Matrix Decoder for Surround Sound with Adaptive Phase Steering
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Solution Overview
Problem
In surround sound systems, encoding four audio channels into two channels often results in increased cross-talk between channels, leading to a reproduced sound field that is not identical to the original, affecting sound quality and image stability.
Innovation Solution
A matrix decoder with filter means to compensate for human hearing response non-linearity, a control unit to produce steering signals based on phase relationships, and matrix means to vary amplitude ratios of encoded signals, improving channel separation and sound field reproduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If four audio channels are encoded into two channels, then the sound field can be reproduced through standard stereo equipment, but cross-talk between channels increases and channel separation deteriorates
Solution Approach 1:
The patent applies dynamics by making the matrix decoding process adaptive rather than fixed. The system dynamically adjusts the decoding matrix based on the encoded signal characteristics, allowing optimal channel separation for different program material while maintaining compatibility with standard stereo equipment. This resolves the contradiction by enabling the system to adapt its behavior to preserve channel separation quality.
Solution Approach 2:
The patent changes parameters by modifying the decoding matrix coefficients based on signal analysis. By adjusting matrix parameters dynamically according to the encoded signal's phase relationships and amplitude ratios, the system optimizes channel separation performance for different types of audio content while maintaining backward compatibility with stereo playback systems.
2Adaptability or versatility
If matrix decoding is used to reproduce four channels from two channels, then surround sound can be achieved from stereo sources, but the reproduced sound field is not identical to the original due to cross-talk
Solution Approach 1:
The patent implements feedback by analyzing the encoded signal characteristics and using this information to adjust the decoding process. The system monitors phase relationships and amplitude ratios in the encoded signal and feeds this information back to optimize the matrix decoding coefficients, thereby improving sound field accuracy and reducing cross-talk in the reproduced surround channels.
Solution Approach 2:
The patent applies preliminary action by pre-processing the encoded signal to extract phase and amplitude information before performing matrix decoding. This preliminary analysis allows the system to prepare optimized decoding parameters in advance, improving the accuracy of the reproduced sound field by accounting for the specific characteristics of the encoded signal before reconstruction.
3Device complexity
If fixed matrix decoding is used, then the decoding process is simple, but cross-talk between adjacent channels increases
Solution Approach 1:
The patent transitions from fixed to dynamic matrix decoding, where the decoding coefficients are adjusted based on the encoded signal characteristics. This dynamic approach maintains relatively simple system architecture while significantly improving channel separation by adapting the decoding process to the specific program material, thereby resolving the contradiction between simplicity and precision.
Data Source
AI summary
A decoder and decoding method for use in surround sound system wherein at least four audio input signals representing an original sound field are encoded into two channel signals and said encoded signals are decoded into at least four audio output signals corresponding to the four audio input signals and have an amplitude ratio and a phase relationship. The decoder and method including means for: compensating the said encoded signals for variations in perceived loudness relative to frequency associated with the encoded two channel signals due to non linearity in human hearing response at least at some frequencies; producing steering signals in responsive to the phase relationship of the said compensated signals; decoding said encoded signals to produce audio output signals corresponding to audio input signals by varying at least the amplitude ratio of said encoded signals contained in each of the output signals in response to said steering signals.