Noise reduction system

Details Noise reduction system Noise reduction system

1988-02-08

1989-11-21

Shepperd, John W.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358167, H04N 5213

Patent

active

048826278

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a noise reduction system with motion detection for digitalized video signals including at least one memory, a filter, a correction circuit, an adder, and/or a subtractor.
DE-OS No. 3,309,715 discloses a noise reduction system which delays a television signal in a frame memory. The drawback here is the digital memory which must be designed for the size of a frame. DE-OS No. 3,121,599 describes the associated lowpass filter, hereinafter called filter. In this filter, all surrounding and adjacent pixels around an interfered-with pixel are included in the weighting. These are the adjacent pixels in the current line and the adjacent pixels from the preceding and subsequent lines.


SUMMARY OF THE INVENTION

It is the object of the invention to provide a simplified noise reduction system with motion detection for digitalized video signals.
This is accomplished according to the invention by the provision of a correction circuit for a digitalized video signal, the video signal including at least one of a luminance signal and a chrominance signal, the system including at least one memory for storing and outputting an enhanced video signal, a filter receiving the output of said at least one memory and producing a filtered output signal, a correcting circuit receiving said filtered output signal, and an algebraic adder for adding a correction produced by said correction circuit to the input video signal to produce the enhanced video signal.
To weight the luminance of a pixel, adjacent pixels are utilized. Adjacent pixels are initially the pixels disposed in the same line, one or more pixels preceding the current pixel and one or more pixels following the current pixel. Additionally, pixels are adjacent if they belong to the preceding field. These pixels of the preceding field are stored in a field memory. It is not necessary to employ a frame memory because the luminance and chrominance values of the current pixel and of the pixels adjacent thereto in the same line are fed directly to a weighting circuit. During read-out from the field memory, pixels of fields lying above one another are compared with one another if the respective first value is delayed by a line duration. In this way, an estimated value can be calculated for the luminance and chrominance value, respectively, of the pixel disposed therebetween in a second field; this corresponds to one-dimensional vertical filtering. This calculated estimated value is compared with the luminance and chrominance values of the pixel in the current field. A two-dimensional filter is limited to two one-dimensional filters. To detect motion, the result of the comparison between the luminance and chrominance values of the current field and the preceding field is fed to a horizontal filter. This horizontal filter now considers only luminance and chrominance values of pixels where the pixels lie in one line. A two-dimensional filter can thus be omitted. The one-dimensional filter delays the chrominance and luminance values by two pixels, compares the current pixel with the preceding pixel and with the next following pixel and transfers the result of this comparison to a table. The table then detects, with the aid of the incoming values, a desired output position and, according to a weighting factor k, assigns an output value to the incoming value. However, this table no only makes a decision according to noise and movement, it simultaneously also causes the signal edges to be steeper. Possible uses for this invention exist, on the one hand, at the transmitting end and, on the other hand, at the receiving end. At the transmitting end, the signal edges need of course not be made steeper. The edges are advantageously made steeper at the receiving end, with the weighting factor from this table then becoming negative.
For better understanding of the invention, one embodiment thereof together with drawing figures will now be described in detail.


BRIEF DESCRIPTION OF THE DRAWINGS

It is shown in:
FIG. 1, a data transmission sy

REFERENCES:
patent: 4058836 (1977-11-01), Drewery et al.
patent: 4223341 (1980-09-01), Drewery
patent: 4275418 (1981-06-01), Trump et al.
patent: 4291333 (1981-09-01), Warnock et al.
patent: 4539594 (1985-09-01), Illetschko
patent: 4549213 (1984-11-01), Illetschko

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