default). It may be
381 enabled with the @code{write_id3v1} private option, but as its capabilities are
382 very limited, its usage is not recommended.
383 @end itemize
385 Examples:
387 Write an mp3 with an ID3v2.3 header and an ID3v1 footer:
388 @example
389 avconv -i INPUT -id3v2_version 3 -write_id3v1 1 out.mp3
390 @end example
392 Attach a picture to an mp3:
393 @example
394 avconv -i input.mp3 -i cover.png -c copy -metadata:s:v title="Album cover"
395 -metadata:s:v comment="Cover (Front)" out.mp3
396 @end example
398 Write a "clean" MP3 without any extra features:
399 @example
400 avconv -i input.wav -write_xing 0 -id3v2_version 0 out.mp3
401 @end example
403 @section mpegts
405 MPEG transport stream muxer.
407 This muxer implements ISO 13818-1 and part of ETSI EN 300 468.
409 The muxer options are:
411 @table @option
412 @item -mpegts_original_network_id @var{number}
413 Set the original_network_id (default 0x0001). This is unique identifier
414 of a network in DVB. Its main use is in the unique identification of a
415 service through the path Original_Network_ID, Transport_Stream_ID.
416 @item -mpegts_transport_stream_id @var{number}
417 Set the transport_stream_id (default 0x0001). This identifies a
418 transponder in DVB.
419 @item -mpegts_service_id @var{number}
420 Set the service_id (default 0x0001) also known as program in DVB.
421 @item -mpegts_pmt_start_pid @var{number}
422 Set the first PID for PMT (default 0x1000, max 0x1f00).
423 @item -mpegts_start_pid @var{number}
424 Set the first PID for data packets (default 0x0100, max 0x0f00).
425 @item -muxrate @var{number}
426 Set a constant muxrate (default VBR).
427 @item -pcr_period @var{numer}
428 Override the default PCR retransmission time (default 20ms), ignored
429 if variable muxrate is selected.
430 @end table
432 The recognized metadata settings in mpegts muxer are @code{service_provider}
433 and @code{service_name}. If they are not set the default for
434 @code{service_provider} is "Libav" and the default for
435 @code{service_name} is "Service01".
437 @example
438 avconv -i file.mpg -c copy \
439 -mpegts_original_network_id 0x1122 \
440 -mpegts_transport_stream_id 0x3344 \
441 -mpegts_service_id 0x5566 \
442 -mpegts_pmt_start_pid 0x1500 \
443 -mpegts_start_pid 0x150 \
444 -metadata service_provider="Some provider" \
445 -metadata service_name="Some Channel" \
446 -y out.ts
447 @end example
449 @section null
451 Null muxer.
453 This muxer does not generate any output file, it is mainly useful for
454 testing or benchmarking purposes.
456 For example to benchmark decoding with @command{avconv} you can use the
457 command:
458 @example
459 avconv -benchmark -i INPUT -f null out.null
460 @end example
462 Note that the above command does not read or write the @file{out.null}
463 file, but specifying the output file is required by the @command{avconv}
464 syntax.
466 Alternatively you can write the command as:
467 @example
468 avconv -benchmark -i INPUT -f null -
469 @end example
471 @section nut
473 @table @option
474 @item -syncpoints @var{flags}
475 Change the syncpoint usage in nut:
476 @table @option
477 @item @var{default} use the normal low-overhead seeking aids.
478 @item @var{none} do not use the syncpoints at all, reducing the overhead but making the stream non-seekable;
479 @item @var{timestamped} extend the syncpoint with a wallclock field.
480 @end table
481 The @var{none} and @var{timestamped} flags are experimental.
482 @end table
484 @example
485 avconv -i INPUT -f_strict experimental -syncpoints none - | processor
486 @end example
488 @section ogg
490 Ogg container muxer.
492 @table @option
493 @item -page_duration @var{duration}
494 Preferred page duration, in microseconds. The muxer will attempt to create
495 pages that are approximately @var{duration} microseconds long. This allows the
496 user to compromise between seek granularity and container overhead. The default
497 is 1 second. A value of 0 will fill all segments, making pages as large as
498 possible. A value of 1 will effectively use 1 packet-per-page in most
499 situations, giving a small seek granularity at the cost of additional container
500 overhead.
501 @end table
503 @section segment
505 Basic stream segmenter.
507 The segmenter muxer outputs streams to a number of separate files of nearly
508 fixed duration. Output filename pattern can be set in a fashion similar to
509 @ref{image2}.
511 Every segment starts with a video keyframe, if a video stream is present.
512 The segment muxer works best with a single constant frame rate video.
514 Optionally it can generate a flat list of the created segments, one segment
515 per line.
517 @table @option
518 @item segment_format @var{format}
519 Override the inner container format, by default it is guessed by the filename
520 extension.
521 @item segment_time @var{t}
522 Set segment duration to @var{t} seconds.
523 @item segment_list @var{name}
524 Generate also a listfile named @var{name}.
525 @item segment_list_type @var{type}
526 Select the listing format.
527 @table @option
528 @item @var{flat} use a simple flat list of entries.
529 @item @var{hls} use a m3u8-like structure.
530 @end table
531 @item segment_list_size @var{size}
532 Overwrite the listfile once it reaches @var{size} entries.
533 @item segment_list_entry_prefix @var{prefix}
534 Prepend @var{prefix} to each entry. Useful to generate absolute paths.
535 @item segment_wrap @var{limit}
536 Wrap around segment index once it reaches @var{limit}.
537 @end table
539 @example
540 avconv -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut
541 @end example
543 @c man end MUXERS