public static void ProcessBiquadFilter(ReadOnlySpan <BiquadFilterParameter> parameters, Span <BiquadFilterState> states, Span <float> outputBuffer, ReadOnlySpan <float> inputBuffer, uint sampleCount)
{
for (int stageIndex = 0; stageIndex < parameters.Length; stageIndex++)
{
BiquadFilterParameter parameter = parameters[stageIndex];
ref BiquadFilterState state = ref states[stageIndex];
float a0 = FixedPointHelper.ToFloat(parameter.Numerator[0], FixedPointPrecisionForParameter);
float a1 = FixedPointHelper.ToFloat(parameter.Numerator[1], FixedPointPrecisionForParameter);
float a2 = FixedPointHelper.ToFloat(parameter.Numerator[2], FixedPointPrecisionForParameter);
float b1 = FixedPointHelper.ToFloat(parameter.Denominator[0], FixedPointPrecisionForParameter);
float b2 = FixedPointHelper.ToFloat(parameter.Denominator[1], FixedPointPrecisionForParameter);
for (int i = 0; i < sampleCount; i++)
{
float input = inputBuffer[i];
float output = input * a0 + state.State0 * a1 + state.State1 * a2 + state.State2 * b1 + state.State3 * b2;
state.State1 = state.State0;
state.State0 = input;
state.State3 = state.State2;
state.State2 = output;
outputBuffer[i] = output;
}
}
public static void ProcessBiquadFilter(ref BiquadFilterParameter parameter, ref BiquadFilterState state, Span <float> outputBuffer, ReadOnlySpan <float> inputBuffer, uint sampleCount)
{
float a0 = FixedPointHelper.ToFloat(parameter.Numerator[0], FixedPointPrecisionForParameter);
float a1 = FixedPointHelper.ToFloat(parameter.Numerator[1], FixedPointPrecisionForParameter);
float a2 = FixedPointHelper.ToFloat(parameter.Numerator[2], FixedPointPrecisionForParameter);
float b1 = FixedPointHelper.ToFloat(parameter.Denominator[0], FixedPointPrecisionForParameter);
float b2 = FixedPointHelper.ToFloat(parameter.Denominator[1], FixedPointPrecisionForParameter);
for (int i = 0; i < sampleCount; i++)
{
float input = inputBuffer[i];
float output = input * a0 + state.State0;
state.State0 = input * a1 + output * b1 + state.State1;
state.State1 = input * a2 + output * b2;
outputBuffer[i] = output;
}
}
public static int Decode(Span <short> output, ReadOnlySpan <byte> input, int startSampleOffset, int endSampleOffset, int offset, int count, ReadOnlySpan <short> coefficients, ref AdpcmLoopContext loopContext)
{
if (input.IsEmpty || endSampleOffset < startSampleOffset)
{
return(0);
}
byte predScale = (byte)loopContext.PredScale;
byte scale = (byte)(predScale & 0xF);
byte coefficientIndex = (byte)((predScale >> 4) & 0xF);
short history0 = loopContext.History0;
short history1 = loopContext.History1;
short coefficient0 = coefficients[coefficientIndex * 2 + 0];
short coefficient1 = coefficients[coefficientIndex * 2 + 1];
int decodedCount = Math.Min(count, endSampleOffset - startSampleOffset - offset);
int nibbles = GetNibblesFromSampleCount(offset + startSampleOffset);
int remaining = decodedCount;
int outputBufferIndex = 0;
int inputIndex = 0;
ReadOnlySpan <byte> targetInput;
targetInput = input.Slice(nibbles / 2);
while (remaining > 0)
{
int samplesCount;
if (((uint)nibbles % NibblesPerFrame) == 0)
{
predScale = targetInput[inputIndex++];
scale = (byte)(predScale & 0xF);
coefficientIndex = (byte)((predScale >> 4) & 0xF);
coefficient0 = coefficients[coefficientIndex * 2 + 0];
coefficient1 = coefficients[coefficientIndex * 2 + 1];
nibbles += 2;
samplesCount = Math.Min(remaining, SamplesPerFrame);
}
else
{
samplesCount = 1;
}
int scaleFixedPoint = FixedPointHelper.ToFixed(1.0f, FixedPointPrecision) << scale;
if (samplesCount < SamplesPerFrame)
{
for (int i = 0; i < samplesCount; i++)
{
int value = targetInput[inputIndex];
int sample;
if ((nibbles & 1) != 0)
{
sample = (value << 28) >> 28;
inputIndex++;
}
else
{
sample = (value << 24) >> 28;
}
nibbles++;
int prediction = coefficient0 * history0 + coefficient1 * history1;
sample = FixedPointHelper.RoundUpAndToInt(sample * scaleFixedPoint + prediction, FixedPointPrecision);
short saturatedSample = Saturate(sample);
history1 = history0;
history0 = saturatedSample;
output[outputBufferIndex++] = saturatedSample;
remaining--;
}
}
else
{
for (int i = 0; i < SamplesPerFrame / 2; i++)
{
int value = targetInput[inputIndex];
int sample0;
int sample1;
sample0 = (value << 24) >> 28;
sample1 = (value << 28) >> 28;
inputIndex++;
int prediction0 = coefficient0 * history0 + coefficient1 * history1;
sample0 = FixedPointHelper.RoundUpAndToInt(sample0 * scaleFixedPoint + prediction0, FixedPointPrecision);
short saturatedSample0 = Saturate(sample0);
int prediction1 = coefficient0 * saturatedSample0 + coefficient1 * history0;
sample1 = FixedPointHelper.RoundUpAndToInt(sample1 * scaleFixedPoint + prediction1, FixedPointPrecision);
short saturatedSample1 = Saturate(sample1);
history1 = saturatedSample0;
history0 = saturatedSample1;
output[outputBufferIndex++] = saturatedSample0;
output[outputBufferIndex++] = saturatedSample1;
}
nibbles += SamplesPerFrame;
remaining -= SamplesPerFrame;
}
}
loopContext.PredScale = predScale;
loopContext.History0 = history0;
loopContext.History1 = history1;
return(decodedCount);
}
