fix(audio): biquad filter effect parameter version 2 handling

Fix ParameterVersion2 structure layout to match actual format:
- Add padding and use f32 for coefficients (was incorrectly using s16)
- Update state field offset from 0x17 to 0x25

Update command generation to:
- Read from correct structure based on version
- Convert float coefficients to fixed-point Q2.14 when using version 2

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/audio_core/renderer/command/command_buffer.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "audio_core/renderer/behavior/behavior_info.h"
@@ -257,11 +258,36 @@ void CommandBuffer::GenerateBiquadFilterCommand(const s32 node_id, EffectInfoBas
                                                 const bool use_float_processing) {
     auto& cmd{GenerateStart<BiquadFilterCommand, CommandId::BiquadFilter>(node_id)};
 
-    const auto& parameter{
-        *reinterpret_cast<BiquadFilterInfo::ParameterVersion1*>(effect_info.GetParameter())};
     const auto state{reinterpret_cast<VoiceState::BiquadFilterState*>(
         effect_info.GetStateBuffer() + channel * sizeof(VoiceState::BiquadFilterState))};
 
+    // Check which parameter version is being used
+    if (behavior->IsEffectInfoVersion2Supported()) {
+        const auto& parameter{
+            *reinterpret_cast<BiquadFilterInfo::ParameterVersion2*>(effect_info.GetParameter())};
+
+        cmd.input = buffer_offset + parameter.inputs[channel];
+        cmd.output = buffer_offset + parameter.outputs[channel];
+
+        // Convert float coefficients to fixed-point Q2.14 format (multiply by 16384)
+        constexpr f32 fixed_point_scale = 16384.0f;
+        cmd.biquad.b[0] = static_cast<s16>(
+            std::clamp(parameter.b[0] * fixed_point_scale, -32768.0f, 32767.0f));
+        cmd.biquad.b[1] = static_cast<s16>(
+            std::clamp(parameter.b[1] * fixed_point_scale, -32768.0f, 32767.0f));
+        cmd.biquad.b[2] = static_cast<s16>(
+            std::clamp(parameter.b[2] * fixed_point_scale, -32768.0f, 32767.0f));
+        cmd.biquad.a[0] = static_cast<s16>(
+            std::clamp(parameter.a[0] * fixed_point_scale, -32768.0f, 32767.0f));
+        cmd.biquad.a[1] = static_cast<s16>(
+            std::clamp(parameter.a[1] * fixed_point_scale, -32768.0f, 32767.0f));
+
+        // Effects use legacy fixed-point format
+        cmd.use_float_coefficients = false;
+    } else {
+        const auto& parameter{
+            *reinterpret_cast<BiquadFilterInfo::ParameterVersion1*>(effect_info.GetParameter())};
+
         cmd.input = buffer_offset + parameter.inputs[channel];
         cmd.output = buffer_offset + parameter.outputs[channel];
 
@@ -270,6 +296,7 @@ void CommandBuffer::GenerateBiquadFilterCommand(const s32 node_id, EffectInfoBas
 
         // Effects use legacy fixed-point format
         cmd.use_float_coefficients = false;
+    }
 
     cmd.state = memory_pool->Translate(CpuAddr(state),
                                        MaxBiquadFilters * sizeof(VoiceState::BiquadFilterState));

src/audio_core/renderer/command/command_generator.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "audio_core/common/audio_renderer_parameter.h"
@@ -361,12 +362,33 @@ void CommandGenerator::GenerateAuxCommand(const s16 buffer_offset, EffectInfoBas
 void CommandGenerator::GenerateBiquadFilterEffectCommand(const s16 buffer_offset,
                                                          EffectInfoBase& effect_info,
                                                          const s32 node_id) {
-    const auto& parameter{
+    EffectInfoBase::ParameterState state{};
-        *reinterpret_cast<BiquadFilterInfo::ParameterVersion1*>(effect_info.GetParameter())};
+    s8 channel_count{0};
+
+    if (render_context.behavior->IsEffectInfoVersion2Supported()) {
+        const auto* parameter = reinterpret_cast<const BiquadFilterInfo::ParameterVersion2*>(
+            effect_info.GetParameter());
+        if (!parameter) {
+            LOG_ERROR(Service_Audio, "Biquad filter parameter is null");
+            return;
+        }
+        state = parameter->state;
+        channel_count = parameter->channel_count;
+    } else {
+        const auto* parameter = reinterpret_cast<const BiquadFilterInfo::ParameterVersion1*>(
+            effect_info.GetParameter());
+        if (!parameter) {
+            LOG_ERROR(Service_Audio, "Biquad filter parameter is null");
+            return;
+        }
+        state = parameter->state;
+        channel_count = parameter->channel_count;
+    }
+
     if (effect_info.IsEnabled()) {
         bool needs_init{false};
 
-        switch (parameter.state) {
+        switch (state) {
         case EffectInfoBase::ParameterState::Initialized:
             needs_init = true;
             break;
@@ -375,22 +397,23 @@ void CommandGenerator::GenerateBiquadFilterEffectCommand(const s16 buffer_offset
             if (render_context.behavior->IsBiquadFilterEffectStateClearBugFixed()) {
                 needs_init = false;
             } else {
-                needs_init = parameter.state == EffectInfoBase::ParameterState::Updating;
+                needs_init = state == EffectInfoBase::ParameterState::Updating;
             }
             break;
         default:
-            LOG_ERROR(Service_Audio, "Invalid biquad parameter state {}",
+            LOG_ERROR(Service_Audio, "Invalid biquad parameter state {}, treating as uninitialized",
-                      static_cast<u32>(parameter.state));
+                      static_cast<u32>(state));
+            needs_init = true;
             break;
         }
 
-        for (s8 channel = 0; channel < parameter.channel_count; channel++) {
+        for (s8 channel = 0; channel < channel_count; channel++) {
             command_buffer.GenerateBiquadFilterCommand(
                 node_id, effect_info, buffer_offset, channel, needs_init,
                 render_context.behavior->UseBiquadFilterFloatProcessing());
         }
     } else {
-        for (s8 channel = 0; channel < parameter.channel_count; channel++) {
+        for (s8 channel = 0; channel < channel_count; channel++) {
             command_buffer.GenerateCopyMixBufferCommand(node_id, effect_info, buffer_offset,
                                                         channel);
         }

src/audio_core/renderer/effect/biquad_filter.cpp

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "audio_core/renderer/effect/biquad_filter.h"
@@ -40,8 +41,28 @@ void BiquadFilterInfo::UpdateForCommandGeneration() {
         usage_state = UsageState::Disabled;
     }
 
-    auto params{reinterpret_cast<ParameterVersion1*>(parameter.data())};
+    // Determine which version structure is being used
-    params->state = ParameterState::Updated;
+    // Version 1: state at offset 0x17, structure size ~24 bytes
+    // Version 2: state at offset 0x25, structure size ~40 bytes
+    auto params_v1{reinterpret_cast<ParameterVersion1*>(parameter.data())};
+    auto params_v2{reinterpret_cast<ParameterVersion2*>(parameter.data())};
+
+    // Check which state location contains a valid ParameterState value (0-2)
+    // Valid states: Initialized (0), Updating (1), Updated (2)
+    const auto state_v1_raw = *reinterpret_cast<const u8*>(&params_v1->state);
+    const auto state_v2_raw = *reinterpret_cast<const u8*>(&params_v2->state);
+
+    if (state_v1_raw <= 2) {
+        // Version 1 location has valid state, update there
+        params_v1->state = ParameterState::Updated;
+    } else if (state_v2_raw <= 2) {
+        // Version 2 location has valid state, update there
+        params_v2->state = ParameterState::Updated;
+    } else {
+        // Neither looks valid, update both (one will be wrong but command generator handles it)
+        params_v1->state = ParameterState::Updated;
+        params_v2->state = ParameterState::Updated;
+    }
 }
 
 void BiquadFilterInfo::InitializeResultState(EffectResultState& result_state) {}

src/audio_core/renderer/effect/biquad_filter.h

@@ -1,4 +1,5 @@
 // SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #pragma once
@@ -27,10 +28,12 @@ public:
     struct ParameterVersion2 {
         /* 0x00 */ std::array<s8, MaxChannels> inputs;
         /* 0x06 */ std::array<s8, MaxChannels> outputs;
-        /* 0x0C */ std::array<s16, 3> b;
+        /* 0x0C */ u32 padding;
-        /* 0x12 */ std::array<s16, 2> a;
+        /* 0x10 */ std::array<f32, 3> b;
-        /* 0x16 */ s8 channel_count;
+        /* 0x1C */ std::array<f32, 2> a;
-        /* 0x17 */ ParameterState state;
+        /* 0x24 */ s8 channel_count;
+        /* 0x25 */ ParameterState state;
+        /* 0x26 */ u16 reserved;
     };
     static_assert(sizeof(ParameterVersion2) <= sizeof(EffectInfoBase::InParameterVersion2),
                   "BiquadFilterInfo::ParameterVersion2 has the wrong size!");