JPS61201589A - Synchronizing signal separator - Google Patents

Abstract

PURPOSE:To reduce signal jitters restored while its time axis is expanded by obtaining a synchronizing signal output coincident with an edge of the order number of the stage of a shift register of a sinusoidal wave burst signal in a video signal. CONSTITUTION:The titled device is provided with a horizontal synchronous separator circuit 1 outputting only a horizontal synchronizing signal (b), a delay circuit 2 retarding the horizontal synchronizing signal, a band pass filter 3 passing the frequency of the sinusoidal burst signal from a video signal, and a shift register 5 using a signal (e) obtained by giving the output of the filter 3 to a waveform shaping circuit 4 and converting it into a square wave as a clock input and using an output of the delay circuit 2 as a reset input. The signal obtained by applying waveform shaping to the sinusoidal wave burst signal as the clock input to the shift register 5 and the signal retarding the horizontal synchronizing signal is used and the shift register is reset just before the sinusoidal wave burst signal. Thus, the pulse coincident with the edge of the wave of the order number of stages of the shift register of the sinusoidal wave burst signal is obtained at the output of the shift register.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a synchronization signal separation device for extracting a synchronization signal from a video signal for use in signal processing when reproducing a video signal recorded on a magnetic tape or the like.

Conventional technology In the past, when recording and reproducing video signals on magnetic tape, etc., a composite signal such as NTSC was separated into a luminance signal and a modulated color difference signal, and the luminance signal was converted to an FM modulated signal and a lower frequency signal. A so-called low-pass conversion method is used in which the modulated color difference signals are mixed and recorded and reproduced.

However, there are interlayers such as cross-modulation and phase noise of color difference signals, making it unsuitable for high-quality recording and reproduction.

Therefore, a method of compressing the time axis of three signals, a luminance signal and two color difference signals (Japanese Unexamined Patent Publication No. 109423/1983), and then performing FM modulation on the compressed signals is considered.

Problems to be Solved by the Invention However, when such a signal is reproduced and demodulated and restored to the original three signals, if the reproduced signal contains jitter, the jitter of the decompressed signal will appear in the restored signal. Also, when decompressing, it is stored in memory, but at this time, if the demodulated synchronization signal is used as the reference signal for setting the start address and generating the clock,
The jitter of the restored signal greatly affects the SN ratio of the synchronization signal. However, during FM modulation, the synchronization signal is located at a lower frequency, and the falling edge of the synchronization signal is located at an even lower frequency due to the pre-emphasis circuit, making it easy for carrier leakage to occur during demodulation. , a high SN ratio cannot be expected. Therefore, if a demodulated synchronization signal is used for setting the start address or as a reference signal for clock generation, it is difficult to reduce the jitter of the restored signal.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a synchronization signal separation device used in video signal processing that can obtain a restored signal with small jitter.

Means for Solving the Problems In order to solve the above problems, the present invention provides a sine wave burst signal at a level Ip higher than the pedestal level between the horizontal synchronization signal lower than the pedestal level and the time axis compressed signal. In order to record the superimposed signal and obtain a synchronization signal that matches a predetermined edge of this sine wave burst signal during playback, a horizontal synchronization separation circuit that outputs only the horizontal synchronization signal and a delay that delays the horizontal synchronization signal are provided. A bandpass filter that outputs only a sine wave burst signal from the reproduced signal, a waveform shaping circuit that makes the output a square wave, and the output of this waveform shaping circuit is used as a cross input to reset the output of the delay circuit. It is provided with a shift register as an input, and obtains a synchronization signal that coincides with the edge of the shift register stage number of the sine wave burst signal from the output of the shift register.

As described above, the sine wave burst signal is at a higher level than the horizontal synchronization signal, so when the horizontal synchronization signal is FM modulated so that it has a lower frequency with a frequency shift, the sine wave burst signal has a higher level than the horizontal synchronization signal. The demodulated sine wave burst signal has less carrier leakage, and by passing the frequency of the sine wave burst signal through a bandpass filter, a higher S/N ratio can be obtained. The jitter of the restored signal can be reduced by extracting a synchronizing signal that coincides with the edge of a predetermined number of the sine wave burst signal and using it for setting the start address of the memory or as a clock generation reference. A method for extracting a synchronization signal that coincides with a predetermined edge of a sine wave burst signal will be described. According to the configuration of the present invention described above, a signal obtained by shaping the waveform of a sine wave burst signal is used as a clock input of the shift register, and a delayed horizontal synchronization signal is used to reset this shift register immediately before the sine wave burst signal. As a result, a pulse matching the edge of the wave of the shift register stage number of this sine wave burst signal is obtained at the output of the shift register.

Embodiment Hereinafter, a synchronization separation device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a horizontal synchronization separation circuit which inputs a video signal a containing a horizontal synchronization signal and a sine wave burst signal and outputs only the horizontal synchronization signal;
2 is a delay circuit that delays the horizontal synchronization signal; 3 is a bandpass filter (BPF) that inputs the video signal & and passes the frequency of the sine wave burst signal; and the output waveform of the output d of bandpass filter 3 is converted into a square wave. waveform shaping circuit,
This is a shift register that uses the output e of the waveform shaping circuit 4 as a clock input and the output C of the delay circuit 2 as a reset input. The synchronization signal separation device configured as above will be explained.

FIG. 2 is a waveform diagram of a time-base compression multiplexed video signal, and FIG. 3 is a waveform diagram of each part of FIG. 1. Figure 3a shows the synchronization signal and sine wave burst signal in Figure 2 expanded in time, where H3 is the horizontal synchronization signal, PDid pedestal level, CB is the achromatic level, and BS is the sine wave burst signal. .

In this figure, since it is a reproduced signal, especially the horizontal synchronization signal H3
It is assumed that the falling part of the signal has jitter due to carrier leakage (bold line part).

With & as input in FIG. 3, the output of the synchronization separation circuit 1 becomes as shown in the figure, and is shifted by the delay circuit 2 to the front of the sine wave burst signal as shown in C of the figure. The input video signal also passes through a bandpass filter 3, and a sine wave burst signal is extracted as shown in FIG. Then, the output of the shift register 5 is reset by the output of the delay circuit 2, as shown in FIG.
A synchronization signal matching the edge of the sine wave burst signal at the stage number of the shift register 5 is obtained.

Since this synchronization signal exhibits an accurate phase regardless of the jitter of the horizontal synchronization signal, the jitter of the restored signal can be reduced.

Effects of the Invention As described above, the present invention includes a horizontal synchronization separation circuit that outputs only a horizontal synchronization signal, a delay circuit that delays the horizontal synchronization signal, and a bandpass filter that passes the frequency of a sine wave burst signal from a video signal. , and a shift register whose output is passed through a waveform shaping circuit and converted into a square wave as a clock input, and whose reset input is the output of the delay circuit. It is possible to obtain a synchronization signal output that coincides with the edge of the stage number, and to reduce jitter in the signal that has been expanded and restored on the time axis.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a synchronization signal separation device according to an embodiment of the present invention, FIG. 2 is a waveform diagram of an example of a time-base compression multiplexed video signal, and FIG. 3 is a waveform diagram of each part of FIG. 1. 1...Horizontal synchronization separation circuit, 2...Delay circuit, 3...Bant pass filter, 4...Waveform shaping circuit, 5...Shift register. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 Figure B, 9

Claims (1)

[Claims] a horizontal synchronization separation circuit that receives a video signal including a horizontal synchronization signal and a sine wave burst signal and outputs only the horizontal synchronization signal; a delay circuit that delays the horizontal synchronization signal; and a delay circuit that receives the video signal and outputs a sinusoidal burst signal. a waveform shaping circuit that makes the output waveform of the bandpass filter a square wave; and a shift register that uses the output of the waveform shaping circuit as a clock input and the output of the delay circuit as a reset input. A synchronization signal separation device comprising: obtaining a synchronization signal that coincides with an edge of the sine wave burst signal in the number of stages of the shift register.