From 8338e199dfbd3b956265dfaf78d2b21b083de895 Mon Sep 17 00:00:00 2001
From: Nebuleon Fumika
Date: Sat, 12 Jan 2013 00:00:29 -0500
Subject: More efficient noise generation taken from blargg's code in Snes9x
 1.53.

---
 source/soundux.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'source/soundux.cpp')

diff --git a/source/soundux.cpp b/source/soundux.cpp
index 329f3bd..d9a3436 100644
--- a/source/soundux.cpp
+++ b/source/soundux.cpp
@@ -1135,9 +1135,10 @@ void MixStereo (int sample_count)
 				}
 				else
 				{
-					for (;VL > 0; VL--)
-						if ((noise_gen <<= 1) & 0x80000000L)
-							noise_gen ^= 0x0040001L;
+					// Snes9x 1.53's SPC_DSP.cpp, by blargg
+					int feedback = (noise_gen << 13) ^ (noise_gen << 14);
+					noise_gen = (feedback & 0x4000) ^ (noise_gen >> 1);
+					VL = 0;
 					ch->sample = (noise_gen << 17) >> 17;
 					ch->interpolate = 0;
 				}
-- 
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