Volume scale issue

[andyjenkinson]

Hi,

I notice that the scale of the volume control is a bit odd when using the ALSA mixer to control the volume control of the Raspberry Pi's internal sound card. For me, almost all of the variability in audible volume occurs in the top 15% of the volume range, and it is also inconsistent with the volume reported through other applications like shairport (another component of pimusicbox, which is the context I am using mopidy in).

I believe this is due to a change to the way amixer reports volume in ALSA. The scale used by mopidy appears to be the one amixer uses, i.e. a simple linear scale of the raw values from the card. By contrast, alsamixer uses a scale that represents human perception volume instead (which I believe is more correct from a user-driven application like mopidy). See this thread for details:
https://bbs.archlinux.org/viewtopic.php?pid=1217759

I guess any change would need to be in the python alsa binding library.

[matt-oakes]

I'm having the same issue. Is this something that will be fixed?

[adamcik]

I would suggest we make the scale a configuration option. Unless there is some sane way to pull the data to just make this work from pyalsa. Not sure if this should be in mopidy-alsamixer, or mopidy itself though.

[tkem]

Same issue with IQAudio PiDAC+; anything below 60 is barely audible. So +1 for a config option for this.

[fluffypony]

Same issue on RPi 3 - @jodal do you have a Bitcoin / Monero address I can donate to in order to get a bit of traction on this issue? Thanks!

[steveb1475]

Still a problem - RPi 2 with DAC+

[karlvr]

@steveb1475 @fluffypony @tkem if you're still interested. I have been successful messing around with the code. It might be enough to things better for you. I'm not sure if it's the right solution, but it makes things much better for me!

Download the three files from https://github.com/karlvr/mopidy-alsamixer/tree/volume-range/mopidy_alsamixer and replace the files in /usr/lib/python2.7/dist-packages/mopidy_alsamixer/ on your RPi.

Add volmin and volmax to your mopidy.conf:

e.g.

[alsamixer]
card = 0
control = Digital
volmin = 30
volmax = 70

Then restart Mopidy. You should now have your Mopidy volume control mapped to the middle of the ALSA range. For me it's now much more usable.

[karlvr]

I've also just added an option for logarithmic volume control to that PR. That is working really nicely for us. The movement of the volume slider in Mopidy now corresponds to the movement of the volume slider in alsamixer (which I understand already uses the logarithmic scale).

[jodal]

Fixed by PR #9. Thanks @karlvr! :-)