Support variable emulation speed.

.vscode/settings.json

@@ -58,6 +58,7 @@
         "cstring": "cpp",
         "iostream": "cpp",
         "cstdint": "cpp",
-        "ostream": "cpp"
+        "ostream": "cpp",
+        "__memory": "cpp"
     }
 }

src/emucore/Console.cxx

@@ -563,7 +563,8 @@ void Console::initializeAudio()
     .updatePlaybackRate(myOSystem.sound().getSampleRate())
     .updatePlaybackPeriod(myOSystem.sound().getFragmentSize())
     .updateAudioQueueExtraFragments(myAudioSettings.bufferSize())
-    .updateAudioQueueHeadroom(myAudioSettings.headroom());
+    .updateAudioQueueHeadroom(myAudioSettings.headroom())
+    .updateSpeedFactor(myOSystem.settings().getFloat("speed"));
 
   (cout << "sample rate: " << myOSystem.sound().getSampleRate() << std::endl).flush();
   (cout << "fragment size: " << myOSystem.sound().getFragmentSize() << std::endl).flush();

src/emucore/EmulationTiming.cxx

@@ -15,6 +15,8 @@
 // this file, and for a DISCLAIMER OF ALL WARRANTIES.
 //============================================================================
 
+#include <cmath>
+
 #include "EmulationTiming.hxx"
 
 namespace {
@@ -32,13 +34,18 @@ EmulationTiming::EmulationTiming(FrameLayout frameLayout) :
   myPlaybackRate(44100),
   myPlaybackPeriod(512),
   myAudioQueueExtraFragments(1),
-  myAudioQueueHeadroom(2)
-{}
+  myAudioQueueHeadroom(2),
+  mySpeedFactor(1)
+{
+  recalculate();
+}
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 EmulationTiming& EmulationTiming::updateFrameLayout(FrameLayout frameLayout)
 {
   myFrameLayout = frameLayout;
+  recalculate();
+
   return *this;
 }
 
@@ -46,6 +53,8 @@ EmulationTiming& EmulationTiming::updateFrameLayout(FrameLayout frameLayout)
 EmulationTiming& EmulationTiming::updatePlaybackRate(uInt32 playbackRate)
 {
   myPlaybackRate = playbackRate;
+  recalculate();
+
   return *this;
 }
 
@@ -53,6 +62,8 @@ EmulationTiming& EmulationTiming::updatePlaybackRate(uInt32 playbackRate)
 EmulationTiming& EmulationTiming::updatePlaybackPeriod(uInt32 playbackPeriod)
 {
   myPlaybackPeriod = playbackPeriod;
+  recalculate();
+
   return *this;
 }
 
@@ -60,6 +71,8 @@ EmulationTiming& EmulationTiming::updatePlaybackPeriod(uInt32 playbackPeriod)
 EmulationTiming& EmulationTiming::updateAudioQueueExtraFragments(uInt32 audioQueueExtraFragments)
 {
   myAudioQueueExtraFragments = audioQueueExtraFragments;
+  recalculate();
+
   return *this;
 }
 
@@ -67,85 +80,123 @@ EmulationTiming& EmulationTiming::updateAudioQueueExtraFragments(uInt32 audioQue
 EmulationTiming& EmulationTiming::updateAudioQueueHeadroom(uInt32 audioQueueHeadroom)
 {
   myAudioQueueHeadroom = audioQueueHeadroom;
+  recalculate();
+
+  return *this;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+EmulationTiming& EmulationTiming::updateSpeedFactor(float speedFactor)
+{
+  mySpeedFactor = speedFactor;
+  recalculate();
+
   return *this;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::maxCyclesPerTimeslice() const
 {
-  return 2 * cyclesPerFrame();
+  return myMaxCyclesPerTimeslice;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::minCyclesPerTimeslice() const
 {
-  return cyclesPerFrame() / 2;
+  return myMinCyclesPerTimeslice;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::linesPerFrame() const
 {
-  switch (myFrameLayout) {
-    case FrameLayout::ntsc:
-      return 262;
-
-    case FrameLayout::pal:
-      return 312;
-
-    default:
-      throw runtime_error("invalid frame layout");
-  }
+  return myLinesPerFrame;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::cyclesPerFrame() const
 {
-  return 76 * linesPerFrame();
+  return myCyclesPerFrame;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::framesPerSecond() const
 {
-  switch (myFrameLayout) {
-    case FrameLayout::ntsc:
-      return 60;
-
-    case FrameLayout::pal:
-      return 50;
-
-    default:
-      throw runtime_error("invalid frame layout");
-  }
+  return myFramesPerSecond;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::cyclesPerSecond() const
 {
-  return cyclesPerFrame() * framesPerSecond();
+  return myCyclesPerSecond;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::audioFragmentSize() const
 {
-  return AUDIO_HALF_FRAMES_PER_FRAGMENT * linesPerFrame();
+  return myAudioFragmentSize;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::audioSampleRate() const
 {
-  return 2 * linesPerFrame() * framesPerSecond();
+  return myAudioSampleRate;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::audioQueueCapacity() const
 {
-  uInt32 minCapacity = discreteDivCeil(maxCyclesPerTimeslice() * audioSampleRate(), audioFragmentSize() * cyclesPerSecond());
-
-  return std::max(prebufferFragmentCount(), minCapacity) + myAudioQueueExtraFragments;
+  return myAudioQueueCapacity;
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 uInt32 EmulationTiming::prebufferFragmentCount() const
 {
-  return discreteDivCeil(myPlaybackPeriod * audioSampleRate(), audioFragmentSize() * myPlaybackRate) + myAudioQueueHeadroom;
+  return myPrebufferFragmentCount;
+}
+
+// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+void EmulationTiming::recalculate()
+{
+  switch (myFrameLayout) {
+    case FrameLayout::ntsc:
+      myLinesPerFrame = 262;
+      break;
+
+    case FrameLayout::pal:
+      myLinesPerFrame = 312;
+      break;
+
+    default:
+      throw runtime_error("invalid frame layout");
+  }
+
+    switch (myFrameLayout) {
+    case FrameLayout::ntsc:
+      myFramesPerSecond = round(mySpeedFactor * 60);
+      break;
+
+    case FrameLayout::pal:
+      myFramesPerSecond = round(mySpeedFactor * 50);
+      break;
+
+    default:
+      throw runtime_error("invalid frame layout");
+  }
+
+  myCyclesPerFrame = 76 * myLinesPerFrame;
+  myMaxCyclesPerTimeslice = round(mySpeedFactor * myCyclesPerFrame * 2);
+  myMinCyclesPerTimeslice = round(mySpeedFactor * myCyclesPerFrame / 2);
+  myCyclesPerSecond = myCyclesPerFrame * myFramesPerSecond;
+  myAudioFragmentSize = round(mySpeedFactor * AUDIO_HALF_FRAMES_PER_FRAGMENT * myLinesPerFrame);
+  myAudioSampleRate = 2 * myLinesPerFrame * myFramesPerSecond;
+
+  myPrebufferFragmentCount = discreteDivCeil(
+    myPlaybackPeriod * myAudioSampleRate,
+    myAudioFragmentSize * myPlaybackRate
+  ) + myAudioQueueHeadroom;
+
+  myAudioQueueCapacity = std::max(
+    myPrebufferFragmentCount,
+    discreteDivCeil(myMaxCyclesPerTimeslice * myAudioSampleRate, myAudioFragmentSize * myCyclesPerSecond)
+  ) + myAudioQueueExtraFragments;
 }

src/emucore/EmulationTiming.hxx

@@ -36,6 +36,8 @@ class EmulationTiming {
 
     EmulationTiming& updateAudioQueueHeadroom(uInt32 audioQueueHeadroom);
 
+    EmulationTiming& updateSpeedFactor(float speedFactor);
+
     uInt32 maxCyclesPerTimeslice() const;
 
     uInt32 minCyclesPerTimeslice() const;
@@ -56,17 +58,32 @@ class EmulationTiming {
 
     uInt32 prebufferFragmentCount() const;
 
+  private:
+
+    void recalculate();
+
   private:
 
     FrameLayout myFrameLayout;
 
     uInt32 myPlaybackRate;
-
     uInt32 myPlaybackPeriod;
-
     uInt32 myAudioQueueExtraFragments;
     uInt32 myAudioQueueHeadroom;
 
+    uInt32 myMaxCyclesPerTimeslice;
+    uInt32 myMinCyclesPerTimeslice;
+    uInt32 myLinesPerFrame;
+    uInt32 myCyclesPerFrame;
+    uInt32 myFramesPerSecond;
+    uInt32 myCyclesPerSecond;
+    uInt32 myAudioFragmentSize;
+    uInt32 myAudioSampleRate;
+    uInt32 myAudioQueueCapacity;
+    uInt32 myPrebufferFragmentCount;
+
+    float mySpeedFactor;
+
   private:
 
     EmulationTiming(const EmulationTiming&) = delete;

src/emucore/Settings.cxx

@@ -35,7 +35,7 @@ Settings::Settings(OSystem& osystem)
 {
   // Video-related options
   setInternal("video", "");
-  setInternal("framerate", "0");
+  setInternal("speed", "1.0");
   setInternal("vsync", "true");
   setInternal("fullscreen", "false");
   setInternal("center", "false");
@@ -303,6 +303,10 @@ void Settings::validate()
 {
   string s;
   int i;
+  float f;
+
+  f = getFloat("speed");
+  if (f <= 0) setInternal("speed", "1.0");
 
   s = getString("timing");
   if(s != "sleep" && s != "busy")  setInternal("timing", "sleep");
@@ -439,7 +443,7 @@ void Settings::usage() const
     << "  -palette      <standard|     Use the specified color palette\n"
     << "                 z26|\n"
     << "                 user>\n"
-    << "  -framerate    <number>       Display the given number of frames per second (0 to auto-calculate)\n"
+    << "  -speed        <number>       Run emulation at the given speed\n"
     << "  -timing       <sleep|busy>   Use the given type of wait between frames\n"
     << "  -uimessages   <1|0>          Show onscreen UI messages for different events\n"
     << endl