double tempo_at_frame (framepos_t frame, double end_bpm, framepos_t end_frame, framecnt_t frame_rate) const;
framepos_t frame_at_tempo (double tempo, double end_bpm, framepos_t end_frame, framecnt_t frame_rate) const;
double tempo_at_frame (framepos_t frame, double end_bpm, framepos_t end_frame, framecnt_t frame_rate) const;
framepos_t frame_at_tempo (double tempo, double end_bpm, framepos_t end_frame, framecnt_t frame_rate) const;