libavformat/mov: Fix memleaks when demuxing DV audio

The code for demuxing DV audio predates the introduction of refcounted
packets and when the latter was added, changes to the former were
forgotten. This meant that when avpriv_dv_produce_packet initialized the
packet containing the AVBufferRef, the AVBufferRef as well as the
underlying AVBuffer leaked; the actual packet data didn't leak: They
were directly freed, but not via their AVBuffer's free function.

https://samples.ffmpeg.org/ffmpeg-bugs/trac/ticket4671/dir1.tar.bz2
contains samples for this (enable_drefs needs to be enabled for them).

Moreover, errors in avpriv_dv_produce_packet were ignored; this has been
changed, too.

Furthermore, in the hypothetical scenario that the track has a palette,
this would leak, too, so reorder the code so that the palette code
appears after the DV audio code.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 61f5c6ab06fc61e0f9f8f8dab5595b8bb202df73)
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavformat/mov.c

@@ -7909,6 +7909,19 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
             }
             return ret;
         }
+#if CONFIG_DV_DEMUXER
+        if (mov->dv_demux && sc->dv_audio_container) {
+            AVBufferRef *buf = pkt->buf;
+            ret = avpriv_dv_produce_packet(mov->dv_demux, pkt, pkt->data, pkt->size, pkt->pos);
+            pkt->buf = buf;
+            av_packet_unref(pkt);
+            if (ret < 0)
+                return ret;
+            ret = avpriv_dv_get_packet(mov->dv_demux, pkt);
+            if (ret < 0)
+                return ret;
+        }
+#endif
         if (sc->has_palette) {
             uint8_t *pal;
 
@@ -7920,16 +7933,6 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
                 sc->has_palette = 0;
             }
         }
-#if CONFIG_DV_DEMUXER
-        if (mov->dv_demux && sc->dv_audio_container) {
-            avpriv_dv_produce_packet(mov->dv_demux, pkt, pkt->data, pkt->size, pkt->pos);
-            av_freep(&pkt->data);
-            pkt->size = 0;
-            ret = avpriv_dv_get_packet(mov->dv_demux, pkt);
-            if (ret < 0)
-                return ret;
-        }
-#endif
         if (st->codecpar->codec_id == AV_CODEC_ID_MP3 && !st->need_parsing && pkt->size > 4) {
             if (ff_mpa_check_header(AV_RB32(pkt->data)) < 0)
                 st->need_parsing = AVSTREAM_PARSE_FULL;