Audio: Change how volume works

Across the entire audio system, audio now works in 0-1 terms instead of
0-100 as before. Therefore, volume is now a double instead of an int.
The master volume of the AudioServer changes smoothly through a
FadingProperty, preventing clicks. Finally, volume computations are done
with logarithmic scaling, which is more natural for the human ear.

Note that this could be 4-5 different commits, but as they change each
other's code all the time, it makes no sense to split them up.

2 files changed, 7 insertions, 3 deletions

diff --git a/Userland/Applications/Piano/Music.h b/Userland/Applications/Piano/Music.h
index a1080155e9..ce2c814735 100644
--- a/Userland/Applications/Piano/Music.h
+++ b/Userland/Applications/Piano/Music.h
@@ -30,7 +30,8 @@ constexpr int buffer_size = sample_count * sizeof(Sample);
 
 constexpr double sample_rate = 44100;
 
-constexpr double volume_factor = 1800;
+// Headroom for the synth
+constexpr double volume_factor = 0.1;
 
 enum Switch {
     Off,
diff --git a/Userland/Applications/Piano/Track.cpp b/Userland/Applications/Piano/Track.cpp
index f077efc994..5727a945f7 100644
--- a/Userland/Applications/Piano/Track.cpp
+++ b/Userland/Applications/Piano/Track.cpp
@@ -95,8 +95,8 @@ void Track::fill_sample(Sample& sample)
         default:
             VERIFY_NOT_REACHED();
         }
-        new_sample.left += note_sample.left * m_power[note] * volume_factor * (static_cast<double>(volume()) / volume_max);
-        new_sample.right += note_sample.right * m_power[note] * volume_factor * (static_cast<double>(volume()) / volume_max);
+        new_sample.left += note_sample.left * m_power[note] * NumericLimits<i16>::max() * volume_factor * (static_cast<double>(volume()) / volume_max);
+        new_sample.right += note_sample.right * m_power[note] * NumericLimits<i16>::max() * volume_factor * (static_cast<double>(volume()) / volume_max);
     }
 
     auto new_sample_dsp = LibDSP::Signal(LibDSP::Sample { new_sample.left / NumericLimits<i16>::max(), new_sample.right / NumericLimits<i16>::max() });
@@ -105,6 +105,9 @@ void Track::fill_sample(Sample& sample)
     new_sample.left = delayed_sample.left * NumericLimits<i16>::max();
     new_sample.right = delayed_sample.right * NumericLimits<i16>::max();
 
+    new_sample.left = clamp(new_sample.left, NumericLimits<i16>::min(), NumericLimits<i16>::max());
+    new_sample.right = clamp(new_sample.right, NumericLimits<i16>::min(), NumericLimits<i16>::max());
+
     sample.left += new_sample.left;
     sample.right += new_sample.right;
 }