[audio_core] Better biquad filter logic (#3235)

This removes all redundant code and improves the logic of the biquad filter.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3235
Reviewed-by: Maufeat <sahyno1996@gmail.com>
Co-authored-by: MaranBr <maranbr@outlook.com>
Co-committed-by: MaranBr <maranbr@outlook.com>

src/audio_core/renderer/command/command_buffer.cpp

@@ -275,7 +275,6 @@ void CommandBuffer::GenerateBiquadFilterCommand(const s32 node_id, EffectInfoBas
         const auto& parameter{
             *reinterpret_cast<BiquadFilterInfo::ParameterVersion2*>(effect_info.GetParameter())};
 
-        if (parameter.state <= EffectInfoBase::ParameterState::Updated && IsChannelCountValid(parameter.channel_count) && channel >= 0 && channel < parameter.channel_count) {
         cmd.input = buffer_offset + parameter.inputs[channel];
         cmd.output = buffer_offset + parameter.outputs[channel];
 
@@ -285,19 +284,16 @@ void CommandBuffer::GenerateBiquadFilterCommand(const s32 node_id, EffectInfoBas
         cmd.biquad.b[2] = ToQ14Clamped(parameter.b[2]);
         cmd.biquad.a[0] = ToQ14Clamped(parameter.a[0]);
         cmd.biquad.a[1] = ToQ14Clamped(parameter.a[1]);
-        }
     } else {
         const auto& parameter{
             *reinterpret_cast<BiquadFilterInfo::ParameterVersion1*>(effect_info.GetParameter())};
 
-        if (IsChannelCountValid(parameter.channel_count) && channel >= 0 && channel < parameter.channel_count) {
         cmd.input = buffer_offset + parameter.inputs[channel];
         cmd.output = buffer_offset + parameter.outputs[channel];
 
         cmd.biquad.b = parameter.b;
         cmd.biquad.a = parameter.a;
     }
-    }
 
     // Effects always use the fixed-point coefficient path on the DSP.
     cmd.use_float_coefficients = false;

src/audio_core/renderer/command/command_generator.cpp

@@ -370,29 +370,16 @@ void CommandGenerator::GenerateBiquadFilterEffectCommand(const s16 buffer_offset
     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;
-        }
-        if (parameter->state <= EffectInfoBase::ParameterState::Updated) {
         param_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;
-        }
         param_state = parameter->state;
         channel_count = parameter->channel_count;
     }
 
-    if (channel_count <= 0) {
-        return;
-    }
-
+    if (channel_count > 0 && param_state <= EffectInfoBase::ParameterState::Updated) {
         if (effect_info.IsEnabled()) {
             bool needs_init{false};
 
@@ -401,18 +388,10 @@ void CommandGenerator::GenerateBiquadFilterEffectCommand(const s16 buffer_offset
                 needs_init = true;
                 break;
             case EffectInfoBase::ParameterState::Updating:
+                needs_init = !render_context.behavior->IsBiquadFilterEffectStateClearBugFixed();
+                break;
             case EffectInfoBase::ParameterState::Updated:
-            if (render_context.behavior->IsBiquadFilterEffectStateClearBugFixed()) {
                 needs_init = false;
-            } else {
-                needs_init = param_state == EffectInfoBase::ParameterState::Updating;
-            }
-            break;
-        default:
-            LOG_ERROR(Service_Audio,
-                      "Invalid biquad parameter state {}, treating as uninitialized",
-                      static_cast<u32>(param_state));
-            needs_init = true;
                 break;
             }
 
@@ -430,6 +409,7 @@ void CommandGenerator::GenerateBiquadFilterEffectCommand(const s16 buffer_offset
             }
         }
     }
+}
 
 void CommandGenerator::GenerateLightLimiterEffectCommand(const s16 buffer_offset,
                                                          EffectInfoBase& effect_info,