avformat/mpegvideodec: use avpriv_find_start_code in mpegvideo_probe()

Signed-off-by: Zeng Zhaoxiu <zhaoxiu.zeng@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mpegvideodec.c

@@ -24,6 +24,7 @@
 #include "rawdec.h"
 
 #include "libavutil/intreadwrite.h"
+#include "libavcodec/internal.h"
 
 #define SEQ_START_CODE          0x000001b3
 #define GOP_START_CODE          0x000001b8
@@ -37,26 +38,27 @@ static int mpegvideo_probe(AVProbeData *p)
 {
     uint32_t code= -1;
     int pic=0, seq=0, slice=0, pspack=0, vpes=0, apes=0, res=0, sicle=0;
-    int i, j;
+    const uint8_t *ptr = p->buf, *end = ptr + p->buf_size;
     uint32_t last = 0;
+    int j;
 
-    for(i=0; i<p->buf_size; i++){
-        code = (code<<8) + p->buf[i];
+    while (ptr < end) {
+        ptr = avpriv_find_start_code(ptr, end, &code);
         if ((code & 0xffffff00) == 0x100) {
             switch(code){
             case     SEQ_START_CODE:
-                if (!(p->buf[i+1+3+1+2] & 0x20))
+                if (!(ptr[3 + 1 + 2] & 0x20))
                     break;
-                j = i;
-                if (p->buf[j+8] & 2)
+                j = -1;
+                if (ptr[j + 8] & 2)
                     j+= 64;
-                if (j >= p->buf_size)
+                if (ptr + j >= end)
                     break;
-                if (p->buf[j+8] & 1)
+                if (ptr[j + 8] & 1)
                     j+= 64;
-                if (j >= p->buf_size)
+                if (ptr + j >= end)
                     break;
-                if (AV_RB24(p->buf + j + 9) & 0xFFFFFE)
+                if (AV_RB24(ptr + j + 9) & 0xFFFFFE)
                     break;
                 seq++;
             break;