avformat/mux: Move packet references

In the common case that the input packet was already refcounted,
ff_interleave_add_packet would allocate a new AVPacketList, use
av_packet_ref to create a new reference to the buffer for the
AVPacketList's packet, interleave the packet and finally unreference
the original input packet.
This commit changes this: It uses av_packet_move_ref to transfer
the packet to its destination. In case the input packet is refcounted,
this saves an allocation and a free (of an AVBufferRef); if not, the
packet is made refcounted before moving it. When the input packet has
side data, one saves even more than one allocation+free.

Furthermore, when the packet is in reality an uncoded frame, a hacky
ad-hoc variant of av_packet_move_ref has been employed. Not any more.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mux.c

@@ -937,17 +937,16 @@ int ff_interleave_add_packet(AVFormatContext *s, AVPacket *pkt,
     if ((pkt->flags & AV_PKT_FLAG_UNCODED_FRAME)) {
         av_assert0(pkt->size == UNCODED_FRAME_PACKET_SIZE);
         av_assert0(((AVFrame *)pkt->data)->buf);
-        this_pktl->pkt = *pkt;
-        pkt->buf = NULL;
-        pkt->side_data = NULL;
-        pkt->side_data_elems = 0;
     } else {
-        if ((ret = av_packet_ref(&this_pktl->pkt, pkt)) < 0) {
+        if ((ret = av_packet_make_refcounted(pkt)) < 0) {
             av_free(this_pktl);
             return ret;
         }
     }
 
+    av_packet_move_ref(&this_pktl->pkt, pkt);
+    pkt = &this_pktl->pkt;
+
     if (s->streams[pkt->stream_index]->last_in_packet_buffer) {
         next_point = &(st->last_in_packet_buffer->next);
     } else {
@@ -996,8 +995,6 @@ next_non_null:
     s->streams[pkt->stream_index]->last_in_packet_buffer =
         *next_point                                      = this_pktl;
 
-    av_packet_unref(pkt);
-
     return 0;
 }