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Re: Core audio driver

At 10:04 PM +0100 2/17/05, pwicker wrote:
On Feb 17, 2005, at 9:17 PM, Mark Cookson wrote:

Be careful in your terminology here. There is NO USB Audio 2.0 Device specification (that's released to the public). There is only a USB Audio 1.0 Device specification. There is of course USB 2.0, and you can put USB Audio 1.0 Device functionality on a device that connects to the host over USB 2.0 and runs at high speed, but that doesn't make it a USB Audio 2.0 device, and you will find a couple of short comings in the USB Audio 1.0 Device specification that limit the device's usefulness.

The problem that you are seeing is that there is a bug in the USB stack that prevents the USB Audio 1.0 driver from working correctly on the USB 2.0 stack. Until that is fixed, there is nothing that the driver can do to talk to a USB 2.0 device.

Could you please elaborate on this point? I'm currently working on a project that involves the connection of an audio/midi external USB 2.0 device (high speed needed). Until now, our plan was to rely on the generic Mac OS X audio and midi drivers. IIRC this could be not possible and we may have to develop our own driver :(

You are probably already aware of this, but the erata posted on AMD's web site (http://www.amd.com/us-en/Processors/TechnicalResources/0,,30_182_739_9004,00.html) for the AMD-8111 chip claims that the USB 2.0 port doesn't work in high speed mode. If your testbed has this in it, you may need to use a PCI card.

Also, the AMD-8131 PCI-X chip has severe performance problems with the pass-through port to the 8111. A number of users are reporting they cannot run a single 8 channel audio interface and a hard drive on the same 1394 bus. They are also buying PCI cards to get around this (or buying slower machines that don't have PCI-X slots). Given that the USB 2.0 port will be in the same place in the bus architecture, it's probably going to be crippled on those machines, too.

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 >Re: Core audio driver (From: Mark Cookson <email@hidden>)
 >Re: Core audio driver (From: pwicker <email@hidden>)



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