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LibVideo: Read Matroska lazily so that large files can start quickly

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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.
This commit is contained in:
Zaggy1024 2022-11-11 17:14:27 -06:00 • committed by Andreas Kling
parent f4c476b26f
commit 393cfdd5c5
11 changed files with 576 additions and 310 deletions
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36
Tests/LibVideo/TestVP9Decode.cpp
View file

@ -11,29 +11,33 @@
static void decode_video(StringView path, size_t expected_frame_count)
{
auto matroska_document = MUST(Video::Matroska::Reader::parse_matroska_from_file(path));
auto video_track_optional = matroska_document->track_for_track_type(Video::Matroska::TrackEntry::TrackType::Video);
VERIFY(video_track_optional.has_value());
auto video_track_entry = video_track_optional.value();
auto matroska_reader = MUST(Video::Matroska::Reader::from_file(path));
u64 video_track = 0;
MUST(matroska_reader.for_each_track_of_type(Video::Matroska::TrackEntry::TrackType::Video, [&](Video::Matroska::TrackEntry const& track_entry) -> Video::DecoderErrorOr<IterationDecision> {
video_track = track_entry.track_number();
return IterationDecision::Break;
}));
VERIFY(video_track != 0);
auto iterator = MUST(matroska_reader.create_sample_iterator(video_track));
size_t frame_count = 0;
size_t cluster_index, block_index, frame_index;
Video::VP9::Decoder vp9_decoder;
for (cluster_index = 0; cluster_index < matroska_document->clusters().size(); cluster_index++) {
auto const& cluster = matroska_document->clusters()[cluster_index];
for (block_index = 0; block_index < cluster.blocks().size(); block_index++) {
auto const& block = cluster.blocks()[block_index];
if (block.track_number() != video_track_entry.track_number())
continue;
while (frame_count <= expected_frame_count) {
auto block_result = iterator.next_block();
if (block_result.is_error() && block_result.error().category() == Video::DecoderErrorCategory::EndOfStream) {
VERIFY(frame_count == expected_frame_count);
return;
}
for (frame_index = 0; frame_index < block.frames().size(); frame_index++) {
MUST(vp9_decoder.receive_sample(block.frames()[frame_index]));
frame_count++;
}
auto block = block_result.release_value();
for (auto const& frame : block.frames()) {
MUST(vp9_decoder.receive_sample(frame));
frame_count++;
}
}
VERIFY(frame_count == expected_frame_count);
VERIFY_NOT_REACHED();
}
TEST_CASE(webm_in_vp9)