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LibVideo: Implement accurate seeking to inter frames in PlaybackManager

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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.
This commit is contained in:
Zaggy1024 2022-11-14 00:54:21 -06:00 • committed by Andreas Kling
parent 9a9fe08449
commit 5c2cede2c9
3 changed files with 65 additions and 24 deletions
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59
Userland/Libraries/LibVideo/PlaybackManager.cpp
View file

@ -58,7 +58,7 @@ void PlaybackManager::set_playback_status(PlaybackStatus status)
restart_playback();
m_last_present_in_real_time = Time::now_monotonic();
m_present_timer->start(0);
} else {
} else if (!is_seeking()) {
m_last_present_in_media_time = current_playback_time();
m_last_present_in_real_time = Time::zero();
m_present_timer->stop();
@ -70,16 +70,27 @@ void PlaybackManager::set_playback_status(PlaybackStatus status)
void PlaybackManager::resume_playback()
{
if (is_seeking()) {
set_playback_status(PlaybackStatus::SeekingPlaying);
return;
}
set_playback_status(PlaybackStatus::Playing);
}
void PlaybackManager::pause_playback()
{
if (is_seeking()) {
set_playback_status(PlaybackStatus::SeekingPaused);
return;
}
set_playback_status(PlaybackStatus::Paused);
}
Time PlaybackManager::current_playback_time()
{
if (is_seeking())
return m_seek_to_media_time;
VERIFY(!m_last_present_in_media_time.is_negative());
if (m_status == PlaybackStatus::Playing)
return m_last_present_in_media_time + (Time::now_monotonic() - m_last_present_in_real_time);
return m_last_present_in_media_time;
@ -108,13 +119,28 @@ void PlaybackManager::on_decoder_error(DecoderError error)
}
}
void PlaybackManager::end_seek()
{
dbgln_if(PLAYBACK_MANAGER_DEBUG, "We've finished seeking, reset seek target and play");
VERIFY(!m_seek_to_media_time.is_negative());
m_last_present_in_media_time = m_seek_to_media_time;
m_seek_to_media_time = Time::min();
if (m_status == PlaybackStatus::SeekingPlaying) {
set_playback_status(PlaybackStatus::Playing);
return;
}
VERIFY(m_status == PlaybackStatus::SeekingPaused);
set_playback_status(PlaybackStatus::Paused);
}
void PlaybackManager::update_presented_frame()
{
Optional<FrameQueueItem> future_frame_item;
bool should_present_frame = false;
// Skip frames until we find a frame past the current playback time, and keep the one that precedes it to display.
while (m_status == PlaybackStatus::Playing && !m_frame_queue->is_empty()) {
while ((m_status == PlaybackStatus::Playing || is_seeking()) && !m_frame_queue->is_empty()) {
future_frame_item.emplace(m_frame_queue->dequeue());
m_decode_timer->start(0);
@ -124,7 +150,7 @@ void PlaybackManager::update_presented_frame()
break;
}
if (m_next_frame.has_value()) {
if (m_next_frame.has_value() && !is_seeking()) {
dbgln_if(PLAYBACK_MANAGER_DEBUG, "At {}ms: Dropped {} in favor of {}", current_playback_time().to_milliseconds(), m_next_frame->debug_string(), future_frame_item->debug_string());
m_skipped_frames++;
}
@ -162,7 +188,10 @@ void PlaybackManager::update_presented_frame()
// If we have a frame, send it for presentation.
if (should_present_frame) {
m_last_present_in_media_time = current_playback_time();
if (is_seeking())
end_seek();
else
m_last_present_in_media_time = current_playback_time();
m_last_present_in_real_time = Time::now_monotonic();
m_main_loop.post_event(m_event_handler, make<VideoFramePresentEvent>(m_next_frame.value().bitmap()));
dbgln_if(PLAYBACK_MANAGER_DEBUG, "Sent frame for presentation");
@ -194,16 +223,24 @@ void PlaybackManager::update_presented_frame()
void PlaybackManager::seek_to_timestamp(Time timestamp)
{
dbgln_if(PLAYBACK_MANAGER_DEBUG, "Seeking to {}ms", timestamp.to_milliseconds());
m_last_present_in_media_time = Time::zero();
m_last_present_in_real_time = Time::zero();
m_frame_queue->clear();
m_next_frame.clear();
m_skipped_frames = 0;
// FIXME: When the demuxer is getting samples off the main thread in the future, this needs to
// mutex so that seeking can't happen while that thread is getting a sample.
auto result = m_demuxer->seek_to_most_recent_keyframe(m_selected_video_track, timestamp);
if (result.is_error())
on_decoder_error(result.release_error());
if (is_playing())
set_playback_status(PlaybackStatus::SeekingPlaying);
else
set_playback_status(PlaybackStatus::SeekingPaused);
m_frame_queue->clear();
m_next_frame.clear();
m_skipped_frames = 0;
m_seek_to_media_time = timestamp;
m_last_present_in_media_time = Time::min();
m_last_present_in_real_time = Time::zero();
m_present_timer->stop();
m_decode_timer->start(0);
}
void PlaybackManager::restart_playback()
@ -232,7 +269,7 @@ bool PlaybackManager::decode_and_queue_one_sample()
if (_temporary_result.is_error()) { \
dbgln_if(PLAYBACK_MANAGER_DEBUG, "Enqueued decoder error: {}", _temporary_result.error().string_literal()); \
m_frame_queue->enqueue(FrameQueueItem::error_marker(_temporary_result.release_error())); \
m_present_timer->start(0); \
m_present_timer->start(0); \
return false; \
} \
_temporary_result.release_value(); \
@ -298,7 +335,7 @@ void PlaybackManager::on_decode_timer()
}
// Continually decode until buffering is complete
if (is_buffering())
if (is_buffering() || is_seeking())
m_decode_timer->start(0);
}