+ boost::shared_ptr<MidiDiskstream> diskstream = midi_diskstream();
+ framecnt_t playback_distance = diskstream->calculate_playback_distance(nframes);
+ if (can_internal_playback_seek(llabs(playback_distance))) {
+ /* TODO should declick, and/or note-off */
+ internal_playback_seek(playback_distance);
+ }