Add support for equalization via alsaeq

[jcass77]

Adds software-based equalisation using alsaeq, based on the guide published over at HifiBerry as well as this one.

Requires that the alsaeq modules be installed first using sudo apt-get install -y libasound2-plugin-equal, so will have to be incorporated in a future distribution of MusicBox.

I wasn't able to test the fallback to USB in the first part of the if statement, so if someone with a USB DAC could run a quick check before merging that would be great.

Implements the enhancement requested at #306

[kingosticks]

What is this controls but for? This path doesn't exist.

[jcass77]

The .alsaequal.bin file should be created automatically on the first reboot after the equalizer module is installed.

The file is used to store the user-defined equalizer profile that can be configured with alsamixer -D equal

[jcass77]

Here's some sample output of alsamixer -D equal, but you'll have to run sudo apt-get install -y libasound2-plugin-equal first.

[kingosticks]

Ok Yeh I figured it was to store the state. And then I remembered that
/home/mopidy does exist in 0.6. But it won't exist in 0.7 since we'll be
using mopidy from apt which sets up the mopidy user account properly. Since
this is system state, it probably deserves to go somewhere system-ish
anyway.
On 25 Jul 2015 09:37, "John Cass" notifications@github.com wrote:

In filechanges/opt/musicbox/setsound.sh
#307 (comment)
:

@@ -179,33 +179,56 @@ then
cat << EOF > /etc/asound.conf
pcm.!default {
type plug

• slave.pcm plugequal;
  +}
  +pcm.plugequal {
• type dmix
• ipc_key 1024
• controls "/home/mopidy/.alsaequal.bin"

Here's some sample output of alsamixer -D equal, but you'll have to run sudo
apt-get install -y libasound2-plugin-equal first.

[image: mopidy ssh 180x46]
https://cloud.githubusercontent.com/assets/10268911/8888708/e444550a-32b8-11e5-98c4-3c3dae26d8a3.png

—
Reply to this email directly or view it on GitHub
https://github.com/woutervanwijk/Pi-MusicBox/pull/307/files#r35481120.

[jcass77]

Do you think /var/lib/alsa/alsaequal.bin would be appropriate? It is not a folder under Musicbox's control, but seems like a good candidate location for storing alsa-related configuration?

[jcass77]

The latest commit contains the following changes:

• equalizer defaults to 'off' which reverts to the old Musicbox functionality
• setting the qualifier to 'default' will delete the control file on every reboot and revert to default system settings
• I've scaled all of the presets down to 50%-65% to avoid likelihood of sound distortion occurring.

[jcass77]

...pushed 7c1efad to make use of an obvious opportunity to simplify the script logic, which I missed the first time round.

@kingosticks, not sure if you would prefer that we move the .alsaequal.bin file location at this stage?

[jcass77]

Having fiddled around with the sound curve settings for a while, the following sequence has yielded the most pleasing results for me on a set of small speakers:

65 65 65 62 58 52 54 56 62 54

[jcass77]

Update: resynchronised with main development branch.

[maxrozen-codesource]

Just FYI - your sound curve numbers are in the wrong order.
Left-most numbers increase bass, right-most numbers increase treble.

Test this by using
treble) curve="65 65 65 62 58 54 51 51 51 50" ;;
then contrast that with
bass) curve="50 50 50 52 56 60 63 65 65 65" ;;

Your "treble" setting increases bass

[jcass77]

Yes that didn't make sense to me either. The curves are based on an example that I found here: http://www.pclinuxos.com/forum/index.php/topic,110087.msg944835.html#msg944835.

Not sure if just the bass and treble ones are switched around or if the same is true of the other presets - your thoughts?

In the end I decided to just leave them as-is in the hope that the community will improve on it if the PR ever gets merged - but switching treble and bass makes sense as a first step.

[jcass77]

For future reference: instructions for setting up a 15-band equalizer is available at: https://discuss.mopidy.com/t/equalizer-alsaequal-on-pimusicbox-with-dac/1189/8?u=jcass77

[Sytten]

Can we expect to see this anytime? I really need it