20.04.1 selecting audio output device does not work on rpi

[Paul Larson]

Testing the 20.04.1 candidate images on rpi (currently rpi4-2GB) I'm noticing that I can no longer select the audio output device with amixer. This used to be possible by using:
amixer cset numid=3 2 for HDMI0
amixer cset numid=3 3 for HDMI1
amixer cset numid=3 1 for 3.5mm headphone jack

However, now trying to set this gets the following error:
amixer: Cannot find the given element from control default

It seems that by default, it will now use the hdmi output for whichever one is connected, and will only output through the headphones if no hdmi device is connected.

Kernel is:
Linux ubuntu 5.4.0-1015-raspi #15-Ubuntu SMP Fri Jul 10 05:34:24 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux

[Ubuntu QA Website (ubuntuqa)]

This bug has been reported on the Ubuntu ISO testing tracker.

A list of all reports related to this bug can be found here:
http://iso.qa.ubuntu.com/qatracker/reports/bugs/1889468

[Paul Larson (pwlars)]

Apparently it's not just us, this is an upstream change. Dave Jones found this: https://www.raspberrypi.org/blog/latest-raspberry-pi-os-update-may-2020/

To select headphones, the recommended process is now to create a file called .asoundrc in your home dir with these contents:
defaults.pcm.card 1
defaults.ctl.card 1