Implement and connect audio emulation.

src/emucore/tia/Audio.cxx

@@ -18,11 +18,97 @@
 #include "Audio.hxx"
 #include "AudioQueue.hxx"
 
+#include <cmath>
+
+namespace {
+  constexpr double R_MAX = 30.;
+  constexpr double R = 1.;
+
+  Int16 mixingTableEntry(uInt8 v, uInt8 vMax)
+  {
+    return floor(0x7fff * double(v) / double(vMax) * (R_MAX + R * double(vMax)) / (R_MAX + R * double(v)));
+  }
+}
+
+
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-Audio::Audio() {}
+Audio::Audio()
+  : myAudioQueue(0),
+    myCurrentFragment(0)
+{
+  for (uInt8 i = 0; i <= 0x1e; i++) myMixingTableSum[i]= mixingTableEntry(i, 0x1e);
+  for (uInt8 i = 0; i <= 0x0f; i++) myMixingTableIndividual[i] = mixingTableEntry(i, 0x0f);
+
+  reset();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void Audio::reset()
+{
+  myCounter = 0;
+  mySampleIndex = 0;
+
+  myChannel0.reset();
+  myChannel1.reset();
+}
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void Audio::setAudioQueue(AudioQueue* queue)
 {
   myAudioQueue = queue;
+
+  myCurrentFragment = myAudioQueue->enqueue();
+  mySampleIndex = 0;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void Audio::tick()
+{ switch (myCounter) {
+    case 9:
+    case 81:
+      myChannel0.phase0();
+      myChannel1.phase0();
+
+      break;
+
+    case 37:
+    case 149:
+      phase1();
+      break;
+  }
+
+  if (++myCounter == 228) myCounter = 0;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void Audio::phase1()
+{
+  uInt8 sample0 = myChannel0.phase1();
+  uInt8 sample1 = myChannel1.phase1();
+
+  if (!myAudioQueue) return;
+
+  if (myAudioQueue->isStereo()) {
+    myCurrentFragment[2*mySampleIndex] = myMixingTableIndividual[sample0];
+    myCurrentFragment[2*mySampleIndex + 1] = myMixingTableIndividual[sample1];
+  } else {
+    myCurrentFragment[mySampleIndex] = myMixingTableSum[sample0 + sample1];
+  }
+
+  if (++mySampleIndex == myAudioQueue->fragmentSize()) {
+    mySampleIndex = 0;
+    myCurrentFragment = myAudioQueue->enqueue(myCurrentFragment);
+  }
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+AudioChannel& Audio::channel0()
+{
+  return myChannel0;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+AudioChannel& Audio::channel1()
+{
+  return myChannel1;
 }

src/emucore/tia/Audio.hxx

@@ -18,17 +18,43 @@
 #ifndef TIA_AUDIO_HXX
 #define TIA_AUDIO_HXX
 
+#include "bspf.hxx"
+#include "AudioChannel.hxx"
+
 class AudioQueue;
 
-class Audio {
+class Audio
+{
   public:
     Audio();
 
+    void reset();
+
     void setAudioQueue(AudioQueue *queue);
 
+    void tick();
+
+    AudioChannel& channel0();
+
+    AudioChannel& channel1();
+
+  private:
+    void phase1();
+
   private:
     AudioQueue* myAudioQueue;
 
+    uInt8 myCounter;
+
+    AudioChannel myChannel0;
+    AudioChannel myChannel1;
+
+    Int16 myMixingTableSum[0x1e + 1];
+    Int16 myMixingTableIndividual[0x0f + 1];
+
+    Int16* myCurrentFragment;
+    uInt32 mySampleIndex;
+
   private:
     Audio(const Audio&) = delete;
     Audio(Audio&&) = delete;

src/emucore/tia/AudioChannel.cxx

@@ -0,0 +1,143 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2018 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#include "AudioChannel.hxx"
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+AudioChannel::AudioChannel()
+{
+  reset();
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void AudioChannel::reset()
+{
+  myAudc = myAudv = myAudf = 0;
+  myClockEnable = myNoiseFeedback = myNoiseCounterBit4 = myPulseCounterHold = false;
+  myDivCounter = myPulseCounter = myNoiseCounter = 0;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void AudioChannel::phase0()
+{
+  if (myClockEnable) {
+    myNoiseCounterBit4 = myNoiseCounter & 0x01;
+
+    switch (myAudc & 0x03) {
+      case 0x00:
+      case 0x01:
+        myPulseCounterHold = false;
+        break;
+
+      case 0x02:
+        myPulseCounterHold = (myNoiseCounter & 0x1e) != 0x02;
+        break;
+
+      case 0x03:
+        myPulseCounterHold = myNoiseCounterBit4;
+        break;
+    }
+
+    switch (myAudc & 0x03) {
+      case 0x00:
+        myNoiseFeedback =
+          ((myPulseCounter ^ myNoiseCounter) & 0x01) ||
+          !(myNoiseCounter || (myPulseCounter != 0x0a)) ||
+          !(myAudc & 0x0c);
+
+        break;
+
+      default:
+        myNoiseFeedback =
+          ((myNoiseCounter & 0x04 ? 1 : 0) ^ (myNoiseCounter & 0x01)) ||
+          myNoiseCounter == 0;
+
+      break;
+    }
+  }
+
+  myClockEnable = myDivCounter == myAudf;
+
+  if (myDivCounter == myAudf || myDivCounter == 0x1f) {
+    myDivCounter = 0;
+  } else {
+    myDivCounter++;
+  }
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+uInt8 AudioChannel::phase1()
+{
+  bool pulseFeedback = false;
+
+  if (myClockEnable) {
+    switch (myAudc >> 2) {
+      case 0x00:
+        pulseFeedback =
+          ((myPulseCounter & 0x02 ? 1 : 0) ^ (myPulseCounter & 0x01)) &&
+          (myPulseCounter != 0x0a) &&
+          (myAudc & 0x03);
+
+        break;
+
+      case 0x01:
+        pulseFeedback = !(myPulseCounter & 0x08);
+        break;
+
+      case 0x02:
+        pulseFeedback = !myNoiseCounterBit4;
+        break;
+
+      case 0x03:
+        pulseFeedback = !((myPulseCounter & 0x02) || !(myPulseCounter & 0x0e));
+        break;
+    }
+
+    myNoiseCounter >>= 1;
+    if (myNoiseFeedback) {
+      myNoiseCounter |= 0x10;
+    }
+
+    if (!myPulseCounterHold) {
+      myPulseCounter = ~(myPulseCounter >> 1) & 0x07;
+
+      if (pulseFeedback) {
+        myPulseCounter |= 0x08;
+      }
+    }
+  }
+
+  return (myPulseCounter & 0x01) * myAudv;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void AudioChannel::audc(uInt8 value)
+{
+  myAudc = value & 0x0f;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void AudioChannel::audv(uInt8 value)
+{
+  myAudv = value & 0x0f;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void AudioChannel::audf(uInt8 value)
+{
+  myAudc = value & 0x1f;
+}

src/emucore/tia/AudioChannel.hxx

@@ -0,0 +1,61 @@
+//============================================================================
+//
+//   SSSS    tt          lll  lll
+//  SS  SS   tt           ll   ll
+//  SS     tttttt  eeee   ll   ll   aaaa
+//   SSSS    tt   ee  ee  ll   ll      aa
+//      SS   tt   eeeeee  ll   ll   aaaaa  --  "An Atari 2600 VCS Emulator"
+//  SS  SS   tt   ee      ll   ll  aa  aa
+//   SSSS     ttt  eeeee llll llll  aaaaa
+//
+// Copyright (c) 1995-2018 by Bradford W. Mott, Stephen Anthony
+// and the Stella Team
+//
+// See the file "License.txt" for information on usage and redistribution of
+// this file, and for a DISCLAIMER OF ALL WARRANTIES.
+//============================================================================
+
+#ifndef TIA_AUDIO_CHANNEL_HXX
+#define TIA_AUDIO_CHANNEL_HXX
+
+#include "bspf.hxx"
+
+class AudioChannel
+{
+  public:
+    AudioChannel();
+
+    void reset();
+
+    void phase0();
+
+    uInt8 phase1();
+
+    void audc(uInt8 value);
+
+    void audf(uInt8 value);
+
+    void audv(uInt8 value);
+
+  private:
+    uInt8 myAudc;
+    uInt8 myAudv;
+    uInt8 myAudf;
+
+    bool myClockEnable;
+    bool myNoiseFeedback;
+    bool myNoiseCounterBit4;
+    bool myPulseCounterHold;
+
+    uInt8 myDivCounter;
+    uInt8 myPulseCounter;
+    uInt8 myNoiseCounter;
+
+  private:
+    AudioChannel(const AudioChannel&);
+    AudioChannel(AudioChannel&&);
+    AudioChannel& operator=(const AudioChannel&);
+    AudioChannel& operator=(AudioChannel&&);
+};
+
+#endif // TIA_AUDIO_CHANNEL_HXX

src/emucore/tia/TIA.cxx

@@ -521,21 +521,32 @@ bool TIA::poke(uInt16 address, uInt8 value)
       break;
 
     case AUDV0:
+      myAudio.channel0().audv(value);
       myShadowRegisters[address] = value;
       break;
+
     case AUDV1:
+      myAudio.channel1().audv(value);
       myShadowRegisters[address] = value;
       break;
+
     case AUDF0:
+      myAudio.channel0().audf(value);
       myShadowRegisters[address] = value;
       break;
+
     case AUDF1:
+      myAudio.channel1().audf(value);
       myShadowRegisters[address] = value;
       break;
+
     case AUDC0:
+      myAudio.channel0().audc(value);
       myShadowRegisters[address] = value;
       break;
+
     case AUDC1:
+      myAudio.channel1().audc(value);
       myShadowRegisters[address] = value;
       break;
 
@@ -1179,6 +1190,8 @@ void TIA::cycle(uInt32 colorClocks)
     if (++myHctr >= 228)
       nextLine();
 
+    myAudio.tick();
+
     myTimestamp++;
   }
 }

src/emucore/tia/module.mk

@@ -10,7 +10,8 @@ MODULE_OBJS := \
 	src/emucore/tia/Background.o \
 	src/emucore/tia/LatchedInput.o \
 	src/emucore/tia/PaddleReader.o \
-	src/emucore/tia/Audio.o
+	src/emucore/tia/Audio.o \
+	src/emucore/tia/AudioChannel.o
 
 MODULE_DIRS += \
 	src/emucore/tia