ffplay: fix compute_target_delay to better handle frames with long durations

Signed-off-by: Marton Balint <cus@passwd.hu>

ffplay.c

@@ -69,8 +69,12 @@ const int program_birth_year = 2003;
    A/V sync as SDL does not have hardware buffer fullness info. */
 #define SDL_AUDIO_BUFFER_SIZE 1024
 
-/* no AV sync correction is done if below the AV sync threshold */
-#define AV_SYNC_THRESHOLD 0.01
+/* no AV sync correction is done if below the minimum AV sync threshold */
+#define AV_SYNC_THRESHOLD_MIN 0.01
+/* AV sync correction is done if above the maximum AV sync threshold */
+#define AV_SYNC_THRESHOLD_MAX 0.1
+/* If a frame duration is longer than this, it will not be duplicated to compensate AV sync */
+#define AV_SYNC_FRAMEDUP_THRESHOLD 0.1
 /* no AV correction is done if too big error */
 #define AV_NOSYNC_THRESHOLD 10.0
 
@@ -1257,10 +1261,12 @@ static double compute_target_delay(double delay, VideoState *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 (!isnan(diff) && fabs(diff) < AV_NOSYNC_THRESHOLD) {
+        sync_threshold = FFMAX(AV_SYNC_THRESHOLD_MIN, FFMIN(AV_SYNC_THRESHOLD_MAX, delay));
+        if (!isnan(diff) && fabs(diff) < is->max_frame_duration) {
             if (diff <= -sync_threshold)
-                delay = 0;
+                delay = FFMAX(0, delay + diff);
+            else if (diff >= sync_threshold && delay > AV_SYNC_FRAMEDUP_THRESHOLD)
+                delay = delay + diff;
             else if (diff >= sync_threshold)
                 delay = 2 * delay;
         }