From cd59eb5f43a9d4e37160ee8bbb902b1ea4e864a3 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 19 Oct 2016 23:07:51 -0400
Subject: [PATCH] Implemented non-linear volume.

---
 Components/AY38910/AY38910.cpp | 19 ++++++++++++++-----
 Components/AY38910/AY38910.hpp |  1 +
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/Components/AY38910/AY38910.cpp b/Components/AY38910/AY38910.cpp
index 1d7d31fcd..8595db8d9 100644
--- a/Components/AY38910/AY38910.cpp
+++ b/Components/AY38910/AY38910.cpp
@@ -64,6 +64,15 @@ AY38910::AY38910() :
 			}
 		}
 	}
+
+	// set up volume lookup table
+	float max_volume = 8192;
+	float root_two = sqrtf(2.0f);
+	for(int v = 0; v < 16; v++)
+	{
+		_volumes[v] = (int)(max_volume / powf(root_two, (float)(v ^ 0xf)));
+	}
+	_volumes[0] = 0;
 }
 
 void AY38910::set_clock_rate(double clock_rate)
@@ -147,11 +156,11 @@ void AY38910::get_samples(unsigned int number_of_samples, int16_t *target)
 #undef channel_volume
 
 		// Mix additively. TODO: non-linear volume.
-		target[c] = (int16_t)((
-			volumes[0] * channel_levels[0] +
-			volumes[1] * channel_levels[1] +
-			volumes[2] * channel_levels[2]
-		) * 512);
+		target[c] = (int16_t)(
+			_volumes[volumes[0]] * channel_levels[0] +
+			_volumes[volumes[1]] * channel_levels[1] +
+			_volumes[volumes[2]] * channel_levels[2]
+		);
 	}
 }
 
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index e15f75f54..c6b5f7f78 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -59,6 +59,7 @@ class AY38910: public ::Outputs::Filter<AY38910> {
 		int _channel_dividers[3];
 		int _channel_output[3];
 
+		int _volumes[16];
 
 		int _master_divider;