Most WebM files don't have their default duration defined, so we need
to parse the Opus frame header to determine the duration. This is
needed for buffered range calculation.
Instead of using a single track entry for all blocks in the file, use a
lookup to get the info needed to calculate the timestamp for the
specific track a block belongs to. No change in behavior for
SampleIterator, since that only returns blocks from the track that was
passed. This will be useful for MSE, since it demuxes all tracks at
once.
...and abstract away the stream/cursor blocking/aborting functionality
so that demuxers can implement or ignore those methods as they see fit.
This is a step towards implementing a wrapper demuxer for MSE streams.
We were allowing Matroska blocks with fixed-size lacing to contain
frames with non-divisible sizes. This should not be possible, as it
inherently means that trailing bytes will be discarded.
We now have a valid and invalid testcase for fixed-size lacing to
ensure our handling remains correct.
We don't actually need a Vector stack of bytes read for each element
we're reading out of a Matroska file, we already have the C++ stack
in which we can store the start and end of the master elements we're
reading.
This fixes an issue where seeks while parsing master elements would not
increment m_octets_read, so the master element could continue reading
further than intended.
This could cause a BlockGroup followed by a SimpleBlock to read as if
the BlockGroup contained the SimpleBlock, meaning that SampleIterator
would skip the SimpleBlock.
A test is added to ensure this doesn't regress again.
Refactor the FFmpeg and Matroska demuxers to consume data through
`IncrementallyPopulatedStream::Cursor` instead of a pointer to fully
buffered.
This change establishes a new rule: each track must be initialized with
its own cursor. Data providers now explicitly create a per-track context
via `Demuxer::create_context_for_track(track, cursor)`, and own pointer
to that cursor. In the upcoming changes, holding the cursor in the
provider would allow to signal "cancel blocking reads" so an
in-flight seek can fail immediately when a newer seek request arrives.
Otherwise, if the sample iterator resides in a block with multiple
frames before the seek, the demuxer will output all the remaining
frames from that block before moving on to the block at the seeked
position.
