update

src/win32_handmade.cpp

@@ -224,6 +224,8 @@ struct Win32SoundOutput {
     uint32 runningSampleIndex;
     int bytesPerSample;
     int secondaryBufferSize;
+    real32 tSine;
+    int latencySampleCount;
 };
 
 internal void win32FillSoundBuffer(Win32SoundOutput *soundOutput, DWORD byteToLock, DWORD bytesToWrite) {
@@ -236,19 +238,19 @@ internal void win32FillSoundBuffer(Win32SoundOutput *soundOutput, DWORD byteToLo
         DWORD region1SampleCount = region1Size/soundOutput->bytesPerSample;
         int16 *sampleOut = (int16*)region1;
         for (DWORD sampleIndex = 0; sampleIndex < region1SampleCount; sampleIndex++) {
-            real32 t = 2.0f * PI32 * (real32)soundOutput->runningSampleIndex / (real32)soundOutput->wavePeriod;
-            int16 sampleValue =  (int16)(sin(t) * (real32)soundOutput->toneVolume);
+            int16 sampleValue =  (int16)(sin(soundOutput->tSine) * (real32)soundOutput->toneVolume);
             *sampleOut++ = sampleValue;
             *sampleOut++ = sampleValue;
+            soundOutput->tSine += 2.0f * PI32 / (real32)soundOutput->wavePeriod;
             soundOutput->runningSampleIndex++;
         }
         DWORD region2SampleCount = region2Size/soundOutput->bytesPerSample;
         sampleOut = (int16*)region2;
         for (DWORD sampleIndex = 0; sampleIndex < region2SampleCount; sampleIndex++) {
-            real32 t = 2.0f * PI32 * (real32)soundOutput->runningSampleIndex / (real32)soundOutput->wavePeriod;
-            int16 sampleValue =  (int16)(sin(t) * soundOutput->toneVolume);
+            int16 sampleValue =  (int16)(sin(soundOutput->tSine) * (real32)soundOutput->toneVolume);
             *sampleOut++ = sampleValue;
             *sampleOut++ = sampleValue;
+            soundOutput->tSine += 2.0f * PI32 / (real32)soundOutput->wavePeriod;
             soundOutput->runningSampleIndex++;
         }
         globalSecondaryBuffer->Unlock(region1, region1Size, region2, region2Size);
@@ -305,11 +307,12 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
             soundOutput.runningSampleIndex = 0;
             soundOutput.bytesPerSample = sizeof(int16)*2;
             soundOutput.secondaryBufferSize = soundOutput.samplesPerSecond*soundOutput.bytesPerSample;
+            soundOutput.latencySampleCount = soundOutput.samplesPerSecond / 15.0f;
 
             win32LoadXInput();
             win32InitSound(window, soundOutput.samplesPerSecond, soundOutput.secondaryBufferSize);
 
-            win32FillSoundBuffer(&soundOutput, 0, soundOutput.secondaryBufferSize);
+            win32FillSoundBuffer(&soundOutput, 0, soundOutput.latencySampleCount*soundOutput.bytesPerSample);
             globalSecondaryBuffer->Play(0, 0, DSBPLAY_LOOPING);
 
             LARGE_INTEGER lastCounter;
@@ -361,6 +364,9 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
                 yOffset += stickY/5000.0 * factor;
                 xOffset -= stickX/5000.0 * factor;
 
+                soundOutput.toneHz = 220 + (stickYNorm + 1.0)/2.0 * 220.0;
+                soundOutput.wavePeriod = soundOutput.samplesPerSecond / soundOutput.toneHz;
+
                 GameOffscreenBuffer buffer = {};
                 buffer.memory = globalBackBuffer.memory;
                 buffer.width = globalBackBuffer.width;
@@ -376,13 +382,14 @@ int APIENTRY WinMain(HINSTANCE instance, HINSTANCE prevInstance, PSTR commandLin
                 DWORD writeCursor;
                 if (SUCCEEDED(globalSecondaryBuffer->GetCurrentPosition(&playCursor, &writeCursor))) {
                     DWORD byteToLock = (soundOutput.runningSampleIndex*soundOutput.bytesPerSample) % soundOutput.secondaryBufferSize;
+                    DWORD targetCursor = (playCursor + soundOutput.latencySampleCount*soundOutput.bytesPerSample) % soundOutput.secondaryBufferSize;
                     DWORD bytesToWrite;
-                    if (byteToLock == playCursor) {
+                    if (byteToLock == targetCursor) {
                         bytesToWrite = 0;
-                    } else if (byteToLock > playCursor) {
-                        bytesToWrite = soundOutput.secondaryBufferSize - byteToLock + playCursor;
+                    } else if (byteToLock > targetCursor) {
+                        bytesToWrite = soundOutput.secondaryBufferSize - byteToLock + targetCursor;
                     } else {
-                        bytesToWrite = playCursor - byteToLock;
+                        bytesToWrite = targetCursor - byteToLock;
                     }
                     win32FillSoundBuffer(&soundOutput, byteToLock, bytesToWrite);
                 }