[openMSX-commits] SF.net SVN: openmsx: [6662] openmsx/trunk/src/sound/BlipBuffer.cc

[<m97...@us...>]

Revision: 6662
          http://svn.sourceforge.net/openmsx/?rev=6662&view=rev
Author:   m9710797
Date:     2007-06-26 01:01:25 -0700 (Tue, 26 Jun 2007)

Log Message:
-----------
small optimization

Modified Paths:
--------------
    openmsx/trunk/src/sound/BlipBuffer.cc

Modified: openmsx/trunk/src/sound/BlipBuffer.cc
===================================================================
--- openmsx/trunk/src/sound/BlipBuffer.cc	2007-06-24 00:18:05 UTC (rev 6661)
+++ openmsx/trunk/src/sound/BlipBuffer.cc	2007-06-26 08:01:25 UTC (rev 6662)
@@ -11,9 +11,8 @@
 static const int BLIP_SAMPLE_BITS = 30;
 static const int BLIP_RES = 1 << BlipBuffer::BLIP_PHASE_BITS;
 static const int IMPULSE_WIDTH = 16;
-static const int IMPULSES_SIZE = BLIP_RES * (IMPULSE_WIDTH / 2) + 1;
 
-static int impulses[IMPULSES_SIZE];
+static int impulses[BLIP_RES][IMPULSE_WIDTH];
 
 static void initImpulse()
 {
@@ -58,10 +57,12 @@
 	double rescale = kernelUnit / (2.0 * total);
 
 	// integrate, first difference, rescale, convert to int
+	static const int IMPULSES_SIZE = BLIP_RES * (IMPULSE_WIDTH / 2) + 1;
+	static int imp[IMPULSES_SIZE];
 	double sum = 0.0;
 	double next = 0.0;
 	for (int i = 0; i < IMPULSES_SIZE; ++i) {
-		impulses[i] = (int)floor((next - sum) * rescale + 0.5);
+		imp[i] = (int)floor((next - sum) * rescale + 0.5);
 		sum += fimpulse[i];
 		next += fimpulse[i + BLIP_RES];
 	}
@@ -71,15 +72,25 @@
 		int p2 = BLIP_RES - 2 - p;
 		int error = kernelUnit;
 		for (int i = 1; i < IMPULSES_SIZE; i += BLIP_RES) {
-			error -= impulses[i + p ];
-			error -= impulses[i + p2];
+			error -= imp[i + p ];
+			error -= imp[i + p2];
 		}
 		if (p == p2) {
 			// phase = 0.5 impulse uses same half for both sides
 			error /= 2;
 		}
-		impulses[IMPULSES_SIZE - BLIP_RES + p] += error;
+		imp[IMPULSES_SIZE - BLIP_RES + p] += error;
 	}
+
+	// reshuffle to a more cache friendly order
+	for (int phase = 0; phase < BLIP_RES; ++phase) {
+		const int* imp_fwd = &imp[BLIP_RES - phase];
+		const int* imp_rev = &imp[phase];
+		for (int i = 0; i < IMPULSE_WIDTH / 2; ++i) {
+			impulses[phase][     i] = imp_fwd[BLIP_RES * i];
+			impulses[phase][15 - i] = imp_rev[BLIP_RES * i];
+		}
+	}
 }
 
 BlipBuffer::BlipBuffer()
@@ -102,27 +113,10 @@
 	lastAmp = amp;
 
 	unsigned phase = time.fractAsInt();
-	const int* imp_fwd = &impulses[BLIP_RES - phase];
-	const int* imp_rev = &impulses[phase];
 	unsigned ofst = time.toInt() + offset;
-
-	buffer[(ofst +  0) & BUFFER_MASK] += imp_fwd[BLIP_RES * 0] * delta;
-	buffer[(ofst +  1) & BUFFER_MASK] += imp_fwd[BLIP_RES * 1] * delta;
-	buffer[(ofst +  2) & BUFFER_MASK] += imp_fwd[BLIP_RES * 2] * delta;
-	buffer[(ofst +  3) & BUFFER_MASK] += imp_fwd[BLIP_RES * 3] * delta;
-	buffer[(ofst +  4) & BUFFER_MASK] += imp_fwd[BLIP_RES * 4] * delta;
-	buffer[(ofst +  5) & BUFFER_MASK] += imp_fwd[BLIP_RES * 5] * delta;
-	buffer[(ofst +  6) & BUFFER_MASK] += imp_fwd[BLIP_RES * 6] * delta;
-	buffer[(ofst +  7) & BUFFER_MASK] += imp_fwd[BLIP_RES * 7] * delta;
-
-	buffer[(ofst +  8) & BUFFER_MASK] += imp_rev[BLIP_RES * 7] * delta;
-	buffer[(ofst +  9) & BUFFER_MASK] += imp_rev[BLIP_RES * 6] * delta;
-	buffer[(ofst + 10) & BUFFER_MASK] += imp_rev[BLIP_RES * 5] * delta;
-	buffer[(ofst + 11) & BUFFER_MASK] += imp_rev[BLIP_RES * 4] * delta;
-	buffer[(ofst + 12) & BUFFER_MASK] += imp_rev[BLIP_RES * 3] * delta;
-	buffer[(ofst + 13) & BUFFER_MASK] += imp_rev[BLIP_RES * 2] * delta;
-	buffer[(ofst + 14) & BUFFER_MASK] += imp_rev[BLIP_RES * 1] * delta;
-	buffer[(ofst + 15) & BUFFER_MASK] += imp_rev[BLIP_RES * 0] * delta;
+	for (int i = 0; i < IMPULSE_WIDTH; ++i) {
+		buffer[(ofst + i) & BUFFER_MASK] += impulses[phase][i] * delta;
+	}
 }
 
 bool BlipBuffer::readSamples(int* out, unsigned samples, unsigned pitch)


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