m4vdec: Check for non-startcode 00 00 00 sequences in probe

This makes the m4v detection less trigger-happy.

Bug-Id: 949
Signed-off-by: Diego Biurrun <diego@biurrun.de>

libavformat/m4vdec.c

@@ -33,16 +33,18 @@ static int mpeg4video_probe(AVProbeData *probe_packet)
 
     for (i = 0; i < probe_packet->buf_size; i++) {
         temp_buffer = (temp_buffer << 8) + probe_packet->buf[i];
-        if ((temp_buffer & 0xffffff00) != 0x100)
+        if (temp_buffer & 0xfffffe00)
+            continue;
+        if (temp_buffer < 2)
             continue;
 
         if (temp_buffer == VOP_START_CODE)
             VOP++;
         else if (temp_buffer == VISUAL_OBJECT_START_CODE)
             VISO++;
-        else if (temp_buffer < 0x120)
+        else if (temp_buffer >= 0x100 && temp_buffer < 0x120)
             VO++;
-        else if (temp_buffer < 0x130)
+        else if (temp_buffer >= 0x120 && temp_buffer < 0x130)
             VOL++;
         else if (!(0x1AF < temp_buffer && temp_buffer < 0x1B7) &&
                  !(0x1B9 < temp_buffer && temp_buffer < 0x1C4))