Configure ALSA Sound card

Question

I have 2 playback device where one is HDMI and the other is HAT sound card. The requirement is to play audio from card 0 or 1 without rebooting the system.

aplay -l

**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]                                  
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: sndrpistest [snd_rpi_s5_adcdac], device 0: Test HiFi tlv320aic31xx-hifi-0 []         
  Subdevices: 0/1
  Subdevice #0: subdevice #0

1) If I configure the following in ~./asoundrc and reboot, the audio is playing from HDMI

pcm.!default {
    type hw
    card 0                      ----> HDMI
}

ctl.!default {
    type hw           
    card 0                     ----> HDMI
}

If I configure the following in ~./asoundrc and reboot, the audio is playing from HAT sound card

pcm.!default {
    type hw
    card 1                      ----> HAT sound card
}

ctl.!default {
    type hw           
    card 1                     ----> HAT sound card
}

Is there is a way to configure the sound card from card 0 card 1 or vise versa without rebooting?

Answer 1

You can play from either, as long as the kernel modules for both are loaded.

The method for doing this is as follows :

1. Stop lxpanel
2. Unload the audio drivers (rmmod or modprobe -r)
3. Load the audio drivers (modprobe)
4. Start lxpanel

The reason why you have to disable or stop/start lxpanel is that the volume plugin hangs the system when you try to unload audio modules.

In this example, I will remove the volume plugin from lxpanel and pulse audio.

1. Uninstall pulseaudio

   sudo apt remove pulseaudio

2. Disable the volume plugin from lxpanel

   sed -i 's/\=volumealsa/\=REMOVEvolumealsa/' .config/lxpanel/LXDE-pi/panels/panel

3. Reload your audio drivers

sudo modprobe -r snd_soc_audioinjector_pi_soundcard                             
sudo modprobe -r snd_soc_wm8731                                                 
sudo modprobe snd_soc_wm8731                                                    
sudo modprobe snd_soc_audioinjector_pi_soundcard   

It should now be working with the card you reloaded. In my case, I unloaded the audio injector stereo sound card and reloaded it. In your case, you should unload the sound card you have running in the "modprobe -r" calls and load in the other card.

You can see what snd modules are loaded using the lsmod command.