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using Ryujinx.Audio.Renderer.Server.Upsampler;
using Ryujinx.Common.Memory;
using System;
using System.Diagnostics;
using System.Numerics;
using System.Runtime.CompilerServices;
namespace Ryujinx.Audio.Renderer.Dsp
{
public class UpsamplerHelper
{
private const int HistoryLength = UpsamplerBufferState.HistoryLength;
private const int FilterBankLength = 20;
// Bank0 = [0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];
private const int Bank0CenterIndex = 9;
private static readonly Array20<float> _bank1 = PrecomputeFilterBank(1.0f / 6.0f);
private static readonly Array20<float> _bank2 = PrecomputeFilterBank(2.0f / 6.0f);
private static readonly Array20<float> _bank3 = PrecomputeFilterBank(3.0f / 6.0f);
private static readonly Array20<float> _bank4 = PrecomputeFilterBank(4.0f / 6.0f);
private static readonly Array20<float> _bank5 = PrecomputeFilterBank(5.0f / 6.0f);
private static Array20<float> PrecomputeFilterBank(float offset)
{
float Sinc(float x)
{
if (x == 0)
{
return 1.0f;
}
return (MathF.Sin(MathF.PI * x) / (MathF.PI * x));
}
float BlackmanWindow(float x)
{
const float A = 0.18f;
const float A0 = 0.5f - 0.5f * A;
const float A1 = -0.5f;
const float A2 = 0.5f * A;
return A0 + A1 * MathF.Cos(2 * MathF.PI * x) + A2 * MathF.Cos(4 * MathF.PI * x);
}
Array20<float> result = new();
for (int i = 0; i < FilterBankLength; i++)
{
float x = (Bank0CenterIndex - i) + offset;
result[i] = Sinc(x) * BlackmanWindow(x / FilterBankLength + 0.5f);
}
return result;
}
// Polyphase upsampling algorithm
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static void Upsample(Span<float> outputBuffer, ReadOnlySpan<float> inputBuffer, int outputSampleCount, int inputSampleCount, ref UpsamplerBufferState state)
{
if (!state.Initialized)
{
state.Scale = inputSampleCount switch
{
40 => 6.0f,
80 => 3.0f,
160 => 1.5f,
_ => throw new ArgumentOutOfRangeException(nameof(inputSampleCount), inputSampleCount, null),
};
state.Initialized = true;
}
if (outputSampleCount == 0)
{
return;
}
float DoFilterBank(ref UpsamplerBufferState state, in Array20<float> bank)
{
float result = 0.0f;
Debug.Assert(state.History.Length == HistoryLength);
Debug.Assert(bank.Length == FilterBankLength);
int curIdx = 0;
if (Vector.IsHardwareAccelerated)
{
// Do SIMD-accelerated block operations where possible.
// Only about a 2x speedup since filter bank length is short
int stopIdx = FilterBankLength - (FilterBankLength % Vector<float>.Count);
while (curIdx < stopIdx)
{
result += Vector.Dot(
new Vector<float>(bank.AsSpan().Slice(curIdx, Vector<float>.Count)),
new Vector<float>(state.History.AsSpan().Slice(curIdx, Vector<float>.Count)));
curIdx += Vector<float>.Count;
}
}
while (curIdx < FilterBankLength)
{
result += bank[curIdx] * state.History[curIdx];
curIdx++;
}
return result;
}
[MethodImpl(MethodImplOptions.AggressiveInlining)]
void NextInput(ref UpsamplerBufferState state, float input)
{
state.History.AsSpan()[1..].CopyTo(state.History.AsSpan());
state.History[HistoryLength - 1] = input;
}
int inputBufferIndex = 0;
switch (state.Scale)
{
case 6.0f:
for (int i = 0; i < outputSampleCount; i++)
{
switch (state.Phase)
{
case 0:
NextInput(ref state, inputBuffer[inputBufferIndex++]);
outputBuffer[i] = state.History[Bank0CenterIndex];
break;
case 1:
outputBuffer[i] = DoFilterBank(ref state, _bank1);
break;
case 2:
outputBuffer[i] = DoFilterBank(ref state, _bank2);
break;
case 3:
outputBuffer[i] = DoFilterBank(ref state, _bank3);
break;
case 4:
outputBuffer[i] = DoFilterBank(ref state, _bank4);
break;
case 5:
outputBuffer[i] = DoFilterBank(ref state, _bank5);
break;
}
state.Phase = (state.Phase + 1) % 6;
}
break;
case 3.0f:
for (int i = 0; i < outputSampleCount; i++)
{
switch (state.Phase)
{
case 0:
NextInput(ref state, inputBuffer[inputBufferIndex++]);
outputBuffer[i] = state.History[Bank0CenterIndex];
break;
case 1:
outputBuffer[i] = DoFilterBank(ref state, _bank2);
break;
case 2:
outputBuffer[i] = DoFilterBank(ref state, _bank4);
break;
}
state.Phase = (state.Phase + 1) % 3;
}
break;
case 1.5f:
// Upsample by 3 then decimate by 2.
for (int i = 0; i < outputSampleCount; i++)
{
switch (state.Phase)
{
case 0:
NextInput(ref state, inputBuffer[inputBufferIndex++]);
outputBuffer[i] = state.History[Bank0CenterIndex];
break;
case 1:
outputBuffer[i] = DoFilterBank(ref state, _bank4);
break;
case 2:
NextInput(ref state, inputBuffer[inputBufferIndex++]);
outputBuffer[i] = DoFilterBank(ref state, _bank2);
break;
}
state.Phase = (state.Phase + 1) % 3;
}
break;
default:
throw new ArgumentOutOfRangeException(nameof(state), state.Scale, null);
}
}
}
}
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