* Valid values for the audio device property are 'jack', 'hdmi0', 'hdmi1',
and 'dac'.
* If 'jack' is selected, first PCM card with name 'Headphones' is used.
If 'dac' is selected, first PCM card that doesn't match the name for 3.5mm
or HDMI devices is used. HDMI audio uses virtual ALSA devices instead of
using tinyalsa to open a PCM card directly.
* Allow forcing specific PCM card for debugging/development purposes.
* PCM card numbers are different between Pi 4 and Pi 5 and order can change
depending on the DAC driver that's enabled.
Pi 4:
console:/ # cat /proc/asound/cards
0 [Headphones ]: bcm2835_headpho - bcm2835 Headphones
bcm2835 Headphones
1 [vc4hdmi0 ]: vc4-hdmi - vc4-hdmi-0
vc4-hdmi-0
2 [vc4hdmi1 ]: vc4-hdmi - vc4-hdmi-1
vc4-hdmi-1
Pi 5 with DAC:
console:/ # cat /proc/asound/cards
0 [vc4hdmi0 ]: vc4-hdmi - vc4-hdmi-0
vc4-hdmi-0
1 [vc4hdmi1 ]: vc4-hdmi - vc4-hdmi-1
vc4-hdmi-1
2 [sndrpihifiberry]: HifiberryDacp - snd_rpi_hifiberry_dacplus
snd_rpi_hifiberry_dacplus
688b88189e