CN1104809C - SECAM video signal recording/reproducing apparatus having function of picture quality compensation - Google Patents

Abstract

The present invention relates to an SECAM system video signal recording/reproducing device which has an image quality compensating function. This device is provided with a 4.3 MHz band-pass filter which passes only a chroma signal, a 4.28 MHz bell filter which emphasizes the chroma signal that passes through the 4.3 MHz band-pass filter and an image quality compensation circuit which amplifies the size of a chroma signal in accordance with the fluctuation of a burst level to a reference signal. It is further provided with a limiter to fixedly limit the amplitude of a chroma signal and eliminates noise and an amplitude modulation part and a low-pass conversion circuit which performs low-pass conversion of the frequency of chroma signal that is outputted from the limiter.

Description

SECAM video signal recording/playback device with image quality compensation function

The present invention relates to a SECAM (Sequential Transfer and Stored Color System) video signal recording/playback device with a function of compensating image quality, more specifically, to a device for compensating by the color burst signal level of a SECAM video signal A SECAM video signal recording/reproducing device with a function of compensating for image quality degradation to reproduce the video signal at the level of a chrominance signal.

Fig. 1 is a block diagram showing a recording process of a chrominance signal in a conventional SECAM video signal recording/reproducing apparatus. A band pass filter (BPF) 11 receives a composite video signal to separate and output only the chroma signal. Although the bandpass filter 11 preferably has its center frequency of 4.28 MHz, the BPF actually has a center frequency of 4.3 MHz so that the center frequencies differ by 0.02 MHz, which does not cause any problem from a performance point of view. When the video signal is sent from a broadcast station, an FM chroma signal is converted to a luminance signal in a black and white television set as the video signal passes through an inverse bell filter. The converted signal then appears on its screen, and thus produces spot noise. Accordingly, the chrominance signal passes through a band-pass filter 11 and then passes through a bell filter 12, thereby making the chrominance signal uniform and preventing spot noise from being generated. The chrominance signal may contain noise during transmission or the signal itself may be attenuated to amplitude modulation. Therefore, a limiter 13 receives the output of the bell filter 12 to limit the amplitude of the chrominance signal to be uniform, separates and removes noise and amplitude modulation components, and removes them, and then outputs the remaining signal to a frequency divider 14 portion. The frequency divider 14 low-pass converts the chrominance signal output from the limiter 13 . The low-pass converted chrominance signal passes through a 1.1 MHz BPF 15 , is emphasized at a 1.072 MHz bell filter 16 , and is output to an adder 17 . Adder 17 adds the low-pass frequency-converted chrominance signal to a frequency-converted luminance signal.

FIG. 2A shows the composite video signal A of FIG. 1 transmitted from a broadcast station as a range of frequencies. Figure 2B shows the signal passing through the 4.3MHz BPF11, which is equivalent to the symbol X in Figure 1. FIG. 2C shows a signal to be recorded on the magnetic tape, that is, a signal obtained by adding a low-pass frequency-converted chrominance signal to a frequency-converted luminance signal in an adder 17, which corresponds to the symbol S in FIG.

In general, the SECAM VHS (Video Home System) format cannot be recorded using an Automatic Chroma Controller (ACC) but is recorded using a frequency direct recording method that cannot be used with PAL (Phase Alternative Color by Line) systems or NTSC (the color television system established by the National Television System Committee of the United States) system. Therefore, if the level of the color burst signal to be input is low, the quality of the SECAM video signal to be recorded is degraded, so that chrominance signal noise is generated when the video signal is reproduced. That is, since the SECAM video signal recording/reproducing apparatus does not have a compensation circuit for a change in the level of the chrominance signal of the image signal, there is a problem in that the reproduction capability of the image quality is low due to the low Reduced by frequency converting the recording format characteristics of SECAM video signals.

Therefore, in order to solve the above problems, an object of the present invention is to provide a SECAM video signal recording/reproducing apparatus with a function of compensating image quality by detecting a color burst signal from a composite video signal and The signal level is varied to amplify the video signal to record the amplified signal.

In order to achieve the above objects, the present invention provides a SECAM video signal recording/reproducing apparatus with a function of compensating image quality, which apparatus includes: A 4.3MHz bandpass filter that passes chroma signals only; a 4.28MHz bell filter that emphasizes chrominance signals that pass the 4.3MHz bandpass filter; an output that accepts the 4.3MHz bandpass filter and a color burst strobe to generate a DC voltage based on color burst level changes, and receive an output of the 4.28MHz bell filter to amplify the color burst based on color burst level changes relative to a reference signal an image quality compensation circuit for a chrominance signal; a limiter for receiving an output of the bell filter so as to limit the amplitude of the chrominance signal to be uniform and remove noise and amplitude modulation components from the chrominance signal; and a A low-pass switching circuit for quartering the frequency of the chrominance signal output by the limiter.

In a kind of SECAM video signal recording/playback apparatus with the function of compensating picture quality, preferably this picture quality compensating circuit comprises one for receiving the output of this 4.3MHz band-pass filter and this color burst gate pulse, a color burst level detector for generating a DC voltage according to the color burst level; A voltage-controlled amplifier that amplifies the magnitude of the composite signal by varying the burst signal level relative to the reference signal. Furthermore, it is preferable that the voltage control amplifier amplifies a difference between a burst level in a standard state and an output voltage of the burst level detector.

In order to achieve other objects of the present invention, the present invention also provides a SECAM video signal recording/playback device with a function of compensating image quality, which includes: A 4.3MHz band-pass filter that only passes the chrominance signal through the luminance signal; a 4.28MHz bell filter that emphasizes the chrominance signal passing through the 4.3MHz band-pass filter; an amplifier for amplifying the filtered composite signal to a predetermined amplitude; an amplifier for receiving the output of the amplifier for limiting the amplitude of the chrominance signal to be uniform and from a limiter for removing noise and amplitude modulation components in the chrominance signal; and a low-pass conversion circuit for quarter-dividing the frequency of the hue signal output from the limiter to low-pass convert the quarter-divided frequency.

The above objects and advantages of the present invention will become more apparent by describing in detail some preferred embodiments of the present invention with reference to the accompanying drawings. In these drawings:

Fig. 1 is a block diagram for showing the recording process of a chrominance signal in a kind of conventional SECAM video signal recording/reproducing apparatus;

2A to 2C represent a signal of each part shown in Fig. 1;

Fig. 3 A is a block diagram, is used to represent an embodiment of a kind of SECAM video signal recording/reproducing apparatus with the function of compensating image quality according to the present invention;

Fig. 3 B is a block diagram, is used for representing another embodiment of a kind of SECAM video signal recording/playback apparatus of the function of compensating image quality according to the present invention;

4A to 4D represent a signal of each part shown in FIG. 3A; and

Figure 5 is a circuit diagram for implementing a detector shown in Figure 3A.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3A is a block diagram showing an embodiment of a SECAM video signal recording/reproducing apparatus with a function of compensating image quality according to the present invention. With reference to Fig. 3 A, this video signal recording/playback equipment comprises a 4.3MHz band-pass filter 11 that is used for clearing brightness signal and only passing chrominance signal from a composite video signal sent by a broadcasting station; A 4.28MHz bell filter 12 for the chrominance signal of the 4.3MHz bandpass filter 11; one is used to receive the output of the 4.3MHz bandpass filter 11 and the burst gate pulse (BGP) so as to vary according to the burst signal level And produce DC voltage, and receive the output of 4.28MHz bell-shaped filter 12, so that amplify the image quality compensating circuit 20 of this chrominance signal according to the change of this synchronous signal level relative to a reference signal; One is used for receiving image quality the output of the compensation circuit 20, so that the amplitude of the chrominance signal is limited to a limiter 13 that is uniform and removes noise and amplitude modulation components; Divider 14.

Bandpass filter 11 receives the composite video signal to separate only the chroma signal and outputs the separated signal. A 4.28 MHz bell filter 12 receives the chrominance signal filtered by the bandpass filter 11 in order to make the chrominance signal uniform and prevent generation of spot noise. The chrominance signal may contain noise during transmission or the signal itself is partially attenuated to amplitude-modulated noise. A burst level detector 22 receives the signal B filtered by the 4.3 MHz bandpass filter 11 and the burst gate to detect a burst during the burst gate. Detector 22 then detects the DC voltage relative to the burst level, ie, the peak value of the burst.

The voltage control amplifier 24 not only receives the output signal of the 4.24 MHz bell filter 12, but also receives the DC voltage D output from the color burst level detector 22, so as to set gain. Then, the amplifier 24 greatly amplifies the output signal of the 4.28 MHz bell filter 12 as a difference in DC voltage in accordance with the level change of the burst signal, and outputs the amplified signal to the limiter 13 . The limiter 13 limits the amplitude of the chrominance signal output from the voltage control amplifier 24 to be uniform and removes noise and amplitude modulation components, thereby outputting the remaining signal to the frequency divider 14 . The frequency divider 14 low-pass converts the chrominance signal output from the limiter 13, and then the low-pass converted chrominance signal is emphasized in a 1.07MHz bell filter 16 through a 1.1MHz BPF15, and is output to an adder 17 . An adder 17 adds the low-pass frequency-converted SECAM chrominance signal to the frequency-converted luminance signal.

FIG. 3B is a block diagram showing another embodiment of a SECAM video signal recording/reproducing apparatus with a function of compensating image quality according to the present invention. This video signal recording/reproducing apparatus comprises the 4.3MHz band-pass filter 11 that is used to remove the luminance signal from the composite video signal sent by the broadcasting station and only passes the chrominance signal, and is used to emphasize the 4.3MHz band-pass filter 11 A 4.28MHz bell filter 12 of the filtered chrominance signal; an amplifier 26 for receiving the chrominance signal filtered by the 4.28MHz bell filter 12 to amplify the chrominance signal to a predetermined size; and The limiter 13 receives the output of the amplifier 26 to limit the amplitude of the chrominance signal to be uniform and remove noise and amplitude modulation components.

FIG. 4A shows the composite video signal A in FIG. 3A transmitted by a broadcast station on a frequency plane. FIG. 4B shows the burst signal B in FIG. 3A input to the burst level detector 22 on a frequency axis. FIG. 4C shows the burst gate pulse C in FIG. 3A input to the burst level detector 22 on a time axis. FIG. 4D shows the DC voltage output from the burst level detector 22. As shown in FIG.

FIG. 5 is a circuit diagram for implementing detector 22 in FIG. 3A. 5, the chrominance signal B filtered by the 4.3MHz bandpass filter 11 is supplied to the base of a transistor Q2, and BGPC is supplied to the base of a transistor Q1, so that the transistor Q1 is "on" during BGP gating. ". Then, the chrominance signal B is amplified by transistor Q2 to charge and discharge the burst signal while passing through a diode D1, a resistor R6 and a capacitor C3, thereby causing a DC voltage as shown in FIG. 4D.

As described above, according to the SECAM video signal recording/reproducing apparatus with the function of compensating image quality of the present invention, the output of the 4.3MHz bandpass filter and the burst gate pulse are received so as to vary according to the burst signal level. A DC voltage is generated and the output of the 4.28MHz bell filter is received to amplify the chrominance signal according to the change of the color burst signal level relative to the reference signal, so as to improve the recorded/reproduced image according to the chrominance signal quality.

Claims (3)

1. A SECAM video signal recording/playback device with a function of compensating image quality, comprising: A 4.3MHz bandpass filter used to remove the luminance signal from a composite video signal and pass only the chrominance signal; a 4.28MHz bell filter for emphasizing the chrominance signal passing through said 4.3MHz bandpass filter; one for receiving the output of the 4.3 MHz bandpass filter, the color burst strobe and the output of the 4.28 MHz bell filter to amplify the color burst in response to changes in the color burst level relative to a reference signal The image quality compensation circuit of the size of the degree signal; a limiter for receiving the output of said picture quality compensation circuit so as to limit the amplitude of the chrominance signal to be uniform and remove noise and amplitude modulation components from the chrominance signal; and a low-pass conversion circuit for low-pass conversion of the frequency of the chrominance signal output from said limiter. 2. The SECAM video signal recording/playback apparatus with the function of compensating picture quality as described in claim 1, wherein said picture quality compensating circuit comprises one and is used to receive above-mentioned output of said 4.3MHz band-pass filter the color burst gate pulse, so as to generate a DC voltage color burst level detector according to the color burst signal level; and a color burst signal level detector for receiving the output voltage of the color burst signal level detector and the 4.28MHz The output of the bell filter is a voltage-controlled amplifier for amplifying the amplitude of the chrominance signal according to the variation of the color burst signal level relative to the reference signal. 3. The SECAM video signal recording/reproducing apparatus with the function of compensating image quality as described in claim 2, wherein said voltage control amplifier includes a signal for amplifying the color burst signal level in a standard state and said means for the difference between the output voltages of the color burst level detectors.

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