Re: kMIDIPropertyMaxSysExSpeed
Re: kMIDIPropertyMaxSysExSpeed
- Subject: Re: kMIDIPropertyMaxSysExSpeed
- From: Brian Willoughby <email@hidden>
- Date: Fri, 14 Sep 2001 11:24:11 -0700
[ I noticed the default value of kMIDIPropertyMaxSysExSpeed is
[ described as 3125 (Bytes/sec), on page 88 in the document "Audio
[ and MIDI on MacOS X" (coreaudio.pdf).
[
[ I think the correct value is 2500, as only 8 bits are utilized
[ for each 10-bit data (exclude a START bit and a STOP bit). i.e.,
[ (31250 / (1 + 8 + 1)) * (8 / (1 + 8 + 1))
[ = 2500 (Bytes/sec)
[
[ Am I misunderstanding something?
Yes, you cannot exclude the Start and Stop bit. They are required because
MIDI is an asynchronous serial communication. 31250 is the bit rate, and even
back-to-back MIDI data bytes each require their own individual Start and Stop
bits. So CoreAudio is correct in dividing by 10. This is an established
figure.
Brian Willoughby
Sound Consulting