avformat/m4vdec: Detect raw mpeg4video with unidentified non mpeg headers with a very low score

Fixes Ticket 6018

This fixes a regression, and allows playback of files containing mpeg4video that are otherwise
not supported
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/m4vdec.c

@@ -53,6 +53,9 @@ static int mpeg4video_probe(AVProbeData *probe_packet)
 
     if (VOP >= VISO && VOP >= VOL && VO >= VOL && VOL > 0 && res == 0)
         return VOP+VO > 4 ? AVPROBE_SCORE_EXTENSION : AVPROBE_SCORE_EXTENSION/2;
+
+    if (VOP >= VISO && VOP >= VOL && VO >= VOL && VOL > 0 && VOP+VO > 4)
+        return AVPROBE_SCORE_EXTENSION/10;
     return 0;
 }