avformat/m4vdec: Fix detection of raw MPEG-4 ES Studio

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/m4vdec.c

@@ -24,11 +24,14 @@
 
 #define VISUAL_OBJECT_START_CODE       0x000001b5
 #define VOP_START_CODE                 0x000001b6
+#define SLICE_STARTCODE      0x1B7
+#define EXT_STARTCODE        0x1B8
 
 static int mpeg4video_probe(AVProbeData *probe_packet)
 {
     uint32_t temp_buffer = -1;
     int VO = 0, VOL = 0, VOP = 0, VISO = 0, res = 0;
+    int res_main = 0;
     int i;
 
     for (i = 0; i < probe_packet->buf_size; i++) {
@@ -46,11 +49,19 @@ static int mpeg4video_probe(AVProbeData *probe_packet)
             VO++;
         else if (temp_buffer >= 0x120 && temp_buffer < 0x130)
             VOL++;
+        else if (temp_buffer == SLICE_STARTCODE || temp_buffer == EXT_STARTCODE)
+            res_main++;
         else if (!(0x1AF < temp_buffer && temp_buffer < 0x1B7) &&
                  !(0x1B9 < temp_buffer && temp_buffer < 0x1C4))
             res++;
     }
 
+    // res_main repesents the reserved codes within the "main" profile, they are
+    // added to the reserved ones if it appears that this is a "main" profile
+    // stream
+    if (res_main && 2*res_main < VOP)
+        res += res_main;
+
     if (VOP >= VISO && VOP >= VOL && VO >= VOL && VOL > 0 && res == 0)
         return VOP+VO > 4 ? AVPROBE_SCORE_EXTENSION : AVPROBE_SCORE_EXTENSION/2;