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Ambisonic.cs
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Ambisonic.cs
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using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using System.Globalization;
// Copyright (c) 2007 by Hugh Pyle, inguzaudio.com
namespace DSPUtil
{
public class UHJCoeffs
{
public Complex LX;
public Complex LW;
public Complex LY;
public Complex RX;
public Complex RW;
public Complex RY;
public UHJCoeffs()
{
// Proper UHJ
// Transformation filters
// Gerzon 1985 "Ambisonics in Multichannel Broadcasting and Video"
//
// Coefficients: http://www.york.ac.uk/inst/mustech/3d_audio/ambis2.htm
// Left = (0.0928 + 0.255j)X + (0.4699 - 0.171j)W + (0.3277)Y
// Right= (0.0928 - 0.255j)X + (0.4699 + 0.171j)W - (0.3277)Y
// Higher precision versions on http://en.wikipedia.org/wiki/Ambisonic_UHJ_format
// S = 0.9396926*W + 0.1855740*X
// D = j(-0.3420201*W + 0.5098604*X) + 0.6554516*Y
// Left = (S + D)/2.0 = ( (0.94 - 0.342j)W + (0.1856 + 0.51j)X + 0.655Y )/2
// Right = (S - D)/2.0 = ( (0.94 + 0.342j)W + (0.1856 - 0.51j)X - 0.655Y )/2
// The Mid-Side versions are simpler
// L+R = (0.0928 + 0.255j)X + (0.4699 - 0.171j)W + (0.3277)Y + ((0.0928 - 0.255j)X + (0.4699 + 0.171j)W - (0.3277)Y)
// = (0.1856)X + (0.9398)W
// L-R = (0.0928 + 0.255j)X + (0.4699 - 0.171j)W + (0.3277)Y - ((0.0928 - 0.255j)X + (0.4699 + 0.171j)W - (0.3277)Y)
// = (0.510j)X + (-0.342j)W + (0.6554)Y
// but since we're delaying signal via convolution anyway, not *too* much extra processing to do in LR mode...
LX = new Complex( 0.0927870, 0.25493020);
LW = new Complex( 0.4698463, -0.17101005);
LY = new Complex( 0.3277258, 0.00000000);
RX = new Complex( 0.0927870, -0.25493020);
RW = new Complex( 0.4698463, 0.17101005);
RY = new Complex(-0.3277258, 0.00000000);
}
public UHJCoeffs(double j)
{
// Blumlein with a j*W mix (mucks up the low-mid timbre a little but adds really nice spaciousness)
// For default mic angle of 90 degrees, mulX=mulY=sqrt(2)/2
double mulX = Math.Sqrt(2); // Math.Cos(MathUtil.Radians(_ambiMicAngle / 2));
double mulY = Math.Sqrt(2); // Math.Sin(MathUtil.Radians(_ambiMicAngle / 2));
// Left = (mulX)X + ( - 0.171j)W + (mulY)Y
// Right= (mulX)X + ( + 0.171j)W - (mulY)Y
LW = new Complex(0, -j);
LX = new Complex(mulX, 0);
LY = new Complex(mulY, 0);
RW = new Complex(0, j);
RX = new Complex(mulX, 0);
RY = new Complex(-mulY, 0);
}
public UHJCoeffs(double angleDegrees, double w, double j)
{
// Blumlein with a j*W mix
// For default mic angle of 90 degrees, mulX=mulY=sqrt(2)/2
double mulX = Math.Cos(MathUtil.Radians(angleDegrees / 2));
double mulY = Math.Sin(MathUtil.Radians(angleDegrees / 2));
// Left = (mulX)X + ( - 0.171j)W + (mulY)Y
// Right= (mulX)X + ( + 0.171j)W - (mulY)Y
LW = new Complex(w * MathUtil.INVSQRT2, -j * MathUtil.INVSQRT2);
LX = new Complex(mulX, 0);
LY = new Complex(mulY, 0);
RW = new Complex(w * MathUtil.INVSQRT2, j * MathUtil.INVSQRT2);
RX = new Complex(mulX, 0);
RY = new Complex(-mulY, 0);
}
}
/*
* this intended to become a general multi-band amb decoder
* design is incomplete
*
class Transform
{
public Transform()
{
}
}
struct Band
{
double from;
double to;
}
public class AmbisonicDecoder : SoundObj
{
string _name;
bool _useShelf;
bool _useDistance;
int _inputs;
int _outputs;
bool[] _usesInput;
List<Transform[]> _frequencyBands;
public AmbisonicDecoder(uint sampleRate)
{
_sr = sampleRate;
_usesInput = new bool[4]; // W, X, Y, Z (and so on)
_frequencyBands = new List<Transform[]>();
}
public void Load(XmlDocument config)
{
XmlNode node;
node = config.SelectSingleNode("//Matrix/@Name");
_name = (node == null) ? null : node.Value;
node = config.SelectSingleNode("//Matrix/@Outputs");
_outputs = (node == null) ? 0 : int.Parse(node.Value, CultureInfo.InvariantCulture);
node = config.SelectSingleNode("//Matrix/@Shelf");
_useShelf = (node == null) ? false : bool.Parse(node.Value, CultureInfo.InvariantCulture);
node = config.SelectSingleNode("//Matrix/@Distance");
_useDistance = (node == null) ? false : bool.Parse(node.Value, CultureInfo.InvariantCulture);
if (_useShelf)
{
}
else
{
// Start with a "null-band" transform
// (no band, meaning full-frequency-range or shelved)
}
// Count the inputs
_inputs = 0;
XmlNodeList inputs = config.SelectNodes("//In");
foreach (XmlNode input in inputs)
{
// Check each iput channel is actually sensible
int c = int.Parse(input.Attributes["Channel"].Value, CultureInfo.InvariantCulture);
if (c >= _inputs)
{
_inputs = c+1;
}
}
_usesInput = new bool[_inputs];
// Count the outputs
XmlNodeList outputs = config.SelectNodes("//Matrix/Out");
foreach (XmlNode output in outputs)
{
// Check each output channel is actually sensible
int c = int.Parse(output.Attributes["Channel"].Value, CultureInfo.InvariantCulture);
if (c >= _outputs)
{
throw new NotSupportedException("Output channel " + c + " must be in the range 0 to " + (_outputs-1));
}
}
// _ambiChannels = new Complex[_ambiOutputs][];
// for (int cOut = 0; cOut < _ambiOutputs; cOut++)
// {
// _ambiChannels[cOut] = new Complex[4];
// for (int cIn = 0; cIn < 4; cIn++)
// {
// double re = nodeValueDouble(ambiMatrixDoc, String.Format("//Matrix/Out[@Channel={0}]/In[@Channel={1}]/Re", cOut, cIn));
// double im = nodeValueDouble(ambiMatrixDoc, String.Format("//Matrix/Out[@Channel={0}]/In[@Channel={1}]/Im", cOut, cIn));
// _ambiChannels[cOut][cIn] = new Complex(re, im);
// }
// }
}
}
*/
}