Re: [LAU] Sound Devices USBPre2, UAC2 status

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From: <shal@...>
To: <linux-audio-user@...>
Date: Monday, January 7, 2013 - 7:25 pm

----- Mail original -----

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.

So IMHO, it's why, we are already limited to 48khz framerate.

If a usb audio guru can confirm my idea...

I have no problem in high speed since kernel 3.2. Ubuntu kernel or vanilla kernel are OK (today, I use a 3.7.1 vanilla kernel).

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Messages in current thread:
Re: [LAU] Sound Devices USBPre2, UAC2 status, alexander, (Mon Jan 21, 3:00 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, alexander, (Fri Jan 25, 10:37 pm)
Re: [LAU] USB2 Audio, PreSonus Audiobox 1818VSL, Robin Gareus, (Tue Jan 15, 8:34 pm)
Re: [LAU] USB2 Audio, PreSonus Audiobox 1818VSL, Louis Gorenfeld, (Tue Jan 15, 10:44 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, alexander, (Mon Jan 7, 5:28 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, , (Mon Jan 7, 7:25 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, Hans Wilmers, (Thu Jan 10, 12:24 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, Hans Wilmers, (Thu Jan 10, 9:11 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, Hans Wilmers, (Thu Jan 10, 10:24 pm)
Re: [LAU] Sound Devices USBPre2, UAC2 status, alexander, (Mon Jan 14, 9:20 pm)