Re: USB audio class - kIOAudioControlUsagePassThru implementation
Re: USB audio class - kIOAudioControlUsagePassThru implementation
- Subject: Re: USB audio class - kIOAudioControlUsagePassThru implementation
- From: Jeff Moore <email@hidden>
- Date: Wed, 12 May 2010 09:15:49 -0700
As I said initially, I can't tell you what it looks for in the descriptors to implement play-through controls because I don't believe that the USB Audio class driver has _any_ support for them. If there is a piece of hardware you know of/are building that has things that should be treated as play-through controls, the right thing to do is to write a bug so we can look at it and do the right thing. Otherwise, your only recourse is to write either a plug-in for the class driver or your own driver.
On May 12, 2010, at 9:05 AM, Daniel Mack wrote:
> Hi Jeff,
>
> On Wed, May 12, 2010 at 08:38:46AM -0700, Jeff Moore wrote:
>> I don't believe that our current USB Audio class driver has any support for play-through controls. So, it isn't really looking for anything in that area. If you have a device that has such controls and would like to see support added, please file a bug and let us know what that device is.
>>
>> If you are looking to create a driver that supports play-through controls, then there really isn't any guidance to give as you have free reign. Presumably, you know your hardware and know how to implement such support. From the IOAudio perspective, connecting it to the outside world becomes just a matter of implementing and instantiating the appropriate IOAudioControl objects.
>
> Of course. What I'm trying to do, though, is _avoiding_ writing an own
> driver and let the AppleUSBAudio driver handle everything. And if a
> pass-through control would map to AudioMIDISetup.app's per-channel
> checkboxes, that would be nice.
>
> The question is just (if the AppleUSBAudio driver supports it) how the
> descriptors should look like to correctly announce the presence of such
> a feature. I was just searching for 'kIOAudioControlUsagePassThru' in
> the driver sources and got hits in code I didn't fully understand. Hence
> I considered asking :)
--
Jeff Moore
Core Audio
Apple
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