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diff --git a/DOCS/edl-mpv.rst b/DOCS/edl-mpv.rst new file mode 100644 index 0000000..0e4d2b4 --- /dev/null +++ b/DOCS/edl-mpv.rst @@ -0,0 +1,396 @@ +EDL files +========= + +EDL files basically concatenate ranges of video/audio from multiple source +files into a single continuous virtual file. Each such range is called a +segment, and consists of source file, source offset, and segment length. + +For example:: + + # mpv EDL v0 + f1.mkv,10,20 + f2.mkv + f1.mkv,40,10 + +This would skip the first 10 seconds of the file f1.mkv, then play the next +20 seconds, then switch to the file f2.mkv and play all of it, then switch +back to f1.mkv, skip to the 40 second mark, and play 10 seconds, and then +stop playback. The difference to specifying the files directly on command +line (and using ``--{ --start=10 --length=20 f1.mkv --}`` etc.) is that the +virtual EDL file appears as a virtual timeline (like a single file), instead +as a playlist. + +The general simplified syntax is:: + + # mpv EDL v0 + <filename> + <filename>,<start in seconds>,<length in seconds> + +If the start time is omitted, 0 is used. If the length is omitted, the +estimated remaining duration of the source file is used. + +Note:: + + Usage of relative or absolute paths as well as any protocol prefixes may be + prevented for security reasons. + + +Syntax of mpv EDL files +======================= + +Generally, the format is relatively strict. No superfluous whitespace (except +empty lines and commented lines) are allowed. You must use UNIX line breaks. + +The first line in the file must be ``# mpv EDL v0``. This designates that the +file uses format version 0, which is not frozen yet and may change any time. +(If you need a stable EDL file format, make a feature request. Likewise, if +you have suggestions for improvements, it's not too late yet.) + +The rest of the lines belong to one of these classes: + +1) An empty or commented line. A comment starts with ``#``, which must be the + first character in the line. The rest of the line (up until the next line + break) is ignored. An empty line has 0 bytes between two line feed bytes. +2) A header entry if the line starts with ``!``. +3) A segment entry in all other cases. + +Each segment entry consists of a list of named or unnamed parameters. +Parameters are separated with ``,``. Named parameters consist of a name, +followed by ``=``, followed by the value. Unnamed parameters have only a +value, and the name is implicit from the parameter position. + +Syntax:: + + segment_entry ::= <param> ( <param> ',' )* + param ::= [ <name> '=' ] ( <value> | '%' <number> '%' <valuebytes> ) + +The ``name`` string can consist of any characters, except ``=%,;\n!``. The +``value`` string can consist of any characters except of ``,;\n!``. + +The construct starting with ``%`` allows defining any value with arbitrary +contents inline, where ``number`` is an integer giving the number of bytes in +``valuebytes``. If a parameter value contains disallowed characters, it has to +be guarded by a length specifier using this syntax. + +The parameter name defines the meaning of the parameter: + +1) ``file``, the source file to use for this segment. +2) ``start``, a time value that specifies the start offset into the source file. +3) ``length``, a time value that specifies the length of the segment. + +See the section below for the format of timestamps. + +Unnamed parameters carry implicit names. The parameter position determines +which of the parameters listed above is set. For example, the second parameter +implicitly uses the name ``start``. + +Example:: + + # mpv EDL v0 + %18%filename,with,.mkv,10,length=20,param3=%13%value,escaped,param4=value2 + +this sets ``file`` to ``filename,with,.mkv``, ``start`` to ``10``, ``length`` +to ``20``, ``param3`` to ``value,escaped``, ``param4`` to ``value2``. + +Instead of line breaks, the character ``;`` can be used. Line feed bytes and +``;`` are treated equally. + +Header entries start with ``!`` as first character after a line break. Header +entries affect all other file entries in the EDL file. Their format is highly +implementation specific. They should generally follow the file header, and come +before any file entries. + +Disabling chapter generation and copying +======================================== + +By default, chapters from the source ranges are copied to the virtual file's +chapters. Also, a chapter is inserted after each range. This can be disabled +with the ``no_chapters`` header. + +Example:: + + !no_chapters + + +MP4 DASH +======== + +This is a header that helps implementing DASH, although it only provides a low +level mechanism. + +If this header is set, the given url designates an mp4 init fragment. It's +downloaded, and every URL in the EDL is prefixed with the init fragment on the +byte stream level. This is mostly for use by mpv's internal ytdl support. The +ytdl script will call youtube-dl, which in turn actually processes DASH +manifests. It may work only for this very specific purpose and fail to be +useful in other scenarios. It can be removed or changed in incompatible ways +at any times. + +Example:: + + !mp4_dash,init=url + +The ``url`` is encoded as parameter value as defined in the general EDL syntax. +It's expected to point to an "initialization fragment", which will be prefixed +to every entry in the EDL on the byte stream level. + +The current implementation will + +- ignore stream start times +- use durations as hint for seeking only +- not adjust source timestamps +- open and close segments (i.e. fragments) as needed +- not add segment boundaries as chapter points +- require full compatibility between all segments (same codec etc.) + +Another header part of this mechanism is ``no_clip``. This header is similar +to ``mp4_dash``, but does not include on-demand opening/closing of segments, +and does not support init segments. It also exists solely to support internal +ytdl requirements. Using ``no_clip`` with segments is not recommended and +probably breaks. ``mp4_dash`` already implicitly does a variant of ``no_clip``. + +The ``mp4_dash`` and ``no_clip`` headers are not part of the core EDL format. +They may be changed or removed at any time, depending on mpv's internal +requirements. + +Separate files for tracks +========================= + +The special ``new_stream`` header lets you specify separate parts and time +offsets for separate tracks. This can for example be used to source audio and +video track from separate files. + +Example:: + + # mpv EDL v0 + video.mkv + !new_stream + audio.mkv + +This adds all tracks from both files to the virtual track list. Upon playback, +the tracks will be played at the same time, instead of appending them. The files +can contain more than 1 stream; the apparent effect is the same as if the second +part after the ``!new_stream`` part were in a separate ``.edl`` file and added +with ``--external-file``. + +Note that all metadata between the stream sets created by ``new_stream`` is +disjoint. Global metadata is taken from the first part only. + +In context of mpv, this is redundant to the ``--audio-file`` and +``--external-file`` options, but (as of this writing) has the advantage that +this will use a unified cache for all streams. + +The ``new_stream`` header is not part of the core EDL format. It may be changed +or removed at any time, depending on mpv's internal requirements. + +If the first ``!new_stream`` is redundant, it is ignored. This is the same +example as above:: + + # mpv EDL v0 + !new_stream + video.mkv + !new_stream + audio.mkv + +Note that ``!new_stream`` must be the first header. Whether the parser accepts +(i.e. ignores) or rejects other headers before that is implementation specific. + +Track metadata +============== + +The special ``track_meta`` header can set some specific metadata fields of the +current ``!new_stream`` partition. The tags are applied to all tracks within +the partition. It is not possible to set the metadata for individual tracks (the +feature was needed only for single-track media). + +It provides following parameters change track metadata: + +``lang`` + Set the language tag. + +``title`` + Set the title tag. + +``byterate`` + Number of bytes per second this stream uses. (Purely informational.) + +``index`` + The numeric index of the track this should map to (default: -1). This is + the 0-based index of the virtual stream as seen by the player, enumerating + all audio/video/subtitle streams. If nothing matches, this is silently + discarded. The special index -1 (the default) has two meanings: if there + was a previous meta data entry (either ``!track_meta`` or ``!delay_open`` + element since the last ``!new_stream``), then this element manipulates + the previous meta data entry. If there was no previous entry, a new meta + data entry that matches all streams is created. + +Example:: + + # mpv EDL v0 + !track_meta,lang=bla,title=blabla + file.mkv + !new_stream + !track_meta,title=ducks + sub.srt + +If ``file.mkv`` has an audio and a video stream, both will use ``blabla`` as +title. The subtitle stream will use ``ducks`` as title. + +The ``track_meta`` header is not part of the core EDL format. It may be changed +or removed at any time, depending on mpv's internal requirements. + +Global metadata +=============== + +The special ``global_tags`` header can set metadata fields (aka tags) of the EDL +file. This metadata is supposed to be informational, much like for example ID3 +tags in audio files. Due to lack of separation of different kinds of metadata it +is unspecified what names are allowed, how they are interpreted, and whether +some of them affect playback functionally. (Much of this is unfortunately +inherited from FFmpeg. Another consequence of this is that FFmpeg "normalized" +tags are recognized, or stuff like replaygain tags.) + +Example:: + + !global_tags,title=bla,something_arbitrary=even_more_arbitrary + +Any parameter names are allowed. Repeated use of this adds to the tag list. If +``!new_stream`` is used, the location doesn't matter. + +May possibly be ignored in some cases, such as delayed media opening. + +Delayed media opening +===================== + +The special ``delay_open`` header can be used to open the media URL of the +stream only when the track is selected for the first time. This is supposed to +be an optimization to speed up opening of a remote stream if there are many +tracks for whatever reasons. + +This has various tricky restrictions, and also will defer failure to open a +stream to "later". By design, it's supposed to be used for single-track streams. + +Using multiple segments requires you to specify all offsets and durations (also +it was never tested whether it works at all). Interaction with ``mp4_dash`` may +be strange. + +You can describe multiple sub-tracks by using multiple ``delay_open`` headers +before the same source URL. (If there are multiple sub-tracks of the same media +type, then the mapping to the real stream is probably rather arbitrary.) If the +source contains tracks not described, a warning is logged when the delayed +opening happens, and the track is hidden. + +This has the following parameters: + +``media_type`` + Required. Must be set to ``video``, ``audio``, or ``sub``. (Other tracks in + the opened URL are ignored.) + +``codec`` + The mpv codec name that is expected. Although mpv tries to initialize a + decoder with it currently (and will fail track selection if it does not + initialize successfully), it is not used for decoding - decoding still uses + the information retrieved from opening the actual media information, and may + be a different codec (you should try to avoid this, of course). Defaults to + ``null``. + + Above also applies for similar fields such as ``w``. These fields are + mostly to help with user track pre-selection. + +``flags`` + A ``+`` separated list of boolean flags. Currently defined flags: + + ``default`` + Set the default track flag. + + ``forced`` + Set the forced track flag. + + Other values are ignored after triggering a warning. + +``w``, ``h`` + For video codecs: expected video size. See ``codec`` for details. + +``fps`` + For video codecs: expected video framerate, as integer. (The rate is usually + only crudely reported, and it makes no sense to expect exact values.) + +``samplerate`` + For audio codecs: expected sample rate, as integer. + +The ``delay_open`` header is not part of the core EDL format. It may be changed +or removed at any time, depending on mpv's internal requirements. + +Timestamp format +================ + +Currently, time values are floating point values in seconds. + +As an extension, you can set the ``timestamps=chapters`` option. If this option +is set, timestamps have to be integers, and refer to chapter numbers, starting +with 0. The default value for this parameter is ``seconds``, which means the +time is as described in the previous paragraph. + +Example:: + + # mpv EDL v0 + file.mkv,2,4,timestamps=chapters + +Plays chapter 3 and ends with the start of chapter 7 (4 chapters later). + +Implicit chapters +================= + +mpv will add one chapter per segment entry to the virtual timeline. + +By default, the chapter's titles will match the entries' filenames. +You can override set the ``title`` option to override the chapter title for +that segment. + +Example:: + + # mpv EDL v0 + cap.ts,5,240 + OP.mkv,0,90,title=Show Opening + +The virtual timeline will have two chapters, one called "cap.ts" from 0-240s +and a second one called "Show Opening" from 240-330s. + +Entry which defines the track layout +==================================== + +Normally, you're supposed to put only files with compatible layouts into an EDL +file. However, at least the mpv implementation accepts entries that use +different codecs, or even have a different number of audio/video/subtitle +tracks. In this case, it's not obvious, which virtual tracks the EDL show should +expose when being played. + +Currently, mpv will apply an arbitrary heuristic which tracks the EDL file +should expose. (Before mpv 0.30.0, it always used the first source file in the +segment list.) + +You can set the ``layout`` option to ``this`` to make a specific entry define +the track layout. + +Example:: + + # mpv EDL v0 + file_with_2_streams.ts,5,240 + file_with_5_streams.mkv,0,90,layout=this + +The way the different virtual EDL tracks are associated with the per-segment +ones is highly implementation-defined, and uses a heuristic. If a segment is +missing a track, there will be a "hole", and bad behavior may result. Improving +this is subject to further development (due to being fringe cases, they don't +have a high priority). + +If future versions of mpv change this again, this option may be ignored. + +Syntax of EDL URIs +================== + +mpv accepts inline EDL data in form of ``edl://`` URIs. Other than the +header, the syntax is exactly the same. It's far more convenient to use ``;`` +instead of line breaks, but that is orthogonal. + +Example: ``edl://f1.mkv,length=5,start=10;f2.mkv,30,20;f3.mkv`` |