12 files changed, 738 insertions, 71 deletions
diff --git a/src/audio_core/adsp/adsp.cpp b/src/audio_core/adsp/adsp.cpp
index 0580990f5..6c53c98fd 100644
--- a/src/audio_core/adsp/adsp.cpp
+++ b/src/audio_core/adsp/adsp.cpp
@@ -7,12 +7,21 @@
 namespace AudioCore::ADSP {
 
 ADSP::ADSP(Core::System& system, Sink::Sink& sink) {
-    audio_renderer =
-        std::make_unique<AudioRenderer::AudioRenderer>(system, system.ApplicationMemory(), sink);
+    audio_renderer = std::make_unique<AudioRenderer::AudioRenderer>(system, sink);
+    opus_decoder = std::make_unique<OpusDecoder::OpusDecoder>(system);
+    opus_decoder->Send(Direction::DSP, OpusDecoder::Message::Start);
+    if (opus_decoder->Receive(Direction::Host) != OpusDecoder::Message::StartOK) {
+        LOG_ERROR(Service_Audio, "OpusDeocder failed to initialize.");
+        return;
+    }
 }
 
 AudioRenderer::AudioRenderer& ADSP::AudioRenderer() {
     return *audio_renderer.get();
 }
 
+OpusDecoder::OpusDecoder& ADSP::OpusDecoder() {
+    return *opus_decoder.get();
+}
+
 } // namespace AudioCore::ADSP
diff --git a/src/audio_core/adsp/adsp.h b/src/audio_core/adsp/adsp.h
index bd5bcc63b..a0c24a16a 100644
--- a/src/audio_core/adsp/adsp.h
+++ b/src/audio_core/adsp/adsp.h
@@ -4,6 +4,7 @@
 #pragma once
 
 #include "audio_core/adsp/apps/audio_renderer/audio_renderer.h"
+#include "audio_core/adsp/apps/opus/opus_decoder.h"
 #include "common/common_types.h"
 
 namespace Core {
@@ -40,10 +41,12 @@ public:
     ~ADSP() = default;
 
     AudioRenderer::AudioRenderer& AudioRenderer();
+    OpusDecoder::OpusDecoder& OpusDecoder();
 
 private:
     /// AudioRenderer app
     std::unique_ptr<AudioRenderer::AudioRenderer> audio_renderer{};
+    std::unique_ptr<OpusDecoder::OpusDecoder> opus_decoder{};
 };
 
 } // namespace ADSP
diff --git a/src/audio_core/adsp/apps/audio_renderer/audio_renderer.cpp b/src/audio_core/adsp/apps/audio_renderer/audio_renderer.cpp
index 2e549bc6f..972d5e45b 100644
--- a/src/audio_core/adsp/apps/audio_renderer/audio_renderer.cpp
+++ b/src/audio_core/adsp/apps/audio_renderer/audio_renderer.cpp
@@ -14,13 +14,12 @@
 #include "core/core.h"
 #include "core/core_timing.h"
 
-MICROPROFILE_DEFINE(Audio_Renderer, "Audio", "DSP", MP_RGB(60, 19, 97));
+MICROPROFILE_DEFINE(Audio_Renderer, "Audio", "DSP_AudioRenderer", MP_RGB(60, 19, 97));
 
 namespace AudioCore::ADSP::AudioRenderer {
 
-AudioRenderer::AudioRenderer(Core::System& system_, Core::Memory::Memory& memory_,
-                             Sink::Sink& sink_)
-    : system{system_}, memory{memory_}, sink{sink_} {}
+AudioRenderer::AudioRenderer(Core::System& system_, Sink::Sink& sink_)
+    : system{system_}, sink{sink_} {}
 
 AudioRenderer::~AudioRenderer() {
     Stop();
@@ -33,8 +32,8 @@ void AudioRenderer::Start() {
 
     main_thread = std::jthread([this](std::stop_token stop_token) { Main(stop_token); });
 
-    mailbox.Send(Direction::DSP, {Message::InitializeOK, {}});
-    if (mailbox.Receive(Direction::Host).msg != Message::InitializeOK) {
+    mailbox.Send(Direction::DSP, Message::InitializeOK);
+    if (mailbox.Receive(Direction::Host) != Message::InitializeOK) {
         LOG_ERROR(Service_Audio, "Host Audio Renderer -- Failed to receive shutdown "
                                  "message response from ADSP!");
         return;
@@ -47,8 +46,8 @@ void AudioRenderer::Stop() {
         return;
     }
 
-    mailbox.Send(Direction::DSP, {Message::Shutdown, {}});
-    if (mailbox.Receive(Direction::Host).msg != Message::Shutdown) {
+    mailbox.Send(Direction::DSP, Message::Shutdown);
+    if (mailbox.Receive(Direction::Host) != Message::Shutdown) {
         LOG_ERROR(Service_Audio, "Host Audio Renderer -- Failed to receive shutdown "
                                  "message response from ADSP!");
     }
@@ -67,25 +66,25 @@ void AudioRenderer::Stop() {
 
 void AudioRenderer::Signal() {
     signalled_tick = system.CoreTiming().GetGlobalTimeNs().count();
-    Send(Direction::DSP, {Message::Render, {}});
+    Send(Direction::DSP, Message::Render);
 }
 
 void AudioRenderer::Wait() {
-    auto received = Receive(Direction::Host);
-    if (received.msg != Message::RenderResponse) {
+    auto msg = Receive(Direction::Host);
+    if (msg != Message::RenderResponse) {
         LOG_ERROR(Service_Audio,
                   "Did not receive the expected render response from the AudioRenderer! Expected "
                   "{}, got {}",
-                  Message::RenderResponse, received.msg);
+                  Message::RenderResponse, msg);
     }
 }
 
-void AudioRenderer::Send(Direction dir, MailboxMessage message) {
+void AudioRenderer::Send(Direction dir, u32 message) {
     mailbox.Send(dir, std::move(message));
 }
 
-MailboxMessage AudioRenderer::Receive(Direction dir, bool block) {
-    return mailbox.Receive(dir, block);
+u32 AudioRenderer::Receive(Direction dir) {
+    return mailbox.Receive(dir);
 }
 
 void AudioRenderer::SetCommandBuffer(s32 session_id, CpuAddr buffer, u64 size, u64 time_limit,
@@ -120,7 +119,7 @@ void AudioRenderer::CreateSinkStreams() {
 }
 
 void AudioRenderer::Main(std::stop_token stop_token) {
-    static constexpr char name[]{"AudioRenderer"};
+    static constexpr char name[]{"DSP_AudioRenderer_Main"};
     MicroProfileOnThreadCreate(name);
     Common::SetCurrentThreadName(name);
     Common::SetCurrentThreadPriority(Common::ThreadPriority::High);
@@ -128,28 +127,28 @@ void AudioRenderer::Main(std::stop_token stop_token) {
     // TODO: Create buffer map/unmap thread + mailbox
     // TODO: Create gMix devices, initialize them here
 
-    if (mailbox.Receive(Direction::DSP).msg != Message::InitializeOK) {
+    if (mailbox.Receive(Direction::DSP) != Message::InitializeOK) {
         LOG_ERROR(Service_Audio,
                   "ADSP Audio Renderer -- Failed to receive initialize message from host!");
         return;
     }
 
-    mailbox.Send(Direction::Host, {Message::InitializeOK, {}});
+    mailbox.Send(Direction::Host, Message::InitializeOK);
 
     // 0.12 seconds (2,304,000 / 19,200,000)
     constexpr u64 max_process_time{2'304'000ULL};
 
     while (!stop_token.stop_requested()) {
-        auto received{mailbox.Receive(Direction::DSP)};
-        switch (received.msg) {
+        auto msg{mailbox.Receive(Direction::DSP)};
+        switch (msg) {
         case Message::Shutdown:
-            mailbox.Send(Direction::Host, {Message::Shutdown, {}});
+            mailbox.Send(Direction::Host, Message::Shutdown);
             return;
 
         case Message::Render: {
             if (system.IsShuttingDown()) [[unlikely]] {
                 std::this_thread::sleep_for(std::chrono::milliseconds(5));
-                mailbox.Send(Direction::Host, {Message::RenderResponse, {}});
+                mailbox.Send(Direction::Host, Message::RenderResponse);
                 continue;
             }
             std::array<bool, MaxRendererSessions> buffers_reset{};
@@ -205,13 +204,12 @@ void AudioRenderer::Main(std::stop_token stop_token) {
                 }
             }
 
-            mailbox.Send(Direction::Host, {Message::RenderResponse, {}});
+            mailbox.Send(Direction::Host, Message::RenderResponse);
         } break;
 
         default:
             LOG_WARNING(Service_Audio,
-                        "ADSP AudioRenderer received an invalid message, msg={:02X}!",
-                        received.msg);
+                        "ADSP AudioRenderer received an invalid message, msg={:02X}!", msg);
             break;
         }
     }
diff --git a/src/audio_core/adsp/apps/audio_renderer/audio_renderer.h b/src/audio_core/adsp/apps/audio_renderer/audio_renderer.h
index 3f5b7dca2..85874d88a 100644
--- a/src/audio_core/adsp/apps/audio_renderer/audio_renderer.h
+++ b/src/audio_core/adsp/apps/audio_renderer/audio_renderer.h
@@ -17,13 +17,6 @@
 
 namespace Core {
 class System;
-namespace Timing {
-struct EventType;
-}
-namespace Memory {
-class Memory;
-}
-class System;
 } // namespace Core
 
 namespace AudioCore {
@@ -34,19 +27,19 @@ class Sink;
 namespace ADSP::AudioRenderer {
 
 enum Message : u32 {
-    Invalid = 0x00,
-    MapUnmap_Map = 0x01,
-    MapUnmap_MapResponse = 0x02,
-    MapUnmap_Unmap = 0x03,
-    MapUnmap_UnmapResponse = 0x04,
-    MapUnmap_InvalidateCache = 0x05,
-    MapUnmap_InvalidateCacheResponse = 0x06,
-    MapUnmap_Shutdown = 0x07,
-    MapUnmap_ShutdownResponse = 0x08,
-    InitializeOK = 0x16,
-    RenderResponse = 0x20,
-    Render = 0x2A,
-    Shutdown = 0x34,
+    Invalid = 0,
+    MapUnmap_Map = 1,
+    MapUnmap_MapResponse = 2,
+    MapUnmap_Unmap = 3,
+    MapUnmap_UnmapResponse = 4,
+    MapUnmap_InvalidateCache = 5,
+    MapUnmap_InvalidateCacheResponse = 6,
+    MapUnmap_Shutdown = 7,
+    MapUnmap_ShutdownResponse = 8,
+    InitializeOK = 22,
+    RenderResponse = 32,
+    Render = 42,
+    Shutdown = 52,
 };
 
 /**
@@ -54,7 +47,7 @@ enum Message : u32 {
  */
 class AudioRenderer {
 public:
-    explicit AudioRenderer(Core::System& system, Core::Memory::Memory& memory, Sink::Sink& sink);
+    explicit AudioRenderer(Core::System& system, Sink::Sink& sink);
     ~AudioRenderer();
 
     /**
@@ -72,8 +65,8 @@ public:
     void Signal();
     void Wait();
 
-    void Send(Direction dir, MailboxMessage message);
-    MailboxMessage Receive(Direction dir, bool block = true);
+    void Send(Direction dir, u32 message);
+    u32 Receive(Direction dir);
 
     void SetCommandBuffer(s32 session_id, CpuAddr buffer, u64 size, u64 time_limit,
                           u64 applet_resource_user_id, bool reset) noexcept;
@@ -94,9 +87,7 @@ private:
 
     /// Core system
     Core::System& system;
-    /// Memory
-    Core::Memory::Memory& memory;
-    /// The output sink the AudioRenderer will use
+    /// The output sink the AudioRenderer will send samples to
     Sink::Sink& sink;
     /// The active mailbox
     Mailbox mailbox;
@@ -104,11 +95,13 @@ private:
     std::jthread main_thread{};
     /// The current state
     std::atomic<bool> running{};
+    /// Shared memory of input command buffers, set by host, read by DSP
     std::array<CommandBuffer, MaxRendererSessions> command_buffers{};
     /// The command lists to process
     std::array<CommandListProcessor, MaxRendererSessions> command_list_processors{};
     /// The streams which will receive the processed samples
     std::array<Sink::SinkStream*, MaxRendererSessions> streams{};
+    /// CPU Tick when the DSP was signalled to process, uses time rather than tick
     u64 signalled_tick{0};
 };
 
diff --git a/src/audio_core/adsp/apps/opus/opus_decode_object.cpp b/src/audio_core/adsp/apps/opus/opus_decode_object.cpp
new file mode 100644
index 000000000..2c16d3769
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/opus_decode_object.cpp
@@ -0,0 +1,107 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "audio_core/adsp/apps/opus/opus_decode_object.h"
+#include "common/assert.h"
+
+namespace AudioCore::ADSP::OpusDecoder {
+namespace {
+bool IsValidChannelCount(u32 channel_count) {
+    return channel_count == 1 || channel_count == 2;
+}
+} // namespace
+
+u32 OpusDecodeObject::GetWorkBufferSize(u32 channel_count) {
+    if (!IsValidChannelCount(channel_count)) {
+        return 0;
+    }
+    return static_cast<u32>(sizeof(OpusDecodeObject)) + opus_decoder_get_size(channel_count);
+}
+
+OpusDecodeObject& OpusDecodeObject::Initialize(u64 buffer, u64 buffer2) {
+    auto* new_decoder = reinterpret_cast<OpusDecodeObject*>(buffer);
+    auto* comparison = reinterpret_cast<OpusDecodeObject*>(buffer2);
+
+    if (new_decoder->magic == DecodeObjectMagic) {
+        if (!new_decoder->initialized ||
+            (new_decoder->initialized && new_decoder->self == comparison)) {
+            new_decoder->state_valid = true;
+        }
+    } else {
+        new_decoder->initialized = false;
+        new_decoder->state_valid = true;
+    }
+    return *new_decoder;
+}
+
+s32 OpusDecodeObject::InitializeDecoder(u32 sample_rate, u32 channel_count) {
+    if (!state_valid) {
+        return OPUS_INVALID_STATE;
+    }
+
+    if (initialized) {
+        return OPUS_OK;
+    }
+
+    // Unfortunately libopus does not expose the OpusDecoder struct publicly, so we can't include
+    // it in this class. Nintendo does not allocate memory, which is why we have a workbuffer
+    // provided.
+    // We could use _create and have libopus allocate it for us, but then we have to separately
+    // track which decoder is being used between this and multistream in order to call the correct
+    // destroy from the host side.
+    // This is a bit cringe, but is safe as these objects are only ever initialized inside the given
+    // workbuffer, and GetWorkBufferSize will guarantee there's enough space to follow.
+    decoder = (LibOpusDecoder*)(this + 1);
+    s32 ret = opus_decoder_init(decoder, sample_rate, channel_count);
+    if (ret == OPUS_OK) {
+        magic = DecodeObjectMagic;
+        initialized = true;
+        state_valid = true;
+        self = this;
+        final_range = 0;
+    }
+    return ret;
+}
+
+s32 OpusDecodeObject::Shutdown() {
+    if (!state_valid) {
+        return OPUS_INVALID_STATE;
+    }
+
+    if (initialized) {
+        magic = 0x0;
+        initialized = false;
+        state_valid = false;
+        self = nullptr;
+        final_range = 0;
+        decoder = nullptr;
+    }
+    return OPUS_OK;
+}
+
+s32 OpusDecodeObject::ResetDecoder() {
+    return opus_decoder_ctl(decoder, OPUS_RESET_STATE);
+}
+
+s32 OpusDecodeObject::Decode(u32& out_sample_count, u64 output_data, u64 output_data_size,
+                             u64 input_data, u64 input_data_size) {
+    ASSERT(initialized);
+    out_sample_count = 0;
+
+    if (!state_valid) {
+        return OPUS_INVALID_STATE;
+    }
+
+    auto ret_code_or_samples = opus_decode(
+        decoder, reinterpret_cast<const u8*>(input_data), static_cast<opus_int32>(input_data_size),
+        reinterpret_cast<opus_int16*>(output_data), static_cast<opus_int32>(output_data_size), 0);
+
+    if (ret_code_or_samples < OPUS_OK) {
+        return ret_code_or_samples;
+    }
+
+    out_sample_count = ret_code_or_samples;
+    return opus_decoder_ctl(decoder, OPUS_GET_FINAL_RANGE_REQUEST, &final_range);
+}
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/apps/opus/opus_decode_object.h b/src/audio_core/adsp/apps/opus/opus_decode_object.h
new file mode 100644
index 000000000..6425f987c
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/opus_decode_object.h
@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <opus.h>
+
+#include "common/common_types.h"
+
+namespace AudioCore::ADSP::OpusDecoder {
+using LibOpusDecoder = ::OpusDecoder;
+static constexpr u32 DecodeObjectMagic = 0xDEADBEEF;
+
+class OpusDecodeObject {
+public:
+    static u32 GetWorkBufferSize(u32 channel_count);
+    static OpusDecodeObject& Initialize(u64 buffer, u64 buffer2);
+
+    s32 InitializeDecoder(u32 sample_rate, u32 channel_count);
+    s32 Shutdown();
+    s32 ResetDecoder();
+    s32 Decode(u32& out_sample_count, u64 output_data, u64 output_data_size, u64 input_data,
+               u64 input_data_size);
+    u32 GetFinalRange() const noexcept {
+        return final_range;
+    }
+
+private:
+    u32 magic;
+    bool initialized;
+    bool state_valid;
+    OpusDecodeObject* self;
+    u32 final_range;
+    LibOpusDecoder* decoder;
+};
+static_assert(std::is_trivially_constructible_v<OpusDecodeObject>);
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/apps/opus/opus_decoder.cpp b/src/audio_core/adsp/apps/opus/opus_decoder.cpp
new file mode 100644
index 000000000..2084de128
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/opus_decoder.cpp
@@ -0,0 +1,269 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <array>
+#include <chrono>
+
+#include "audio_core/adsp/apps/opus/opus_decode_object.h"
+#include "audio_core/adsp/apps/opus/opus_multistream_decode_object.h"
+#include "audio_core/adsp/apps/opus/shared_memory.h"
+#include "audio_core/audio_core.h"
+#include "audio_core/common/common.h"
+#include "common/logging/log.h"
+#include "common/microprofile.h"
+#include "common/thread.h"
+#include "core/core.h"
+#include "core/core_timing.h"
+
+MICROPROFILE_DEFINE(OpusDecoder, "Audio", "DSP_OpusDecoder", MP_RGB(60, 19, 97));
+
+namespace AudioCore::ADSP::OpusDecoder {
+
+namespace {
+constexpr size_t OpusStreamCountMax = 255;
+
+bool IsValidChannelCount(u32 channel_count) {
+    return channel_count == 1 || channel_count == 2;
+}
+
+bool IsValidMultiStreamChannelCount(u32 channel_count) {
+    return channel_count <= OpusStreamCountMax;
+}
+
+bool IsValidMultiStreamStreamCounts(s32 total_stream_count, s32 sterero_stream_count) {
+    return IsValidMultiStreamChannelCount(total_stream_count) && total_stream_count > 0 &&
+           sterero_stream_count > 0 && sterero_stream_count <= total_stream_count;
+}
+} // namespace
+
+OpusDecoder::OpusDecoder(Core::System& system_) : system{system_} {
+    init_thread = std::jthread([this](std::stop_token stop_token) { Init(stop_token); });
+}
+
+OpusDecoder::~OpusDecoder() {
+    if (!running) {
+        init_thread.request_stop();
+        return;
+    }
+
+    // Shutdown the thread
+    Send(Direction::DSP, Message::Shutdown);
+    auto msg = Receive(Direction::Host);
+    ASSERT_MSG(msg == Message::ShutdownOK, "Expected Opus shutdown code {}, got {}",
+               Message::ShutdownOK, msg);
+    main_thread.request_stop();
+    main_thread.join();
+    running = false;
+}
+
+void OpusDecoder::Send(Direction dir, u32 message) {
+    mailbox.Send(dir, std::move(message));
+}
+
+u32 OpusDecoder::Receive(Direction dir, std::stop_token stop_token) {
+    return mailbox.Receive(dir, stop_token);
+}
+
+void OpusDecoder::Init(std::stop_token stop_token) {
+    Common::SetCurrentThreadName("DSP_OpusDecoder_Init");
+
+    if (Receive(Direction::DSP, stop_token) != Message::Start) {
+        LOG_ERROR(Service_Audio,
+                  "DSP OpusDecoder failed to receive Start message. Opus initialization failed.");
+        return;
+    }
+    main_thread = std::jthread([this](std::stop_token st) { Main(st); });
+    running = true;
+    Send(Direction::Host, Message::StartOK);
+}
+
+void OpusDecoder::Main(std::stop_token stop_token) {
+    Common::SetCurrentThreadName("DSP_OpusDecoder_Main");
+
+    while (!stop_token.stop_requested()) {
+        auto msg = Receive(Direction::DSP, stop_token);
+        switch (msg) {
+        case Shutdown:
+            Send(Direction::Host, Message::ShutdownOK);
+            return;
+
+        case GetWorkBufferSize: {
+            auto channel_count = static_cast<s32>(shared_memory->host_send_data[0]);
+
+            ASSERT(IsValidChannelCount(channel_count));
+
+            shared_memory->dsp_return_data[0] = OpusDecodeObject::GetWorkBufferSize(channel_count);
+            Send(Direction::Host, Message::GetWorkBufferSizeOK);
+        } break;
+
+        case InitializeDecodeObject: {
+            auto buffer = shared_memory->host_send_data[0];
+            auto buffer_size = shared_memory->host_send_data[1];
+            auto sample_rate = static_cast<s32>(shared_memory->host_send_data[2]);
+            auto channel_count = static_cast<s32>(shared_memory->host_send_data[3]);
+
+            ASSERT(sample_rate >= 0);
+            ASSERT(IsValidChannelCount(channel_count));
+            ASSERT(buffer_size >= OpusDecodeObject::GetWorkBufferSize(channel_count));
+
+            auto& decoder_object = OpusDecodeObject::Initialize(buffer, buffer);
+            shared_memory->dsp_return_data[0] =
+                decoder_object.InitializeDecoder(sample_rate, channel_count);
+
+            Send(Direction::Host, Message::InitializeDecodeObjectOK);
+        } break;
+
+        case ShutdownDecodeObject: {
+            auto buffer = shared_memory->host_send_data[0];
+            [[maybe_unused]] auto buffer_size = shared_memory->host_send_data[1];
+
+            auto& decoder_object = OpusDecodeObject::Initialize(buffer, buffer);
+            shared_memory->dsp_return_data[0] = decoder_object.Shutdown();
+
+            Send(Direction::Host, Message::ShutdownDecodeObjectOK);
+        } break;
+
+        case DecodeInterleaved: {
+            auto start_time = system.CoreTiming().GetGlobalTimeUs();
+
+            auto buffer = shared_memory->host_send_data[0];
+            auto input_data = shared_memory->host_send_data[1];
+            auto input_data_size = shared_memory->host_send_data[2];
+            auto output_data = shared_memory->host_send_data[3];
+            auto output_data_size = shared_memory->host_send_data[4];
+            auto final_range = static_cast<u32>(shared_memory->host_send_data[5]);
+            auto reset_requested = shared_memory->host_send_data[6];
+
+            u32 decoded_samples{0};
+
+            auto& decoder_object = OpusDecodeObject::Initialize(buffer, buffer);
+            s32 error_code{OPUS_OK};
+            if (reset_requested) {
+                error_code = decoder_object.ResetDecoder();
+            }
+
+            if (error_code == OPUS_OK) {
+                error_code = decoder_object.Decode(decoded_samples, output_data, output_data_size,
+                                                   input_data, input_data_size);
+            }
+
+            if (error_code == OPUS_OK) {
+                if (final_range && decoder_object.GetFinalRange() != final_range) {
+                    error_code = OPUS_INVALID_PACKET;
+                }
+            }
+
+            auto end_time = system.CoreTiming().GetGlobalTimeUs();
+            shared_memory->dsp_return_data[0] = error_code;
+            shared_memory->dsp_return_data[1] = decoded_samples;
+            shared_memory->dsp_return_data[2] = (end_time - start_time).count();
+
+            Send(Direction::Host, Message::DecodeInterleavedOK);
+        } break;
+
+        case MapMemory: {
+            [[maybe_unused]] auto buffer = shared_memory->host_send_data[0];
+            [[maybe_unused]] auto buffer_size = shared_memory->host_send_data[1];
+            Send(Direction::Host, Message::MapMemoryOK);
+        } break;
+
+        case UnmapMemory: {
+            [[maybe_unused]] auto buffer = shared_memory->host_send_data[0];
+            [[maybe_unused]] auto buffer_size = shared_memory->host_send_data[1];
+            Send(Direction::Host, Message::UnmapMemoryOK);
+        } break;
+
+        case GetWorkBufferSizeForMultiStream: {
+            auto total_stream_count = static_cast<s32>(shared_memory->host_send_data[0]);
+            auto stereo_stream_count = static_cast<s32>(shared_memory->host_send_data[1]);
+
+            ASSERT(IsValidMultiStreamStreamCounts(total_stream_count, stereo_stream_count));
+
+            shared_memory->dsp_return_data[0] = OpusMultiStreamDecodeObject::GetWorkBufferSize(
+                total_stream_count, stereo_stream_count);
+            Send(Direction::Host, Message::GetWorkBufferSizeForMultiStreamOK);
+        } break;
+
+        case InitializeMultiStreamDecodeObject: {
+            auto buffer = shared_memory->host_send_data[0];
+            auto buffer_size = shared_memory->host_send_data[1];
+            auto sample_rate = static_cast<s32>(shared_memory->host_send_data[2]);
+            auto channel_count = static_cast<s32>(shared_memory->host_send_data[3]);
+            auto total_stream_count = static_cast<s32>(shared_memory->host_send_data[4]);
+            auto stereo_stream_count = static_cast<s32>(shared_memory->host_send_data[5]);
+            // Nintendo seem to have a bug here, they try to use &host_send_data[6] for the channel
+            // mappings, but [6] is never set, and there is not enough room in the argument data for
+            // more than 40 channels, when 255 are possible.
+            // It also means the mapping values are undefined, though likely always 0,
+            // and the mappings given by the game are ignored. The mappings are copied to this
+            // dedicated buffer host side, so let's do as intended.
+            auto mappings = shared_memory->channel_mapping.data();
+
+            ASSERT(IsValidMultiStreamStreamCounts(total_stream_count, stereo_stream_count));
+            ASSERT(sample_rate >= 0);
+            ASSERT(buffer_size >= OpusMultiStreamDecodeObject::GetWorkBufferSize(
+                                      total_stream_count, stereo_stream_count));
+
+            auto& decoder_object = OpusMultiStreamDecodeObject::Initialize(buffer, buffer);
+            shared_memory->dsp_return_data[0] = decoder_object.InitializeDecoder(
+                sample_rate, total_stream_count, channel_count, stereo_stream_count, mappings);
+
+            Send(Direction::Host, Message::InitializeMultiStreamDecodeObjectOK);
+        } break;
+
+        case ShutdownMultiStreamDecodeObject: {
+            auto buffer = shared_memory->host_send_data[0];
+            [[maybe_unused]] auto buffer_size = shared_memory->host_send_data[1];
+
+            auto& decoder_object = OpusMultiStreamDecodeObject::Initialize(buffer, buffer);
+            shared_memory->dsp_return_data[0] = decoder_object.Shutdown();
+
+            Send(Direction::Host, Message::ShutdownMultiStreamDecodeObjectOK);
+        } break;
+
+        case DecodeInterleavedForMultiStream: {
+            auto start_time = system.CoreTiming().GetGlobalTimeUs();
+
+            auto buffer = shared_memory->host_send_data[0];
+            auto input_data = shared_memory->host_send_data[1];
+            auto input_data_size = shared_memory->host_send_data[2];
+            auto output_data = shared_memory->host_send_data[3];
+            auto output_data_size = shared_memory->host_send_data[4];
+            auto final_range = static_cast<u32>(shared_memory->host_send_data[5]);
+            auto reset_requested = shared_memory->host_send_data[6];
+
+            u32 decoded_samples{0};
+
+            auto& decoder_object = OpusMultiStreamDecodeObject::Initialize(buffer, buffer);
+            s32 error_code{OPUS_OK};
+            if (reset_requested) {
+                error_code = decoder_object.ResetDecoder();
+            }
+
+            if (error_code == OPUS_OK) {
+                error_code = decoder_object.Decode(decoded_samples, output_data, output_data_size,
+                                                   input_data, input_data_size);
+            }
+
+            if (error_code == OPUS_OK) {
+                if (final_range && decoder_object.GetFinalRange() != final_range) {
+                    error_code = OPUS_INVALID_PACKET;
+                }
+            }
+
+            auto end_time = system.CoreTiming().GetGlobalTimeUs();
+            shared_memory->dsp_return_data[0] = error_code;
+            shared_memory->dsp_return_data[1] = decoded_samples;
+            shared_memory->dsp_return_data[2] = (end_time - start_time).count();
+
+            Send(Direction::Host, Message::DecodeInterleavedForMultiStreamOK);
+        } break;
+
+        default:
+            LOG_ERROR(Service_Audio, "Invalid OpusDecoder command {}", msg);
+            continue;
+        }
+    }
+}
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/apps/opus/opus_decoder.h b/src/audio_core/adsp/apps/opus/opus_decoder.h
new file mode 100644
index 000000000..fcb89bb40
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/opus_decoder.h
@@ -0,0 +1,92 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <memory>
+#include <thread>
+
+#include "audio_core/adsp/apps/opus/shared_memory.h"
+#include "audio_core/adsp/mailbox.h"
+#include "common/common_types.h"
+
+namespace Core {
+class System;
+} // namespace Core
+
+namespace AudioCore::ADSP::OpusDecoder {
+
+enum Message : u32 {
+    Invalid = 0,
+    Start = 1,
+    Shutdown = 2,
+    StartOK = 11,
+    ShutdownOK = 12,
+    GetWorkBufferSize = 21,
+    InitializeDecodeObject = 22,
+    ShutdownDecodeObject = 23,
+    DecodeInterleaved = 24,
+    MapMemory = 25,
+    UnmapMemory = 26,
+    GetWorkBufferSizeForMultiStream = 27,
+    InitializeMultiStreamDecodeObject = 28,
+    ShutdownMultiStreamDecodeObject = 29,
+    DecodeInterleavedForMultiStream = 30,
+
+    GetWorkBufferSizeOK = 41,
+    InitializeDecodeObjectOK = 42,
+    ShutdownDecodeObjectOK = 43,
+    DecodeInterleavedOK = 44,
+    MapMemoryOK = 45,
+    UnmapMemoryOK = 46,
+    GetWorkBufferSizeForMultiStreamOK = 47,
+    InitializeMultiStreamDecodeObjectOK = 48,
+    ShutdownMultiStreamDecodeObjectOK = 49,
+    DecodeInterleavedForMultiStreamOK = 50,
+};
+
+/**
+ * The AudioRenderer application running on the ADSP.
+ */
+class OpusDecoder {
+public:
+    explicit OpusDecoder(Core::System& system);
+    ~OpusDecoder();
+
+    bool IsRunning() const noexcept {
+        return running;
+    }
+
+    void Send(Direction dir, u32 message);
+    u32 Receive(Direction dir, std::stop_token stop_token = {});
+
+    void SetSharedMemory(SharedMemory& shared_memory_) {
+        shared_memory = &shared_memory_;
+    }
+
+private:
+    /**
+     * Initializing thread, launched at audio_core boot to avoid blocking the main emu boot thread.
+     */
+    void Init(std::stop_token stop_token);
+    /**
+     * Main OpusDecoder thread, responsible for processing the incoming Opus packets.
+     */
+    void Main(std::stop_token stop_token);
+
+    /// Core system
+    Core::System& system;
+    /// Mailbox to communicate messages with the host, drives the main thread
+    Mailbox mailbox;
+    /// Init thread
+    std::jthread init_thread{};
+    /// Main thread
+    std::jthread main_thread{};
+    /// The current state
+    bool running{};
+    /// Structure shared with the host, input data set by the host before sending a mailbox message,
+    /// and the responses are written back by the OpusDecoder.
+    SharedMemory* shared_memory{};
+};
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/apps/opus/opus_multistream_decode_object.cpp b/src/audio_core/adsp/apps/opus/opus_multistream_decode_object.cpp
new file mode 100644
index 000000000..f6d362e68
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/opus_multistream_decode_object.cpp
@@ -0,0 +1,111 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "audio_core/adsp/apps/opus/opus_multistream_decode_object.h"
+#include "common/assert.h"
+
+namespace AudioCore::ADSP::OpusDecoder {
+
+namespace {
+bool IsValidChannelCount(u32 channel_count) {
+    return channel_count == 1 || channel_count == 2;
+}
+
+bool IsValidStreamCounts(u32 total_stream_count, u32 stereo_stream_count) {
+    return total_stream_count > 0 && stereo_stream_count > 0 &&
+           stereo_stream_count <= total_stream_count && IsValidChannelCount(total_stream_count);
+}
+} // namespace
+
+u32 OpusMultiStreamDecodeObject::GetWorkBufferSize(u32 total_stream_count,
+                                                   u32 stereo_stream_count) {
+    if (IsValidStreamCounts(total_stream_count, stereo_stream_count)) {
+        return static_cast<u32>(sizeof(OpusMultiStreamDecodeObject)) +
+               opus_multistream_decoder_get_size(total_stream_count, stereo_stream_count);
+    }
+    return 0;
+}
+
+OpusMultiStreamDecodeObject& OpusMultiStreamDecodeObject::Initialize(u64 buffer, u64 buffer2) {
+    auto* new_decoder = reinterpret_cast<OpusMultiStreamDecodeObject*>(buffer);
+    auto* comparison = reinterpret_cast<OpusMultiStreamDecodeObject*>(buffer2);
+
+    if (new_decoder->magic == DecodeMultiStreamObjectMagic) {
+        if (!new_decoder->initialized ||
+            (new_decoder->initialized && new_decoder->self == comparison)) {
+            new_decoder->state_valid = true;
+        }
+    } else {
+        new_decoder->initialized = false;
+        new_decoder->state_valid = true;
+    }
+    return *new_decoder;
+}
+
+s32 OpusMultiStreamDecodeObject::InitializeDecoder(u32 sample_rate, u32 total_stream_count,
+                                                   u32 channel_count, u32 stereo_stream_count,
+                                                   u8* mappings) {
+    if (!state_valid) {
+        return OPUS_INVALID_STATE;
+    }
+
+    if (initialized) {
+        return OPUS_OK;
+    }
+
+    // See OpusDecodeObject::InitializeDecoder for an explanation of this
+    decoder = (LibOpusMSDecoder*)(this + 1);
+    s32 ret = opus_multistream_decoder_init(decoder, sample_rate, channel_count, total_stream_count,
+                                            stereo_stream_count, mappings);
+    if (ret == OPUS_OK) {
+        magic = DecodeMultiStreamObjectMagic;
+        initialized = true;
+        state_valid = true;
+        self = this;
+        final_range = 0;
+    }
+    return ret;
+}
+
+s32 OpusMultiStreamDecodeObject::Shutdown() {
+    if (!state_valid) {
+        return OPUS_INVALID_STATE;
+    }
+
+    if (initialized) {
+        magic = 0x0;
+        initialized = false;
+        state_valid = false;
+        self = nullptr;
+        final_range = 0;
+        decoder = nullptr;
+    }
+    return OPUS_OK;
+}
+
+s32 OpusMultiStreamDecodeObject::ResetDecoder() {
+    return opus_multistream_decoder_ctl(decoder, OPUS_RESET_STATE);
+}
+
+s32 OpusMultiStreamDecodeObject::Decode(u32& out_sample_count, u64 output_data,
+                                        u64 output_data_size, u64 input_data, u64 input_data_size) {
+    ASSERT(initialized);
+    out_sample_count = 0;
+
+    if (!state_valid) {
+        return OPUS_INVALID_STATE;
+    }
+
+    auto ret_code_or_samples = opus_multistream_decode(
+        decoder, reinterpret_cast<const u8*>(input_data), static_cast<opus_int32>(input_data_size),
+        reinterpret_cast<opus_int16*>(output_data), static_cast<opus_int32>(output_data_size), 0);
+
+    if (ret_code_or_samples < OPUS_OK) {
+        return ret_code_or_samples;
+    }
+
+    out_sample_count = ret_code_or_samples;
+    return opus_multistream_decoder_ctl(decoder, OPUS_GET_FINAL_RANGE_REQUEST, &final_range);
+}
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/apps/opus/opus_multistream_decode_object.h b/src/audio_core/adsp/apps/opus/opus_multistream_decode_object.h
new file mode 100644
index 000000000..93558ded5
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/opus_multistream_decode_object.h
@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include <opus_multistream.h>
+
+#include "common/common_types.h"
+
+namespace AudioCore::ADSP::OpusDecoder {
+using LibOpusMSDecoder = ::OpusMSDecoder;
+static constexpr u32 DecodeMultiStreamObjectMagic = 0xDEADBEEF;
+
+class OpusMultiStreamDecodeObject {
+public:
+    static u32 GetWorkBufferSize(u32 total_stream_count, u32 stereo_stream_count);
+    static OpusMultiStreamDecodeObject& Initialize(u64 buffer, u64 buffer2);
+
+    s32 InitializeDecoder(u32 sample_rate, u32 total_stream_count, u32 channel_count,
+                          u32 stereo_stream_count, u8* mappings);
+    s32 Shutdown();
+    s32 ResetDecoder();
+    s32 Decode(u32& out_sample_count, u64 output_data, u64 output_data_size, u64 input_data,
+               u64 input_data_size);
+    u32 GetFinalRange() const noexcept {
+        return final_range;
+    }
+
+private:
+    u32 magic;
+    bool initialized;
+    bool state_valid;
+    OpusMultiStreamDecodeObject* self;
+    u32 final_range;
+    LibOpusMSDecoder* decoder;
+};
+static_assert(std::is_trivially_constructible_v<OpusMultiStreamDecodeObject>);
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/apps/opus/shared_memory.h b/src/audio_core/adsp/apps/opus/shared_memory.h
new file mode 100644
index 000000000..c696731ed
--- /dev/null
+++ b/src/audio_core/adsp/apps/opus/shared_memory.h
@@ -0,0 +1,17 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/common_funcs.h"
+#include "common/common_types.h"
+
+namespace AudioCore::ADSP::OpusDecoder {
+
+struct SharedMemory {
+    std::array<u8, 0x100> channel_mapping{};
+    std::array<u64, 16> host_send_data{};
+    std::array<u64, 16> dsp_return_data{};
+};
+
+} // namespace AudioCore::ADSP::OpusDecoder
diff --git a/src/audio_core/adsp/mailbox.h b/src/audio_core/adsp/mailbox.h
index c31b73717..1dd40ebfa 100644
--- a/src/audio_core/adsp/mailbox.h
+++ b/src/audio_core/adsp/mailbox.h
@@ -3,6 +3,8 @@
 
 #pragma once
 
+#include <span>
+
 #include "common/bounded_threadsafe_queue.h"
 #include "common/common_types.h"
 
@@ -19,11 +21,6 @@ enum class Direction : u32 {
     DSP,
 };
 
-struct MailboxMessage {
-    u32 msg;
-    std::span<u8> data;
-};
-
 class Mailbox {
 public:
     void Initialize(AppMailboxId id_) {
@@ -35,25 +32,19 @@ public:
         return id;
     }
 
-    void Send(Direction dir, MailboxMessage&& message) {
+    void Send(Direction dir, u32 message) {
         auto& queue = dir == Direction::Host ? host_queue : adsp_queue;
-        queue.EmplaceWait(std::move(message));
+        queue.EmplaceWait(message);
     }
 
-    MailboxMessage Receive(Direction dir, bool block = true) {
+    u32 Receive(Direction dir, std::stop_token stop_token = {}) {
         auto& queue = dir == Direction::Host ? host_queue : adsp_queue;
-        MailboxMessage t;
-        if (block) {
-            queue.PopWait(t);
-        } else {
-            queue.TryPop(t);
-        }
-        return t;
+        return queue.PopWait(stop_token);
     }
 
     void Reset() {
         id = AppMailboxId::Invalid;
-        MailboxMessage t;
+        u32 t{};
         while (host_queue.TryPop(t)) {
         }
         while (adsp_queue.TryPop(t)) {
@@ -62,8 +53,8 @@ public:
 
 private:
     AppMailboxId id{0};
-    Common::SPSCQueue<MailboxMessage> host_queue;
-    Common::SPSCQueue<MailboxMessage> adsp_queue;
+    Common::SPSCQueue<u32> host_queue;
+    Common::SPSCQueue<u32> adsp_queue;
 };
 
 } // namespace AudioCore::ADSP