Directional enhancement system for quadraphonic decoders

In combination with a sound system which reproduces on four separate speakers four audio information signals contained in first, second, third and fourth composite signals derived from two other composite signals, each of said first, second, third and fourth composite signals including a combination of at least three of four said audio information signals with preselected amplitude and phase relationships, a system for enhancing the directional information content of said first, second, third and fourth composite signals to produce first, second, third and fourth output signals by means of a matrix multiplication process, comprising:

• a. detector means for producing a plurality of direction control signals in response to said first, second, third and fourth composite signals;
• b. processor means having a plurality of inputs equal in number to said plurality of direction control signals for producing in response to said plurality of direction control signals a plurality of matrix coefficient signals, the value of each of said coefficient signals at any time being determined by the values of said plurality of direction control signals;
• and,
• c. matrix multiplier means for multiplying said first, second, third and fourth composite signals by said plurality of coefficient signals, in accordance with the mathematical convention of multiplication of a vector by a matrix, to produce said first, second, third and fourth output signals, the values of said plurality of coefficient signals being such that when said first, second, third and fourth composite signals are multiplied by said plurality of coefficient signals to produce said first, second, third and fourth output signals, the predominant directional information contained in said first, second, third and fourth composite signals is substantially removed from all output signals other than those in which said predominant directional information should appear while the total effective power in the output signals due to every component of directional information present in said first, second, third and fourth composite signals is simultaneously maintained substantially unchanged.

A method for enhancing the directional information content of a plurality of input signals containing directional information to produce a plurality of output signals by means of a matrix multiplication process comprising the steps of:

• a. deriving from said plurality of signals containing directional information a plurality of directional control signals;
• b. deriving in response to said plurality of directional control signals a plurality of coefficient signals, the value of each coefficient signal at any given time being determined by the values of said plurality of direction control signals;
• and
• c. multiplying said plurality of input signals containing directional information by said plurality of coefficient signals, in accordance with the mathematical convention of multiplication of a vector by a matrix, to produce said plurality of output signals, the values of said plurality of coefficient signals being such that when said plurality of input signals is multiplied by said plurality of coefficient signals to produce said plurality of output signals, the predominant directional information contained in said plurality of input signals is substantially removed from all said output signals other than those in which said predominant directional information should appear while the total effective power in said output signals due to every component of directional information in said input signals is simultaneously maintained substantially unchanged.

A method for enhancing the directional information content of first, second, third and fourth composite signals by a matrix multiplication process to produce first, second, third and fourth output signals comprising the steps of:

• a. deriving from said first, second, third and fourth composite signals a plurality of direction control signals;
• b. deriving from said plurality of direction control signals a plurality of matrix coefficient signals, the value of each of said plurality of matrix coefficient signals at any given time being determined by the values of said plurality of direction control signals;
• c. multiplying said first, second, third and fourth composite signals considered as a time-varying vector of dimension four as defined in mathematics by said plurality of matrix coefficient signals, in accordance with the mathematical convention of multiplication of a vector by a matrix, to produce first, second, third and fourth output signals in which the predominant directional information contained in said first, second, third and fourth composite signals is substantially removed from all of said output signals except those output signals in which it should appear while at the same time the total effective power in said output signals due to every component of directional information present in said first, second, third and fourth composite signal is maintained substantially unchanged.