friend struct best_dcp_frame_rate_test_single;
friend struct best_dcp_frame_rate_test_double;
friend struct audio_sampling_rate_test;
friend struct best_dcp_frame_rate_test_single;
friend struct best_dcp_frame_rate_test_double;
friend struct audio_sampling_rate_test;
template<class, class> friend class ChangeSignaller;
void signal_change (ChangeType, int);
template<class, class> friend class ChangeSignaller;
void signal_change (ChangeType, int);