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LibVideo/PlaybackManager: Decode frames off the main thread

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Running decoding on the main thread can cause frames to be delayed due
to the presentation timer waiting for a decode to finish. If a frame
takes too long to decode, this delay can be quite visible. Therefore,
decoding has been moved to a separate thread, with frames sent to the
main thread through a thread-safe queue.

This results in frame times going from being late by up to 16ms to a
very consistent ~1-2ms.
This commit is contained in:
Zaggy1024 2023-04-19 17:11:51 -05:00 • committed by Andrew Kaster
parent eae7422ebc
commit 71d70df34f
2 changed files with 203 additions and 126 deletions
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40
Userland/Libraries/LibVideo/PlaybackManager.h
View file

@ -25,6 +25,12 @@ namespace Video {
class FrameQueueItem {
public:
FrameQueueItem()
: m_data(Empty())
, m_timestamp(Time::zero())
{
}
static constexpr Time no_timestamp = Time::min();
enum class Type {
@ -55,6 +61,8 @@ public:
return error;
}
bool is_empty() const { return m_data.has<Empty>(); }
DeprecatedString debug_string() const
{
if (is_error())
@ -76,12 +84,12 @@ private:
{
}
Variant<Empty, RefPtr<Gfx::Bitmap>, DecoderError> m_data;
Time m_timestamp;
Variant<Empty, RefPtr<Gfx::Bitmap>, DecoderError> m_data { Empty() };
Time m_timestamp { no_timestamp };
};
static constexpr size_t FRAME_BUFFER_COUNT = 4;
using VideoFrameQueue = Queue<FrameQueueItem, FRAME_BUFFER_COUNT>;
static constexpr size_t frame_buffer_count = 4;
using VideoFrameQueue = Core::SharedSingleProducerCircularQueue<FrameQueueItem, frame_buffer_count>;
enum class PlaybackState {
Playing,
@ -92,6 +100,9 @@ enum class PlaybackState {
};
class PlaybackManager {
AK_MAKE_NONCOPYABLE(PlaybackManager);
AK_MAKE_NONMOVABLE(PlaybackManager);
public:
enum class SeekMode {
Accurate,
@ -105,7 +116,7 @@ public:
static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_data(ReadonlyBytes data);
PlaybackManager(NonnullOwnPtr<Demuxer>& demuxer, Track video_track, NonnullOwnPtr<VideoDecoder>&& decoder, NonnullOwnPtr<VideoFrameQueue>&& frame_queue);
PlaybackManager(NonnullOwnPtr<Demuxer>& demuxer, Track video_track, NonnullOwnPtr<VideoDecoder>&& decoder, VideoFrameQueue&& frame_queue);
~PlaybackManager();
void resume_playback();
@ -145,12 +156,13 @@ private:
static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> create(NonnullOwnPtr<Demuxer> demuxer);
void start_timer(int milliseconds);
void timer_callback();
// This must be called with m_demuxer_mutex locked!
Optional<Time> seek_demuxer_to_most_recent_keyframe(Time timestamp, Optional<Time> earliest_available_sample = OptionalNone());
bool decode_and_queue_one_sample();
void on_decode_timer();
Optional<FrameQueueItem> dequeue_one_frame();
void decode_and_queue_one_sample();
void dispatch_decoder_error(DecoderError error);
void dispatch_new_frame(RefPtr<Gfx::Bitmap> frame);
@ -162,15 +174,20 @@ private:
Time m_last_present_in_media_time = Time::zero();
NonnullOwnPtr<Demuxer> m_demuxer;
Threading::Mutex m_demuxer_mutex;
Track m_selected_video_track;
NonnullOwnPtr<VideoDecoder> m_decoder;
NonnullOwnPtr<VideoFrameQueue> m_frame_queue;
VideoFrameQueue m_frame_queue;
RefPtr<Core::Timer> m_present_timer;
unsigned m_decoding_buffer_time_ms = 16;
RefPtr<Core::Timer> m_decode_timer;
RefPtr<Threading::Thread> m_decode_thread;
NonnullOwnPtr<VideoDecoder> m_decoder;
Atomic<bool> m_stop_decoding { false };
Threading::Mutex m_decode_wait_mutex;
Threading::ConditionVariable m_decode_wait_condition;
Atomic<bool> m_buffer_is_full { false };
OwnPtr<PlaybackStateHandler> m_playback_handler;
Optional<FrameQueueItem> m_next_frame;
@ -200,7 +217,6 @@ private:
virtual Time current_time() const;
virtual ErrorOr<void> on_timer_callback() { return {}; };
virtual ErrorOr<void> on_buffer_filled() { return {}; };
protected:
template<class T, class... Args>