CoreAudio::HLE: Add FFmpeg aac decoder

src/audio_core/hle/decoder.cpp

@@ -0,0 +1,36 @@
+// Copyright 2018 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "audio_core/hle/decoder.h"
+
+namespace AudioCore::HLE {
+
+NullDecoder::NullDecoder() {}
+
+NullDecoder::~NullDecoder() = default;
+
+std::optional<BinaryResponse> NullDecoder::ProcessRequest(const BinaryRequest& request) {
+    BinaryResponse response;
+    switch (request.cmd) {
+    case DecoderCommand::Init:
+    case DecoderCommand::Unknown:
+        std::memcpy(&response, &request, sizeof(response));
+        response.unknown1 = 0x0;
+        return response;
+        break;
+    case DecoderCommand::Decode:
+        response.codec = request.codec;
+        response.cmd = DecoderCommand::Decode;
+        response.num_channels = 2; // Just assume stereo here
+        response.size = request.size;
+        response.num_samples = 1024; // Just assume 1024 here
+        return response;
+        break;
+    default:
+        LOG_ERROR(Audio_DSP, "Got unknown binary request: {}", static_cast<u16>(request.cmd));
+        return {};
+        break;
+    }
+};
+} // namespace AudioCore::HLE