[alsa-devel] Jack sensing in snd_usb_audio ?

[Felipe Ferreri Tonello]

Hi Bastien,

On 12/10/16 07:10, Bastien Nocera wrote:
> Hey,
> 
> I recently bought some cheap USB soundcards for a computer that doesn't
> have any audio output other than through the HDMI output, and the
> screen I'm attaching doesn't have an audio output.
> 
> So I'm looking to plug in 2 of those USB soundcards, and switch between
> them depending on whether I'm using headphones, or want to use the
> standalone speaker.
> 
> Obviously, it would be so much nicer if I didn't have to switch between
> the outputs by hand, and ignored the "headphones" sound card when not
> plugged in.
> 
> My questions are:
> - does the USB audio driver support jack sensing?
> - is this something standard that's just not implemented yet? In which
> case, I'd be up for at least trying, given specs.
> - or is it something that depends on the device, and in which case, how
> would I find out?

What you need is PulseAudio server instead. PulseAudio supports this via
kcontrol for quite some time.

Jack is supposed to be a low-latency audio server for audio
applications, not for normal desktop usage.

> 
> Some details about the device itself below.
> 
> Cheers
> 
> /proc/asound/cards:
>  4 [Device         ]: USB-Audio - USB Audio Device
>                       GeneralPlus USB Audio Device at usb-0000:00:14.0-9, full speed
> 
> $ amixer -c 4
> Simple mixer control 'Speaker',0
>   Capabilities: pvolume pswitch pswitch-joined
>   Playback channels: Front Left - Front Right
>   Limits: Playback 0 - 30
>   Mono:
>   Front Left: Playback 16 [53%] [-21.00dB] [on]
>   Front Right: Playback 16 [53%] [-21.00dB] [on]
> Simple mixer control 'Mic',0
>   Capabilities: pvolume pvolume-joined cvolume cvolume-joined pswitch
> pswitch-joined cswitch cswitch-joined
>   Playback channels: Mono
>   Capture channels: Mono
>   Limits: Playback 0 - 14 Capture 0 - 30
>   Mono: Playback 1 [7%] [-10.50dB] [off] Capture 26 [87%] [27.00dB]
> [on]
> Simple mixer control 'Auto Gain Control',0
>   Capabilities: pswitch pswitch-joined
>   Playback channels: Mono
>   Mono: Playback [off]
> --
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-- 
Felipe
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