blip_buffer 0.4.0 -> 0CC blip_buffer

blip_buffer.diff

diff --git a/3rdparty/Blip_Buffer/Blip_Buffer.cpp b/3rdparty/Blip_Buffer/Blip_Buffer.cpp
index cd1f9e3..dc01adb 100644
--- a/3rdparty/Blip_Buffer/Blip_Buffer.cpp
+++ b/3rdparty/Blip_Buffer/Blip_Buffer.cpp
@@ -1,6 +1,8 @@
 
 // Blip_Buffer 0.4.0. http://www.slack.net/~ant/
 
+#include "../stdafx.h"
+
 #include "Blip_Buffer.h"
 
 #include <assert.h>
@@ -9,6 +11,8 @@
 #include <stdlib.h>
 #include <math.h>
 
+//#define DITHERING
+
 /* Copyright (C) 2003-2006 Shay Green. This module is free software; you
 can redistribute it and/or modify it under the terms of the GNU Lesser
 General Public License as published by the Free Software Foundation; either
@@ -38,12 +42,14 @@ Blip_Buffer::Blip_Buffer()
 	// assumptions code makes about implementation-defined features
 	#ifndef NDEBUG
 		// right shift of negative value preserves sign
-		int i = INT_MIN;
-		assert( (i >> 1) == INT_MIN / 2 );
+		long i = LONG_MIN;
+		assert( (i >> 1) == LONG_MIN / 2 );
+		i = LONG_MIN;
+		assert( (i >> 31) == -1 );
 		
 		// casting to smaller signed type truncates bits and extends sign
-		long l = (SHRT_MAX + 1) * 5;
-		assert( (short) l == SHRT_MIN );
+		i = (SHRT_MAX + 1) * 5;
+		assert( (short) i == SHRT_MIN );
 	#endif
 }
 
@@ -222,7 +228,9 @@ void blip_eq_t::generate( float* out, int count ) const
 	// apply (half of) hamming window
 	double to_fraction = pi / (count - 1);
 	for ( int i = count; i--; )
-		out [i] *= 0.54 - 0.46 * cos( i * to_fraction );
+		out [i] *= 0.53836f - 0.46164f * cosf( float(i * to_fraction) );
+		//out [i] *= 1.0f;
+		//out [i] *= 0.5f * (1.0f - cosf( float(i * to_fraction) ));
 }
 
 void Blip_Synth_::adjust_impulse()
@@ -240,7 +248,7 @@ void Blip_Synth_::adjust_impulse()
 		}
 		if ( p == p2 )
 			error /= 2; // phase = 0.5 impulse uses same half for both sides
-		impulses [size - blip_res + p] += error;
+		impulses [size - blip_res + p] += (short)error;
 		//printf( "error: %ld\n", error );
 	}
 	
@@ -339,6 +347,24 @@ void Blip_Synth_::volume_unit( double new_unit )
 	}
 }
 
+#ifdef DITHERING
+int dither(long size)
+{
+	static unsigned int lfsr = 0xACE1u;
+	unsigned bit;
+	unsigned period = 0;
+ 
+	bit  = ((lfsr >> 0) ^ (lfsr >> 2) ^ (lfsr >> 3) ^ (lfsr >> 5) ) & 1;
+	lfsr =  (lfsr >> 1) | (bit << 15);
+
+	switch (lfsr % 3) {
+		case 1: return size * 1;
+		case 2: return size * -1;
+	}
+	return 0;
+}
+#endif
+
 long Blip_Buffer::read_samples( blip_sample_t* out, long max_samples, int stereo )
 {
 	long count = samples_avail();
@@ -356,7 +382,11 @@ long Blip_Buffer::read_samples( blip_sample_t* out, long max_samples, int stereo
 		{
 			for ( long n = count; n--; )
 			{
+#ifdef DITHERING
+				long s = (accum + dither(1 << sample_shift)) >> sample_shift;
+#else
 				long s = accum >> sample_shift;
+#endif
 				accum -= accum >> bass_shift;
 				accum += *in++;
 				*out++ = (blip_sample_t) s;