* @param buf if set, it contains the data and size information to be used
* for the attached pic; if unset, data is read from pb.
* @param size the size of the data to read if buf is unset.
+ *
+ * @return 0 on success, < 0 on error. On error, this function removes
+ * the stream it has added (if any).
*/
int ff_add_attached_pic(AVFormatContext *s, AVStream *st, AVIOContext *pb,
AVBufferRef **buf, int size);