13 files changed, 194 insertions, 102 deletions

diff --git a/src/audio_core/audio_out.cpp b/src/audio_core/audio_out.cpp
index 8619a3f03..fe3a898ad 100644
--- a/src/audio_core/audio_out.cpp
+++ b/src/audio_core/audio_out.cpp
@@ -43,6 +43,10 @@ std::vector<Buffer::Tag> AudioOut::GetTagsAndReleaseBuffers(StreamPtr stream,
     return stream->GetTagsAndReleaseBuffers(max_count);
 }
 
+std::vector<Buffer::Tag> AudioOut::GetTagsAndReleaseBuffers(StreamPtr stream) {
+    return stream->GetTagsAndReleaseBuffers();
+}
+
 void AudioOut::StartStream(StreamPtr stream) {
     stream->Play();
 }
diff --git a/src/audio_core/audio_out.h b/src/audio_core/audio_out.h
index b07588287..6ce08cd0d 100644
--- a/src/audio_core/audio_out.h
+++ b/src/audio_core/audio_out.h
@@ -31,6 +31,9 @@ public:
     /// Returns a vector of recently released buffers specified by tag for the specified stream
     std::vector<Buffer::Tag> GetTagsAndReleaseBuffers(StreamPtr stream, std::size_t max_count);
 
+    /// Returns a vector of all recently released buffers specified by tag for the specified stream
+    std::vector<Buffer::Tag> GetTagsAndReleaseBuffers(StreamPtr stream);
+
     /// Starts an audio stream for playback
     void StartStream(StreamPtr stream);
 
diff --git a/src/audio_core/audio_renderer.cpp b/src/audio_core/audio_renderer.cpp
index a7e851bb8..03a133640 100644
--- a/src/audio_core/audio_renderer.cpp
+++ b/src/audio_core/audio_renderer.cpp
@@ -2,6 +2,7 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <limits>
 #include <vector>
 
 #include "audio_core/audio_out.h"
@@ -14,6 +15,59 @@
 #include "core/memory.h"
 #include "core/settings.h"
 
+namespace {
+[[nodiscard]] static constexpr s16 ClampToS16(s32 value) {
+    return static_cast<s16>(std::clamp(value, static_cast<s32>(std::numeric_limits<s16>::min()),
+                                       static_cast<s32>(std::numeric_limits<s16>::max())));
+}
+
+[[nodiscard]] static constexpr s16 Mix2To1(s16 l_channel, s16 r_channel) {
+    // Mix 50% from left and 50% from right channel
+    constexpr float l_mix_amount = 50.0f / 100.0f;
+    constexpr float r_mix_amount = 50.0f / 100.0f;
+    return ClampToS16(static_cast<s32>((static_cast<float>(l_channel) * l_mix_amount) +
+                                       (static_cast<float>(r_channel) * r_mix_amount)));
+}
+
+[[nodiscard]] static constexpr std::tuple<s16, s16> Mix6To2(s16 fl_channel, s16 fr_channel,
+                                                            s16 fc_channel,
+                                                            [[maybe_unused]] s16 lf_channel,
+                                                            s16 bl_channel, s16 br_channel) {
+    // Front channels are mixed 36.94%, Center channels are mixed to be 26.12% & the back channels
+    // are mixed to be 36.94%
+
+    constexpr float front_mix_amount = 36.94f / 100.0f;
+    constexpr float center_mix_amount = 26.12f / 100.0f;
+    constexpr float back_mix_amount = 36.94f / 100.0f;
+
+    // Mix 50% from left and 50% from right channel
+    const auto left = front_mix_amount * static_cast<float>(fl_channel) +
+                      center_mix_amount * static_cast<float>(fc_channel) +
+                      back_mix_amount * static_cast<float>(bl_channel);
+
+    const auto right = front_mix_amount * static_cast<float>(fr_channel) +
+                       center_mix_amount * static_cast<float>(fc_channel) +
+                       back_mix_amount * static_cast<float>(br_channel);
+
+    return {ClampToS16(static_cast<s32>(left)), ClampToS16(static_cast<s32>(right))};
+}
+
+[[nodiscard]] static constexpr std::tuple<s16, s16> Mix6To2WithCoefficients(
+    s16 fl_channel, s16 fr_channel, s16 fc_channel, s16 lf_channel, s16 bl_channel, s16 br_channel,
+    const std::array<float_le, 4>& coeff) {
+    const auto left =
+        static_cast<float>(fl_channel) * coeff[0] + static_cast<float>(fc_channel) * coeff[1] +
+        static_cast<float>(lf_channel) * coeff[2] + static_cast<float>(bl_channel) * coeff[0];
+
+    const auto right =
+        static_cast<float>(fr_channel) * coeff[0] + static_cast<float>(fc_channel) * coeff[1] +
+        static_cast<float>(lf_channel) * coeff[2] + static_cast<float>(br_channel) * coeff[0];
+
+    return {ClampToS16(static_cast<s32>(left)), ClampToS16(static_cast<s32>(right))};
+}
+
+} // namespace
+
 namespace AudioCore {
 AudioRenderer::AudioRenderer(Core::Timing::CoreTiming& core_timing, Core::Memory::Memory& memory_,
                              AudioCommon::AudioRendererParameter params,
@@ -62,10 +116,6 @@ Stream::State AudioRenderer::GetStreamState() const {
     return stream->GetState();
 }
 
-static constexpr s16 ClampToS16(s32 value) {
-    return static_cast<s16>(std::clamp(value, -32768, 32767));
-}
-
 ResultCode AudioRenderer::UpdateAudioRenderer(const std::vector<u8>& input_params,
                                               std::vector<u8>& output_params) {
 
@@ -104,8 +154,8 @@ ResultCode AudioRenderer::UpdateAudioRenderer(const std::vector<u8>& input_param
         }
     }
 
-    auto mix_result = info_updater.UpdateMixes(mix_context, worker_params.mix_buffer_count,
-                                               splitter_context, effect_context);
+    const auto mix_result = info_updater.UpdateMixes(mix_context, worker_params.mix_buffer_count,
+                                                     splitter_context, effect_context);
 
     if (mix_result.IsError()) {
         LOG_ERROR(Audio, "Failed to update mix parameters");
@@ -194,20 +244,22 @@ void AudioRenderer::QueueMixedBuffer(Buffer::Tag tag) {
         for (std::size_t i = 0; i < BUFFER_SIZE; i++) {
             if (channel_count == 1) {
                 const auto sample = ClampToS16(mix_buffers[0][i]);
-                buffer[i * stream_channel_count + 0] = sample;
-                if (stream_channel_count > 1) {
-                    buffer[i * stream_channel_count + 1] = sample;
+
+                // Place sample in all channels
+                for (u32 channel = 0; channel < stream_channel_count; channel++) {
+                    buffer[i * stream_channel_count + channel] = sample;
                 }
+
                 if (stream_channel_count == 6) {
-                    buffer[i * stream_channel_count + 2] = sample;
-                    buffer[i * stream_channel_count + 4] = sample;
-                    buffer[i * stream_channel_count + 5] = sample;
+                    // Output stream has a LF channel, mute it!
+                    buffer[i * stream_channel_count + 3] = 0;
                 }
+
             } else if (channel_count == 2) {
                 const auto l_sample = ClampToS16(mix_buffers[0][i]);
                 const auto r_sample = ClampToS16(mix_buffers[1][i]);
                 if (stream_channel_count == 1) {
-                    buffer[i * stream_channel_count + 0] = l_sample;
+                    buffer[i * stream_channel_count + 0] = Mix2To1(l_sample, r_sample);
                 } else if (stream_channel_count == 2) {
                     buffer[i * stream_channel_count + 0] = l_sample;
                     buffer[i * stream_channel_count + 1] = r_sample;
@@ -215,8 +267,8 @@ void AudioRenderer::QueueMixedBuffer(Buffer::Tag tag) {
                     buffer[i * stream_channel_count + 0] = l_sample;
                     buffer[i * stream_channel_count + 1] = r_sample;
 
-                    buffer[i * stream_channel_count + 2] =
-                        ClampToS16((static_cast<s32>(l_sample) + static_cast<s32>(r_sample)) / 2);
+                    // Combine both left and right channels to the center channel
+                    buffer[i * stream_channel_count + 2] = Mix2To1(l_sample, r_sample);
 
                     buffer[i * stream_channel_count + 4] = l_sample;
                     buffer[i * stream_channel_count + 5] = r_sample;
@@ -231,17 +283,25 @@ void AudioRenderer::QueueMixedBuffer(Buffer::Tag tag) {
                 const auto br_sample = ClampToS16(mix_buffers[5][i]);
 
                 if (stream_channel_count == 1) {
-                    buffer[i * stream_channel_count + 0] = fc_sample;
+                    // Games seem to ignore the center channel half the time, we use the front left
+                    // and right channel for mixing as that's where majority of the audio goes
+                    buffer[i * stream_channel_count + 0] = Mix2To1(fl_sample, fr_sample);
                 } else if (stream_channel_count == 2) {
-                    buffer[i * stream_channel_count + 0] =
-                        static_cast<s16>(0.3694f * static_cast<float>(fl_sample) +
-                                         0.2612f * static_cast<float>(fc_sample) +
-                                         0.3694f * static_cast<float>(bl_sample));
-                    buffer[i * stream_channel_count + 1] =
-                        static_cast<s16>(0.3694f * static_cast<float>(fr_sample) +
-                                         0.2612f * static_cast<float>(fc_sample) +
-                                         0.3694f * static_cast<float>(br_sample));
+                    // Mix all channels into 2 channels
+                    if (sink_context.HasDownMixingCoefficients()) {
+                        const auto [left, right] = Mix6To2WithCoefficients(
+                            fl_sample, fr_sample, fc_sample, lf_sample, bl_sample, br_sample,
+                            sink_context.GetDownmixCoefficients());
+                        buffer[i * stream_channel_count + 0] = left;
+                        buffer[i * stream_channel_count + 1] = right;
+                    } else {
+                        const auto [left, right] = Mix6To2(fl_sample, fr_sample, fc_sample,
+                                                           lf_sample, bl_sample, br_sample);
+                        buffer[i * stream_channel_count + 0] = left;
+                        buffer[i * stream_channel_count + 1] = right;
+                    }
                 } else if (stream_channel_count == 6) {
+                    // Pass through
                     buffer[i * stream_channel_count + 0] = fl_sample;
                     buffer[i * stream_channel_count + 1] = fr_sample;
                     buffer[i * stream_channel_count + 2] = fc_sample;
@@ -259,7 +319,7 @@ void AudioRenderer::QueueMixedBuffer(Buffer::Tag tag) {
 }
 
 void AudioRenderer::ReleaseAndQueueBuffers() {
-    const auto released_buffers{audio_out->GetTagsAndReleaseBuffers(stream, 2)};
+    const auto released_buffers{audio_out->GetTagsAndReleaseBuffers(stream)};
     for (const auto& tag : released_buffers) {
         QueueMixedBuffer(tag);
     }
diff --git a/src/audio_core/audio_renderer.h b/src/audio_core/audio_renderer.h
index 2fd93e058..a85219045 100644
--- a/src/audio_core/audio_renderer.h
+++ b/src/audio_core/audio_renderer.h
@@ -36,16 +36,10 @@ class Memory;
 }
 
 namespace AudioCore {
-using DSPStateHolder = std::array<VoiceState*, 6>;
+using DSPStateHolder = std::array<VoiceState*, AudioCommon::MAX_CHANNEL_COUNT>;
 
 class AudioOut;
 
-struct RendererInfo {
-    u64_le elasped_frame_count{};
-    INSERT_PADDING_WORDS(2);
-};
-static_assert(sizeof(RendererInfo) == 0x10, "RendererInfo is an invalid size");
-
 class AudioRenderer {
 public:
     AudioRenderer(Core::Timing::CoreTiming& core_timing, Core::Memory::Memory& memory_,
@@ -53,14 +47,14 @@ public:
                   std::shared_ptr<Kernel::WritableEvent> buffer_event, std::size_t instance_number);
     ~AudioRenderer();
 
-    ResultCode UpdateAudioRenderer(const std::vector<u8>& input_params,
-                                   std::vector<u8>& output_params);
+    [[nodiscard]] ResultCode UpdateAudioRenderer(const std::vector<u8>& input_params,
+                                                 std::vector<u8>& output_params);
     void QueueMixedBuffer(Buffer::Tag tag);
     void ReleaseAndQueueBuffers();
-    u32 GetSampleRate() const;
-    u32 GetSampleCount() const;
-    u32 GetMixBufferCount() const;
-    Stream::State GetStreamState() const;
+    [[nodiscard]] u32 GetSampleRate() const;
+    [[nodiscard]] u32 GetSampleCount() const;
+    [[nodiscard]] u32 GetMixBufferCount() const;
+    [[nodiscard]] Stream::State GetStreamState() const;
 
 private:
     BehaviorInfo behavior_info{};
diff --git a/src/audio_core/behavior_info.h b/src/audio_core/behavior_info.h
index 512a4ebe3..5a96bf75e 100644
--- a/src/audio_core/behavior_info.h
+++ b/src/audio_core/behavior_info.h
@@ -43,22 +43,22 @@ public:
     void ClearError();
     void UpdateFlags(u64_le dest_flags);
     void SetUserRevision(u32_le revision);
-    u32_le GetUserRevision() const;
-    u32_le GetProcessRevision() const;
+    [[nodiscard]] u32_le GetUserRevision() const;
+    [[nodiscard]] u32_le GetProcessRevision() const;
 
-    bool IsAdpcmLoopContextBugFixed() const;
-    bool IsSplitterSupported() const;
-    bool IsLongSizePreDelaySupported() const;
-    bool IsAudioRendererProcessingTimeLimit80PercentSupported() const;
-    bool IsAudioRendererProcessingTimeLimit75PercentSupported() const;
-    bool IsAudioRendererProcessingTimeLimit70PercentSupported() const;
-    bool IsElapsedFrameCountSupported() const;
-    bool IsMemoryPoolForceMappingEnabled() const;
-    bool IsFlushVoiceWaveBuffersSupported() const;
-    bool IsVoicePlayedSampleCountResetAtLoopPointSupported() const;
-    bool IsVoicePitchAndSrcSkippedSupported() const;
-    bool IsMixInParameterDirtyOnlyUpdateSupported() const;
-    bool IsSplitterBugFixed() const;
+    [[nodiscard]] bool IsAdpcmLoopContextBugFixed() const;
+    [[nodiscard]] bool IsSplitterSupported() const;
+    [[nodiscard]] bool IsLongSizePreDelaySupported() const;
+    [[nodiscard]] bool IsAudioRendererProcessingTimeLimit80PercentSupported() const;
+    [[nodiscard]] bool IsAudioRendererProcessingTimeLimit75PercentSupported() const;
+    [[nodiscard]] bool IsAudioRendererProcessingTimeLimit70PercentSupported() const;
+    [[nodiscard]] bool IsElapsedFrameCountSupported() const;
+    [[nodiscard]] bool IsMemoryPoolForceMappingEnabled() const;
+    [[nodiscard]] bool IsFlushVoiceWaveBuffersSupported() const;
+    [[nodiscard]] bool IsVoicePlayedSampleCountResetAtLoopPointSupported() const;
+    [[nodiscard]] bool IsVoicePitchAndSrcSkippedSupported() const;
+    [[nodiscard]] bool IsMixInParameterDirtyOnlyUpdateSupported() const;
+    [[nodiscard]] bool IsSplitterBugFixed() const;
     void CopyErrorInfo(OutParams& dst);
 
 private:
diff --git a/src/audio_core/command_generator.h b/src/audio_core/command_generator.h
index 53e57748b..87ece00c4 100644
--- a/src/audio_core/command_generator.h
+++ b/src/audio_core/command_generator.h
@@ -39,13 +39,13 @@ public:
     void PreCommand();
     void PostCommand();
 
-    s32* GetChannelMixBuffer(s32 channel);
-    const s32* GetChannelMixBuffer(s32 channel) const;
-    s32* GetMixBuffer(std::size_t index);
-    const s32* GetMixBuffer(std::size_t index) const;
-    std::size_t GetMixChannelBufferOffset(s32 channel) const;
+    [[nodiscard]] s32* GetChannelMixBuffer(s32 channel);
+    [[nodiscard]] const s32* GetChannelMixBuffer(s32 channel) const;
+    [[nodiscard]] s32* GetMixBuffer(std::size_t index);
+    [[nodiscard]] const s32* GetMixBuffer(std::size_t index) const;
+    [[nodiscard]] std::size_t GetMixChannelBufferOffset(s32 channel) const;
 
-    std::size_t GetTotalMixBufferCount() const;
+    [[nodiscard]] std::size_t GetTotalMixBufferCount() const;
 
 private:
     void GenerateDataSourceCommand(ServerVoiceInfo& voice_info, VoiceState& dsp_state, s32 channel);
@@ -73,7 +73,7 @@ private:
     void GenerateI3dl2ReverbEffectCommand(s32 mix_buffer_offset, EffectBase* info, bool enabled);
     void GenerateBiquadFilterEffectCommand(s32 mix_buffer_offset, EffectBase* info, bool enabled);
     void GenerateAuxCommand(s32 mix_buffer_offset, EffectBase* info, bool enabled);
-    ServerSplitterDestinationData* GetDestinationData(s32 splitter_id, s32 index);
+    [[nodiscard]] ServerSplitterDestinationData* GetDestinationData(s32 splitter_id, s32 index);
 
     s32 WriteAuxBuffer(AuxInfoDSP& dsp_info, VAddr send_buffer, u32 max_samples, const s32* data,
                        u32 sample_count, u32 write_offset, u32 write_count);
diff --git a/src/audio_core/common.h b/src/audio_core/common.h
index 7b4a1e9e8..ec59a3ba9 100644
--- a/src/audio_core/common.h
+++ b/src/audio_core/common.h
@@ -22,7 +22,7 @@ constexpr std::size_t MAX_CHANNEL_COUNT = 6;
 constexpr std::size_t MAX_WAVE_BUFFERS = 4;
 constexpr std::size_t MAX_SAMPLE_HISTORY = 4;
 constexpr u32 STREAM_SAMPLE_RATE = 48000;
-constexpr u32 STREAM_NUM_CHANNELS = 6;
+constexpr u32 STREAM_NUM_CHANNELS = 2;
 constexpr s32 NO_SPLITTER = -1;
 constexpr s32 NO_MIX = 0x7fffffff;
 constexpr s32 NO_FINAL_MIX = std::numeric_limits<s32>::min();
diff --git a/src/audio_core/effect_context.h b/src/audio_core/effect_context.h
index 2c4ce53ef..03c5a0f04 100644
--- a/src/audio_core/effect_context.h
+++ b/src/audio_core/effect_context.h
@@ -189,11 +189,11 @@ public:
 
     virtual void Update(EffectInfo::InParams& in_params) = 0;
     virtual void UpdateForCommandGeneration() = 0;
-    UsageState GetUsage() const;
-    EffectType GetType() const;
-    bool IsEnabled() const;
-    s32 GetMixID() const;
-    s32 GetProcessingOrder() const;
+    [[nodiscard]] UsageState GetUsage() const;
+    [[nodiscard]] EffectType GetType() const;
+    [[nodiscard]] bool IsEnabled() const;
+    [[nodiscard]] s32 GetMixID() const;
+    [[nodiscard]] s32 GetProcessingOrder() const;
 
 protected:
     UsageState usage{UsageState::Invalid};
@@ -257,10 +257,10 @@ public:
 
     void Update(EffectInfo::InParams& in_params) override;
     void UpdateForCommandGeneration() override;
-    VAddr GetSendInfo() const;
-    VAddr GetSendBuffer() const;
-    VAddr GetRecvInfo() const;
-    VAddr GetRecvBuffer() const;
+    [[nodiscard]] VAddr GetSendInfo() const;
+    [[nodiscard]] VAddr GetSendBuffer() const;
+    [[nodiscard]] VAddr GetRecvInfo() const;
+    [[nodiscard]] VAddr GetRecvBuffer() const;
 
 private:
     VAddr send_info{};
@@ -309,10 +309,10 @@ public:
     explicit EffectContext(std::size_t effect_count);
     ~EffectContext();
 
-    std::size_t GetCount() const;
-    EffectBase* GetInfo(std::size_t i);
-    EffectBase* RetargetEffect(std::size_t i, EffectType effect);
-    const EffectBase* GetInfo(std::size_t i) const;
+    [[nodiscard]] std::size_t GetCount() const;
+    [[nodiscard]] EffectBase* GetInfo(std::size_t i);
+    [[nodiscard]] EffectBase* RetargetEffect(std::size_t i, EffectType effect);
+    [[nodiscard]] const EffectBase* GetInfo(std::size_t i) const;
 
 private:
     std::size_t effect_count{};
diff --git a/src/audio_core/mix_context.h b/src/audio_core/mix_context.h
index 6a588eeb4..68bc673c6 100644
--- a/src/audio_core/mix_context.h
+++ b/src/audio_core/mix_context.h
@@ -62,17 +62,17 @@ public:
     ServerMixInfo();
     ~ServerMixInfo();
 
-    const ServerMixInfo::InParams& GetInParams() const;
-    ServerMixInfo::InParams& GetInParams();
+    [[nodiscard]] const ServerMixInfo::InParams& GetInParams() const;
+    [[nodiscard]] ServerMixInfo::InParams& GetInParams();
 
     bool Update(EdgeMatrix& edge_matrix, const MixInfo::InParams& mix_in,
                 BehaviorInfo& behavior_info, SplitterContext& splitter_context,
                 EffectContext& effect_context);
-    bool HasAnyConnection() const;
+    [[nodiscard]] bool HasAnyConnection() const;
     void Cleanup();
     void SetEffectCount(std::size_t count);
     void ResetEffectProcessingOrder();
-    s32 GetEffectOrder(std::size_t i) const;
+    [[nodiscard]] s32 GetEffectOrder(std::size_t i) const;
 
 private:
     std::vector<s32> effect_processing_order;
@@ -91,15 +91,15 @@ public:
     void SortInfo();
     bool TsortInfo(SplitterContext& splitter_context);
 
-    std::size_t GetCount() const;
-    ServerMixInfo& GetInfo(std::size_t i);
-    const ServerMixInfo& GetInfo(std::size_t i) const;
-    ServerMixInfo& GetSortedInfo(std::size_t i);
-    const ServerMixInfo& GetSortedInfo(std::size_t i) const;
-    ServerMixInfo& GetFinalMixInfo();
-    const ServerMixInfo& GetFinalMixInfo() const;
-    EdgeMatrix& GetEdgeMatrix();
-    const EdgeMatrix& GetEdgeMatrix() const;
+    [[nodiscard]] std::size_t GetCount() const;
+    [[nodiscard]] ServerMixInfo& GetInfo(std::size_t i);
+    [[nodiscard]] const ServerMixInfo& GetInfo(std::size_t i) const;
+    [[nodiscard]] ServerMixInfo& GetSortedInfo(std::size_t i);
+    [[nodiscard]] const ServerMixInfo& GetSortedInfo(std::size_t i) const;
+    [[nodiscard]] ServerMixInfo& GetFinalMixInfo();
+    [[nodiscard]] const ServerMixInfo& GetFinalMixInfo() const;
+    [[nodiscard]] EdgeMatrix& GetEdgeMatrix();
+    [[nodiscard]] const EdgeMatrix& GetEdgeMatrix() const;
 
 private:
     void CalcMixBufferOffset();
diff --git a/src/audio_core/sink_context.cpp b/src/audio_core/sink_context.cpp
index 0882b411a..cdb47ba81 100644
--- a/src/audio_core/sink_context.cpp
+++ b/src/audio_core/sink_context.cpp
@@ -12,10 +12,16 @@ std::size_t SinkContext::GetCount() const {
     return sink_count;
 }
 
-void SinkContext::UpdateMainSink(SinkInfo::InParams& in) {
+void SinkContext::UpdateMainSink(const SinkInfo::InParams& in) {
+    ASSERT(in.type == SinkTypes::Device);
+
+    downmix = in.device.down_matrix_enabled;
+    if (downmix) {
+        downmix_coefficients = in.device.down_matrix_coef;
+    }
     in_use = in.in_use;
     use_count = in.device.input_count;
-    std::memcpy(buffers.data(), in.device.input.data(), AudioCommon::MAX_CHANNEL_COUNT);
+    buffers = in.device.input;
 }
 
 bool SinkContext::InUse() const {
@@ -28,4 +34,12 @@ std::vector<u8> SinkContext::OutputBuffers() const {
     return buffer_ret;
 }
 
+bool SinkContext::HasDownMixingCoefficients() const {
+    return downmix;
+}
+
+const std::array<float_le, 4>& SinkContext::GetDownmixCoefficients() const {
+    return downmix_coefficients;
+}
+
 } // namespace AudioCore
diff --git a/src/audio_core/sink_context.h b/src/audio_core/sink_context.h
index d7aa72ba7..5a757a4ef 100644
--- a/src/audio_core/sink_context.h
+++ b/src/audio_core/sink_context.h
@@ -74,16 +74,21 @@ public:
     explicit SinkContext(std::size_t sink_count);
     ~SinkContext();
 
-    std::size_t GetCount() const;
+    [[nodiscard]] std::size_t GetCount() const;
 
-    void UpdateMainSink(SinkInfo::InParams& in);
-    bool InUse() const;
-    std::vector<u8> OutputBuffers() const;
+    void UpdateMainSink(const SinkInfo::InParams& in);
+    [[nodiscard]] bool InUse() const;
+    [[nodiscard]] std::vector<u8> OutputBuffers() const;
+
+    [[nodiscard]] bool HasDownMixingCoefficients() const;
+    [[nodiscard]] const std::array<float_le, 4>& GetDownmixCoefficients() const;
 
 private:
     bool in_use{false};
     s32 use_count{};
     std::array<u8, AudioCommon::MAX_CHANNEL_COUNT> buffers{};
     std::size_t sink_count{};
+    bool downmix{false};
+    std::array<float_le, 4> downmix_coefficients{};
 };
 } // namespace AudioCore
diff --git a/src/audio_core/stream.cpp b/src/audio_core/stream.cpp
index 4bbb1e0c4..3f11b84ae 100644
--- a/src/audio_core/stream.cpp
+++ b/src/audio_core/stream.cpp
@@ -136,4 +136,13 @@ std::vector<Buffer::Tag> Stream::GetTagsAndReleaseBuffers(std::size_t max_count)
     return tags;
 }
 
+std::vector<Buffer::Tag> Stream::GetTagsAndReleaseBuffers() {
+    std::vector<Buffer::Tag> tags;
+    while (!released_buffers.empty()) {
+        tags.push_back(released_buffers.front()->GetTag());
+        released_buffers.pop();
+    }
+    return tags;
+}
+
 } // namespace AudioCore
diff --git a/src/audio_core/stream.h b/src/audio_core/stream.h
index 6437b8591..71c2d0b4f 100644
--- a/src/audio_core/stream.h
+++ b/src/audio_core/stream.h
@@ -57,37 +57,40 @@ public:
     bool QueueBuffer(BufferPtr&& buffer);
 
     /// Returns true if the audio stream contains a buffer with the specified tag
-    bool ContainsBuffer(Buffer::Tag tag) const;
+    [[nodiscard]] bool ContainsBuffer(Buffer::Tag tag) const;
 
     /// Returns a vector of recently released buffers specified by tag
-    std::vector<Buffer::Tag> GetTagsAndReleaseBuffers(std::size_t max_count);
+    [[nodiscard]] std::vector<Buffer::Tag> GetTagsAndReleaseBuffers(std::size_t max_count);
+
+    /// Returns a vector of all recently released buffers specified by tag
+    [[nodiscard]] std::vector<Buffer::Tag> GetTagsAndReleaseBuffers();
 
     void SetVolume(float volume);
 
-    float GetVolume() const {
+    [[nodiscard]] float GetVolume() const {
         return game_volume;
     }
 
     /// Returns true if the stream is currently playing
-    bool IsPlaying() const {
+    [[nodiscard]] bool IsPlaying() const {
         return state == State::Playing;
     }
 
     /// Returns the number of queued buffers
-    std::size_t GetQueueSize() const {
+    [[nodiscard]] std::size_t GetQueueSize() const {
         return queued_buffers.size();
     }
 
     /// Gets the sample rate
-    u32 GetSampleRate() const {
+    [[nodiscard]] u32 GetSampleRate() const {
         return sample_rate;
     }
 
     /// Gets the number of channels
-    u32 GetNumChannels() const;
+    [[nodiscard]] u32 GetNumChannels() const;
 
     /// Get the state
-    State GetState() const;
+    [[nodiscard]] State GetState() const;
 
 private:
     /// Plays the next queued buffer in the audio stream, starting playback if necessary
@@ -97,7 +100,7 @@ private:
     void ReleaseActiveBuffer(std::chrono::nanoseconds ns_late = {});
 
     /// Gets the number of core cycles when the specified buffer will be released
-    std::chrono::nanoseconds GetBufferReleaseNS(const Buffer& buffer) const;
+    [[nodiscard]] std::chrono::nanoseconds GetBufferReleaseNS(const Buffer& buffer) const;
 
     u32 sample_rate;                  ///< Sample rate of the stream
     Format format;                    ///< Format of the stream