avformat/movenc: always check for new extradata on a packet

Don't just look at zero sized packets, and also check for AAC extradata
updates, in preparation for the following patches.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/movenc.c

@@ -5313,16 +5313,8 @@ 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;
-            }
-
         if (trk->par->codec_id == AV_CODEC_ID_MP4ALS ||
+            trk->par->codec_id == AV_CODEC_ID_AAC ||
             trk->par->codec_id == AV_CODEC_ID_FLAC) {
             int side_size = 0;
             uint8_t *side = av_packet_get_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA, &side_size);
@@ -5334,10 +5326,20 @@ static int mov_write_single_packet(AVFormatContext *s, AVPacket *pkt)
                 par->extradata = newextra;
                 memcpy(par->extradata, side, side_size);
                 par->extradata_size = side_size;
+                if (!pkt->size) // Flush packet
                     mov->need_rewrite_extradata = 1;
             }
         }
 
+        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 */
         }