Download the JAVA-Application: QuadrophonicMatrixEncoder.zip (version 1.0 - 01/01/2011 - 12kByte) which works for Windows, Mac and Linux.
If you don't have the JRE (JAVA Runtime Environment) installed then you'll get it here: http://www.java.com/download/manual.jsp
The Principles of Quadrophonics:
The technology developed and used in the 1970's applies an encoding matrix to the four input channels LF (Left Front), RF, LB (Left Back) and RB to record them into 2 channels. Playing back such an encoded recording by applying the correct decoding matrix brings back most of the original four channels (4:2:4 Encoding/Decoding).
For decoding software go to Quadrophonic Matrix Decoder & Player
Implemented Encoding Matrixes:
LT = LF - 0.707 * jLB + 0.707 * RB
RT = RF - 0.707 * LB + 0.707 * jRB
LT = 0.92 * LF + 0.38 * RF + 0.92 * jLB + 0.38 * jRB
RT = 0.38 * LF + 0.92 * RF - 0.38 * jLB - 0.92 * jRB
LT = 0.96 * LF + 0.29 * RF + 0.89 * LB - 0.45 * RB
RT = 0.29 * LF + 0.96 * RF - 0.45 * LB + 0.89 * RB
LT = 0.97 * LF + 0.24 * RF + 0.89 * LB - 0.45 * RB
RT = 0.24 * LF + 0.97 * RF - 0.45 * LB + 0.89 * RB
Encoding Matrix Selection:
Select the encoding matrix for the target record.
Load LF/RF & Load LB/RB:
Open the 2 channel wav files (16Bit / 44.1kHz) for the front and back channels.
Attenuation and Clipping:
The encoding process creates amplitudes higher than the input signal. To avoid digital clipping set the attenuation to a value where the clipping counter stays at 0.
Save the encoded 2 channel (left and right total signal) wav audio file (16Bit / 44.1kHz).
Click the "Encoding" button to start the encoding process. The percentaged progress will be displayed in the status line.
- The 90 degree phase shift (Hilbert Transformation) to complexify the input signals has been implemented in the time domain by using IIR-All-Pass filters with a precision better than 1 degree.
- For the listed matrixes the imaginary signal term j is defined as leading phase shift of 90 degrees
- Sampling Frequency: 44.1 kHz
- Sampling Resolution: 16Bit
- Digital Signal Processing in 64Bit floating point precision
Disclaimer and License:
This Software is provided "as-is", without any express or implied warranty.
In no event will the author be held liable for any damages arising from the use of this software.
Permission is granted to anyone to use this software except for commercial use.
Please contact me (Stephan Hotto) if there is a wish for a commercial implementation.