From c0179e7ed4a337c4eebb4d993f126c1f93713bbc Mon Sep 17 00:00:00 2001
From: ekeeke31 <ekeeke31@fcb46045-4337-0410-a722-cd382f7ce8f6>
Date: Sun, 9 Aug 2009 16:10:44 +0000
Subject: [PATCH] fixed YM2612 output limiter modified resampler frame length
 calculation

---
 source/gx/config.c           |  4 ++--
 source/sound/Fir_Resampler.c | 18 ++++++++++++------
 source/sound/ym2612.c        | 15 +++++++--------
 source/system.c              | 15 ++++++++-------
 4 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/source/gx/config.c b/source/gx/config.c
index 7be36eb..46e23a0 100644
--- a/source/gx/config.c
+++ b/source/gx/config.c
@@ -71,8 +71,8 @@ void config_default(void)
   config.hq_fm          = 1;
   config.psgBoostNoise  = 0;
   config.filter         = 1;
-  config.low_freq       = 200;
-  config.high_freq      = 8000;
+  config.low_freq       = 880;
+  config.high_freq      = 5000;
   config.lg             = 1.0;
   config.mg             = 1.0;
   config.hg             = 1.0;
diff --git a/source/sound/Fir_Resampler.c b/source/sound/Fir_Resampler.c
index ac648b2..6d80ef1 100644
--- a/source/sound/Fir_Resampler.c
+++ b/source/sound/Fir_Resampler.c
@@ -1,6 +1,6 @@
 /* Game_Music_Emu 0.5.2. http://www.slack.net/~ant/ */
 /* Copyright (C) 2004-2006 Shay Green. */
-/* Modified by Eke-Eke for use in Genesis Plus (2009). */
+/* C Conversion by Eke-Eke for use in Genesis Plus (2009). */
 
 #include "Fir_Resampler.h"
 
@@ -23,7 +23,7 @@ static int step = STEREO;
 static int input_per_cycle;
 static double ratio = 1.0;
 
-static void gen_sinc(double rolloff, int width, double offset, double spacing, double scale, int count, sample_t *out )
+static void gen_sinc(double rolloff, int width, double offset, double spacing, double scale, int count, short *out )
 {
   double const maxh = 256;
   double const fstep = M_PI / maxh * spacing;
@@ -38,11 +38,11 @@ static void gen_sinc(double rolloff, int width, double offset, double spacing, d
     double w = angle * to_w;
     if ( fabs( w ) < M_PI )
     {
-      double rolloff_cos_a = ROLLOFF * cos( angle );
+      double rolloff_cos_a = rolloff * cos( angle );
       double num = 1 - rolloff_cos_a -
           pow_a_n * cos( maxh * angle ) +
-          pow_a_n * ROLLOFF * cos( (maxh - 1) * angle );
-      double den = 1 - rolloff_cos_a - rolloff_cos_a + ROLLOFF * ROLLOFF;
+          pow_a_n * rolloff * cos( (maxh - 1) * angle );
+      double den = 1 - rolloff_cos_a - rolloff_cos_a + rolloff * rolloff;
       double sinc = scale * num / den - scale;
 
       out [-1] = (short) (cos( w ) * sinc + sinc);
@@ -78,6 +78,12 @@ int Fir_Resampler_initialize( int new_size )
   buffer = (sample_t *) realloc( buffer, (new_size + WRITE_OFFSET) * sizeof (sample_t) );
   if ( !buffer && new_size ) return 0;
   buffer_size = new_size + WRITE_OFFSET;
+  write_pos = 0;
+  res       = 1;
+  imp_phase = 0;
+  skip_bits = 0;
+  step      = STEREO;
+  ratio     = 1.0;
   Fir_Resampler_clear();
   return 1;
 }
@@ -265,7 +271,7 @@ int Fir_Resampler_input_needed( unsigned long output_count )
 
   unsigned long skip = skip_bits >> imp_phase;
   int remain = res - imp_phase;
-  while ( (output_count -= 2) > 0 )
+  while ( (output_count) > 0 ) /* fixed (Eke_Eke) */
   {
     input_count += step + (skip & 1) * STEREO;
     skip >>= 1;
diff --git a/source/sound/ym2612.c b/source/sound/ym2612.c
index 89ddb32..76c18bb 100644
--- a/source/sound/ym2612.c
+++ b/source/sound/ym2612.c
@@ -137,9 +137,6 @@
 
 #define FREQ_MASK    ((1<<FREQ_SH)-1)
 
-#define MAXOUT    (+32767)
-#define MINOUT    (-32768)
-
 
 /* envelope generator */
 #define ENV_BITS    10
@@ -162,6 +159,11 @@
 
 #define TL_RES_LEN    (256) /* 8 bits addressing (real chip) */
 
+
+#define MAXOUT    (+16383)
+#define MINOUT    (-16384)
+
+
 /*  TL_TAB_LEN is calculated as:
 *   13 - sinus amplitude bits     (Y axis)
 *   2  - sinus sign bit           (Y axis)
@@ -1913,7 +1915,8 @@ void YM2612Update(int length)
 
   /* Output samples buffers */
   int16 *bufFIR = Fir_Resampler_buffer();
-  if (!bufFIR)
+  if (bufFIR) bufFIR += snd.fm.pos*2;
+  else
   {
     bufL  = snd.fm.buffer[0] + snd.fm.pos;
     bufR  = snd.fm.buffer[1] + snd.fm.pos;
@@ -2041,10 +2044,6 @@ void YM2612Update(int length)
 
   /* timer B control */
   INTERNAL_TIMER_B(length);
-
-  /* update FIR resampler */
-  if (bufFIR) 
-    Fir_Resampler_write(length * 2);
 }
 
 /* initialize ym2612 emulator(s) */
diff --git a/source/system.c b/source/system.c
index a6693ae..ab2a13d 100644
--- a/source/system.c
+++ b/source/system.c
@@ -73,8 +73,9 @@ void audio_update (int size)
   /* resampling */
   if (config.hq_fm)
   {
-    int fm_len = (int) ((double)size * Fir_Resampler_ratio() + 0.5) ;
-    sound_update(fm_len,size);
+    int len = Fir_Resampler_input_needed(size * 2);
+    sound_update(len/2,size);
+    Fir_Resampler_write(len);
     Fir_Resampler_read(fm,size);
   }
   else
@@ -96,10 +97,10 @@ void audio_update (int size)
     if (filter & 1)
     {
       /* single-pole low-pass filter (6 dB/octave) */
-      ll = (ll + l) >> 1;
-      rr = (rr + r) >> 1;
-      l = ll;
-      r = rr;
+      l = (ll + l) >> 1;
+      r = (rr + r) >> 1;
+      ll = l;
+      rr = r;
     }
     else if (filter & 2)
     {
@@ -141,7 +142,7 @@ int audio_init (int rate)
   snd.sample_rate = rate;
 
   /* Calculate the sound buffer size (for one frame) */
-  snd.buffer_size = (rate / vdp_rate) + 8;
+  snd.buffer_size = (rate / vdp_rate) + 32;
 
 #ifndef NGC
   /* Output buffers */