Factor out resampling.

.vscode/settings.json

@@ -42,6 +42,7 @@
         "type_traits": "cpp",
         "stdexcept": "cpp",
         "fstream": "cpp",
-        "__locale": "cpp"
+        "__locale": "cpp",
+        "__string": "cpp"
     }
 }

Makefile

@@ -101,7 +101,8 @@ MODULES += \
 	src/emucore/tia/frame-manager \
 	src/gui \
 	src/common \
-	src/common/tv_filters
+	src/common/tv_filters \
+	src/common/audio
 
 ######################################################################
 # The build rules follow - normally you should have no need to

src/common/SoundSDL2.cxx

@@ -30,6 +30,7 @@
 #include "SoundSDL2.hxx"
 #include "AudioQueue.hxx"
 #include "EmulationTiming.hxx"
+#include "audio/SimpleResampler.hxx"
 
 namespace {
   inline Int16 applyVolume(Int16 sample, Int32 volumeFactor)
@@ -45,8 +46,7 @@ SoundSDL2::SoundSDL2(OSystem& osystem)
     myVolume(100),
     myVolumeFactor(0xffff),
     myAudioQueue(0),
-    myCurrentFragment(0),
+    myCurrentFragment(0)
-    myFragmentBufferSize(0)
 {
   myOSystem.logMessage("SoundSDL2::SoundSDL2 started ...", 2);
 
@@ -132,14 +132,6 @@ void SoundSDL2::open(shared_ptr<AudioQueue> audioQueue, EmulationTiming* emulati
   myAudioQueue = audioQueue;
   myUnderrun = true;
   myCurrentFragment = 0;
-  myTimeIndex = 0;
-  myFragmentIndex = 0;
-  myFragmentBufferSize = static_cast<uInt32>(
-    ceil(
-      1.5 * static_cast<double>(myHardwareSpec.samples) / static_cast<double>(myAudioQueue->fragmentSize())
-          * static_cast<double>(myAudioQueue->sampleRate()) / static_cast<double>(myHardwareSpec.freq)
-    )
-  );
 
   // Adjust volume to that defined in settings
   setVolume(myOSystem.settings().getInt("volume"));
@@ -154,6 +146,8 @@ void SoundSDL2::open(shared_ptr<AudioQueue> audioQueue, EmulationTiming* emulati
       << endl;
   myOSystem.logMessage(buf.str(), 1);
 
+  initResampler();
+
   // And start the SDL sound subsystem ...
   mute(false);
 
@@ -243,62 +237,33 @@ uInt32 SoundSDL2::getSampleRate() const
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void SoundSDL2::processFragment(Int16* stream, uInt32 length)
 {
-  if (myUnderrun && myAudioQueue->size() > emulationTiming->prebufferFragmentCount()) {
+  myResampler->fillFragment(stream, length);
-    myUnderrun = false;
-    myCurrentFragment = myAudioQueue->dequeue(myCurrentFragment);
-    myFragmentIndex = 0;
-  }
 
-  if (!myCurrentFragment) {
+  for (uInt32 i = 0; i < length; i++) stream[i] = applyVolume(stream[i], myVolumeFactor);
-    memset(stream, 0, 2 * length);
+}
-    return;
-  }
 
-  const bool isStereoTIA = myAudioQueue->isStereo();
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-  const bool isStereo = myHardwareSpec.channels == 2;
+void SoundSDL2::initResampler()
-  const uInt32 sampleRateTIA = myAudioQueue->sampleRate();
+{
-  const uInt32 sampleRate = myHardwareSpec.freq;
+  Resampler::NextFragmentCallback nextFragmentCallback = [this] () -> Int16* {
-  const uInt32 fragmentSize = myAudioQueue->fragmentSize();
+    Int16* nextFragment = 0;
-  const uInt32 outputSamples = isStereo ? (length >> 1) : length;
 
-  for (uInt32 i = 0; i < outputSamples; i++) {
+    if (myUnderrun)
-    myTimeIndex += sampleRateTIA;
+      nextFragment = myAudioQueue->size() > emulationTiming->prebufferFragmentCount() ? myAudioQueue->dequeue(myCurrentFragment) : 0;
+    else
+      nextFragment = myAudioQueue->dequeue(myCurrentFragment);
 
-    if (myTimeIndex >= sampleRate) {
+    myUnderrun = nextFragment == 0;
-      myFragmentIndex += myTimeIndex / sampleRate;
+    if (nextFragment) myCurrentFragment = nextFragment;
-      myTimeIndex %= sampleRate;
-    }
 
-    if (myFragmentIndex >= fragmentSize) {
+    return nextFragment;
-      myFragmentIndex %= fragmentSize;
+  };
 
-      Int16* nextFragment = myAudioQueue->dequeue(myCurrentFragment);
+  myResampler = make_unique<SimpleResampler>(
-      if (nextFragment)
+    Resampler::Format(myAudioQueue->sampleRate(), myAudioQueue->fragmentSize(), myAudioQueue->isStereo()),
-        myCurrentFragment = nextFragment;
+    Resampler::Format(myHardwareSpec.freq, myHardwareSpec.samples, myHardwareSpec.channels > 1),
-      else {
+    nextFragmentCallback
-        myUnderrun = true;
+  );
-        (cout << "audio underrun!\n").flush();
-      }
-    }
-
-    if (isStereo) {
-      if (isStereoTIA) {
-        stream[2*i]     = applyVolume(myCurrentFragment[2*myFragmentIndex], myVolumeFactor);
-        stream[2*i + 1] = applyVolume(myCurrentFragment[2*myFragmentIndex + 1], myVolumeFactor);
-      } else {
-        stream[2*i] = stream[2*i + 1] = applyVolume(myCurrentFragment[myFragmentIndex], myVolumeFactor);
-      }
-    } else {
-      if (isStereoTIA) {
-        stream[i] = applyVolume(
-          (myCurrentFragment[2*myFragmentIndex] / 2) + (myCurrentFragment[2*myFragmentIndex + 1] / 2),
-          myVolumeFactor
-        );
-      } else {
-        stream[i] = applyVolume(myCurrentFragment[myFragmentIndex], myVolumeFactor);
-      }
-    }
-  }
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

src/common/SoundSDL2.hxx

@@ -28,6 +28,7 @@ class EmulationTiming;
 
 #include "bspf.hxx"
 #include "Sound.hxx"
+#include "audio/Resampler.hxx"
 
 /**
   This class implements the sound API for SDL.
@@ -112,6 +113,10 @@ class SoundSDL2 : public Sound
     */
     void processFragment(Int16* stream, uInt32 length);
 
+  private:
+
+    void initResampler();
+
   private:
     // Indicates if the sound device was successfully initialized
     bool myIsInitializedFlag;
@@ -128,11 +133,10 @@ class SoundSDL2 : public Sound
     EmulationTiming* emulationTiming;
 
     Int16* myCurrentFragment;
-    uInt32 myTimeIndex;
-    uInt32 myFragmentIndex;
-    uInt32 myFragmentBufferSize;
     bool myUnderrun;
 
+    unique_ptr<Resampler> myResampler;
+
   private:
     // Callback function invoked by the SDL Audio library when it needs data
     static void callback(void* udata, uInt8* stream, int len);

src/common/audio/Resampler.hxx

@@ -0,0 +1,79 @@
+//============================================================================
+//
+//   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 RESAMPLER_HXX
+#define RESAMPLER_HXX
+
+#include <functional>
+
+#include "bspf.hxx"
+
+class Resampler {
+  public:
+
+    using NextFragmentCallback = std::function<Int16*()>;
+
+    class Format {
+      public:
+
+        Format(uInt32 sampleRate, uInt32 fragmentSize, bool stereo) :
+          sampleRate(sampleRate),
+          fragmentSize(fragmentSize),
+          stereo(stereo)
+        {}
+
+      public:
+
+        uInt32 sampleRate;
+        uInt32 fragmentSize;
+        bool stereo;
+
+      private:
+
+        Format() = delete;
+    };
+
+  public:
+
+    Resampler(Format formatFrom, Format formatTo, NextFragmentCallback nextFragmentCallback) :
+      myFormatFrom(formatFrom),
+      myFormatTo(formatTo),
+      myNextFragmentCallback(nextFragmentCallback)
+    {}
+
+    virtual void fillFragment(Int16* fragment, uInt32 length) = 0;
+
+    virtual ~Resampler() {}
+
+  protected:
+
+    Format myFormatFrom;
+    Format myFormatTo;
+
+    NextFragmentCallback myNextFragmentCallback;
+
+  private:
+
+    Resampler() = delete;
+    Resampler(const Resampler&) = delete;
+    Resampler(Resampler&&) = delete;
+    Resampler& operator=(const Resampler&) = delete;
+    Resampler& operator=(Resampler&&) = delete;
+
+};
+
+#endif // RESAMPLER_HXX

src/common/audio/SimpleResampler.cxx

@@ -0,0 +1,91 @@
+//============================================================================
+//
+//   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 "SimpleResampler.hxx"
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+SimpleResampler::SimpleResampler(
+  Resampler::Format formatFrom,
+  Resampler::Format formatTo,
+  Resampler::NextFragmentCallback nextFragmentCallback)
+:
+  Resampler(formatFrom, formatTo, nextFragmentCallback),
+  myCurrentFragment(0),
+  myTimeIndex(0),
+  myFragmentIndex(0),
+  myIsUnderrun(true)
+{}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void SimpleResampler::fillFragment(Int16* fragment, uInt32 length)
+{
+  if (myIsUnderrun) {
+    Int16* nextFragment = myNextFragmentCallback();
+
+    if (nextFragment) {
+      myCurrentFragment = nextFragment;
+      myFragmentIndex = 0;
+      myIsUnderrun = false;
+    }
+  }
+
+  if (!myCurrentFragment) {
+    memset(fragment, 0, 2 * length);
+    return;
+  }
+
+  const uInt32 outputSamples = myFormatTo.stereo ? (length >> 1) : length;
+
+  // For the following math, remember that myTimeIndex = time * myFormatFrom.sampleRate * myFormatTo.sampleRate
+  for (uInt32 i = 0; i < outputSamples; i++) {
+    // time += 1 / myFormatTo.sampleRate
+    myTimeIndex += myFormatFrom.sampleRate;
+
+    // time >= 1 / myFormatFrom.sampleRate
+    if (myTimeIndex >= myFormatTo.sampleRate) {
+      // myFragmentIndex += time * myFormatFrom.sampleRate
+      myFragmentIndex += myTimeIndex / myFormatTo.sampleRate;
+      myTimeIndex %= myFormatTo.sampleRate;
+    }
+
+    if (myFragmentIndex >= myFormatFrom.fragmentSize) {
+      myFragmentIndex %= myFormatFrom.fragmentSize;
+
+      Int16* nextFragment = myNextFragmentCallback();
+      if (nextFragment)
+        myCurrentFragment = nextFragment;
+      else {
+        (cerr << "audio buffer underrun\n").flush();
+        myIsUnderrun = true;
+      }
+    }
+
+    if (myFormatTo.stereo) {
+      if (myFormatFrom.stereo) {
+        fragment[2*i] = myCurrentFragment[2*myFragmentIndex];
+        fragment[2*i + 1] = myCurrentFragment[2*myFragmentIndex + 1];
+      }
+      else
+        fragment[2*i] = fragment[2*i + 1] = myCurrentFragment[myFragmentIndex];
+    } else {
+      if (myFormatFrom.stereo)
+        fragment[i] = (myCurrentFragment[2*myFragmentIndex] / 2) + (myCurrentFragment[2*myFragmentIndex + 1] / 2);
+      else
+        fragment[i] = myCurrentFragment[myFragmentIndex];
+    }
+  }
+}

src/common/audio/SimpleResampler.hxx

@@ -0,0 +1,50 @@
+//============================================================================
+//
+//   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 SIMPLE_RESAMPLER_HXX
+#define SIMPLE_RESAMPLER_HXX
+
+#include "Resampler.hxx"
+
+class SimpleResampler : public Resampler {
+  public:
+    SimpleResampler(
+      Resampler::Format formatFrom,
+      Resampler::Format formatTo,
+      Resampler::NextFragmentCallback NextFragmentCallback
+    );
+
+    virtual void fillFragment(Int16* fragment, uInt32 length);
+
+  private:
+
+    Int16* myCurrentFragment;
+    uInt32 myTimeIndex;
+    uInt32 myFragmentIndex;
+    bool myIsUnderrun;
+
+  private:
+
+    SimpleResampler() = delete;
+    SimpleResampler(const SimpleResampler&) = delete;
+    SimpleResampler(SimpleResampler&&) = delete;
+    SimpleResampler& operator=(const SimpleResampler&) = delete;
+    SimpleResampler& operator=(const SimpleResampler&&) = delete;
+
+};
+
+#endif // SIMPLE_RESAMPLER_HXX

src/common/audio/module.mk

@@ -0,0 +1,10 @@
+MODULE := src/common/audio
+
+MODULE_OBJS := \
+	src/common/audio/SimpleResampler.o
+
+MODULE_DIRS += \
+	src/emucore/tia
+
+# Include common rules
+include $(srcdir)/common.rules

src/emucore/EmulationTiming.hxx

@@ -60,6 +60,13 @@ class EmulationTiming {
 
     uInt32 myPlaybackPeriod;
 
+  private:
+
+    EmulationTiming(const EmulationTiming&) = delete;
+    EmulationTiming(EmulationTiming&&) = delete;
+    EmulationTiming& operator=(const EmulationTiming&) = delete;
+    EmulationTiming& operator=(EmulationTiming&&) = delete;
+
 };
 
 #endif // EMULATION_TIMING_HXX