[LAU] Sound Devices USBPre2, UAC2 status

[Hans Wilmers]

On 01/10/2013 06:08 PM, shal at free.fr wrote:
>
>
> ----- Mail original -----
>> De: "Hans Wilmers" <hanswil at notam02.no>
>> À: linux-audio-user at lists.linuxaudio.org
>> Envoyé: Jeudi 10 Janvier 2013 13:23:57
>> Objet: Re: [LAU] Sound Devices USBPre2, UAC2 status
>>
>> On 01/07/2013 08:25 PM, shal at free.fr wrote:
>>>
>>> ----- Mail original -----
>>>> De: "alexander" <axeldenstore at gmail.com>
>>>> À: linux-audio-user at lists.linuxaudio.org
>>>> Envoyé: Lundi 7 Janvier 2013 18:27:42
>>>> Objet: Re: [LAU] Sound Devices USBPre2, UAC2 status
>>>> I also own this interface, recently it has started to work in uac2
>>>> mode,
>>>> I still cant raise the samplerate, but it runs.. however, It still
>>>> runs
>>>> alot better in uac1.. when in uac2 jack mysteriously shuts down
>>>> for
>>>> no
>>>> appearant reason. I run archlinux, allways uptodated with vanilla
>>>> kernel.
>>>>
>>>> This is when I connect it without pressing 1. eg, uac2
>>>> http://pastebin.com/BFJTwXnJ
>>>> And as with pressing 1. http://pastebin.com/ZJ1jbPUK
>>>
>>>
>>> Hi,
>>>
>>> In my understanding, you are not in UAC2 , you are in high-speed
>>> mode but the usb audio protocol remains UAC1.
>>>
>>>
>>> In the kernel source in the file include/uapi/linux/usb/audio.h is
>>> defined two values:
>>> /* bInterfaceProtocol values to denote the version of the standard
>>> used */
>>> #define UAC_VERSION_1			0x00
>>> #define UAC_VERSION_2			0x20
>>>
>>> So if the card is in UAC2 , you should see bInterfaceProtocol at 32
>>> (or 0x20)
>>> By example, now the RME babyface is recognize as UAC2 device, you
>>> can view its "lsub -v" here  : http://minilien.fr/a0m3kc
>>>
>>> But for the usbPre2 device with ou without pressing the "1" button,
>>>   we have bInterfaceProtocol = 0. So we stays in UAC1, even the
>>> speed increase to high-speed.
>>>
>>
>> I was also surprised to see that the USBPre2 now works duplex without
>> pressing the "1" button while connecting.
>>
>> This was tested on Fedora 17 with stock kernel 3.6.6-1.fc17.
>> Jack was set to 512 Frames/period and 3 periods/buffer, and in a 24h
>> recording I got no xruns.
>> I did not manage to choose a sample rate unlike 48000, though.
>>
>> With lsusb, I can see 2 configurations for the same device, and the
>> second one has bInterfaceProtocol = 32 for all interfaces except HID:
>> http://pastebin.com/zwq0VVbM
>
>
> Hi Hans,
>
> Thank you for provided information.
>
> So, some usbPre2 have bNumConfigurations=2 when "1" is not pressed but not all usbPre2 (mine or alexander devices have only one "Configuration Descriptor").  Your device descriptor contains a UAC2 configuration descriptor, This sound good.
>
> Perhaps there is different firmware ?
> I have the 1.03 firmware. Can you provide your firmware level ?

Hmmm, same firmware 1.03 version here.
Which kernel are you running?

> Can you test 192khz value in jackd ?
>

No luck with this either - fastest one I get is 48000. This corresponds 
to the output of lsusb, which does not list samplerates over 48000 for 
this device.

/ Hans