linuxaudio.org

On 01/07/2013 08:25 PM, shal@free.fr wrote:

quoted text
>

> ----- Mail original -----

>> De: "alexander"

>> À: linux-audio-user@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
/ Hans
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