mopidy-alsamixer 1.0.3 patch for logarithmic volume

mopidy-alsamixer-patch.diff

diff --git a/mopidy_alsamixer/__init__.py b/mopidy_alsamixer/__init__.py
index 8f4312a..8916efa 100644
--- a/mopidy_alsamixer/__init__.py
+++ b/mopidy_alsamixer/__init__.py
@@ -22,6 +22,9 @@ class Extension(ext.Extension):
         schema = super(Extension, self).get_config_schema()
         schema['card'] = config.Integer(minimum=0)
         schema['control'] = config.String()
+        schema['min_volume'] = config.Integer(minimum=0, maximum=100)
+        schema['max_volume'] = config.Integer(minimum=0, maximum=100)
+        schema['volume_scale'] = config.String(choices=('linear', 'cubic'))
         return schema
 
     def setup(self, registry):
diff --git a/mopidy_alsamixer/ext.conf b/mopidy_alsamixer/ext.conf
index 2a95443..c365f59 100644
--- a/mopidy_alsamixer/ext.conf
+++ b/mopidy_alsamixer/ext.conf
@@ -2,3 +2,6 @@
 enabled = true
 card = 0
 control = Master
+min_volume = 0
+max_volume = 100
+volume_scale = linear
diff --git a/mopidy_alsamixer/mixer.py b/mopidy_alsamixer/mixer.py
index c133347..a0acf44 100644
--- a/mopidy_alsamixer/mixer.py
+++ b/mopidy_alsamixer/mixer.py
@@ -3,6 +3,7 @@ from __future__ import unicode_literals
 import logging
 import select
 import threading
+import math
 
 import alsaaudio
 
@@ -23,6 +24,9 @@ class AlsaMixer(pykka.ThreadingActor, mixer.Mixer):
         self.config = config
         self.card = self.config['alsamixer']['card']
         self.control = self.config['alsamixer']['control']
+        self.min_volume = self.config['alsamixer']['min_volume']
+        self.max_volume = self.config['alsamixer']['max_volume']
+        self.volume_scale = self.config['alsamixer']['volume_scale']
 
         known_cards = alsaaudio.cards()
         if self.card >= len(known_cards):
@@ -70,15 +74,28 @@ class AlsaMixer(pykka.ThreadingActor, mixer.Mixer):
         if not channels:
             return None
         elif channels.count(channels[0]) == len(channels):
-            return int(channels[0])
+            return self.mixer_volume_to_volume(channels[0])
         else:
             # Not all channels have the same volume
             return None
 
     def set_volume(self, volume):
-        self._mixer.setvolume(volume)
+        self._mixer.setvolume(self.volume_to_mixer_volume(volume))
         return True
 
+    def mixer_volume_to_volume(self, mixer_volume):
+        volume = mixer_volume
+        if self.volume_scale == "cubic":
+            volume = 100.0 * math.pow(volume / 100.0, 3.0)
+        volume = (volume - self.min_volume) * 100.0 / (self.max_volume - self.min_volume)
+        return int(volume)
+
+    def volume_to_mixer_volume(self, volume):
+        mixer_volume = self.min_volume + volume * (self.max_volume - self.min_volume) / 100.0
+        if self.volume_scale == "cubic":
+            mixer_volume = 100.0 * math.pow(mixer_volume / 100.0, 1.0 / 3.0)
+        return int(mixer_volume)
+
     def get_mute(self):
         try:
             channels_muted = self._mixer.getmute()

Used to patch Mopidy-Alsamixer 1.0.3 to include logarithmic volume scale, without requiring an upgrade that comes with other changes that make it incompatible with Pi Musicbox 0.7.

(cd /usr/local/lib/python2.7/dist-packages/mopidy_alsamixer && curl -L https://gist.github.com/karlvr/34e66d2090942dbf9c9bb3c5b2b87260/raw/85edd590bea140b87b3cf2023ecf740e3fd77646/mopidy-alsamixer-patch.diff | patch -p2)
rm /usr/local/lib/python2.7/dist-packages/mopidy_alsamixer/*.pyc

You can then add the following to the [alsamixer] section in your mopidy settings:

volume_scale = cubic