If defined, then the user-stream post-hook is called after all the streams have been defined, once for each of the standard streams. It has a slightly different prototype:
void user_stream_post_hook(void *user_data, int which, SP_stream *str)
str is a pointer to the corresponding
structure. There are no requirements as to what this hook must do;
the default behavior is to do nothing at all.
The post-hook is intended to be used to do things that may require that all streams have been created.
See cpg-ref-SP_set_user_stream_post_hook for details.