Variable matrix decoder for use in 4-2-4 matrix playback system

Claim 2

A decoder for use in a directional sound system wherein at least four directional audio input signals are encoded into two channel signals and the two channel signals are decoded into at least four audio output signals corresponding to said audio input signals, said two channel signals having an amplitude ratio and a phase relationship, said decoder comprising: at least one control unit responsive to the phase relationship between said two channel signals for producing first and second control signals; first matrix means connected to receive said two channel signals for combining said two channel signals to produce two audio output signals corresponding to two directional audio input signals, said first matrix meAns including means responsive to said first control signal for varying at least the amplitude ratio of said two channel signals contained in each of said output signals; and second matrix means connected to receive said two channel signals for combining said two channel signals to produce two audio output signals corresponding to two remaining directional audio input signals, said second matrix means including means responsive to said second control signal for varying at least the amplitude ratio of said two channel signals contained in each of said output signals.

Claim 3

A decoder according to claim 1 wherein each of said first and second matrix means comprises a resistive matrix circuit including at least one variable resistor, said two audio output signals are derived out from the opposite terminals of said variable resistor and the variable resistors of said first and second matrix means are controlled by said first and second control signals to vary the amplitude ratios of said two channel signals contained in said output signals.

Claim 4

A decoder according to claim 2 wherein said variable resistors included in said first and second matrix means comprise photoconductive elements and wherein there are provided first and second light sources for illuminating said photoconductive elements and first and second control circuits responsive to said first and second control signals for controlling the brightness of said first and second light sources.

Claim 5

A decoder according to claim 1 wherein said first matrix means comprises a first differential amplifier having first and second input terminals, said first input terminal being connected to receive one channel signal; means for reversing the phase of the other channel signal; means for coupling the output from said phase reversing means to the second input terminal of said first differential amplifier; and means responsive to said first control signal for controlling the gain of said first differential amplifier, and wherein said second matrix means comprises a second differential amplifier having first and second input terminals connected to receive said two channel signals respectively and means responsive to said second control signal for controlling the gain of said second differential amplifier.

Claim 6

A decoder according to claim 1 further comprising: first means for producing a sum output of said two channel signals; second means for producing a sum output of said two channel signals having the opposite polarity to that of the output of said first means; third means for producing a difference output of said two channel signals; and fourth means for producing a difference output of said two channel signals having the opposite polarity to that of said third means; wherein said first matrix means includes first variable gain amplifier means connected to receive the output of said third means, said variable gain amplifier means being controlled in its gain in response to said first control signal; fifth means for combining the output from said first variable gain amplifier means and the output from said first means; and sixth means for combining the output from said first variable gain amplifier means and the output from said second means; and wherein said second matrix means includes second variable gain amplifier means connected to receive the output from said first means, said variable gain amplifier means being controlled in its gain in response to said second control signal; seventh means for combining the output from said second variable gain amplifier means and the output from said third means; and eighth means for combining the output from said second variable gain amplifier means and the output from said fourth means.

Claim 7

A decoder according to claim 5 wherein said two channel signals are expressed by L FL + Delta FR + jRL + j Delta RR and R FR + Delta FL - jRR - j Delta RL where FL, FR, RL and RR represent directivE audio input signals and Delta represents a constant equal to about 0.414; the gain of said first variable gain amplifier means varies between substantially 0 and 2.41 in response to said first control signal; and wherein the gain of said second variable gain amplifier means varies between substantially 0 and 2.41 in the opposite direction to said gain of said first variable gain amplifier means in response to said second control signal.

Claim 8

A decoder according to claim 1 wherein said control unit includes a phase discriminator for detecting the phase difference between said two channel signals.

Claim 9

A decoder according to claim 7 wherein said phase discriminator comprises first means connected to receive one channel signal for producing a rectangular wave output; second means connected to receive the other channel signal for producing a rectangular wave output; third and fourth means which are connected to receive the output from said first means for producing outputs of opposite polarities; and first and second switching means which are alternately rendered ON and OFF in response to the outputs from said third and fourth means, the input sides of said first and second switching means being connected to receive the output of said second means to thereby produce first and second control signals from the output sides of said first and second switching means, the magnitudes of said first and second control signals varying in opposite directions in accordance with the phase difference between said two channel signals.

Claim 10

A decoder according to claim 1 wherein said control unit includes a comparator for detecting the phase relationship between said two channel signals in accordance with level difference between sum and difference signals of said two channel signals.

Claim 11

A decoder as claimed in claim 9 wherein said comparator comprises a first logarithmic amplifier connected to receive a sum signal of said two channel signals; a second logarithmic amplifier connected to receive a difference signal of said two channel signals; first means to rectify the output of said first logarithmic amplifier; second means for rectifying the output of said second logarithmic amplifier; and a differential amplifier connected to receive the outputs from said first and second means for producing first and second outputs, the magnitudes of which vary in the opposite directions in accordance with the phase relationship between said two channel signals.

Claim 12

A decoder according to claim 5 wherein each of said first and second variable gain amplifier means has a frequency characteristic such that it manifests a relatively low gain for signals having frequencies less than a first predetermined frequency and a relatively high gain for signals having frequencies less than a second predetermined frequency regardless of the magnitudes of said first and second control signals.

Claim 13

A decoder according to claim 11 wherein said first predetermined frequency is about 200 Hz and said second predetermined frequency is about 5000 Hz.

Claim 14

A decoder according to claim 5 wherein each of said first and second variable gain amplifier means includes means for substantially preventing signals contained in the input signal and having frequencies lower than a first predetermined frequency from being applied to said amplifier means and means for operating said amplifier means at a high gain for signals contained in the input signal and having frequencies higher than a second predetermined frequency which is higher than said first predetermined frequency regardless of the magnitudes of said first and second control signals.

Claim 15

A decoder according to claim 5 wherein each of said first and second variable gain amplifier means comprises a variable gain amplifier connected to mainly receive input signals having intermediate frequencies in the entire audible frequency band and a fixed gain amplifier connected to mainly receive input signals having higher freQuencies than said intermediate frequencies.

Claim 16

A decoder according to claim 14 which further comprises a bandpass filter connected to the input of said variable gain amplifier and a high-pass filter connected to the input of said fixed gain amplifier.

Claim 17

A decoder according to claim 5 further comprising a second control unit for producing third and fourth control signals in response to said two channel signals; third variable gain amplifier means connected to receive a first channel signal, said variable gain amplifier means being controlled in its gain by said third control signal; ninth means for producing a sum output of the output of said third variable gain amplifier means and a second channel signal; 10th means for producing a difference output of the output said third variable gain amplifier and the second channel signal; fourth variable gain amplifier means connected to receive the second channel signal, said fourth variable gain amplifier means being controlled in its gain by said fourth control signal; 11th means for producing a sum output of the output of said fourth variable gain amplifier end the first channel signal; 12th means for producing a difference output of the output of said fourth variable gain amplifier and the first channel signal; 13th means for combining the output of said fifth means and the output of said ninth means at a predetermined amplitude ratio; 14th means for combining the output of said sixth means and the output of said eleventh means with a predetermined amplitude ratio; 15th means for combining the output of said seventh means and the output of said tenth means at a predetermined amplitude ratio; and 16th means for combining the output of said eighth means and the output of said twelfth means with a predetermined amplitude ratio.

Claim 18

A decoder according to claim 16 further comprising first and second phase shifters for introducing a predetermined phase difference between said two channel signals; adder means for adding the outputs of said first and second phase shifters; and subtractor means for producing a difference output of the outputs of said first and second phase shifters; and wherein said second control unit includes a phase discriminator for detecting the phase difference between the outputs of said adder means and subtractor means.

Claim 19

A decoder according to claim 16 wherein said second control unit includes a comparator for detecting level difference between said first and second channel signals.

Claim 20

A decoder according to claim 1 wherein said control unit produces said first control signal of the maximum level and said second control signal of the minimum level when the phase difference between said two channel signals is about 0*; said first and second control signals having the identical level when the phase difference is about 90*, and said first control signal of the minimum level and second control signal of the maximum level when the phase difference is about 180*.

Claim 21

A decoder adapted to decode two channel signals L and R each containing at least three of four directional audio signals FR, FL, RL and RR, into reproduced four channel signals FR'', FL'', RL'' and RR'' respectively corresponding to said directional audio signals FR, FL, RL and RR, said decoder comprising: a control unit responsive to the phase relationship between said two channel signals L and R for producing first and second control outputs which vary in opposite directions with reference to a predetermined reference level; first matrix means connected to receive said two channel signals L and R for producing said reproduced signals FL'' and FR'' which are expressed by mL + nR and nL + mR, respectively, where m and n represent variable matrix coefficients which vary in the opposite directions in accordance with said first control output; and second matrix means connected to receiVe said two channel signals L and R for producing reproduced signals RL'' and RR'' which are expressed by pL - qR and qL - pR, respectively, where p and q represent variable matrix coefficients which vary in the opposite directions in accordance with said second control output and said coefficients m and p vary in the opposite directions by said first and second control outputs.

Claim 22

A decoder adapted to decode two channel signals L and R each containing at least three of four directional audio signals FR, FL, RL and RR, into reproduced four channel signals FR'', FL'', RL'' and RR'' respectively corresponding to said directional audio signals FR, FL, RL and RR, said decoder comprising: a control unit responsive to the phase relationship between said two channel signals L and R for producing first and second control outputs which vary in opposite directions with reference to a predetermined reference level; first matrix means connected to receive said two channel signals L and R for producing said reproduced signals FL'' and FR'' which are expressed by mL + nR and nL + mR, respectively, where m and n represent variable matrix coefficients which vary in the opposite directions in accordance with said first control output; and second matrix means connected to receiVe said two channel signals L and R for producing reproduced signals RL'' and RR'' which are expressed by pL - qR and qL - pR, respectively, where p and q represent variable matrix coefficients which vary in the opposite directions in accordance with said second control output and said coefficients m and p vary in the opposite directions by said first and second control outputs.

Claim 23

A decoder adapted to decode two channel signals L and R, each containing at least three of four directional audio signals FR, FL, RL and RR into reproduced four channel signals FR'', FL'', RL'' and RR'' respectively corresponding to said directional audio signals FR, FL, RL and RR, said decoder comprising: a control unit responsive to the phase relationship between said two channel signals L and R for producing first and second control outputs which vary in the opposite directions with reference to a predetermined reference level; first matrix means connected to receive said two channel signals L and R for forming said reproduced signals FL'' and FR'' which are expressed by (1+f)L + (1-f)R and (1+f)R + (1-f)L, respectively, where f represents a variable matrix coefficient which is controlled by said first control output; second matrix means connected to receive said two channel signals L and R for forming said reproduced signals RL'' and RR'' which are expressed by (1+b)L - (1-b) R and (1+b)R - (1-b)L, respectively, where b represents a variable matrix coefficient which is controlled by said second control output, said coefficients b and f varying in the opposite directions.

Claim 24

A decoder adapted to decode two channel signals L and R, each containing at least three of four directional audio signals FR, FL, RL and RR into reproduced four channel signals FR'', FL'', RL'' and RR'' respectively corresponding to said directional audio signals FR, FL, RL and RR, said decoder comprising: a control unit responsive to the phase relationship between said two channel signals L and R for producing first and second control outputs which vary in the opposite directions with reference to a predetermined reference level; first matrix means connected to receive said two channel signals L and R for forming said reproduced signals FL'' and FR'' which are expressed by (1+f)L + (1-f)R and (1+f)R + (1-f)L, respectively, where f represents a variable matrix coefficient which is controlled by said first control output; second matrix means connected to receive said two channel signals L and R for forming said reproduced signals RL'' and RR'' which are expressed by (1+b)L - (1-b) R and (1+b)R - (1-b)L, respectively, where b represents a variable matrix coefficient which is controlled by said second control output, said coefficients b and f varying in the opposite directions.

Claim 25

A decoder according to claim 21 wherein said two channel signals L and R are expressed respectively by FL + Delta FR + jRL + j Delta RR and FR + Delta FL - jRR - j Delta RL where Delta equals substantially 0.414 and wherein said variable matrix coefficients f and b vary in opposite directions between substantially 0 and 2.41 in response to said first and second control outputs.

Claim 26

A decoder adapted to decode two channel signals L and R, each containing at least three of four directional audio input signals FL and FR associated with front left and right channels, RL and RR associated with rear-left and right channels, into reproduced four channel output signals, said decoder comprising: a first control unit responsive to the level ratio between the front and rear audio input signals contained in the two channel signals for producing first and second control signals, the magnitudes of which vary in opposite directions; a second control unit responsive to the level ratio between the left and right audio input signals contained in the two channel signals for producing third and fourth control signals, the magnitudes of which vary in opposite directions; first means connected to receive said two channel signals L and R for producing an output proportional to a signal (1+f+ Square Root 2)L + (1-f+ Square Root 2l)R, where f and l represent coefficients which vary over a predetermined range; second means connected to receive said two channel signals L and R for producing an output proportional to a signal (1+ f+ Square Root 2)R + (1- f+ Square Root 2r)L, where f and r represent coefficient which vary over a predetermined range; third means connected to receive said two channel signals L and R for producing an output proportional to a signal (1+ b+ Square Root 2)L - (1- b+ Square Root 2l)R, where b and l represent coefficients which vary over a predetermined range; fourth means connected to receive said two channel signals L and R foR producing an output proportional to a signal (1+b+ Square Root 2)R - (1-b+ Square Root 2r)L, where b and r represent coefficients which vary over a predetermined range; fifth means responsive to said first control signal for varying said coefficient f; sixth means responsive to said second control signal for varying said coefficient b; seventh means responsive to said third control signal for varying said coefficient r; and eigth means responsive to said fourth control signal for varying said coefficient l.

Claim 27

A decoder adapted to decode two channel signals L and R, each containing at least three of four directional audio input signals FL and FR associated with front left and right channels, RL and RR associated with rear-left and right channels, into reproduced four channel output signals, said decoder comprising: a first control unit responsive to the level ratio between the front and rear audio input signals contained in the two channel signals for producing first and second control signals, the magnitudes of which vary in opposite directions; a second control unit responsive to the level ratio between the left and right audio input signals contained in the two channel signals for producing third and fourth control signals, the magnitudes of which vary in opposite directions; first means connected to receive said two channel signals L and R for producing an output proportional to a signal (1+f+ Square Root 2)L + (1-f+ Square Root 2l)R, where f and l represent coefficients which vary over a predetermined range; second means connected to receive said two channel signals L and R for producing an output proportional to a signal (1+ f+ Square Root 2)R + (1- f+ Square Root 2r)L, where f and r represent coefficient which vary over a predetermined range; third means connected to receive said two channel signals L and R for producing an output proportional to a signal (1+ b+ Square Root 2)L - (1- b+ Square Root 2l)R, where b and l represent coefficients which vary over a predetermined range; fourth means connected to receive said two channel signals L and R foR producing an output proportional to a signal (1+b+ Square Root 2)R - (1-b+ Square Root 2r)L, where b and r represent coefficients which vary over a predetermined range; fifth means responsive to said first control signal for varying said coefficient f; sixth means responsive to said second control signal for varying said coefficient b; seventh means responsive to said third control signal for varying said coefficient r; and eigth means responsive to said fourth control signal for varying said coefficient l.

Claim 28

A decoder according to claim 23 wherein said two channel signals L and R are expressed respectively by FL + Delta FR + jRL + j Delta RR and FR + Delta FL - jRR - j Delta RL where Delta equals substantially 0.414 and said coefficients f, b, r and l vary respectively between substantially 0 and 3.414.

Claim 29

A decoder adapted to decode first and second channel signals, each containing at least three of four audio signals associated with front-left and right channels and rear-left and right channels, into four channel signals, said decoder comprising: first means responsive to the level ratio between the front and rear audio input signals contained in the two channel signals for producing first and second control signals; the magnitudes of which vary in opposite directions; second means responsive to the level ratio between the left and right audio input signals contained in the two channel signals for producing third and fourth control signals the magnitudes of which vary in opposite directions; third means for producing a difference signal of the first and second channel signals; fourth means responsive to said first control signal for varying the amplitude of the output signal from said third means; fifth means for producing a sum signal of the first and second channel signals; sixth means responsive to said second control signal for varying the amplitude of the output signal from said fifth means; seventh means responsive to said third control signal for varying the amplitude of the first channel signal; eighth means responsive to said fourth control signal for varying the amplitude of the second channel signal; ninth means for combining the first and second channel signals, the output signal from said fourth means, and the output signal from said eighth means with the same polarities and a first predetermined relative amplitude ratio; 10th means for combining the first and second channel signals, the output signal from said fourth means, and the output from said seventh means with a relationship wherein the output signal from said fourth means is opposite in polarity to the remaining three signals, and a second predetermined relative amplitude ratio; eleventh means for combining the first and second channel signals, the output signal from said sixth means, and the output signal from said eighth means with a relationship wherein the first channel signal and the output signal from said sixth means are opposite in polarity to the remaining two signals, and a third predetermined relative amplitude ratio; and 12th means for combining the first and second channel signals, the output signal from said sixth means and the output signal from said seventh means with a relationship wherein the second channel signal and the output signal from said sixth means are opposite in polarity to the remaining two signals, and a fourth predetermined relative amplitude ratio.

Claim 30

A decoder adapted to decode first and second channel signals, each containing at least three of four audio signals associated with front-left and right channels and rear-left and right channels, into four channel signals, said decoder comprising: first means responsive to the level ratio between the front and rear audio input signals contained in the two channel signals for producing first and second control signals; the magnitudes of which vary in opposite directions; second means responsive to the level ratio between the left and right audio input signals contained in the two channel signals for producing third and fourth control signals the magnitudes of which vary in opposite directions; third means for producing a difference signal of the first and second channel signals; fourth means responsive to said first control signal for varying the amplitude of the output signal from said third means; fifth means for producing a sum signal of the first and second channel signals; sixth means responsive to said second control signal for varying the amplitude of the output signal from said fifth means; seventh means responsive to said third control signal for varying the amplitude of the first channel signal; eighth means responsive to said fourth control signal for varying the amplitude of the second channel signal; ninth means for combining the first and second channel signals, the output signal from said fourth means, and the output signal from said eighth means with the same polarities and a first predetermined relative amplitude ratio; 10th means for combining the first and second channel signals, the output signal from said fourth means, and the output from said seventh means with a relationship wherein the output signal from said fourth means is opposite in polarity to the remaining three signals, and a second predetermined relative amplitude ratio; eleventh means for combining the first and second channel signals, the output signal from said sixth means, and the output signal from said eighth means with a relationship wherein the first channel signal and the output signal from said sixth means are opposite in polarity to the remaining two signals, and a third predetermined relative amplitude ratio; and 12th means for combining the first and second channel signals, the output signal from said sixth means and the output signal from said seventh means with a relationship wherein the second channel signal and the output signal from said sixth means are opposite in polarity to the remaining two signals, and a fourth predetermined relative amplitude ratio.

Claim 31

A decoder according to claim 25 wherein said first amplitude ratio is substantially (1+ Square Root 2) : 1 : 1 : Square Root 2, said second amplitude ratio substantially 1 : (1+ Square Root 2) : 1 : Square Root 2, said third amplitude ratio substantially (1+ Square Root 2) : 1: 1 : Square Root 2, and said fourth amplitude ratio substantially 1 : 1 (1+ Square Root 2) : 1 : Square Root 2.

Claim 32

A decoder according to claim 25 wherein said fourth and sixth means vary in opposite directions the amplitudes of the input signals therefor over a range between substantially 0 and 3.414, and said seventh and eighth means vary in opposite directions the amplitudes of the input signals therefor over a range between substantially 0 and 3.414.

Claim 33

A decoder adapted to decode first and second channel signals, each containing at least three of four audio signals associated with front-left and right channels and rear-left and right channels, into four channel signals, said decoder comprising: first means responsive to phase relationship between the front and rear channels for producing first and second control signals, the magnitudes of which vary in opposite directions; second means for producing a difference signal of the first and second channel signals; third means responsive to said first control signal for varying the amplitude of the output signal from said second means; fourth means for producing a sum signal of the first and second channel signals; fifth means responsive to said second control signal for varying the amplitude of the output signal from said fourth means; sixth means for combining the first and second channel signals, and the output signal from said third means with the same polarities; seventh means for combining the first and second channel signals, and the output signal from said third means with a relationship wherein the first and second channel signals are opposite in polarity to the output signal from said third means; eighth means for combining the first and second channel signals and the output signal from said fifth means with a relationship wherein the second channel signal is opposite in polarity to the remaining two signals; and ninth means for combining the first and second channel signals and the output signal from said fifth means with a relationship wherein the first channel signal is opposite in polarity to the remaining two signals.

Claim 34

A decoder adapted to decode first and second channel signals, each containing at least three of four audio signals associated with front-left and right channels and rear-left and right channels, into four channel signals, said decoder comprising: first means responsive to phase relationship between the front and rear channels for producing first and second control signals, the magnitudes of which vary in opposite directions; second means for producing a difference signal of the first and second channel signals; third means responsive to said first control signal for varying the amplitude of the output signal from said second means; fourth means for producing a sum signal of the first and second channel signals; fifth means responsive to said second control signal for varying the amplitude of the output signal from said fourth means; sixth means for combining the first and second channel signals, and the output signal from said third means with the same polarities; seventh means for combining the first and second channel signals, and the output signal from said third means with a relationship wherein the first and second channel signals are opposite in polarity to the output signal from said third means; eighth means for combining the first and second channel signals and the output signal from said fifth means with a relationship wherein the second channel signal is opposite in polarity to the remaining two signals; and ninth means for combining the first and second channel signals and the output signal from said fifth means with a relationship wherein the first channel signal is opposite in polarity to the remaining two signals.

Claim 35

A decoder according to claim 28 wherein said third and fifth means vary in opposite directions the amplitudes of the input signals therefor over a range from about 0 to 2.414.

Claim 36

A decoder according to claim 16 wherein each of said variable gain amplifier means has a frequency characteristic such that is manifests a relatively low gain for signals having frequencies less than a first predetermined frequency and a relatively high gain for signals have frequencies less than a second predetermined frequency regardless of the magnitudes of said first and second control signals.

Claim 37

A decoder according to claim 30 wherein said first predetermined frequency is about 200 Hz and said second predetermined frequency is about 5000 Hz.

Claim 38

A decoder according to claim 16 wherein each of said variable gain amplifier means includes means for substantially preventing signals contained in the input signal and having frequencies lower than a first predetermined frequency from being applied to said amplifier means and means for operating said amplifier means at a high gain for signals contained in the input signal and having frequencies higher than a second predetermined frequency which is higher than said first predetermined frequency regardless of the magnitudes of said first and second control signals.

Claim 39

A decoder according to claim 16 wherein each of said variable gain amplifier means comprises a variable gain amplifier connected to mainly receive input signals having intermediate frequencies in the entire audible frequency band and a fixed gain amplifier connected to mainly receive input signals having higher frequencies than said intermediate frequencies.

Claim 40

A decoder according to claim 33 which further comprises a bandpass filter connected to the input of said variable gain amplifier and a high-pass filter connected to the input of said fixed gain amplifier.