The segments are parsed for the SourceBufferProcessor by the
WebMByteStreamParser. It parses the initialization segment to update
its internal set of tracks, then SourceBufferProcessor/SourceBuffer set
them up for playback. When a media segment is received, it also parses
as much of it as is available, returning all the coded frames found so
far. SourceBufferProcessor then tells TrackBufferDemuxer to remove any
overlapping frames and insert the new ones.
TrackBufferDemuxer implements the Demuxer interface in terms of the
coded frame store maintained by the SourceBufferProcessor. It returns
the frames in decode order when requested by a data provider. When a
is needed, it finds the keyframe prior to the target timestamp, and
checks that there are no gaps in data up to the target timestamp. If
there are any gaps, it blocks until the gaps are gone.
...giving tracks a kind attribute, and renaming name to label.
Demuxers will need to determine the kind attribute, since the spec for
sourcing tracks requires us to select based on info we don't expose.
By making use of the WEB_PLATFORM_OBJECT macro we can remove
the boilerplate of needing to add this override for every
serializable platform object so that we can check whether they
are exposed or not.
The two classes now inherit from a common base MediaTrackBase, to
deduplicate the attributes that are shared between the two.
The integer ID from the container is used for each track's id
attribute.
The kind attribute is set to "main" or "translation" according to:
https://dev.w3.org/html5/html-sourcing-inband-tracks/
The label attribute is set to the human-readable name of the track, if
one is present.
The language attribute is set to a BCP 47 language tag, if one can be
parsed successfully.
