responses in line
On Apr 13, 2010, at 5:09 AM, Gordon Rankin wrote:
>> > Does class compliant USB Audio devices being supported imply being supported through the USB dongle from the iPad Camera Connection Kit? Because that would be just about perfect.
> Well this is really exciting! Just a couple of obvious questions....
> 1) Is this Full Speed or High Speed USB as the protocols are a little different? With HS Class 1 you are still utilizing multiple microFrames were as with Full Speed it is only a single frame per 1ms SOF.
USB-Audio 1.0 class specification only supporting full speed.
> 2) Will standard Feature items like Volume and Mute be included?
yes, assuming that the audio topology is not too complicated. we have some issues around retaining these values across different changes in the system, but plan to address those
> 3) I take it that developers with MFI will be able to make docks that integrate the authentication and have USB Audio device I/O. Correct?
I would imagine so - that is part of our intention to provide this, that the cost and reliability of developing these solutions is mitigated and made more reliable as you can use off-the-shelf parts, etc.
> 4) I take it that self powered Class 1 Audio devices could be connected directly to the the Camera Connection Kit?
if they draw less than 100mA, otherwise you need a powered hub.
> 5) Would sample rates be limited to 32, 44.1, 48 @ 16 bits or would high res devices to 24/96 (Class 1 top end) be supported?
at the moment we only support 16bit (and the device needs to be in that mode before it is connected). We are planning on supporting 24bit in the future. Sample rate is an interesting issue.. up to 48kHz is already supported cleanly. If you want more than that, you should file a feature request (bug report).
> Bill of course the first thing I did when I saw this was plug in my iPad to a powered hub as the host and then put my Proton dac into one of the available down ports and ran iTunes.... oh well no audio or stream.
please file a radar. we've done a preliminary sweep of devices.
I am actually not sure how much I want to get into supporting non-compliant devices. This is a never ending problem, and I am sorely tempted to not support devices that veer from the letter of the spec (or customary changes). At some point the device manufacturers need to be responsible for clean implementations. Of course, our side of this is making sure that our driver and h.w is also compliant with the spec!, so anything that advertises as being compliant that doesn't work we would appreciate a bug report with
- sw version of ipad/etc.
- details of the device
firmware version, is it up to date?
- also, for the moment, make sure the device is in 16bit mode before connecting.
We'd like to see this be successful, so are happy to help go through problems encountered with various configurations, but will need accurate information to reproduce these. Bug reports will also allow us to send back to you the results of our investigation, etc
> Paul devices that require device drivers (i.e. M-Audio Transit) would not be considered a Class 1 compliant device.
correct. we aren't support custom drivers at this point.
> Class 2 USB Audio
> In answer to Paul's questions... I have a number of USB Class 2 Audio devices we are going to ship this month. There is a few things to remember. Class 2 is really only supported under Snow. There will be an updated AppleUSBAudio.kext to correct some minor problems with slower machines.
> J. Gordon Rankin
> Owner and Chief Scientist
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