Re: [Q] Why is it needed to add an alsa module to v4l audio capture devices?

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Ezequiel,

On Thursday 07 June 2012 15:26:04 Ezequiel Garcia wrote:
> Hi all,
> 
> (I hope this is a genuine question, and I'm not avoiding my own homework
> here.)
> 
> I'm trying to support the audio part of the stk1160 usb bridge (similar to
> em28xx). Currently, the snd-usb-audio module is being loaded when I
> physically plug my device, but I can't seem to capture any sound with vlc.
> 
> I still have to research and work a lot to understand the connection between
> my device and alsa, and altough I could write a working module similar to
> em28xx-alsa.ko, I still can't figure out why do I need to write one in the
> first place.
> 
> Why is this module suffficient for gspca microphone devices (gspca, to name
> one) and why is a new alsa driver needed for em28xx (or stk1160)?

Some devices expose audio functionality by implementing the UAC (USB Audio 
Class) specification. The snd-usb-audio module is all you should need for 
those devices.

Other vendors support audio by using their own proprietary protocol. In those 
cases you will need a device-specific kernel module.

-- 
Regards,

Laurent Pinchart