mpeg4parser: fix initial qp precission

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpeg4video_parser.c

@@ -99,6 +99,7 @@ static av_cold int mpeg4video_parse_init(AVCodecParserContext *s)
     if (!pc->enc)
         return -1;
     pc->first_picture = 1;
+    pc->enc->quant_precision=5;
     return 0;
 }