mjpeg_parser: Rewrite to skip marker segments

Based on code by Aaron Miller <amiller@atlasdigital.tv>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mjpeg_parser.c

@@ -30,6 +30,7 @@
 
 typedef struct MJPEGParserContext{
     ParseContext pc;
+    int size;
 }MJPEGParserContext;
 
 /**
@@ -39,35 +40,59 @@ typedef struct MJPEGParserContext{
 static int find_frame_end(MJPEGParserContext *m, const uint8_t *buf, int buf_size){
     ParseContext *pc= &m->pc;
     int vop_found, i;
-    uint16_t state;
+    uint32_t state;
 
     vop_found= pc->frame_start_found;
     state= pc->state;
 
     i=0;
     if(!vop_found){
-        for(i=0; i<buf_size; i++){
+        for(i=0; i<buf_size;){
             state= (state<<8) | buf[i];
-            if(state == 0xFFD8){
+            if(state>=0xFFC00000 && state<=0xFFFEFFFF){
+                if(state>=0xFFD80000 && state<=0xFFD8FFFF){
                     i++;
                     vop_found=1;
                     break;
+                }else if(state<0xFFD00000 || state>0xFFD9FFFF){
+                    m->size= (state&0xFFFF)-1;
                 }
             }
+            if(m->size>0){
+                int size= FFMIN(buf_size-i, m->size);
+                i+=size;
+                m->size-=size;
+                state=0;
+                continue;
+            }else
+                i++;
+        }
     }
 
     if(vop_found){
         /* EOF considered as end of frame */
         if (buf_size == 0)
             return 0;
-        for(; i<buf_size; i++){
+        for(; i<buf_size;){
             state= (state<<8) | buf[i];
-            if(state == 0xFFD8){
+            if(state>=0xFFC00000 && state<=0xFFFEFFFF){
+                if(state>=0xFFD80000 && state<=0xFFD8FFFF){
                     pc->frame_start_found=0;
                     pc->state=0;
-                return i-1;
+                    return i-3;
+                } else if(state<0xFFD00000 || state>0xFFD9FFFF){
+                    m->size= (state&0xFFFF)-1;
                 }
             }
+            if(m->size>0){
+                int size= FFMIN(buf_size-i, m->size);
+                i+=size;
+                m->size-=size;
+                state=0;
+                continue;
+            }else
+                i++;
+        }
     }
     pc->frame_start_found= vop_found;
     pc->state= state;