output last ac3 frame and simplify

Originally committed as revision 4926 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/parser.c

@@ -873,9 +873,8 @@ static int ac3_parse(AVCodecParserContext *s1,
         len = s->inbuf_ptr - s->inbuf;
         if (s->frame_size == 0) {
             /* no header seen : find one. We need at least 7 bytes to parse it */
-            len = AC3_HEADER_SIZE - len;
+            len = FFMIN(AC3_HEADER_SIZE - len, buf_size);
-            if (len > buf_size)
+
-                len = buf_size;
             memcpy(s->inbuf_ptr, buf_ptr, len);
             buf_ptr += len;
             s->inbuf_ptr += len;
@@ -898,16 +897,15 @@ static int ac3_parse(AVCodecParserContext *s1,
                     avctx->frame_size = 6 * 256;
                 }
             }
-        } else if (len < s->frame_size) {
+        } else {
-            len = s->frame_size - len;
+            len = FFMIN(s->frame_size - len, buf_size);
-            if (len > buf_size)
-                len = buf_size;
 
             memcpy(s->inbuf_ptr, buf_ptr, len);
             buf_ptr += len;
             s->inbuf_ptr += len;
             buf_size -= len;
-        } else {
+
+            if(s->inbuf_ptr - s->inbuf == s->frame_size){
                 *poutbuf = s->inbuf;
                 *poutbuf_size = s->frame_size;
                 s->inbuf_ptr = s->inbuf;
@@ -915,6 +913,7 @@ static int ac3_parse(AVCodecParserContext *s1,
                 break;
             }
         }
+    }
     return buf_ptr - buf;
 }