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https://github.com/ryujinx-mirror/ryujinx.git
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175 lines
6.8 KiB
C#
175 lines
6.8 KiB
C#
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using Ryujinx.Audio.Renderer.Server.Upsampler;
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using Ryujinx.Common.Memory;
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using System;
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using System.Diagnostics;
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using System.Runtime.CompilerServices;
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namespace Ryujinx.Audio.Renderer.Dsp
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{
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public class UpsamplerHelper
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{
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private const int HistoryLength = UpsamplerBufferState.HistoryLength;
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private const int FilterBankLength = 20;
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// Bank0 = [0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
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private const int Bank0CenterIndex = 9;
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private static readonly Array20<float> Bank1 = PrecomputeFilterBank(1.0f / 6.0f);
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private static readonly Array20<float> Bank2 = PrecomputeFilterBank(2.0f / 6.0f);
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private static readonly Array20<float> Bank3 = PrecomputeFilterBank(3.0f / 6.0f);
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private static readonly Array20<float> Bank4 = PrecomputeFilterBank(4.0f / 6.0f);
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private static readonly Array20<float> Bank5 = PrecomputeFilterBank(5.0f / 6.0f);
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private static Array20<float> PrecomputeFilterBank(float offset)
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{
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float Sinc(float x)
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{
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if (x == 0)
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{
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return 1.0f;
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}
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return (MathF.Sin(MathF.PI * x) / (MathF.PI * x));
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}
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float BlackmanWindow(float x)
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{
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const float a = 0.18f;
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const float a0 = 0.5f - 0.5f * a;
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const float a1 = -0.5f;
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const float a2 = 0.5f * a;
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return a0 + a1 * MathF.Cos(2 * MathF.PI * x) + a2 * MathF.Cos(4 * MathF.PI * x);
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}
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Array20<float> result = new Array20<float>();
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for (int i = 0; i < FilterBankLength; i++)
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{
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float x = (Bank0CenterIndex - i) + offset;
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result[i] = Sinc(x) * BlackmanWindow(x / FilterBankLength + 0.5f);
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}
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return result;
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}
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// Polyphase upsampling algorithm
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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public static void Upsample(Span<float> outputBuffer, ReadOnlySpan<float> inputBuffer, int outputSampleCount, int inputSampleCount, ref UpsamplerBufferState state)
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{
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if (!state.Initialized)
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{
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state.Scale = inputSampleCount switch
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{
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40 => 6.0f,
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80 => 3.0f,
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160 => 1.5f,
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_ => throw new ArgumentOutOfRangeException()
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};
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state.Initialized = true;
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}
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if (outputSampleCount == 0)
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{
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return;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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float DoFilterBank(ref UpsamplerBufferState state, in Array20<float> bank)
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{
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float result = 0.0f;
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Debug.Assert(state.History.Length == HistoryLength);
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Debug.Assert(bank.Length == FilterBankLength);
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for (int j = 0; j < FilterBankLength; j++)
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{
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result += bank[j] * state.History[j];
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}
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return result;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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void NextInput(ref UpsamplerBufferState state, float input)
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{
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state.History.AsSpan().Slice(1).CopyTo(state.History.AsSpan());
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state.History[HistoryLength - 1] = input;
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}
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int inputBufferIndex = 0;
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switch (state.Scale)
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{
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case 6.0f:
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for (int i = 0; i < outputSampleCount; i++)
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{
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switch (state.Phase)
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{
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case 0:
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NextInput(ref state, inputBuffer[inputBufferIndex++]);
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outputBuffer[i] = state.History[Bank0CenterIndex];
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break;
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case 1:
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outputBuffer[i] = DoFilterBank(ref state, Bank1);
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break;
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case 2:
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outputBuffer[i] = DoFilterBank(ref state, Bank2);
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break;
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case 3:
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outputBuffer[i] = DoFilterBank(ref state, Bank3);
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break;
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case 4:
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outputBuffer[i] = DoFilterBank(ref state, Bank4);
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break;
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case 5:
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outputBuffer[i] = DoFilterBank(ref state, Bank5);
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break;
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}
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state.Phase = (state.Phase + 1) % 6;
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}
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break;
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case 3.0f:
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for (int i = 0; i < outputSampleCount; i++)
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{
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switch (state.Phase)
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{
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case 0:
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NextInput(ref state, inputBuffer[inputBufferIndex++]);
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outputBuffer[i] = state.History[Bank0CenterIndex];
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break;
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case 1:
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outputBuffer[i] = DoFilterBank(ref state, Bank2);
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break;
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case 2:
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outputBuffer[i] = DoFilterBank(ref state, Bank4);
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break;
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}
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state.Phase = (state.Phase + 1) % 3;
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}
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break;
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case 1.5f:
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// Upsample by 3 then decimate by 2.
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for (int i = 0; i < outputSampleCount; i++)
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{
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switch (state.Phase)
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{
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case 0:
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NextInput(ref state, inputBuffer[inputBufferIndex++]);
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outputBuffer[i] = state.History[Bank0CenterIndex];
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break;
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case 1:
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outputBuffer[i] = DoFilterBank(ref state, Bank4);
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break;
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case 2:
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NextInput(ref state, inputBuffer[inputBufferIndex++]);
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outputBuffer[i] = DoFilterBank(ref state, Bank2);
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break;
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}
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state.Phase = (state.Phase + 1) % 3;
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}
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break;
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default:
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throw new ArgumentOutOfRangeException();
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}
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}
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}
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}
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