Download the JAVA-Application: QuadrophonicMatrixDecoder.zip (version 1.7 - 01/01/2011 - 20kByte) 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 encoding software go to Quadrophonic Matrix Encoder
Implemented Decoding Matrixes:
Stereo (Just the stereo channels):
LF = L
RF = R
LF = L
RF = R
LB = 0.707 * jL - 0.707 * R
RB = 0.707 * L - 0.707 * jR
LF = 0.92 * L + 0.38 * R
RF = 0.38 * L + 0.92 * R
LB = -0.92 * jL + 0.38 * jR
RB = -0.38 * jL + 0.92 * jR
LF = 0.98 * L + 0.2 * R
RF = 0.2 * L + 0.98 * R
LB = 0.78 * L - 0.62 * R
RB = -0.62 * L + 0.78 * R
LF = L
RF = R
LB = 0.86 * L - 0.5 * R
RB = -0.5 * L + 0.86 * R
Next step would be the implementation of some kind of Variable Gain Matrix (e.g. Shadow Vector, Tate DES or Vario Matrix) to improve the channel separation.
Opens audio files in WAV-Format (16Bit / 44.1kHz).
To enable the player Buttons you need to open at least one audio file.
Load and Save Configuration:
All presets are saved in a configuration file for later re-use.
Leave the program
Source Selector set to WAV Audio Player:
Start Audio & Decoding Matrix Selection:
Select the decoding matrix matching the encoding of your record and click "Play" to start the playback of the loaded wav files. Please keep in mind that the buttons are only enabled if you have loaded some audio wav files.
Source Selector set to Audio Input Device:
Activate/Deactivate & Decoding Matrix Selection:
Select the decoding matrix matching the encoding of your record and click activate to start the decoder. Make sure that the right input and output devices are selected.
Input- & Output-Devices:
Select real or virtual input and output devices to route the dedicated audio signals.
If the internal WAV Audio Player is selected then there is no need for an audio input device.
The attenuation slider allows gain reduction of up to 12dB to avoid digital clipping caused by the decoding process which creates higher amplitudes than those of the input signal.
Volume & Balance:
It is possible to adapt independently the volume and balance of the front and back channels.
Complex-Signal-Scope and Quadro-Scope:
The two complex signal scopes represent the real and imaginary part of the complexified signals for the left and right channels whereas the quadro scope indicates the direction and amplitude of the signal. Furthermore, there is a red colored vector which represents the direction of the virtual sound source averaged over the last 50ms.
WAV Audio Player - Play-List:
The play list shows which audio file currently plays and allows the direct selection of a title (one-click).
1.) Place the speakers as recommended for the different formats
2.) Make sure that you activate the audio input and output devices you want to use by applying the appropriate operating system configuration. Furthermore, it is essential to adjust the input-level to avoid overmodulation of the input signal.
3.) Launch the Quadrophonic Matrix Decoder
4.) Select the Input- and Output-Mixer/Devices. Or select the built in WAV Audio Player
5.) Click "Activate" or "Play" to start the decoding process
ATTENTION: It is a limitation of JAVA to recognize just the first stereo channel output of a sound-device. This is even true for a multi-channel card. You can either use two sound devices or configure virtual devices by using software like JACK AUDIO.
Connect an external audio source (record player, tape, cd, etc.) or just configure the input device to "What you Hear / Stereo Mix" to use your favorite software audio player.
- 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
It can happen that there is a time delay between the front and back speakers or that there is no output after the first start. In such cases just restart the Quadrophonic Matrix Decoder.
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.