Fix index_entries pos:

It was being set wrong for files with data_offset > 0

Patch by Michael Chinen, mchinen gmail

Originally committed as revision 25239 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/parser.c

@@ -150,6 +150,12 @@ int av_parser_parse2(AVCodecParserContext *s,
     int index, i;
     uint8_t dummy_buf[FF_INPUT_BUFFER_PADDING_SIZE];
 
+    if(!(s->flags & PARSER_FLAG_FETCHED_OFFSET)) {
+        s->next_frame_offset =
+        s->cur_offset        = pos;
+        s->flags |= PARSER_FLAG_FETCHED_OFFSET;
+    }
+
     if (buf_size == 0) {
         /* padding is always necessary even if EOF, so we add it here */
         memset(dummy_buf, 0, sizeof(dummy_buf));