HwOpus service implementation (#201)

* Started to implement the hwopus service

* Write outputs on decode method, some basic error handling

* Fix buffer size read from header and check

* Fix order of values

Ryujinx.HLE/HOS/Services/Aud/IHardwareOpusDecoderManager.cs

@@ -0,0 +1,72 @@
+using Ryujinx.HLE.HOS.Ipc;
+using System.Collections.Generic;
+
+namespace Ryujinx.HLE.HOS.Services.Aud
+{
+    class IHardwareOpusDecoderManager : IpcService
+    {
+        private Dictionary<int, ServiceProcessRequest> m_Commands;
+
+        public override IReadOnlyDictionary<int, ServiceProcessRequest> Commands => m_Commands;
+
+        public IHardwareOpusDecoderManager()
+        {
+            m_Commands = new Dictionary<int, ServiceProcessRequest>()
+            {
+                { 0, Initialize        },
+                { 1, GetWorkBufferSize }
+            };
+        }
+
+        public long Initialize(ServiceCtx Context)
+        {
+            int SampleRate    = Context.RequestData.ReadInt32();
+            int ChannelsCount = Context.RequestData.ReadInt32();
+
+            MakeObject(Context, new IHardwareOpusDecoder(SampleRate, ChannelsCount));
+
+            return 0;
+        }
+
+        public long GetWorkBufferSize(ServiceCtx Context)
+        {
+            //Note: The sample rate is ignored because it is fixed to 48KHz.
+            int SampleRate    = Context.RequestData.ReadInt32();
+            int ChannelsCount = Context.RequestData.ReadInt32();
+
+            Context.ResponseData.Write(GetOpusDecoderSize(ChannelsCount));
+
+            return 0;
+        }
+
+        private static int GetOpusDecoderSize(int ChannelsCount)
+        {
+            const int SilkDecoderSize = 0x2198;
+
+            if (ChannelsCount < 1 || ChannelsCount > 2)
+            {
+                return 0;
+            }
+
+            int CeltDecoderSize = GetCeltDecoderSize(ChannelsCount);
+
+            int OpusDecoderSize = (ChannelsCount * 0x800 + 0x4807) & -0x800 | 0x50;
+
+            return OpusDecoderSize + SilkDecoderSize + CeltDecoderSize;
+        }
+
+        private static int GetCeltDecoderSize(int ChannelsCount)
+        {
+            const int DecodeBufferSize = 0x2030;
+            const int CeltDecoderSize  = 0x58;
+            const int CeltSigSize      = 0x4;
+            const int Overlap          = 120;
+            const int EBandsCount      = 21;
+
+            return (DecodeBufferSize + Overlap * 4) * ChannelsCount +
+                    EBandsCount * 16 +
+                    CeltDecoderSize +
+                    CeltSigSize;
+        }
+    }
+}