Since it will become a stream in a little bit, it should behave like all
non-trivial stream classes, who are not primarily intended to have
shared ownership to make closing behavior more predictable. Across all
uses of MappedFile, there is only one use case of shared mapped files in
LibVideo, which now uses the thin SharedMappedFile wrapper.
That's what this class really is; in fact that's what the first line of
the comment says it is.
This commit does not rename the main files, since those will contain
other time-related classes in a little bit.
This allows us to create a PlaybackManager from a file which has already
been mapped, instead of passing a file name.
This means that anyone who uses `PlaybackManager` can now use LibFSAC :)
This copies the video data from the Matroska document into the Track
structure that outside users have access to. Because Track can actually
represent other media types, this is set up such that the Track can hold
metadata for those other types when they are needed.
This is needed for LibWeb's HTMLMediaElement implementation.
In cases where the PlaybackManager's earliest buffered or displayed
sample is closer to the seek target than the demuxer's chosen keyframe,
we don't want to seek at all. To enable this, demuxers now receive an
optional parameter with the earliest timestamp that the caller can
still access.
The demuxer in turn returns an optional to indicate when a seek was not
needed, which allows PlaybackManager to avoid clearing its queue and
re-decoding frames.
Now that we're able to find the nearest keyframe, we can have a fast
seeking mode that only seeks to keyframes, so that it doesn't have to
also decode inter frames until it reaches the timestamp.
The default is still accurate seeking, so that the entire seeking
implementation can be tested.
This just searches sequentially through each block in a SampleIterator
until it finds a block after the specified seek timestamp. Once it
finds one, it will try to set the input/output iterator to the most
recent keyframe. If the iterator's original position is closer to the
target, however, it leaves it at that original position, allowing
callers to continue decoding from that position until they reach the
target timestamp.
This implements the PlaybackManager portion of seeking, so that it can
seek to any frame in the video by dropping all preceding frames until
it reaches the seek point.
MatroskaDemuxer currently will only seek to the start of the video.
That means that every seek has to drop all the frames until it comes
across the target timestamp.
With these changes, the seek bar can be used, but only to seek to the
start of the file. Seeking to anywhere else in the file will cause an
error in the demuxer.
The timestamp label that was previously invisible now has its text set
according to either the playback or seek slider's position.
The Demuxer class was changed to return errors for more functions so
that all of the underlying reading can be done lazily. Other than that,
the demuxer interface is unchanged, and only the underlying reader was
modified.
The MatroskaDocument class is no more, and MatroskaReader's getter
functions replace it. Every MatroskaReader getter beyond the Segment
element's position is parsed lazily from the file as needed. This means
that all getter functions can return DecoderErrors which must be
handled by callers.
Matroska::Reader functions now return DecoderErrorOr instead of values
being declared Optional. Useful errors can be handled by the users of
the parser, similarly to the VP9 decoder. A lot of the error checking
in the reader is a lot cleaner thanks to this change, since all reads
can be range checked in Streamer::read_octet() now.
Most functions for the Streamer class are now also out-of-line in
Reader.cpp now instead of residing in the header.
As new demuxers are added, this will get quite full of files, so it'll
be good to have a separate folder for these.
To avoid too many chained namespaces, the Containers subdirectory is
not also a namespace, but the Matroska folder is for the sake of
separating the multiple classes for parsed information entering the
Video namespace.
2022-11-25 23:28:39 +01:00
Renamed from Userland/Libraries/LibVideo/MatroskaDemuxer.cpp (Browse further)
