JPS63149981A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce random noise by providing a 1st filter to reduce a chrominance signal band to the input side of an A/D converter and providing a 2nd filter having an inverted characteristic to the 1st filter to the output side of a D/A converter. CONSTITUTION:The amplitude of a color signal band is decreased by the 1st filter 9 from a composite video signal fed to an input terminal 1 and the result is inputted to an A/D converter 2. The output signal of the A/d converter 2 is compared by the correlation detection circuit 3 from the signal before one field or frame obtained from the memory device 6 and a prescribed weighting is applied when the difference of the data of the both is within a prescribed range, the result is subjected to addition processing by an adder 5, the result is stored as the data into the memory device 6 again and fed to the D/A converter 7 simultaneously. The output of the D/A converter 7 is restored into the composite video signal having a flat frequency characteristic again for the color signal band attenuated by a 2nd filter having the inverted characteristic to that the 1st filter 9. Thus, sufficient noise reduction effect is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording and reproducing apparatus such as a video tape recorder that records and reproduces video signals, and more particularly, to a magnetic recording and reproducing apparatus such as a video tape recorder that records and reproduces a video signal. The digital signal data is stored in a memory device by converting it into a digital signal, and the digital signal data of one field or one frame before is obtained by appropriately controlling the memory device and is compared with the current digital signal data. The present invention relates to a magnetic recording/reproducing apparatus having a function of reducing random noise contained in a composite video signal by performing an addition operation between the two in a correlated portion thereof.

Conventionally, in order to reduce random noise contained in a composite video signal to be recorded or a reproduced composite video signal using digital technology, conventionally, first, a composite video signal 1 is converted to an analog-to-digital converter 2. Analog-digital conversion (
(hereinafter referred to as A/D conversion), and at the same time stores the composite video signal in the memory device 6, one field or one
The composite video signal data of the previous frame is stored in the memory device 6.
The correlation detection circuit 3 compares the signals with the current composite video signal, and if there is a correlation, the signals are weighted through the weighting circuit 4 and added by the adder 6, thereby reducing random noise. Conductor D/A converter 7
was converted into an analog signal.

Problems to be Solved by the Invention However, in the conventional technology, the S/N of the color signal is higher than the S/N of the luminance signal.
/N, or when the current signal does not match exactly due to jitter, or the current signal does not match exactly due to jitter, the correlation detection circuit 3
Since it was determined that there was no correlation, the random noise reduction effect was insufficient.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a color signal band (in the case of an NTSC signal, A first filter is provided to reduce the 3.68 M field and 4.43 M)+1) in the case of a PAL signal, and a D A second filter having characteristics opposite to those of the first filter is provided on the output side of the /A converter.

Operation With the above configuration, the first filter added to the input end of the A/D converter acts to reduce the color signal amplitude and the amplitude of noise included in the color signal in the composite video signal. Therefore, in the original composite video signal, the chrominance signal noise, which had a larger amplitude than the noise in the luminance signal band, becomes equal to or smaller than the noise in the luminance signal band. In this state, since correlation detection and addition processing with the signal of one field or one frame before is performed, it is possible to obtain the optimum noise reduction effect in each band of the color signal and the luminance signal.

Example Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a block diagram of essential parts showing an embodiment of the present invention. In the figure, 9 is a first filter for reducing the amplitude of the color signal band of the composite video signal. 2 is an A/D converter, and 6 is a memory device having a storage capacity for one field or one frame.

Here, the composite video signal applied to the input terminal 1 has the amplitude of the color signal band reduced by the filter 9, and the A/
The signal is input to the D converter 2. The output signal of the A/D converter 2 is one field or one field obtained from the memory device 6.
The data value is compared with the signal before the frame by the correlation detection circuit 3, and if the difference between the two data is within a certain range, the weighting circuit 4 performs a predetermined weighting, and the adder 6 The addition process is executed, and the result is
At the same time as being stored as data in the memory device again, D
/A converter 7. The output of the D/A converter 7 is
A second filter 10 with opposite characteristics to the first filter 9
As a result, the attenuated color signal band is returned to a composite video signal having flat frequency characteristics.

FIG. 2 is a diagram showing an example of the frequency characteristics of the first filter 9, and FIG. 3 is a diagram showing an example of the frequency characteristics of the second filter 1Q.

Effects of the Invention According to the present invention, in a video tape recorder, etc., the S/N of the color signal is inferior to the S/N of the luminance signal, and the signal of one field or frame before and the current signal are
Even for signals whose correlation cannot necessarily be detected accurately due to jitter components, it is possible to obtain a sufficient noise reduction effect for both the luminance signal and one color signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of the first filter in FIG. 1, and FIG. 3 is a diagram of the characteristics of the first filter in FIG. FIG. 4 is a block diagram of a conventional example. 1... Input terminal, 2... A/D converter, 3... Correlation detection circuit, 4... Weighting circuit, 5... ... Adder, 6 ... Memory device, 7 ... D/A converter, 8 ... ° ... Output terminal, 9 ... First filter, 1o...
...Second filter.

Claims (1)

[Claims] Equipped with a device that reduces random noise contained in a reproduced signal or a signal to be recorded by digitally calculating the correlation between a signal obtained by digitally converting a composite video signal and the signal of one field or one frame before, Further, a first filter is provided on the input side of the device that converts the composite video signal into a digital signal for reducing the color signal component included in the signal relative to the luminance signal component, and the noise reduction processing is performed. on the output side of the device that converts the digital signal into the original analog signal, the composite video signal.
A magnetic recording/reproducing device characterized in that a second filter having characteristics opposite to those of the first filter is provided.