Add perceptual volume adjustment

The perceived loudness change of a change in volume depends
on the listening volume: at high volumes a 1 dB increment is
noticeable, but at low volumes a larger increment is needed
to get a comparable change in loudness.

Perceptual volume adjustment accounts for this fact, and
divides the hardware volume range into a number of steps.
Each step changes the dB volume by a variable amount, with
most of the steps concentrated at higher volumes. This
makes it possible to sweep over the entire hardware volume
range quickly, without losing the ability to finely adjust
the volume at normal listening levels.

Use "Volume Adjustment Mode" in the system settings menu
to select perceptual volume mode. The number of steps used
is controlled by "Number of Volume Steps". (Number of steps
has no effect in direct adjustment mode.)

It's still possible to set a specific dB volume level from
the sound settings menu when perceptual volume is enabled,
and perceptual volume does not affect the volume displayed
by themes.

Change-Id: I6f91fd3f7c5e2d323a914e47b5653033e92b4b3b

1 files changed, 2 insertions, 4 deletions

diff --git a/apps/gui/list.c b/apps/gui/list.c
index 83d12289f2..652279a9de 100644
--- a/apps/gui/list.c
+++ b/apps/gui/list.c
@@ -663,12 +663,10 @@ bool gui_synclist_do_button(struct gui_synclist * lists, int *actionptr)
 
 #ifdef HAVE_VOLUME_IN_LIST
         case ACTION_LIST_VOLUP:
-            global_settings.volume += sound_steps(SOUND_VOLUME);
-            setvol();
+            adjust_volume(1);
             return true;
         case ACTION_LIST_VOLDOWN:
-            global_settings.volume -= sound_steps(SOUND_VOLUME);
-            setvol();
+            adjust_volume(-1);
             return true;
 #endif
         case ACTION_STD_PREV: