Re: IAC driver problems
Re: IAC driver problems
- Subject: Re: IAC driver problems
- From: "X. J. Scott" <email@hidden>
- Date: Fri, 23 Jan 2004 19:42:53 -0500
on 1/23/04 5:38 PM, Pete Yandell wrote:
>
In the course of testing for some new releases of my apps, I've
>
discovered what looks to be a fairly major problem with the IAC bus
>
driver:
Agreed.
>
Only IAC bus 1 works. Data sent to any other IAC bus simply disappears
>
into the void.
Data sent to the other busses goes to the first bus, in my testing on
10.3.2.
>
(This is on 10.3.2, and I've tested this using a few different apps.)
>
>
Before I file this as a bug report, does anybody else see the same
>
problem on their system? If it's common then I would think that it
>
would have come up for discussion long before this!
I think we're the first to try using the IAC device. Or possibly most people
trying it so far have only had for one IAC port.
>
I've also had reports of strange IAC bus behaviour from other people
>
too: corruption of long MIDI packets, data going into one IAC bus
>
showing up on the output of another. I haven't been able to confirm any
>
of this though.
Yes, I'm one of the other persons so I'll make myself known and confirm this
publically. What I see is that sysex packets of greater than 256 bytes
contain random data after the 256th byte UNLESS the IAC port is being
observed with MIDI Monitor, in which case Heisenberg arrives and makes the
data transmit cleanly.
I would assume this has something to do with a plain MIDIPacket being
allocated on the stack in the IAC code somewhere since it defaults to 256
bytes long. Larger packets are supposed to allocate a bigger buffer or break
it into multiple packets.
Another possible bug is that when you create a new IAC port, it makes your
MIDI driver go off-line (dimmed, all ports connected vanish) until you quit
all CoreMIDI apps and relaunch. This is with the MIDISport driver, so it
might be an issue for Pete Gontier to look into. The IAC works by creating a
new hardware device and not a new set of virtual ports, so maybe the driver
is not able to handle new hardware devices appearing willy-nilly.
Also, I was able to infer the IAC's purpose and use since I was familiar
with the OMS IAC design, but user-level documentation on the IAC device
would probably be helpful for musicians.
- Jeff
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