Do not claim that every unknown rm stream is a video stream.

Also reduce verbosity for the unsupported stream message, use
an AVFormatContext for av_log and and print the tag of the
unknown stream.

Improves ticket #672.

libavformat/rmdec.c

@@ -313,7 +313,7 @@ ff_rm_read_mdpr_codecdata (AVFormatContext *s, AVIOContext *pb,
         int fps;
         if (avio_rl32(pb) != MKTAG('V', 'I', 'D', 'O')) {
         fail1:
-            av_log(st->codec, AV_LOG_ERROR, "Unsupported video codec\n");
+            av_log(s, AV_LOG_WARNING, "Unsupported stream type %08x\n", v);
             goto skip;
         }
         st->codec->codec_tag = avio_rl32(pb);