Fwd: Re: CoreMIDI behavior?
Fwd: Re: CoreMIDI behavior?
- Subject: Fwd: Re: CoreMIDI behavior?
- From: Jarrell Irvin <email@hidden>
- Date: Mon, 7 Jan 2002 23:27:42 -0800
>
On Monday, January 7, 2002, at 05:37 , Kurt Revis wrote:
>
> I suppose I should have said "is similar" rather than "maps quite
>
> closely". Anyway, reading about MIDI over USB helped me understand
>
> what I was empirically seeing in the packets, especially why the
>
> packets were so small (in the case of sysex). Of course now I know that
>
> it doesn't matter so much, but it was an interesting diversion.
>
>
Yes, CoreMIDI is endeavoring to deliver the incoming data to your app as
>
quickly as possible, so if there's a full-bandwidth sysex stream coming
>
in, and you're getting only 3 bytes of sysex at a time, you're getting
>
woken up rougly once per millisecond to receive the incoming data. If
>
you're getting more at a time, then either the interface or the Mac is
>
CPU loaded to the point where things are getting buffered up.
>
>
Doug
>
Not to put too fine a point on it, but a full-bandwidth sysex stream does
not necessarily imply 3 bytes a second coming into the computer
(buffering considerations aside). If the incoming sysex is sent via a
physical MIDI cable, it will be limited to 3 bytes/second due to the
speed of transport, but if it is sent via USB, that is, no MIDI cable
involved in transmitting it to the computer, for example a synth that
only has a USB port, it could arrive at the computer at 8,16, 32 or 64
bytes per second.
- jarrell