Disklavier

On Wed, 31 Dec 2003, fkagel wrote:

> Is there anyone in the group that has dissected the MIDI data when
> accompanying a CD? The system 'knows' which CD is supposed to be in
> place and will indicate that the wrong one has been inserted if that
> is the case.


I would guess that the Disklavier identifies the CD based upon the
UPC/EAN code read from the audio CD's table of contents.

If you manually read this code from a CD (a program like NERO will
probably be able to do this) you could find it in the corresponding hex
dump and figure out how to make a SYSEX message that checks for the
correct CD.


> I've noted 3 SYSEXs at the beginning:
> F0 05 7E 7F 09 01 F7 - Turns on GM, but what is the 2nd Byte 05 mean?
> F0 08 43 10 4C 00 00 7E 00 F7 - XG on, but what does 2nd Byte 08 mean?
> F0 05 43 71 05 01 F7 - Don't know???

The second byte appears to be the length of the message that follows,
including the terminating F7.

This size is probably coded as a variable-length quantity (in MIDI
file lingo) so be prepared for this length to occupy more than one byte.


> Where is the MTC or what controls the CD sync? What should I be
> looking for in the hex dump?

As for the sync, no MIDI-specific time events are required in the MIDI
file.

During playback against a CD, the MIDI timing is probably slaved to the
44.1 KHz CD sample rate, and MIDI playback is probably set to begin at a
particular time marker (0:00:00?) in the CD subcode.  This only
gets tricky when the user skips forward or backwards during playback;
the playback engine would need to be coded very carefully to maintain
sync.

Mark Fontana