struct mp4; /* opaque */
-int mp4_set_sample_position(struct mp4 *f, int32_t sample);
+int mp4_set_sample_position(struct mp4 *f, uint32_t sample);
int mp4_open_read(const struct mp4_callback *cb, struct mp4 **result);
void mp4_close(struct mp4 *f);
int32_t mp4_get_sample_size(const struct mp4 *f, int sample);