From 3a6e75ca7d5728a8f88b987d77dabd511e135211 Mon Sep 17 00:00:00 2001
From: MetalliC <0vetal0@gmail.com>
Date: Fri, 19 Aug 2016 18:49:11 +0300
Subject: [PATCH] aica: add ADPCM diff value clamp based on encoder research
 [kode54, MetalliC]

if there is known issues with YMZ280B it might be worth try to same decoder there
---
 src/devices/sound/aica.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/devices/sound/aica.cpp b/src/devices/sound/aica.cpp
index 4e1b4d5fd40..99fa33a4ea4 100644
--- a/src/devices/sound/aica.cpp
+++ b/src/devices/sound/aica.cpp
@@ -351,8 +351,14 @@ void aica_device::InitADPCM(int *PrevSignal, int *PrevQuant)
 
 signed short aica_device::DecodeADPCM(int *PrevSignal, unsigned char Delta, int *PrevQuant)
 {
+	int x = (*PrevQuant * quant_mul[Delta & 7]) / 8;
+	if (x > 0x7FFF) x = 0x7FFF;
+	if (Delta & 8)	x = -x;
+	x += *PrevSignal;
+#if 0 // older implementation
 	int x = *PrevQuant * quant_mul [Delta & 15];
 		x = *PrevSignal + ((int)(x + ((UINT32)x >> 29)) >> 3);
+#endif
 	*PrevSignal=ICLIP16(x);
 	*PrevQuant=(*PrevQuant*TableQuant[Delta&7])>>ADPCMSHIFT;
 	*PrevQuant=(*PrevQuant<0x7f)?0x7f:((*PrevQuant>0x6000)?0x6000:*PrevQuant);