Rework the audio/video sync algorithm.

[nageru] / decklink_output.cpp

diff --git a/decklink_output.cpp b/decklink_output.cpp
index a826dfe22ee95c5588f86edebec1c2ad1ce64ed3..38f44ee96c4d614e2d9ed2729ad2cc42e185eec8 100644 (file)
--- a/decklink_output.cpp
+++ b/decklink_output.cpp
@@ -242,7 +242,7 @@ void DeckLinkOutput::send_audio(int64_t pts, const std::vector<float> &samples)
        }
 }
 
-void DeckLinkOutput::wait_for_frame(int64_t pts, int *dropped_frames, int64_t *frame_duration, bool *is_preroll)
+void DeckLinkOutput::wait_for_frame(int64_t pts, int *dropped_frames, int64_t *frame_duration, bool *is_preroll, steady_clock::time_point *frame_timestamp)
 {
        assert(!should_quit);
 
@@ -277,11 +277,12 @@ void DeckLinkOutput::wait_for_frame(int64_t pts, int *dropped_frames, int64_t *f
        double playback_speed;
        output->GetScheduledStreamTime(TIMEBASE, &stream_frame_time, &playback_speed);
 
+       *frame_timestamp = steady_clock::now() +
+               nanoseconds((target_time - stream_frame_time) * 1000000000 / TIMEBASE);
+
        // If we're ahead of time, wait for the frame to (approximately) start.
        if (stream_frame_time < target_time) {
-               steady_clock::time_point t = steady_clock::now() +
-                       nanoseconds((target_time - stream_frame_time) * 1000000000 / TIMEBASE);
-               this_thread::sleep_until(t);
+               this_thread::sleep_until(*frame_timestamp);
                return;
        }
 
@@ -296,6 +297,8 @@ void DeckLinkOutput::wait_for_frame(int64_t pts, int *dropped_frames, int64_t *f
        // Oops, we missed by more than one frame. Return immediately,
        // but drop so that we catch up.
        *dropped_frames = (stream_frame_time - target_time + *frame_duration - 1) / *frame_duration;
+       const int64_t ns_per_frame = this->frame_duration * 1000000000 / TIMEBASE;
+       *frame_timestamp += nanoseconds(*dropped_frames * ns_per_frame);
        fprintf(stderr, "Dropped %d output frames; skipping.\n", *dropped_frames);
 }