int mp4_open_meta(const struct mp4_callback *cb, struct mp4 **result);
struct mp4_metadata *mp4_get_meta(struct mp4 *f);
int mp4_update_meta(struct mp4 *f);
-char *mp4_get_tag_value(const struct mp4 *f, const char *item);
+__malloc char *mp4_get_tag_value(const struct mp4 *f, const char *item);