Replace while loop with division (technically a right shift).

hrydgard · Dec 20, 2016 · 1e09595 · 1e09595
1 parent ff4b99d
commit 1e09595
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Showing 2 changed files with 7 additions and 13 deletions.
diff --git a/Core/HW/SasAudio.cpp b/Core/HW/SasAudio.cpp
@@ -495,23 +495,16 @@ void SasInstance::MixVoice(SasVoice &voice) {
 
 		// Resample to the correct pitch, writing exactly "grainSize" samples.
 		// TODO: Special case no-resample case (and 2x and 0.5x) for speed, it's not uncommon
-		int16_t temp[256 * 4];
-		int tempPos = 0;
+		int16_t temp[PSP_SAS_MAX_GRAIN + 2];
 
 		// Two passes: First read, then resample.
 		u32 sampleFrac = voice.sampleFrac;
-		temp[tempPos++] = voice.resampleHist[0];
-		temp[tempPos++] = voice.resampleHist[1];
-
-		int samplesToRead = 0;
-		uint32_t t = sampleFrac + voice.pitch * (grainSize - delay);
-		while (t >= PSP_SAS_PITCH_BASE) {
-			samplesToRead++;
-			t -= PSP_SAS_PITCH_BASE;
-		}
+		temp[0] = voice.resampleHist[0];
+		temp[1] = voice.resampleHist[1];
 
-		voice.ReadSamples(&temp[tempPos], samplesToRead);
-		tempPos += samplesToRead;
+		int samplesToRead = (sampleFrac + voice.pitch * (grainSize - delay)) >> PSP_SAS_PITCH_BASE_SHIFT;
+		voice.ReadSamples(&temp[2], samplesToRead);
+		int tempPos = 2 + samplesToRead;
 
 		for (int i = delay; i < grainSize; i++) {
 			const int16_t *s = temp + (sampleFrac >> PSP_SAS_PITCH_BASE_SHIFT);

diff --git a/Core/HW/SasAudio.h b/Core/HW/SasAudio.h
@@ -38,6 +38,7 @@ enum {
 	PSP_SAS_PITCH_MAX = 0x4000,
 
 	PSP_SAS_VOL_MAX = 0x1000,
+	PSP_SAS_MAX_GRAIN = 1024,   // VERY conservative! 256 is quite common but don't think I've ever seen bigger.
 
 	PSP_SAS_ADSR_CURVE_MODE_LINEAR_INCREASE = 0,
 	PSP_SAS_ADSR_CURVE_MODE_LINEAR_DECREASE = 1,