Control voltage generator multiplier and one-shot for integrated surround sound processor
First Claim
1. An audio signal processor for multichannel redistribution of stereophonic sound on a plurality of loudspeakers surrounding the listener comprising an input conditioning and matrixing means, a variable matrixing means and a control voltage generator means for producing a plurality of control voltages from the output signals of said input conditioning and matrixing means and for controlling the variable parameters of said variable matrixing means, said control voltage generator means comprising:
- at least one pair of input terminals for receiving from said input conditioning and matrixing means a pair of partially correlated audio signals containing directional information;
at least one directional detector means for comparing each said pair of correlated audio signals to produce a corresponding directional information signal; and
at least one variable time constant smoothing means for smoothing each of said directional information signals to produce a corresponding control voltage signal, each said smoothing means being responsive to the difference between its input said directional information signal and the corresponding output said control voltage signal,each said variable time constant smoothing means comprising;
a controlled current source means having a control terminal and an output;
a capacitor means connected to the output of said controlled current source means and ground;
a differencing means for producing a difference signal corresponding to the difference between the input said directional information signal and the output said control voltage signal; and
a current control means for providing a current source control signal to the control terminal of said controlled current source means for varying the current provided by said controlled current source means to said capacitor means;
said control voltage signal being developed across said capacitor means.
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Accused Products
Abstract
A surround sound processor for presentation of a stereophonic source program on a multiple loudspeaker array surrounding the listening area. The processor includes input signal conditioning and matrixing circuits, a control voltage generator responsive to the directional information contained in the stereophonic source signals, and a variable matrixing circuit for generating appropriate loudspeaker feed signals to create the illusion of the sound field wrapping around the listening area. The control voltage generator includes a servologic circuit employing variable time constant smoothing circuits each responsive to the difference signal between its input and its output and to a pulse signal from a one-shot triggered by threshold detectors which compare the difference signals with fixed threshold voltages. In one aspect, suitable for incorporation into an integrated circuit, a multiplier circuit and a controlled bidirectional current source charging and discharging a capacitor provides the smoothing function. Alternatively a symmetrical nonlinear resistive circuit or element is used to charge and discharge the capacitor. A novel and economical combined threshold detector and one-shot suitable for integrated circuits is also disclosed.
95 Citations
52 Claims
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1. An audio signal processor for multichannel redistribution of stereophonic sound on a plurality of loudspeakers surrounding the listener comprising an input conditioning and matrixing means, a variable matrixing means and a control voltage generator means for producing a plurality of control voltages from the output signals of said input conditioning and matrixing means and for controlling the variable parameters of said variable matrixing means, said control voltage generator means comprising:
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at least one pair of input terminals for receiving from said input conditioning and matrixing means a pair of partially correlated audio signals containing directional information; at least one directional detector means for comparing each said pair of correlated audio signals to produce a corresponding directional information signal; and at least one variable time constant smoothing means for smoothing each of said directional information signals to produce a corresponding control voltage signal, each said smoothing means being responsive to the difference between its input said directional information signal and the corresponding output said control voltage signal, each said variable time constant smoothing means comprising; a controlled current source means having a control terminal and an output; a capacitor means connected to the output of said controlled current source means and ground; a differencing means for producing a difference signal corresponding to the difference between the input said directional information signal and the output said control voltage signal; and a current control means for providing a current source control signal to the control terminal of said controlled current source means for varying the current provided by said controlled current source means to said capacitor means; said control voltage signal being developed across said capacitor means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An audio signal processor for multichannel redistribution of stereophonic sound on a plurality of loudspeakers surrounding the listener comprising an input conditioning and matrixing means, a variable matrixing means and a control voltage generator means for producing a plurality of control voltages from the output signals of said input conditioning and matrixing means and for controlling the variable parameters of said variable matrixing means, said control voltage generator means comprising:
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at least one pair of input terminals for receiving from said input conditioning and matrixing means a pair of partially correlated audio signals containing directional information; at least one directional detector means for comparing each said pair of correlated audio signals to produce a corresponding directional information signal; and at least one variable time constant smoothing means for smoothing each of said directional information signals to produce a corresponding control voltage signal, each said smoothing means being responsive to the difference between its input said directional information signal and the corresponding output said control voltage signal, each said variable time constant smoothing means comprising; a symmetrical nonlinear resistor means connected to the said directional information signal; a capacitor means connected to the other terminal of said resistor means and to ground; said control voltage signal being developed across said capacitor means. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32)
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33. A method for smoothing an input signal to produce a smoothed signal with a variable time constant responsive to the difference between said input signal and the smoothed signal, comprising:
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generating a difference signal proportional to the difference between said input signal and [the]said smoothed signal; causing said difference signal to control a voltage dependent variable current source of high output impedance; and applying the output current of said variable current source to charge and discharge a capacitor, in the direction required for the voltage thereon to change towards the value of said input signal, said smoothed signal being the voltage across said capacitor. - View Dependent Claims (34, 35, 36, 37)
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38. A method for smoothing an input signal to produce a smoothed signal with a variable time constant responsive to the difference between said input signal and said smoothed signal, comprising:
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generating a difference signal proportional to the difference between said input signal and said smoothed signal; causing said difference signal to control a voltage dependent variable current source of high output impedance providing a current which is nonlinearly dependent upon said difference signal; and applying the said current to charge and discharge a capacitor so that the voltage thereon changes in a direction towards the instantaneous voltage of the input signal; said voltage on said capacitor being said smoothed signal. - View Dependent Claims (39, 40, 41)
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42. A method for smoothing a digital input signal to produce a digital smoothed signal in real time with a variable time constant responsive to the difference between said digital input signal and said digital smoothed signal, comprising:
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storing the successive values of said digital smoothed signal in a digital storage register means; evaluating the digital difference signal between successive values of said digital input signal and concurrent successive values of said digital smoothed signal in real time; deriving therefrom in real time a digital control signal symmetrically and approximately piecewise polynomially nonlinearly related to said digital difference signal; and incrementing or decrementing the value of said digital smoothed signal in real time at a rate proportional to the successive values of said digital control signal in the direction towards the current value of said digital input signal. - View Dependent Claims (43, 44, 45, 46)
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47. A method for smoothing an analog input signal to produce a smoothed signal with a signal voltage dependent variable time constant responsive to the difference between said input signal and said smoothed signal, comprising:
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deriving a current which is symmetrically nonlinearly resistively dependent upon the difference between said input signal and said smoothed signal, said nonlinear resistive dependency being approximately piecewise polynomial in form, having at least a second degree dependency below a threshold value of said difference and linear dependency above said threshold value; and applying the said current to charge and discharge a capacitor so that the voltage thereon changes in a direction towards the instantaneous voltage of the input signal; said voltage on said capacitor being said smoothed signal. - View Dependent Claims (48, 49, 50, 51, 52)
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Specification