private static int[] RemoveLastItem(int[] array)
{
return(ArrayUtils.CutArray(array, 0, array.Length - 1));
}
private FlacMethod FindBestLpcMethod(int[] channelSamples, int bitsPerSample, FlacEncodingPolicy policy)
{
if (!policy.LpcOrder.HasValue)
{
return(null);
}
int minLpcOrder = policy.LpcOrder.Value.MinValue;
int maxLpcOrder = Math.Min(policy.LpcOrder.Value.MaxValue,
channelSamples.Length - 1);
double[] r = new double[maxLpcOrder + 1];
parallel.For(0, r.Length, i =>
{
double sum = 0;
for (int j = 0, q = channelSamples.Length - i; j < i; j++, q++)
{
sum += (double)channelSamples[j] * channelSamples[q];
}
for (int j = i, q = 0; j < channelSamples.Length; j++, q++)
{
sum += (double)channelSamples[j] * channelSamples[q];
}
r[i] = sum;
});
FlacMethod[] methods = new FlacMethod[maxLpcOrder];
parallel.For(minLpcOrder, maxLpcOrder + 1, order =>
{
double[] coef = SolveLpc(r, order);
int[] integerCoefficients;
int shift;
int precision;
ConvertLpcCoeficientsToIntegers(coef, out integerCoefficients, out precision, out shift);
IPredictor predictor = PredictorFactory.CreateLpcPredictor(integerCoefficients, shift, ArrayUtils.CutArray(channelSamples, 0, order - 1));
FlacResidualCoefficeints residual = FindBestResidual(channelSamples, order, predictor, policy);
FlacLpcMethodCoefficeints lpcCoefficients = new FlacLpcMethodCoefficeints(
precision, integerCoefficients, shift);
FlacMethod method = new FlacLpcMethod(bitsPerSample, lpcCoefficients, residual);
methods[order - 1] = method;
});
return(FindBestMethod(methods));
}