[LAU] Sound Devices USBPre2, UAC2 status

[alexander]

On 11/01/13 17:42, 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 23:23:56
>> Objet: Re: [LAU] Sound Devices USBPre2, UAC2 status
>>
>> On 01/10/2013 10:30 PM, shal at free.fr wrote:
>>>> De: "Hans Wilmers" <hanswil at notam02.no>
>>>> 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.
>>>
>>> I have tried different kernel, 3.2 to 3.7.1, vanilla or ubuntu
>>> kernel.
>>>
>>> The lsusb does not means that you are limited to 48000.
>>>
>>> The lsusb provides the "devices descriptor" and a devices
>>> descriptors has one or more "configuration descriptor". The kernel
>>> chooses one of the "configuration descriptor".
>>> In your device descriptor (provided directly by the device) there
>>> is two possibles configuration descriptons (the
>>> bNumConfigurations=2). The first one corresponds to the UAC1 mode
>>> in high-speed (this is my one configuration) and so limited to
>>> 48000. The second one is the UAC2 mode (the expected mode).
>>>
>>> Perhaps the kernel choose the fist good one, so UAC1  .
>>>
>>> Can you send the result of  cat /proc/asound/USBPre2/stream0  ?
>>>
>> Yes, see below.
>>
>> / Hans
>>
>>
>> --------------- /proc/asound/USBPre2/stream0 -------------
>>
>> Sound Devices USBPre2 at usb-0000:00:1a.0-1.2, high speed : USB Audio
>>
>> Playback:
>>     Status: Stop
>>     Interface 1
>>       Altset 1
>>       Format: S16_LE
>>       Channels: 2
>>       Endpoint: 6 OUT (ASYNC)
>>       Rates: 8000, 16000, 24000, 32000, 44100, 48000
>>       Data packet interval: 1000 us
>>     Interface 1
>>       Altset 2
>>       Format: S24_3LE
>>       Channels: 2
>>       Endpoint: 6 OUT (ASYNC)
>>       Rates: 8000, 16000, 24000, 32000, 44100, 48000
>>       Data packet interval: 1000 us
>
> Hi Hans,
>
> So , effectively you are limited to 48000.
> I supposed that the linux kernel chooses this first valid configuration descriptor.
>
> This behavior can be modified in the kernel with adding a quirk in the code.
> If my usbPre2 has the good device descripton, I can devlop and test this patch.
> But my devices does not offer the UAC2 configuration descriptor.
>
> I have write a post on the Sound Devices Forum. Perhaps I will have help to understand why my device has this strange behavior and correct it.
>
> In this case, I think I can patch the kernel to have the UAC2 mode...
>
> Olivier
> _______________________________________________
> Linux-audio-user mailing list
> Linux-audio-user at lists.linuxaudio.org
> http://lists.linuxaudio.org/listinfo/linux-audio-user
that would be amazing! I just joined the forum to raise their awereness 
but I can't post yet it seems!

I submitted a bugreport to alsa's bugtracker aloong time ago where there 
have been some additional discussion and someone actually have written 
somekind of patch, I never got it to work tho.. but the tracker is down 
now it seems.... I also started some threads on the alsa mailing list, 
both users and dev.