Re: USB Class compliant driver in Leopard
Re: USB Class compliant driver in Leopard
- Subject: Re: USB Class compliant driver in Leopard
- From: William Stewart <email@hidden>
- Date: Thu, 27 Mar 2008 14:23:58 -0700
On Mar 27, 2008, at 2:12 PM, Lubor Prikryl DS wrote:
OK, Thanks,
Actually, I am not testing Complex Play Thru, but any time I
experience some problem with a device, I use this Apple code to
compare it with the behavior of our applications.
to reply to the right one:! :)
ComplexPlayThru has any number of inconsistencies. We have talked
about this on the list in the past. In the meantime, we have provide
CAPlayThrough (both on the web and in Leopard in /Developer/Examples/
CoreAudio) and you should be re-basing your code on that.
And in this case it seems to have the same problem as we have. Both
CPT and we use the AU input/output, so there is probably something
wrong with the calls when we initialize the AU. However, all
proprietary drivers and FireWire CC drivers work OK, while the USB
CC driver does not.
Please re-test this with that example
Thanks
Bill
Lubor
On 27.3.2008, at 21:54, Jeff Moore wrote:
It sounds to me that the problem here is not that the devices don't
run at the small buffer size. Rather, the problem seems to be
related to how ComplexPlayThru correlates it's input with it's
output at small buffer sizes. That's a completely different can of
worms.
I'm not all that familiar with how ComplexPlayThru works, so I
don't have any particular advice on that front.
On Mar 27, 2008, at 1:18 PM, Lubor Prikryl DS wrote:
Thanks for your response. I tried to use several devices, always
on Intel Macs. The devices were M-Audio FastTrack (with
uninstalled custom drivers), Crate Profiler and some more. They
completely mute output if I set the buffer size <= 128. We use
AudioUnits for input and output.
When I installed M-Audio drivers for FastTrack, the lower buffer
size started to work OK.
I performed this test:
I have added a set property call to your ComplexPlayThru exaple,
when I had set bufferSizeFrames = 64, the devices using USB CC
driver did not work.
However, the Reset call fixed something and the device started to
play.
Doing the same with buffer size 256, the device started to work
immediately.
I am aware of the principle that USB CC have separated input and
output, so I am handling both parts independently in our codes.
Thanks for any hint.
On 27.3.2008, at 19:50, Jeff Moore wrote:
You'll have to define "doesn't work" a little better. I have an
Edirol UA-3 here in my office that I seems to run just fine with
an IO buffer size of 32 frames.
On Mar 27, 2008, at 11:17 AM, Lubor Prikryl DS wrote:
I have noticed, that the class compliant USB audio driver
doesn't work with smaller buffer sizes in Leopard (under 128
samples). There was no such limitation in Tiger. Is this a known
issue or has it some workaround?
(The class compliant FireWire driver works perfectly, this is
great!)
--
Jeff Moore
Core Audio
Apple
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