-

- [MethodImpl(MethodImplOptions.AggressiveInlining)]

- public static void ResampleForUpsampler(Span<float> outputBuffer, ReadOnlySpan<float> inputBuffer, float ratio, ref float fraction, int sampleCount)

- {

- // Currently a simple cubic interpolation, assuming duplicated values at edges.

- // TODO: Discover and use algorithm that the switch uses.

-

- int inputBufferIndex = 0;

- int maxIndex = inputBuffer.Length - 1;

- int cubicEnd = inputBuffer.Length - 3;

-

- for (int i = 0; i < sampleCount; i++)

- {

- float s0, s1, s2, s3;

-

- s1 = inputBuffer[inputBufferIndex];

-

- if (inputBufferIndex == 0 || inputBufferIndex > cubicEnd)

- {

- // Clamp interplation values at the ends of the input buffer.

- s0 = inputBuffer[Math.Max(0, inputBufferIndex - 1)];

- s2 = inputBuffer[Math.Min(maxIndex, inputBufferIndex + 1)];

- s3 = inputBuffer[Math.Min(maxIndex, inputBufferIndex + 2)];

- }

- else

- {

- s0 = inputBuffer[inputBufferIndex - 1];

- s2 = inputBuffer[inputBufferIndex + 1];

- s3 = inputBuffer[inputBufferIndex + 2];

- }

-

- float a = s3 - s2 - s0 + s1;

- float b = s0 - s1 - a;

- float c = s2 - s0;

- float d = s1;

-

- float f2 = fraction * fraction;

- float f3 = f2 * fraction;

-

- outputBuffer[i] = a * f3 + b * f2 + c * fraction + d;

-

- fraction += ratio;

- inputBufferIndex += (int)MathF.Truncate(fraction);

-

- fraction -= (int)fraction;

- }

- }