ffplay中超过AV_SYNC_THRESHOLD_MAX的是怎么同步的呢？

ffplay同步的时候可以通过以下代码丢帧，
如果代码中time - is->frame_timer > AV_SYNC_THRESHOLD_MAX 成立，
则会将is_frame_timer设置成time，这样在time > is->frame_timer + duration是不会成立的，就不会丢掉该帧，这种情况是怎么实现同步的呢

  /* compute nominal last_duration */
            last_duration = vp_duration(is, lastvp, vp);
            if (redisplay)
                delay = 0.0;
            else
                delay = compute_target_delay(last_duration, is);

            time= av_gettime_relative()/1000000.0;
            if (time < is->frame_timer + delay && !redisplay) {
                *remaining_time = FFMIN(is->frame_timer + delay - time, *remaining_time);
                return;
            }

            is->frame_timer += delay;
            if (delay > 0 && time - is->frame_timer > AV_SYNC_THRESHOLD_MAX)
                is->frame_timer = time;

            SDL_LockMutex(is->pictq.mutex);
            if (!redisplay && !isnan(vp->pts))
                update_video_pts(is, vp->pts, vp->pos, vp->serial);
            SDL_UnlockMutex(is->pictq.mutex);

            if (frame_queue_nb_remaining(&is->pictq) > 1) {
                Frame *nextvp = frame_queue_peek_next(&is->pictq);
                duration = vp_duration(is, vp, nextvp);
                if(!is->step && (redisplay || framedrop>0 || (framedrop && get_master_sync_type(is) != AV_SYNC_VIDEO_MASTER)) && time > is->frame_timer + duration){
                    if (!redisplay)
                        is->frame_drops_late++;
                    frame_queue_next(&is->pictq);
                    redisplay = 0;
                    goto retry;
                }
            }

http://blog.csdn.net/maimang1001/article/details/38640057