private FirstOrderFilterQ31_64x64(FirstOrderFilterQ31_64x64 other)
{
this.a1 = other.a1;
this.b0 = other.b0;
this.b1 = other.b1;
this.postShift = other.postShift;
this.x1 = other.x1;
this.y1 = other.y1;
}
public FirstOrderFilterQ31_64x64(double b0, double b1, double a0, double a1)
{
a1 /= a0;
b0 /= a0;
b1 /= a0;
// see remarks in BiquadQ31_64x64..ctor()
this.postShift = Q63.GetQ31_64x64_PostShift(a1, b0, b1);
double coefficientScaling = Math.Pow(2.0, -this.postShift);
this.a1 = new Q63(coefficientScaling * a1, Q63.MaximumFractionalBits);
this.b0 = new Q63(coefficientScaling * b0, Q63.MaximumFractionalBits);
this.b1 = new Q63(coefficientScaling * b1, Q63.MaximumFractionalBits);
this.x1 = 0;
this.y1 = 0;
}