Fix APU IRQ inhibit flag $4017 and dmc

src/sound.c

@@ -314,6 +314,7 @@ static DECLFW(StatusWrite) {
 	DoTriangle();
 	DoNoise();
 	DoPCM();
+
 	for (x = 0; x < 4; x++)
 		if (!(V & (1 << x))) lengthcount[x] = 0;	/* Force length counters to 0. */
 
@@ -429,19 +430,21 @@ void FrameSoundUpdate(void) {
 	 * Length counter:  Bit 4-7 of $4003, $4007, $400b, $400f
 	 */
 
-	if (!fcnt && !(IRQFrameMode & 0x3)) {
-		SIRQStat |= 0x40;
-		X6502_IRQBegin(FCEU_IQFCOUNT);
-	}
-
 	if (fcnt == 3) {
 		if (IRQFrameMode & 0x2)
 			fhcnt += fhinc;
 	}
+
 	FrameSoundStuff(fcnt);
 	fcnt = (fcnt + 1) & 3;
-}
 
+	/* has to be moved here to fix Dragon Warrior 4
+	 * after irq inhibit fix for $4017 */
+	if (!fcnt && !(IRQFrameMode & 0x3)) {
+		SIRQStat |= 0x40;
+		X6502_IRQBegin(FCEU_IQFCOUNT);
+	}
+}
 
 static INLINE void tester(void) {
 	if (DMCBitCount == 0) {
@@ -468,13 +471,14 @@ static INLINE void DMCDMA(void) {
 			if (DMCFormat & 0x40)
 				PrepDPCM();
 			else {
+				if (DMCFormat & 0x80) {
 					SIRQStat |= 0x80;
-				if (DMCFormat & 0x80)
 					X6502_IRQBegin(FCEU_IQDPCM);
 				}
 			}
 		}
 	}
+}
 
 void FASTAPASS(1) FCEU_SoundCPUHook(int cycles) {
 	fhcnt -= cycles * 48;
@@ -853,7 +857,6 @@ static void RDoTriangleNoisePCMLQ(void) {
 	}
 }
 
-
 static void RDoNoise(void) {
 	uint32 V;
 	int32 outo;
@@ -924,10 +927,12 @@ DECLFW(Write_IRQFM) {
 	fcnt = 0;
 	if (V & 2)
 		FrameSoundUpdate();
-	fcnt = 1;
+	/* fcnt = 1; */
 	fhcnt = fhinc;
+	if (V & 1) {
 		X6502_IRQEnd(FCEU_IQFCOUNT);
 		SIRQStat &= ~0x40;
+	}
 	IRQFrameMode = V;
 }