From fd3ffd88cecd059eaf36cef1814cbe805361c564 Mon Sep 17 00:00:00 2001
From: Zaggy1024 <zaggy1024@gmail.com>
Date: Sun, 13 Nov 2022 20:33:23 -0600
Subject: [PATCH] LibVideo: Add a fast seeking mode to seek only to keyframes

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.
---
 Userland/Libraries/LibVideo/Containers/Demuxer.h      |  3 ++-
 .../LibVideo/Containers/Matroska/MatroskaDemuxer.cpp  |  7 ++++---
 .../LibVideo/Containers/Matroska/MatroskaDemuxer.h    |  2 +-
 Userland/Libraries/LibVideo/PlaybackManager.cpp       |  5 ++++-
 Userland/Libraries/LibVideo/PlaybackManager.h         | 11 +++++++++++
 5 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/Userland/Libraries/LibVideo/Containers/Demuxer.h b/Userland/Libraries/LibVideo/Containers/Demuxer.h
index dacc121678..1a2d2355d2 100644
--- a/Userland/Libraries/LibVideo/Containers/Demuxer.h
+++ b/Userland/Libraries/LibVideo/Containers/Demuxer.h
@@ -28,7 +28,8 @@ public:
         return sample.release_nonnull<VideoSample>();
     }
 
-    virtual DecoderErrorOr<void> seek_to_most_recent_keyframe(Track track, Time timestamp) = 0;
+    // Returns the timestamp of the keyframe that was seeked to.
+    virtual DecoderErrorOr<Time> seek_to_most_recent_keyframe(Track track, Time timestamp) = 0;
 
     virtual DecoderErrorOr<Time> duration() = 0;
 
diff --git a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp
index 8834857a89..dcdaf858f6 100644
--- a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp
+++ b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.cpp
@@ -53,16 +53,17 @@ DecoderErrorOr<MatroskaDemuxer::TrackStatus*> MatroskaDemuxer::get_track_status(
     return &m_track_statuses.get(track).release_value();
 }
 
-DecoderErrorOr<void> MatroskaDemuxer::seek_to_most_recent_keyframe(Track track, Time timestamp)
+DecoderErrorOr<Time> MatroskaDemuxer::seek_to_most_recent_keyframe(Track track, Time timestamp)
 {
     // Removing the track status will cause us to start from the beginning.
     if (timestamp.is_zero()) {
         m_track_statuses.remove(track);
-        return {};
+        return timestamp;
     }
 
     auto& track_status = *TRY(get_track_status(track));
-    return m_reader.seek_to_random_access_point(track_status.iterator, timestamp);
+    TRY(m_reader.seek_to_random_access_point(track_status.iterator, timestamp));
+    return track_status.iterator.last_timestamp();
 }
 
 DecoderErrorOr<NonnullOwnPtr<Sample>> MatroskaDemuxer::get_next_sample_for_track(Track track)
diff --git a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h
index 3578a99cca..bb55a8911d 100644
--- a/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h
+++ b/Userland/Libraries/LibVideo/Containers/Matroska/MatroskaDemuxer.h
@@ -27,7 +27,7 @@ public:
 
     DecoderErrorOr<Vector<Track>> get_tracks_for_type(TrackType type) override;
 
-    DecoderErrorOr<void> seek_to_most_recent_keyframe(Track track, Time timestamp) override;
+    DecoderErrorOr<Time> seek_to_most_recent_keyframe(Track track, Time timestamp) override;
 
     DecoderErrorOr<Time> duration() override;
 
diff --git a/Userland/Libraries/LibVideo/PlaybackManager.cpp b/Userland/Libraries/LibVideo/PlaybackManager.cpp
index bd031c6f87..22941e1149 100644
--- a/Userland/Libraries/LibVideo/PlaybackManager.cpp
+++ b/Userland/Libraries/LibVideo/PlaybackManager.cpp
@@ -236,7 +236,10 @@ void PlaybackManager::seek_to_timestamp(Time timestamp)
     m_frame_queue->clear();
     m_next_frame.clear();
     m_skipped_frames = 0;
-    m_seek_to_media_time = timestamp;
+    if (m_seek_mode == SeekMode::Accurate)
+        m_seek_to_media_time = timestamp;
+    else
+        m_seek_to_media_time = result.release_value();
     m_last_present_in_media_time = Time::min();
     m_last_present_in_real_time = Time::zero();
     m_present_timer->stop();
diff --git a/Userland/Libraries/LibVideo/PlaybackManager.h b/Userland/Libraries/LibVideo/PlaybackManager.h
index beb5e2d5d9..d4b3abf59a 100644
--- a/Userland/Libraries/LibVideo/PlaybackManager.h
+++ b/Userland/Libraries/LibVideo/PlaybackManager.h
@@ -94,6 +94,13 @@ using VideoFrameQueue = Queue<FrameQueueItem, FRAME_BUFFER_COUNT>;
 
 class PlaybackManager {
 public:
+    enum class SeekMode {
+        Accurate,
+        Fast,
+    };
+
+    static constexpr SeekMode DEFAULT_SEEK_MODE = SeekMode::Accurate;
+
     static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_file(Core::Object& event_handler, StringView file);
     static DecoderErrorOr<NonnullOwnPtr<PlaybackManager>> from_data(Core::Object& event_handler, Span<u8> data);
 
@@ -108,6 +115,9 @@ public:
     bool is_buffering() const { return m_status == PlaybackStatus::Buffering; }
     bool is_stopped() const { return m_status == PlaybackStatus::Stopped || m_status == PlaybackStatus::Corrupted; }
 
+    SeekMode seek_mode() { return m_seek_mode; }
+    void set_seek_mode(SeekMode mode) { m_seek_mode = mode; }
+
     u64 number_of_skipped_frames() const { return m_skipped_frames; }
 
     void on_decoder_error(DecoderError error);
@@ -136,6 +146,7 @@ private:
     Time m_last_present_in_real_time = Time::zero();
 
     Time m_seek_to_media_time = Time::min();
+    SeekMode m_seek_mode = DEFAULT_SEEK_MODE;
 
     NonnullOwnPtr<Demuxer> m_demuxer;
     Track m_selected_video_track;