Add static pre-amplification to both DSP and DTK audio output.

This branch was created specifically for GC Spider-Man, which has audio problems that cause it to be extremely loud, and to be so loud at the source that much of the audio in the game is quite clipped by the time it hits the speakers.

Source/Core/Core/HW/DSPHLE/UCodes/AX.cpp

@@ -494,6 +494,9 @@ void AXUCode::SetMainLR(u32 src_addr)
 
 void AXUCode::OutputSamples(u32 lr_addr, u32 surround_addr)
 {
+	// MOD: Pre-amplify by some fraction to prevent clipping in the clamping function.
+	const double pre_amplification_factor = 0.3;
+
 	int surround_buffer[5 * 32];
 
 	for (u32 i = 0; i < 5 * 32; ++i)
@@ -506,8 +509,8 @@ void AXUCode::OutputSamples(u32 lr_addr, u32 surround_addr)
 	// Output samples clamped to 16 bits and interlaced RLRLRLRLRL...
 	for (u32 i = 0; i < 5 * 32; ++i)
 	{
-		int left  = MathUtil::Clamp(m_samples_left[i], -32767, 32767);
-		int right = MathUtil::Clamp(m_samples_right[i], -32767, 32767);
+		int left  = MathUtil::Clamp((int)(m_samples_left[i]*pre_amplification_factor), -32767, 32767);
+		int right = MathUtil::Clamp((int)(m_samples_right[i]*pre_amplification_factor), -32767, 32767);
 
 		buffer[2 * i + 0] = Common::swap16(right);
 		buffer[2 * i + 1] = Common::swap16(left);

Source/Core/Core/HW/DSPHLE/UCodes/AXVoice.h

@@ -179,6 +179,8 @@ u16 AcceleratorGetSample()
 				temp -= 16;
 
 			int val = (scale * temp) + ((0x400 + coef1 * acc_pb->adpcm.yn1 + coef2 * acc_pb->adpcm.yn2) >> 11);
+			// MOD: Prescaling here seems to ruin the quality of the samples
+			//val = (int)((double)val * 0.1);
 			val = MathUtil::Clamp(val, -0x7FFF, 0x7FFF);
 
 			acc_pb->adpcm.yn2 = acc_pb->adpcm.yn1;

Source/Core/Core/HW/StreamADPCM.cpp

@@ -35,14 +35,20 @@ static s16 ADPDecodeSample(s32 bits, s32 q, s32& hist1, s32& hist2)
 		hist = (hist1 * 0x62) - (hist2 * 0x37);
 		break;
 	}
-	hist = MathUtil::Clamp((hist + 0x20) >> 6, -0x200000, 0x1fffff);
+	// MOD: Removing this clamp completely relieves the DTK stream of clipping...
+	//hist = MathUtil::Clamp((hist + 0x20) >> 6, -0x200000, 0x1fffff);
+	hist = (hist + 0x20) >> 6;
 
 	s32 cur = (((s16)(bits << 12) >> (q & 0xf)) << 6) + hist;
 
 	hist2 = hist1;
 	hist1 = cur;
 
 	cur >>= 6;
+
+	// MOD: Reduce amplitude to 30%
+	cur = (s32)((double)cur * 0.3);
+
 	cur = MathUtil::Clamp(cur, -0x8000, 0x7fff);
 
 	return (s16)cur;