static double compute_target_delay(double delay, VideoState *is) { double sync_threshold, diff; /* update delay to follow master synchronisation source */ if (get_master_sync_type(is) != AV_SYNC_VIDEO_MASTER) { /* if video is slave, we try to correct big delays by duplicating or deleting a frame */ diff = get_video_clock(is) - get_master_clock(is); /* skip or repeat frame. We take into account the delay to compute the threshold. I still don't know if it is the best guess */ sync_threshold = FFMAX(AV_SYNC_THRESHOLD, delay); if (fabs(diff) < AV_NOSYNC_THRESHOLD) { if (diff <= -sync_threshold) delay = 0; else if (diff >= sync_threshold) delay = 2 * delay; } } av_dlog(NULL, "video: delay=%0.3f A-V=%f\n", delay, -diff); return delay; }