AX: add support for biquad filtering

This fixes e.g. the overly loud wind in "I SPY: Spooky Mansion".

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

@@ -438,7 +438,7 @@ void AXUCode::ProcessPBList(u32 pb_addr)
 
       ProcessVoice(static_cast<HLEAccelerator*>(m_accelerator.get()), pb, buffers, spms,
                    ConvertMixerControl(pb.mixer_control),
-                   m_coeffs_checksum ? m_coeffs.data() : nullptr);
+                   m_coeffs_checksum ? m_coeffs.data() : nullptr, false);
 
       // Forward the buffers
       for (auto& ptr : buffers.ptrs)

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

@@ -177,7 +177,7 @@ struct PBADPCMLoopInfo
 
 struct PBLowPassFilter
 {
-  u16 enabled;
+  u16 on;
   s16 yn1;
   u16 a0;
   u16 b0;
@@ -215,16 +215,16 @@ struct AXPB
 
 struct PBBiquadFilter
 {
-  u16 on;   // on = 2, off = 0
-  u16 xn1;  // History data
-  u16 xn2;
-  u16 yn1;
-  u16 yn2;
-  u16 b0;  // Filter coefficients
-  u16 b1;
-  u16 b2;
-  u16 a1;
-  u16 a2;
+  u16 on;
+  s16 xn1;  // History data
+  s16 xn2;
+  s16 yn1;
+  s16 yn2;
+  s16 b0;  // Filter coefficients
+  s16 b1;
+  s16 b2;
+  s16 a1;
+  s16 a2;
 };
 
 union PBInfImpulseResponseWM

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

@@ -400,17 +400,45 @@ void MixAdd(int* out, const s16* input, u32 count, VolumeData* vd, s16* dpop, bo
 
 // Execute a low pass filter on the samples using one history value. Returns
 // the new history value.
-s16 LowPassFilter(s16* samples, u32 count, s16 yn1, u16 a0, u16 b0)
+static void LowPassFilter(s16* samples, u32 count, PBLowPassFilter& f)
 {
   for (u32 i = 0; i < count; ++i)
-    yn1 = samples[i] = (a0 * (s32)samples[i] + b0 * (s32)yn1) >> 15;
-  return yn1;
+    f.yn1 = samples[i] = (f.a0 * (s32)samples[i] + f.b0 * (s32)f.yn1) >> 15;
 }
 
+#ifdef AX_WII
+static void BiquadFilter(s16* samples, u32 count, PBBiquadFilter& f)
+{
+  for (u32 i = 0; i < count; ++i)
+  {
+    s16 xn0 = samples[i];
+    s64 tmp = 0;
+    tmp += f.b0 * s32(xn0);
+    tmp += f.b1 * s32(f.xn1);
+    tmp += f.b2 * s32(f.xn2);
+    tmp += f.a1 * s32(f.yn1);
+    tmp += f.a2 * s32(f.yn2);
+    tmp <<= 2;
+    // CLRL
+    if (tmp & 0x10000)
+      tmp += 0x8000;
+    else
+      tmp += 0x7FFF;
+    tmp >>= 16;
+    s16 yn0 = s16(tmp);
+    f.xn2 = f.xn1;
+    f.yn2 = f.yn1;
+    f.xn1 = xn0;
+    f.yn1 = yn0;
+    samples[i] = yn0;
+  }
+}
+#endif
+
 // Process 1ms of audio (for AX GC) or 3ms of audio (for AX Wii) from a PB and
 // mix it to the output buffers.
 void ProcessVoice(HLEAccelerator* accelerator, PB_TYPE& pb, const AXBuffers& buffers, u16 count,
-                  AXMixControl mctrl, const s16* coeffs)
+                  AXMixControl mctrl, const s16* coeffs, bool new_filter)
 {
   // If the voice is not running, nothing to do.
   if (pb.running != 1)
@@ -435,12 +463,19 @@ void ProcessVoice(HLEAccelerator* accelerator, PB_TYPE& pb, const AXBuffers& buf
     pb.vol_env.cur_volume += pb.vol_env.cur_volume_delta;
   }
 
-  // Optionally, execute a low pass filter
-  if (pb.lpf.enabled)
+  // Optionally, execute a low-pass and/or biquad filter.
+  if (pb.lpf.on != 0)
   {
-    pb.lpf.yn1 = LowPassFilter(samples, count, pb.lpf.yn1, pb.lpf.a0, pb.lpf.b0);
+    LowPassFilter(samples, count, pb.lpf);
   }
 
+#ifdef AX_WII
+  if (new_filter && pb.biquad.on != 0)
+  {
+    BiquadFilter(samples, count, pb.biquad);
+  }
+#endif
+
   // Mix LRS, AUXA and AUXB depending on mixer_control
   // TODO: Handle DPL2 on AUXB.
 

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

@@ -28,7 +28,8 @@ AXWiiUCode::AXWiiUCode(DSPHLE* dsphle, u32 crc)
   for (u16& volume : m_last_aux_volumes)
     volume = 0x8000;
 
-  m_old_axwii = (crc == 0xfa450138) || (crc == 0x7699af32);
+  m_old_axwii = crc == 0xfa450138 || crc == 0x7699af32;
+  m_new_filter = crc == 0x347112ba || crc == 0x4cc52064;
 
   m_accelerator = std::make_unique<HLEAccelerator>(dsphle->GetSystem().GetDSP());
 }
@@ -450,7 +451,7 @@ void AXWiiUCode::ProcessPBList(u32 pb_addr)
         ApplyUpdatesForMs(curr_ms, pb, num_updates, updates);
         ProcessVoice(static_cast<HLEAccelerator*>(m_accelerator.get()), pb, buffers, spms,
                      ConvertMixerControl(HILO_TO_32(pb.mixer_control)),
-                     m_coeffs_checksum ? m_coeffs.data() : nullptr);
+                     m_coeffs_checksum ? m_coeffs.data() : nullptr, m_new_filter);
 
         // Forward the buffers
         for (auto& ptr : buffers.ptrs)
@@ -462,7 +463,7 @@ void AXWiiUCode::ProcessPBList(u32 pb_addr)
     {
       ProcessVoice(static_cast<HLEAccelerator*>(m_accelerator.get()), pb, buffers, 96,
                    ConvertMixerControl(HILO_TO_32(pb.mixer_control)),
-                   m_coeffs_checksum ? m_coeffs.data() : nullptr);
+                   m_coeffs_checksum ? m_coeffs.data() : nullptr, m_new_filter);
     }
 
     WritePB(memory, pb_addr, pb, m_crc);

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

@@ -38,6 +38,9 @@ protected:
   // Are we implementing an old version of AXWii which still has updates?
   bool m_old_axwii = false;
 
+  // Late AXWii versions support Wiimote filtering and a biquad filter.
+  bool m_new_filter = false;
+
   // Last volume values for MAIN and AUX. Used to generate volume ramps to
   // interpolate nicely between old and new volume values.
   u16 m_last_main_volume = 0;