[FFmpeg-devel] [PATCH] avformat/mpeg: use avpriv_find_start_code in mpegps_probe()

[zhaoxiu.zeng]

>From 520c5898f2c0372188f17f98e10a40174dde4aac Mon Sep 17 00:00:00 2001
From: Zeng Zhaoxiu <zhaoxiu.zeng at gmail.com>
Date: Sun, 15 Mar 2015 12:01:51 +0800
Subject: [PATCH 5/7] avformat/mpeg: use avpriv_find_start_code in
 mpegps_probe()

Signed-off-by: Zeng Zhaoxiu <zhaoxiu.zeng at gmail.com>
---
 libavformat/mpeg.c | 51 ++++++++++++++++++++++++---------------------------
 1 file changed, 24 insertions(+), 27 deletions(-)

diff --git a/libavformat/mpeg.c b/libavformat/mpeg.c
index a0b5738..ffba786 100644
--- a/libavformat/mpeg.c
+++ b/libavformat/mpeg.c
@@ -29,6 +29,7 @@
 #endif
 
 #include "libavutil/avassert.h"
+#include "libavcodec/internal.h"
 
 /*********************************************/
 /* demux code */
@@ -38,12 +39,12 @@
 static int check_pes(const uint8_t *p, const uint8_t *end)
 {
     int pes1;
-    int pes2 = (p[3] & 0xC0) == 0x80 &&
-               (p[4] & 0xC0) != 0x40 &&
-               ((p[4] & 0xC0) == 0x00 ||
-                (p[4] & 0xC0) >> 2 == (p[6] & 0xF0));
+    int pes2 = (p[2] & 0xC0) == 0x80 &&
+               (p[3] & 0xC0) != 0x40 &&
+               ((p[3] & 0xC0) == 0x00 ||
+                (p[3] & 0xC0) >> 2 == (p[5] & 0xF0));
 
-    for (p += 3; p < end && *p == 0xFF; p++) ;
+    for (p += 2; p < end && *p == 0xFF; p++) ;
     if ((*p & 0xC0) == 0x40)
         p += 2;
 
@@ -59,41 +60,37 @@ static int check_pes(const uint8_t *p, const uint8_t *end)
 
 static int check_pack_header(const uint8_t *buf)
 {
-    return (buf[1] & 0xC0) == 0x40 || (buf[1] & 0xF0) == 0x20;
+    return (buf[0] & 0xC0) == 0x40 || (buf[0] & 0xF0) == 0x20;
 }
 
 static int mpegps_probe(AVProbeData *p)
 {
     uint32_t code = -1;
-    int i;
     int sys = 0, pspack = 0, priv1 = 0, vid = 0;
     int audio = 0, invalid = 0, score = 0;
-    int endpes = 0;
+    const uint8_t *ptr = p->buf, *end = ptr + p->buf_size;
+    const uint8_t *endpes = ptr;
 
-    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) {
-            int len  = p->buf[i + 1] << 8 | p->buf[i + 2];
-            int pes  = endpes <= i && check_pes(p->buf + i, p->buf + p->buf_size);
-            int pack = check_pack_header(p->buf + i);
-
             if (code == SYSTEM_HEADER_START_CODE)
                 sys++;
-            else if (code == PACK_START_CODE && pack)
+            else if (code == PACK_START_CODE && check_pack_header(ptr))
                 pspack++;
-            else if ((code & 0xf0) == VIDEO_ID && pes) {
-                endpes = i + len;
-                vid++;
+            else if (endpes < ptr && check_pes(ptr, end)) {
+                int len  = AV_RB16(ptr);
+                     if ((code & 0xf0) == VIDEO_ID) { vid++; endpes = ptr + len; }
+                // skip pes payload to avoid start code emulation for private
+                // and audio streams
+                else if ((code & 0xe0) == AUDIO_ID) { audio++; ptr += len; code = -1; }
+                else if (code == PRIVATE_STREAM_1 ) { priv1++; ptr += len; code = -1; }
+                else if (code == 0x1fd            )   vid++; //VC1
+            } else {
+                     if ((code & 0xf0) == VIDEO_ID) invalid++;
+                else if ((code & 0xe0) == AUDIO_ID) invalid++;
+                else if (code == PRIVATE_STREAM_1 ) invalid++;
             }
-            // skip pes payload to avoid start code emulation for private
-            // and audio streams
-            else if ((code & 0xe0) == AUDIO_ID &&  pes) {audio++; i+=len;}
-            else if (code == PRIVATE_STREAM_1  &&  pes) {priv1++; i+=len;}
-            else if (code == 0x1fd             &&  pes) vid++; //VC1
-
-            else if ((code & 0xf0) == VIDEO_ID && !pes) invalid++;
-            else if ((code & 0xe0) == AUDIO_ID && !pes) invalid++;
-            else if (code == PRIVATE_STREAM_1  && !pes) invalid++;
         }
     }
 
-- 
2.1.0