lavf/find_stream_info: make sure we decode at least one frame for DTS

The channel layout at the demuxer layer is commonly wrong and would
otherwise be used.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/utils.c

@@ -2314,6 +2314,8 @@ static int has_codec_parameters(AVStream *st, const char **errmsg_ptr)
             FAIL("unspecified sample rate");
         if (!avctx->channels)
             FAIL("unspecified number of channels");
+        if (st->info->found_decoder >= 0 && !st->nb_decoded_frames && avctx->codec_id == AV_CODEC_ID_DTS)
+            FAIL("no decodable DTS frames");
         break;
     case AVMEDIA_TYPE_VIDEO:
         if (!avctx->width)