Merge commit 'bef3b1f59f036aba4a5fe599b2480f6bd9e6b280'

* commit 'bef3b1f59f036aba4a5fe599b2480f6bd9e6b280':
  movenc: Allow setting start_dts/start_cts before writing actual packets

Merged-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavformat/movenc.c

@@ -4564,9 +4564,6 @@ static int mov_write_single_packet(AVFormatContext *s, AVPacket *pkt)
         int64_t frag_duration = 0;
         int size = pkt->size;
 
-        if (!pkt->size)
-            return 0;             /* Discard 0 sized packets */
-
         if (mov->flags & FF_MOV_FLAG_FRAG_DISCONT) {
             int i;
             for (i = 0; i < s->nb_streams; i++)
@@ -4574,6 +4571,18 @@ static int mov_write_single_packet(AVFormatContext *s, AVPacket *pkt)
             mov->flags &= ~FF_MOV_FLAG_FRAG_DISCONT;
         }
 
+        if (!pkt->size) {
+            if (trk->start_dts == AV_NOPTS_VALUE && trk->frag_discont) {
+                trk->start_dts = pkt->dts;
+                if (pkt->pts != AV_NOPTS_VALUE)
+                    trk->start_cts = pkt->pts - pkt->dts;
+                else
+                    trk->start_cts = 0;
+            }
+
+            return 0;             /* Discard 0 sized packets */
+        }
+
         if (trk->entry && pkt->stream_index < s->nb_streams)
             frag_duration = av_rescale_q(pkt->dts - trk->cluster[0].dts,
                                          s->streams[pkt->stream_index]->time_base,
@@ -4628,7 +4637,8 @@ static int mov_write_packet(AVFormatContext *s, AVPacket *pkt)
         int i;
         MOVMuxContext *mov = s->priv_data;
 
-        if (!pkt->size) return 0; /* Discard 0 sized packets */
+        if (!pkt->size)
+            return mov_write_single_packet(s, pkt); /* Passthrough. */
 
         /*
          * Subtitles require special handling.