avconv: don't warn on multiple frames per packet for codecs that expect it

avconv.c

@@ -1380,7 +1380,8 @@ static int output_packet(InputStream *ist, const AVPacket *pkt)
 
         ist->last_dts = ist->next_dts;
 
-        if (avpkt.size && avpkt.size != pkt->size) {
+        if (avpkt.size && avpkt.size != pkt->size &&
+            !(ist->dec->capabilities & CODEC_CAP_SUBFRAMES)) {
             av_log(NULL, ist->showed_multi_packet_warning ? AV_LOG_VERBOSE : AV_LOG_WARNING,
                    "Multiple frames in a packet from stream %d\n", pkt->stream_index);
             ist->showed_multi_packet_warning = 1;