Parallel / multiple audio output with alsa and USB audio mixer

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                          I have a new docking station for my laptop and have a hard time configuring audio/alsa.

After checking cat /proc/asound/cards

     0 [PCH            ]: HDA-Intel - HDA Intel PCH
                          HDA Intel PCH at 0xec248000 irq 158
     1 [Audio          ]: USB-Audio - ThinkPad Dock USB Audio
                          Generic ThinkPad Dock USB Audio at usb-0000:3c:00.0-1.4.4, high speed

I created /etc/asound.conf like this

    pcm.!default {
        type hw
        card 1
    }
    
    ctl.!default {
        type hw           
        card 1
    }

This seems to be working for most applications (Chromium, VLC, mpd, etc.) but I have no audio output in Firefox and I don't have audio output on multiple applications (parallel?) at the same time (ex: If I start Chromium I have no audio in VLC).

VLC gives me this error message for example:

    Audio output failed:
    The audio device "default" could not be used:
    Device or resource busy.

- How do I make it works for multiple applications at the same time?
- Is there something specific to do for Firefox ?
- How to fallback to card0 (laptop) if card1 (docking station) is not plugged in?

ty

Resources: 

- https://superuser.com/questions/626606/how-to-make-alsa-pick-a-preferred-sound-device-automatically 
- https://wiki.archlinux.org/title/Advanced_Linux_Sound_Architecture#Set_the_default_sound_card 

Installed packages: 

    alsa-utils, alsa-firmware, sof-firmware

uname -a: 

    Linux T480s 6.7.4-arch1-1 #1 SMP PREEMPT_DYNAMIC Mon, 05 Feb 2024 22:07:49 +0000 x86_64 GNU/Linux

Edit: multiple audio output and Firefox audio are working fine with card0 (internal)

Edit2:

Following https://wiki.archlinux.org/title/Advanced_Linux_Sound_Architecture#Configuring_the_index_order_via_kernel_module_options  I changed the index order of the cards in /etc/modprobe.d/alsa-base.conf :

    options snd_usb_audio index=0
    options snd_hda_intel index=1

I removed /etc/asound.conf and rebooted. 

When snd_usb_audio is loaded as the default card (card0) it is working. Firefox audio is working fine and I can output audio in multiple application at the same time.

So this means I only need to load snd_usb_audio as card0 if plugged and fallback to snd_hda_intel if not. Can we do this in alsa-base.conf or /etc/asound.conf?



                        
Asked by e___e (55 rep)
Feb 16, 2024, 04:11 PM
Last activity: Feb 16, 2024, 07:06 PM
Parallel / multiple audio output with alsa and USB audio mixer

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