Patent ID: 6697491
Filing Date: 2004-02-24
Classification: H04S

Abstract:
A surround sound decoder for redistributing a pair of left and right audio input signals including directionally encoded and non-directional components into a plurality of output channels for reproduction through loudspeakers surrounding a listening area, and incorporating means for determining the directional content of said left and right audio signals and generating therefrom at least a left-right steering signal and center-surround steering signal, the decoder comprising:left and right input terminals for receiving said corresponding left and right audio input signals; left and right delay means for producing delayed left and right audio signals from said left and right audio input signals; a plurality of multiplier means equal to twice the number of said plurality of output channels, organized in pairs, a first element of each said pair receiving said delayed left audio signal and a second element receiving said delayed right audio signal, each of said multiplier means multiplying its input audio signal by a variable matrix coefficient to provide an output signal; said variable matrix coefficient being controlled by one or both of said steering signals; and a plurality of summing means one for each of said plurality of output channels each said summing means receiving the output signals of a pair of said multiplier means and producing at its output one of said plurality of output signals, the decoder having said variable matrix values so constructed as to reduce directionally encoded audio components in outputs which are not directly involved in reproducing them in the intended direction and enhance directionally encoded audio components in the outputs which are directly involved in reproducing them in the intended direction so as to maintain constant total power for such signals, while preserving high separation between the left and right channel components of non-directional signals regardless of the said steering signals, and maintaining the loudness defined as the total audio power level of non-directional signals effectively constant whether or not directionally encoded signals are present and regardless of their intended direction if present.