Volume slider only uses last 25%

Feature: https://source.puri.sm/Librem5/use-cases/issues/88

What problem did you encounter

What is the actual behaviour?

Volume slider goes silent at 75% mark

What is the expected behaviour?

Volume slider is useful for the full 100% (so 0% is silent, 50% is half of full, and 100% is full volume)

How to reproduce

1. Play audio (testing against https://puri.sm/posts/the-future-of-computing-and-why-you-should-care video)
2. Open volume slider
3. adjust volume from 100% to 75%
4. witness it is nearly silent/muted.

What hardware are you running on?

• amd64 qemu image
• Librem5 devkit
• other (please elaborate)

Relevant OS information

Which kernel are you using?

Please paste the output of uname -a below. Linux pureos 4.18.11-gee84b30c #1 SMP PREEMPT Mon Mar 18 11:29:53 PDT 2019 aarch64

Which OS are you using?

Please paste the output of cat /etc/os-release below.

root@pureos:~# cat /etc/os-release 
PRETTY_NAME="Debian GNU/Linux buster/sid"
NAME="Debian GNU/Linux"                                             
ID=debian                                                           
HOME_URL="https://www.debian.org/"                                  
SUPPORT_URL="https://www.debian.org/support"                        
BUG_REPORT_URL="https://bugs.debian.org/"                           
root@pureos:~#                                                      

Any other information that may be helpful?

n/a