* extended_data must be allocated with av_malloc() and will be freed in
* av_frame_unref().
* * otherwise exended_data must point to data
- * - buf[] must contain references to the buffers that contain the frame
- * data.
+ * - buf[] must contain one or more pointers to AVBufferRef structures. Each of
+ * the frame's data and extended_data pointers must be contained in these. That
+ * is, one AVBufferRef for each allocated chunk of memory, not necessarily one
+ * AVBufferRef per data[] entry. See: av_buffer_create(), av_buffer_alloc(),
+ * and av_buffer_ref().
* - extended_buf and nb_extended_buf must be allocated with av_malloc() by
* this callback and filled with the extra buffers if there are more
* buffers than buf[] can hold. extended_buf will be freed in