CoreAudio::HLE: Add FFmpeg aac decoder

src/audio_core/hle/decoder.h

@@ -0,0 +1,68 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <memory>
+#include <optional>
+#include <vector>
+#include "common/common_types.h"
+#include "common/swap.h"
+#include "core/core.h"
+
+namespace AudioCore::HLE {
+
+enum class DecoderCommand : u16 {
+    Init,
+    Decode,
+    Unknown,
+};
+
+enum class DecoderCodec : u16 {
+    None,
+    AAC,
+};
+
+struct BinaryRequest {
+    enum_le<DecoderCodec> codec =
+        DecoderCodec::None; // this is a guess. until now only 0x1 was observed here
+    enum_le<DecoderCommand> cmd = DecoderCommand::Init;
+    u32_le fixed = 0;
+    u32_le src_addr = 0;
+    u32_le size = 0;
+    u32_le dst_addr_ch0 = 0;
+    u32_le dst_addr_ch1 = 0;
+    u32_le unknown1 = 0;
+    u32_le unknown2 = 0;
+};
+static_assert(sizeof(BinaryRequest) == 32, "Unexpected struct size for BinaryRequest");
+
+struct BinaryResponse {
+    enum_le<DecoderCodec> codec =
+        DecoderCodec::None; // this could be something else. until now only 0x1 was observed here
+    enum_le<DecoderCommand> cmd = DecoderCommand::Init;
+    u32_le unknown1 = 0;
+    u32_le unknown2 = 0;
+    u32_le num_channels = 0; // this is a guess, so far I only observed 2 here
+    u32_le size = 0;
+    u32_le unknown3 = 0;
+    u32_le unknown4 = 0;
+    u32_le num_samples = 0; // this is a guess, so far I only observed 1024 here
+};
+static_assert(sizeof(BinaryResponse) == 32, "Unexpected struct size for BinaryResponse");
+
+class DecoderBase {
+public:
+    virtual ~DecoderBase(){};
+    virtual std::optional<BinaryResponse> ProcessRequest(const BinaryRequest& request) = 0;
+};
+
+class NullDecoder final : public DecoderBase {
+public:
+    NullDecoder();
+    ~NullDecoder() override;
+    std::optional<BinaryResponse> ProcessRequest(const BinaryRequest& request) override;
+};
+
+} // namespace AudioCore::HLE