Went through the sound generation with a fine-tooth comb and made it sound a lot better!

src/main/java/jace/hardware/CardMockingboard.java

@@ -33,6 +33,7 @@ import jace.hardware.mockingboard.R6522;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.LockSupport;
 import java.util.concurrent.locks.ReentrantLock;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -184,6 +185,7 @@ public class CardMockingboard extends Card implements Runnable {
         }
 
         if (isRunning() && !pause) {
+//            buildMixerTable();
             timerSync.lock();
             try {
                 ticksSinceLastPlayback++;
@@ -246,13 +248,13 @@ public class CardMockingboard extends Card implements Runnable {
         out = out * 2.0 / 3.0 / numChips;
         double delta = 1.15;
         for (int i = 15; i > 0; i--) {
-            VolTable[i] = (int) Math.round(out);	/* round to nearest */	// [TC: unsigned int cast]
+            VolTable[i] = (int) (out / Math.pow(Math.sqrt(2),(15-i)));
 //            out /= 1.188502227;	/* = 10 ^ (1.5/20) = 1.5dB */
 //            out /= 1.15;	/* = 10 ^ (3/20) = 3dB */
-
+//            delta += 0.0225;
-            delta += 0.0225;
+//            out /= delta;   // As per applewin's source, the levels don't scale as documented.
-            out /= delta;   // As per applewin's source, the levels don't scale as documented.
         }
+        
         VolTable[0] = 0;
     }
     Thread playbackThread = null;
@@ -321,10 +323,12 @@ public class CardMockingboard extends Card implements Runnable {
             ticksSinceLastPlayback = 0;
             int zeroSamples = 0;
             setRun(true);
+            LockSupport.parkNanos(5000);
             while (isRunning()) {
-                while (!computer.isRunning()) {
+                while (isRunning() && !computer.isRunning()) {
-                    Thread.sleep(500);
+                    Thread.currentThread().yield();
                 }
+                if (isRunning()) {
                     computer.getMotherboard().requestSpeed(this);
                     playSound(leftBuffer, rightBuffer);
                     int p = 0;
@@ -384,11 +388,10 @@ public class CardMockingboard extends Card implements Runnable {
                         timerSync.unlock();
                     }
                 }
+            }
         } catch (LineUnavailableException ex) {
             Logger.getLogger(CardMockingboard.class
                     .getName()).log(Level.SEVERE, null, ex);
-        } catch (InterruptedException ex) {
-            Logger.getLogger(CardMockingboard.class.getName()).log(Level.SEVERE, null, ex);
         } finally {
             computer.getMotherboard().cancelSpeedRequest(this);
             System.out.println("Mockingboard playback stopped");

src/main/java/jace/hardware/mockingboard/EnvelopeGenerator.java

@@ -32,6 +32,11 @@ public class EnvelopeGenerator extends TimedGenerator {
     int direction;
     int amplitude;
 
+    boolean start1high = false;
+    boolean start2high = false;
+    boolean oneShot = false;
+    boolean oddEven = false;
+    
     public EnvelopeGenerator(int _clock, int _sampleRate) {
         super(_clock, _sampleRate);
     }
@@ -50,57 +55,56 @@ public class EnvelopeGenerator extends TimedGenerator {
         }
     }
 
+    int effectiveAmplitude = 0;
     public void step() {
         int stateChanges = updateCounter();
+        int total = 0;
         for (int i = 0; i < stateChanges; i++) {
-            if (amplitude == 0 && direction == -1) {
-                if (!cont) {
-                    direction = 0;
-                } else if (hold) {
-                    direction = 0;
-                    if (alt) {
-                        amplitude = 15;
-                    }
-                } else if (alt) {
-                    direction = 1;
-                } else {
-                    amplitude = 15;
-                }
-            }
-            if (amplitude == 15 && direction == 1) {
-                if (!cont) {
-                    direction = 0;
-                    amplitude = 0;
-                } else if (hold) {
-                    direction = 0;
-                    if (alt) {
-                        amplitude = 0;
-                    }
-                } else if (alt) {
-                    direction = -1;
-                } else {
-                    amplitude = 0;
-                }
-            }
             amplitude += direction;
+            if (amplitude > 15 || amplitude < 0) {
+                setPhase(oddEven ? start1high : start2high);
+                oddEven = !oddEven;
+                if (hold) {
+                    direction = 0;
+                }
+            }
+            total += amplitude;
+        }
+        if (stateChanges == 0) {
+            effectiveAmplitude = amplitude;
+        } else {
+            effectiveAmplitude = Math.min(15, total / stateChanges);
         }
     }
 
     public void setShape(int shape) {
+        oddEven = false;
         counter = 0;
         cont = (shape & 8) != 0;
         attk = (shape & 4) != 0;
         alt = (shape & 2) != 0;
-        hold = (shape & 1) != 0;
+        hold = ((shape ^ 8) & 9) != 0;
-        if (attk) {
+        
-            amplitude = 0;
+        start1high = !attk;
-            direction = 1;
+        start2high = cont && ! (attk ^ alt ^ hold);
-        } else {
+        
+        setPhase(start1high);
+    }
+    
+    public void setPhase(boolean isHigh) {
+        if (isHigh) {
             amplitude = 15;
             direction = -1;            
+        } else {
+            amplitude = 0;
+            direction = 1;
         }        
     }
 
+    public int getEffectiveAmplitude() {
+        return effectiveAmplitude;
+    }
+
     public int getAmplitude() {
         return amplitude;
     }

src/main/java/jace/hardware/mockingboard/NoiseGenerator.java

@@ -30,7 +30,7 @@ public class NoiseGenerator extends TimedGenerator {
     }
     @Override
     public int stepsPerCycle() {
-        return 8;
+        return 4;
     }
     public void step() {
         int stateChanges = updateCounter();
@@ -39,11 +39,14 @@ public class NoiseGenerator extends TimedGenerator {
     }
     public static final int BIT17 = 0x010000;
     public void updateRng() {
-        // noise = (noise >> 1) ^ ((noise & 1) ? 0x14000 : 0);
+        rng = ((rng & 1) != 0 ? rng ^ 0x24000 : rng) >> 1;
-        int newBit17 = (rng & 0x04) > 0 == (rng & 0x01) > 0 ? BIT17 : 0;
+        if ((rng & 1) == 1) {
-        rng = newBit17 + (rng >> 1);
+            state = !state;
         }
+    }
+    
+    boolean state = false;
     public boolean isOn() {
-        return ((rng & 1) == 1);
+        return state;
     }
 }

src/main/java/jace/hardware/mockingboard/SoundGenerator.java

@@ -58,16 +58,11 @@ public class SoundGenerator extends TimedGenerator {
     public int step(NoiseGenerator noiseGen, EnvelopeGenerator envGen) {
         int stateChanges = updateCounter();
         if (((stateChanges & 1) == 1)) inverted = !inverted;
-        if (amplitude == 0 && !useEnvGen) return 0;
+        double amp = stateChanges == 0 ? 1 : 1.0 / Math.max(stateChanges-1, 1);
-        if (!active && !noiseActive) return 0;
+        int vol = useEnvGen ? envGen.getEffectiveAmplitude() : amplitude;
-        boolean invert;
+        boolean on = noiseActive && noiseGen.isOn() || (active && inverted);
-        int vol = useEnvGen ? envGen.getAmplitude() : amplitude;
+//        return invert ? -CardMockingboard.VolTable[vol] : CardMockingboard.VolTable[vol];
-        if (active) {
+        return on ? (int) (CardMockingboard.VolTable[vol] * amp) : 0;
-            invert = noiseActive && noiseGen.isOn() ? false : inverted;
-        } else {
-            invert = noiseActive && !noiseGen.isOn();
-        }
-        return invert ? -CardMockingboard.VolTable[vol] : CardMockingboard.VolTable[vol];
     }
     
     @Override