[alsa-devel] Usb audio - unsuported sampling rates

Daniel Mack zonque at gmail.com
Tue Jul 10 08:53:54 CEST 2012


On 10.07.2012 07:25, Gordon Dilan wrote:
> I'm using an usb mic which(according to it's producer should support up to
> 48kHz sampling rate). The problem is ALSA allows me to use only 16 kHz for
> this device. I do not want to resample the data, I want to sample it at
> 48kHz in order to be able to record some high pitch sounds 18-20kHz.
> I would want to try to do any modifications necessary in order to try
> support 48kHz, but I'm not sure where to start.


> Some more information:
> lsusb
> Bus 001 Device 007: ID 1415:2000 Nam Tai E&E Products Ltd. or OmniVision
> Technologies, Inc. Sony Playstation Eye
> lsusb -t

Please also provide the output of 'lsusb -v'.

> /:  Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci_hcd/2p, 480M
>     |__ Port 1: Dev 2, If 0, Class=hub, Driver=hub/6p, 480M
>         |__ Port 2: Dev 7, If 0, Class=vend., Driver=ov534, 480M
>         |__ Port 2: Dev 7, If 1, Class=audio, Driver=snd-usb-audio, 480M
>         |__ Port 2: Dev 7, If 2, Class=audio, Driver=snd-usb-audio, 480M
> At the moment I'm looking inside ALSA's source code to try to see from
> where this limitation of 16000kHz for my device appears, but I have to
> admit that I'm kind of lost.
> Any pointers on what direction should I go to try make my desired rate
> supported would be greatly appreciated!

The device is queried for its supported sample rates during probe using
class-specific commands. If it doesn't return all rates that are
actually supported, we need to add a quirk and override this list.

The list of known sample rates is included in
/proc/asound/card1/stream0. What does that show for you?


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