avformat: close parser if codec changed

The parser depends on the codec and thus must not be used with a different one.
If it is, the 'avctx->codec_id == s->parser->codec_ids[0] ...' assert in
av_parser_parse2 gets triggered.
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

libavformat/utils.c

@@ -480,6 +480,12 @@ static int update_stream_avctx(AVFormatContext *s)
         if (!st->internal->need_context_update)
             continue;
 
+        /* close parser, because it depends on the codec */
+        if (st->parser && st->internal->avctx->codec_id != st->codecpar->codec_id) {
+            av_parser_close(st->parser);
+            st->parser = NULL;
+        }
+
         /* update internal codec context, for the parser */
         ret = avcodec_parameters_to_context(st->internal->avctx, st->codecpar);
         if (ret < 0)
@@ -1515,6 +1521,12 @@ static int read_frame_internal(AVFormatContext *s, AVPacket *pkt)
                 st->info->found_decoder = 0;
             }
 
+            /* close parser, because it depends on the codec */
+            if (st->parser && st->internal->avctx->codec_id != st->codecpar->codec_id) {
+                av_parser_close(st->parser);
+                st->parser = NULL;
+            }
+
             ret = avcodec_parameters_to_context(st->internal->avctx, st->codecpar);
             if (ret < 0)
                 return ret;