From 2f02e24a2f9185e001dd5531ab44edf5e1182f8a Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Thu, 10 Mar 2022 16:52:59 -0500
Subject: [PATCH] VERA: get rid of rand() and adapt code

---
 src/engine/platform/sound/vera_psg.c | 16 ++++++++++++----
 src/engine/platform/sound/vera_psg.h |  3 ++-
 src/engine/platform/vera.cpp         |  9 ++++++---
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/src/engine/platform/sound/vera_psg.c b/src/engine/platform/sound/vera_psg.c
index 92dac698c..f61bd26a2 100644
--- a/src/engine/platform/sound/vera_psg.c
+++ b/src/engine/platform/sound/vera_psg.c
@@ -20,6 +20,8 @@ void
 psg_reset(struct VERA_PSG* psg)
 {
 	memset(psg->channels, 0, sizeof(psg->channels));
+  psg->noiseState=1;
+  psg->noiseOut=0;
 }
 
 void
@@ -52,13 +54,18 @@ render(struct VERA_PSG* psg, int16_t *left, int16_t *right)
 {
 	int l = 0;
 	int r = 0;
+  // TODO this is a currently speculated noise generation
+  // as the hardware and sources for it are not out in the public
+  // and the official emulator just uses rand()
+  psg->noiseOut=((psg->noiseOut<<1)|(psg->noiseState&1))&63;
+  psg->noiseState=(psg->noiseState<<1)|(((psg->noiseState>>1)^(psg->noiseState>>2)^(psg->noiseState>>4)^(psg->noiseState>>15))&1);
 
 	for (int i = 0; i < 16; i++) {
 		struct VERAChannel *ch = &psg->channels[i];
 
 		unsigned new_phase = (ch->phase + ch->freq) & 0x1FFFF;
 		if ((ch->phase & 0x10000) != (new_phase & 0x10000)) {
-			ch->noiseval = rand() & 63;
+			ch->noiseval = psg->noiseOut;
 		}
 		ch->phase = new_phase;
 
@@ -89,10 +96,11 @@ render(struct VERA_PSG* psg, int16_t *left, int16_t *right)
 }
 
 void
-psg_render(struct VERA_PSG* psg, int16_t *buf, unsigned num_samples)
+psg_render(struct VERA_PSG* psg, int16_t *bufL, int16_t *bufR, unsigned num_samples)
 {
 	while (num_samples--) {
-		render(psg, &buf[0], &buf[1]);
-		buf += 2;
+		render(psg, bufL, bufR);
+		bufL++;
+    bufR++;
 	}
 }
diff --git a/src/engine/platform/sound/vera_psg.h b/src/engine/platform/sound/vera_psg.h
index 9f94bb578..7a6a7f01d 100644
--- a/src/engine/platform/sound/vera_psg.h
+++ b/src/engine/platform/sound/vera_psg.h
@@ -19,9 +19,10 @@ struct VERAChannel {
 };
 
 struct VERA_PSG {
+  unsigned int noiseState, noiseOut;
   struct VERAChannel channels[16];
 };
 
 void psg_reset(struct VERA_PSG* psg);
 void psg_writereg(struct VERA_PSG* psg, uint8_t reg, uint8_t val);
-void psg_render(struct VERA_PSG* psg, int16_t *buf, unsigned num_samples);
+void psg_render(struct VERA_PSG* psg, int16_t *bufL, int16_t *bufR, unsigned num_samples);
diff --git a/src/engine/platform/vera.cpp b/src/engine/platform/vera.cpp
index 99c6517ea..f6fc22f70 100644
--- a/src/engine/platform/vera.cpp
+++ b/src/engine/platform/vera.cpp
@@ -22,10 +22,12 @@
 #include <string.h>
 #include <math.h>
 
-#include "sound/vera_psg.h"
-#include "sound/vera_pcm.h"
+extern "C" {
+  #include "sound/vera_psg.h"
+  #include "sound/vera_pcm.h"
+}
 
-#define rWrite(c,a,d) {regPool[(c)*4+(a)]=(d);}
+#define rWrite(c,a,d) {regPool[(c)*4+(a)]=(d); psg_writereg(psg,((c)*4+(a)),(d));}
 #define rWriteLo(c,a,d) rWrite(c,a,(regPool[(c)*4+(a)]&(~0x3f))|((d)&0x3f))
 #define rWriteHi(c,a,d) rWrite(c,a,(regPool[(c)*4+(a)]&(~0xc0))|(((d)<<6)&0xc0))
 #define rWriteFIFOVol(d) rWrite(16,0,(regPool[64]&(~0x3f))|((d)&0x3f))
@@ -58,6 +60,7 @@ const char* DivPlatformVERA::getEffectName(unsigned char effect) {
 }
 
 void DivPlatformVERA::acquire(short* bufL, short* bufR, size_t start, size_t len) {
+  psg_render(psg,bufL+start,bufR+start,len);
 }
 
 void DivPlatformVERA::reset() {