Make the proper HMI volume model

Thanks to @nukeykt for a research help!

1 files changed, 29 insertions, 17 deletions

diff --git a/src/adlmidi_opl3.cpp b/src/adlmidi_opl3.cpp
index 5a44c13..1185768 100644
--- a/src/adlmidi_opl3.cpp
+++ b/src/adlmidi_opl3.cpp
@@ -239,21 +239,16 @@ static const uint_fast32_t s_ail_vel_graph[16] =
     106, 109, 112, 115, 118, 121, 124, 127
 };
 
-//! a VERY APROXIMAL HMI volume model, TODO: Research accurate one!
-static const uint_fast32_t s_hmi_volume_table[128] =
+static const uint_fast32_t s_hmi_volume_table[64] =
 {
-    0x3f, 0x3f, 0x3a, 0x35, 0x35, 0x30, 0x30, 0x2c, 0x2c, 0x29, 0x29,
-    0x25, 0x25, 0x24, 0x24, 0x23, 0x23, 0x22, 0x21, 0x21, 0x20, 0x20,
-    0x1f, 0x1f, 0x1e, 0x1e, 0x1d, 0x1d, 0x1c, 0x1c, 0x1b, 0x1b, 0x1a,
-    0x1a, 0x1a, 0x19, 0x19, 0x19, 0x18, 0x18, 0x18, 0x17, 0x17, 0x17,
-    0x16, 0x16, 0x16, 0x15, 0x15, 0x15, 0x14, 0x14, 0x14, 0x14, 0x13,
-    0x13, 0x13, 0x13, 0x12, 0x12, 0x12, 0x12, 0x11, 0x11, 0x11, 0x10,
-    0x10, 0x10, 0x0f, 0x0f, 0x0f, 0x0e, 0x0e, 0x0e, 0x0d, 0x0d, 0x0d,
-    0x0c, 0x0c, 0x0c, 0x0b, 0x0b, 0x0b, 0x0b, 0x0a, 0x0a, 0x0a, 0x0a,
-    0x09, 0x09, 0x09, 0x09, 0x08, 0x08, 0x08, 0x08, 0x07, 0x07, 0x07,
-    0x07, 0x06, 0x06, 0x06, 0x06, 0x05, 0x05, 0x05, 0x05, 0x04, 0x04,
-    0x04, 0x04, 0x03, 0x03, 0x03, 0x03, 0x03, 0x02, 0x02, 0x02, 0x02,
-    0x02, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00
+    0x3F, 0x3A, 0x35, 0x30, 0x2C, 0x29, 0x25, 0x24,
+    0x23, 0x22, 0x21, 0x20, 0x1F, 0x1E, 0x1D, 0x1C,
+    0x1B, 0x1A, 0x19, 0x18, 0x17, 0x16, 0x15, 0x14,
+    0x13, 0x12, 0x11, 0x10, 0x0F, 0x0E, 0x0E, 0x0D,
+    0x0D, 0x0C, 0x0C, 0x0B, 0x0B, 0x0A, 0x0A, 0x09,
+    0x09, 0x08, 0x08, 0x07, 0x07, 0x06, 0x06, 0x06,
+    0x05, 0x05, 0x05, 0x04, 0x04, 0x04, 0x04, 0x03,
+    0x03, 0x03, 0x02, 0x02, 0x02, 0x01, 0x01, 0x00,
 };
 
 enum
@@ -657,10 +652,9 @@ void OPL3::touchNote(size_t c,
 
     case Synth::VOLUME_HMI:
     {
-        /* Temporarily copying DMX volume model. TODO: Reverse-engine the actual HMI volume model! */
         volume = (channelVolume * channelExpression * m_masterVolume) / 16129;
-        volume = (((velocity < 128) ? velocity : 127) * volume) / 127;
-        volume = 63 - s_hmi_volume_table[volume];
+        volume = (((volume * 128) / 127) * velocity) >> 7;
+        volume = s_hmi_volume_table[volume >> 1];
     }
     break;
     }
@@ -786,6 +780,24 @@ void OPL3::touchNote(size_t c,
         tlMod = (~v0_val) & 0x3F;
         tlCar = (~v1_val) & 0x3F;
     }
+    else if(m_volumeScale == Synth::VOLUME_HMI)
+    {
+        uint_fast32_t vol;
+
+        if(do_modulator)
+        {
+            vol = (64 - volume) << 1;
+            vol *= (64 - tlMod);
+            tlMod = (8192 - vol) >> 7;
+        }
+
+        if(do_carrier)
+        {
+            vol = (64 - volume) << 1;
+            vol *= (64 - tlCar);
+            tlCar = (8192 - vol) >> 7;
+        }
+    }
     else
     {
         if(do_modulator)