US 4,901,150 A · Automatic noise reduction for individual frequency components of a signal

Abstract

A method and system for separating a noise signal into frequency components, then automatically performing noise reduction on the individual frequency components, and then recombining the processed frequency components to generate an output noise signal. The noise reduction parameters for each frequency component may be independently set. The output noise signal generated during performance of the invention will typically be recombined with a signal (such as a television signal) from which the input noise signal for the invention was originally extracted. In a preferred embodiment, the input noise signal supplied to the system of the invention is generated by subtracting two adjacent frames of a television signal. In a preferred embodiment, the system of the invention includes: circuitry for implementing a Walsh-Hadamard transform to separate the input noise signal into a set of frequency components; a set of automatic gain controlled amplifiers for independently performing noise reduction on each frequency component; and a noise component collator for combining the processed frequency components to generate a "component controlled noise signal". Each automatic gain controlled amplifier is independently controlled in response to a feedback signal representing the noise characteristics of a different frequency component of the input noise signal. Preferably, the system of the invention also includes a gain controlled amplifier for transforming the component controlled noise signal into a gain controlled noise output signal.

Claims27

Dependent claims

An automatic noise reduction method for processing an input signal having a noise portion for each of a set of frequency components, signals indicative of a minimum noise value for each frequency component in the set, and signals indicative of a range of gain values bounded by a minimum gain value and a maximum gain value for each frequency component in the set, including the steps of:

(a) generating a feedback signal indicative of the amplitude of one of the noise portions having a selected frequency component;
(b) generating a gain control signal for the noise portion having said selected frequency component, in response to the feedback signal for said noise portion;
(c) generating a gain controlled component signal by amplifying the noise portion having said selected frequency to an amplitude determined by the gain control signal for said noise portion;
(d) repeating steps (a) through (c) for each frequency component in the set;
and
(e) combining the gain controlled component signals to generate a component controlled noise signal, in a manner so that the amplitude of each frequency component of the component controlled noise signal is determined by the amplitude of the gain controlled component signal for said frequency component.

3 more elements

An automatic noise reduction system, for processing an input signal having a noise portion for each of a set of frequency components, signals indicative of a minimum noise value for each frequency component in the set, and signals indicative of a range of gain values bounded by a minimum gain value and a maximum gain value for each frequency component in the set, including:

(a) a set of detectors, each for generating a feedback signal indicative of the amplitude of one of th noise portions;
(b) a control unit connected to the detectors, for receiving the feedback signals and generating a gain control signal for each noise portion in response to the feedback signals;
(c) a set of gain controlled amplifiers, each for receiving and amplifying one of the noise portions, wherein each said gain controlled amplifier is connected to the control unit and receives one of the gain control signals, and wherein each said gain controlled amplifier generates a gain controlled component signal by amplifying said one of the noise portions to an amplitude determined by the gain control signal for said one of the noise portions;
and
(d) a noise component collator for receiving the gain controlled component signals, and for combining said gain controlled component signals to generate a component controlled noise signal in a manner so that the amplitude of each frequency component of the component controlled noise signal is determined by the amplitude of the gain controlled component signal for said frequency component.

2 more elements

A system for partially reducing the noise component of a noisy signal, where the noise component comprises a noise portion for each of a number of frequency components, including:

(a) a set of detectors, each for generating a feedback signal indicative of the amplitude of one of the noise portions;
(b) a microprocessor connected to the detectors, where said microprocessor includes a memory unit, and has stored in the memory unit a set of signals indicative of a minimum noise value for each frequency component, and a set of signals indicative of a range of gain values bounded by a minimum gain value and a maximum gain value for each frequency component in the set, and wherein the microprocessor is programmed to receive the feedback signals and to generate a gain control signal for each noise portion in response to the feedback signals;
(c) a set of gain controlled amplifiers, each for receiving and amplifying one of the noise portions, wherein each said gain controlled amplifier is connected to the microprocessor for receiving one of the gain control signals, and wherein each said gain controlled amplifier generates a gain controlled component signal by amplifying said one of the noise portions to an amplitude determined by the gain control signal for said one of the noise portions;
and
(d) a noise component collator for receiving the gain controlled component signals, and for combining said gain controlled component signals to generate a component controlled noise signal in a manner so that the amplitude of each frequency component of the component controlled noise signal is determined by the amplitude of the gain controlled component signal for said frequency component.

2 more elements

Dependencies are inferred from the claim text.

Automatic noise reduction for individual frequency components of a signal

Life of this patent

Automatic noise reduction for individual frequency components of a signal

Life of this patent

Abstract

Claims27