avformat/movenc: Use cluster timestamps when available in edts

Also print both if they differ
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/movenc.c

@@ -2232,7 +2232,21 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
     int version = duration < INT32_MAX ? 0 : 1;
     int entry_size, entry_count, size;
     int64_t delay, start_ct = track->start_cts;
-    delay = av_rescale_rnd(track->start_dts + start_ct, MOV_TIMESCALE,
+    int64_t start_dts = track->start_dts;
+
+    if (track->entry) {
+        if (start_dts != track->cluster[0].dts || start_ct != track->cluster[0].cts) {
+
+            av_log(mov->fc, AV_LOG_DEBUG,
+                   "EDTS using dts:%"PRId64" cts:%d instead of dts:%"PRId64" cts:%"PRId64" tid:%d\n",
+                   track->cluster[0].dts, track->cluster[0].cts,
+                   start_dts, start_ct, track->track_id);
+            start_dts = track->cluster[0].dts;
+            start_ct  = track->cluster[0].cts;
+        }
+    }
+
+    delay = av_rescale_rnd(start_dts + start_ct, MOV_TIMESCALE,
                            track->timescale, AV_ROUND_DOWN);
     version |= delay < INT32_MAX ? 0 : 1;
 
@@ -2268,8 +2282,8 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
          * special meaning. Normally start_ct should end up positive or zero
          * here, but use FFMIN in case dts is a a small positive integer
          * rounded to 0 when represented in MOV_TIMESCALE units. */
-        av_assert0(av_rescale_rnd(track->start_dts, MOV_TIMESCALE, track->timescale, AV_ROUND_DOWN) <= 0);
-        start_ct  = -FFMIN(track->start_dts, 0);
+        av_assert0(av_rescale_rnd(start_dts, MOV_TIMESCALE, track->timescale, AV_ROUND_DOWN) <= 0);
+        start_ct  = -FFMIN(start_dts, 0);
         /* Note, this delay is calculated from the pts of the first sample,
          * ensuring that we don't reduce the duration for cases with
          * dts<0 pts=0. */