LibVideo: Reorganize demuxer file hierarchy and rename Matroska files

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.

Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp

@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) 2022, Gregory Bertilson <zaggy1024@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "MatroskaDemuxer.h"
+
+namespace Video::Matroska {
+
+DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> MatroskaDemuxer::from_file(StringView filename)
+{
+    // FIXME: MatroskaReader should return errors.
+    auto nullable_document = Reader::parse_matroska_from_file(filename);
+    if (!nullable_document)
+        return DecoderError::format(DecoderErrorCategory::IO, "Failed to open matroska from file '{}'", filename);
+    auto document = nullable_document.release_nonnull();
+    return make<MatroskaDemuxer>(document);
+}
+
+DecoderErrorOr<NonnullOwnPtr<MatroskaDemuxer>> MatroskaDemuxer::from_data(ReadonlyBytes data)
+{
+    // FIXME: MatroskaReader should return errors.
+    auto nullable_document = Reader::parse_matroska_from_data(data.data(), data.size());
+    if (!nullable_document)
+        return DecoderError::format(DecoderErrorCategory::IO, "Failed to open matroska from data");
+    auto document = nullable_document.release_nonnull();
+    return make<MatroskaDemuxer>(document);
+}
+
+Vector<Track> MatroskaDemuxer::get_tracks_for_type(TrackType type)
+{
+    TrackEntry::TrackType matroska_track_type;
+
+    switch (type) {
+    case TrackType::Video:
+        matroska_track_type = TrackEntry::TrackType::Video;
+        break;
+    case TrackType::Audio:
+        matroska_track_type = TrackEntry::TrackType::Audio;
+        break;
+    case TrackType::Subtitles:
+        matroska_track_type = TrackEntry::TrackType::Subtitle;
+        break;
+    }
+
+    Vector<Track> tracks;
+
+    for (auto const& track_table_entry : m_document->tracks()) {
+        auto const& track_entry = track_table_entry.value;
+        if (matroska_track_type == track_entry->track_type())
+            tracks.append(Track(type, track_entry->track_number()));
+    }
+
+    // FIXME: Sort the vector, presumably the hashtable will not have a consistent order.
+    return tracks;
+}
+
+ErrorOr<MatroskaDemuxer::TrackStatus*> MatroskaDemuxer::get_track_status(Track track)
+{
+    if (!m_track_statuses.contains(track))
+        TRY(m_track_statuses.try_set(track, TrackStatus()));
+
+    return &m_track_statuses.get(track).release_value();
+}
+
+DecoderErrorOr<void> MatroskaDemuxer::seek_to_most_recent_keyframe(Track track, size_t timestamp)
+{
+    if (timestamp == 0) {
+        auto track_status = DECODER_TRY_ALLOC(get_track_status(track));
+        track_status->m_cluster_index = 0;
+        track_status->m_block_index = 0;
+        track_status->m_frame_index = 0;
+        return {};
+    }
+
+    return DecoderError::not_implemented();
+}
+
+DecoderErrorOr<NonnullOwnPtr<Sample>> MatroskaDemuxer::get_next_sample_for_track(Track track)
+{
+    auto track_status = DECODER_TRY_ALLOC(get_track_status(track));
+
+    for (; track_status->m_cluster_index < m_document->clusters().size(); track_status->m_cluster_index++) {
+        auto const& cluster = m_document->clusters()[track_status->m_cluster_index];
+        for (; track_status->m_block_index < cluster.blocks().size(); track_status->m_block_index++) {
+            auto const& block = cluster.blocks()[track_status->m_block_index];
+            if (block.track_number() != track.identifier())
+                continue;
+            if (track_status->m_frame_index < block.frame_count()) {
+                switch (track.type()) {
+                case TrackType::Video: {
+                    // FIXME: This makes a copy of the sample, which shouldn't be necessary.
+                    //        Matroska should make a RefPtr<ByteBuffer>, probably.
+                    auto cicp = m_document->track_for_track_number(track.identifier())->video_track()->color_format.to_cicp();
+                    Time timestamp = Time::from_nanoseconds((cluster.timestamp() + block.timestamp()) * m_document->segment_information()->timestamp_scale());
+                    return make<VideoSample>(block.frame(track_status->m_frame_index++), cicp, timestamp);
+                }
+                default:
+                    return DecoderError::not_implemented();
+                }
+            }
+            track_status->m_frame_index = 0;
+        }
+        track_status->m_block_index = 0;
+    }
+    return DecoderError::with_description(DecoderErrorCategory::EndOfStream, "End of stream reached."sv);
+}
+
+Time MatroskaDemuxer::duration()
+{
+    if (!m_document->segment_information().has_value())
+        return Time::zero();
+    if (!m_document->segment_information()->duration().has_value())
+        return Time::zero();
+    return Time::from_nanoseconds(m_document->segment_information()->duration().value() * m_document->segment_information()->timestamp_scale());
+}
+
+}