I ran into an interesting problem today.
I noticed I don't have a "Master" channel in amixer. I only have PCM. And changing the volume on PCM is really finicky. It seems only 85%+ is actually audible, even though 100% is too loud.
I started poking around to see if I could figure out how to add the "Master" channel, and something broke with my audio. When I start playing something (via omxplayer or mpg123 or whatever), it ignores my current volume setting and plays at 100%. I can look at amixer during playback and see that my volume setting is still as I left it.
The volume will play at 100% regardless of the setting before playback. However, I can change the volume with amixer during playback, and it will work as expected.
Does anybody know what's going on?