Small optimization.

[nageru] / decklink_output.cpp

diff --git a/decklink_output.cpp b/decklink_output.cpp
index b3c4c85457dedef75fd1a115fa9b82689ac27599..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)
+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);
 
@@ -255,9 +255,12 @@ void DeckLinkOutput::wait_for_frame(int64_t pts, int *dropped_frames, int64_t *f
 
        // While prerolling, we send out frames as quickly as we can.
        if (target_time < base_pts) {
+               *is_preroll = true;
                return;
        }
 
+       *is_preroll = !playback_started;
+
        if (!playback_started) {
                if (output->EndAudioPreroll() != S_OK) {
                        fprintf(stderr, "Could not end audio preroll\n");
@@ -274,11 +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;
        }
 
@@ -293,6 +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);
 }