Get sound card available channels

Get sound card available channels

[Dan Hordern]

Hi,

We have a need for our process to poll/monitor the sound cards. This
process needs to provide a unique id for the sound card (e.g. some concat
of name+hardware address) which we can get using snd_ctl_t handle.

However, we also need to provide the number or rx/tx channels each sound
card provides. Doing this using the pcm hw_params after snd_pcm_open won't
work as the device may be in use.

Is there a way for this process to get the number of rx/tx channels without
needing to 'open' the device, e.g. using the snd_ctl_t handle?

One observation I have made is that there is a proc file ( cat
/proc/asound/card1/stream0) that seems to only be populated by the USB
soundcards I have and not the Intel builtin. This has all the information I
require but if it isn't a standard file we can't rely on it.

Thanks

Re: Get sound card available channels

[Clemens Ladisch]

Dan Hordern wrote:
> We have a need for our process to poll/monitor the sound cards.

Something like libudev would help with monitoring /dev/snd/controlC*
devices.

> This process needs to provide a unique id for the sound card (e.g.
> some concat of name+hardware address) which we can get using snd_ctl_t
> handle.

snd_ctl_card_info_get_id()

> However, we also need to provide the number or rx/tx channels each sound
> card provides. Doing this using the pcm hw_params after snd_pcm_open won't
> work as the device may be in use.
>
> Is there a way for this process to get the number of rx/tx channels without
> needing to 'open' the device, e.g. using the snd_ctl_t handle?

No.  The number of channels might depend on the current configuration
and on other resources.

What do you need these numbers for?


Regards,
Clemens