JPS61177887A - Video signal processing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal processing system for recording and reproducing video signals on a magnetic tape or the like.

Conventional technology Conventionally, when recording and reproducing video signals on magnetic tape, etc., a composite signal such as NTSC is separated into a luminance signal and a modulated color difference signal, and the luminance signal is FM modulated and converted to a lower frequency. 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 problems such as cross-modulation and phase noise of color difference signals, making it unsuitable for high-quality recording and playback.

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 to restore the original three signals, if the reproduced signal contains jitter, the jitter will appear in the restored signal as the expansion rate. Further, when the data is stored in memory during decompression, if a demodulated synchronization signal is used as a reference signal for setting the start address or generating a clock, the jitter of the restored signal will greatly affect the S/N ratio of the synchronization signal.

Furthermore, 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 carrier leak likely 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 this point, and an object of the present invention is to provide a video signal processing method that can obtain a restored signal with small jitter.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides an expansion signal between the horizontal synchronization signal lower than the pedestal level and the time-axis compressed signal to a predetermined level higher than the pedestal level. A synchronizing signal, such as a sine wave burst signal, is superimposed to reduce the jitter of the restored signal during reproduction.

Function: As described above, the expansion synchronization signal is at a predetermined level higher than the horizontal synchronization signal, so when the horizontal synchronization signal is FM-modulated to have a lower frequency by frequency shift, the expansion synchronization signal occupies a higher frequency, resulting in less carrier leakage and a higher SN ratio. Therefore, by using this decompression synchronization signal for setting the memory start address or as a clock generation reference, it is possible to reduce the jitter of the restored signal. Furthermore, by using a sine wave burst signal as the expansion dose period signal and using a bandpass filter that passes the burst signal frequency during reproduction, a higher S/N ratio can be obtained and jitter can be further reduced.

Embodiment FIG. 1 shows a waveform diagram of one example of the video signal processing system of the present invention. H3 is a horizontal synchronization signal, PD is a pedestal level, CB is an achromatic color level, BS is a burst signal, CI and C2 are two color difference signals, for example, R-Y, B
-Y signal or I,Q signal, etc., where Y is a luminance signal.

Note that CI and C2°Y are compressed on the time axis.

First, the signal (hereinafter referred to as TC signal) subjected to time axis compression multiplexing in this way is converted into Ci, C2 before time axis compression as shown in Fig. 6.
The case of creating from ', Y' will be explained.

FIG. 6 shows an example of the configuration of a device that generates a TC signal. Input signals C1', C2', Y' are A/
They are each converted into digital data by D converters 11, 12, and 13, and are simultaneously written into memory circuits 21, 22, and 23. The write period at this time is the period of the clock pulse obtained by transmitting the horizontal synchronization pulse separated by the synchronization separation circuit 8 from the input r by the clock generator 61, and is written to the memory address by the address output of the address generator 71. .

At this time, C1', C2/, Y' (7) If the required band is ILI&, 4M, the period of the clock pulse is set to 4 m':1 and is written to the memory. On the other hand, from the horizontal synchronization pulse of the synchronization separator 8, the clock generator 62 generates a read clock pulse with a cycle of 6/7 of the write clock pulse, and the address generator 72 generates a read address, thereby reading data from the memory. . At this time, a putter/memory 3 whose pattern data is a horizontal synchronization signal, a pedestal level, an achromatic color level, and a burst signal which is a synchronization signal for expansion is prepared, and the pattern memory 3, memory 21, memory 22, and memory 23 are Read while switching the multiplexer 4, D/A converter 6
Through this, a TO multiplied signal is generated. At this time, Y' is 5/7
The required bandwidth is 5. :6&tk, CI'.

C2' is compressed to 5/28, and the required bandwidth is still 5.6
The required band for the TC signal will be 6.6 koku.

FIG. 2 shows C1' and C2' from the TC signal.
.

This is an example of a restoring device that has been put back in. The TO multiplied signal produced as described above is converted into digital data by the A/D converter 1, demultiplexed and written. On the other hand, simultaneous reading from memo IJ24.25.26 and D/A
Converter 51. 52. Original 01', C2' by 53
, return to the signal Y'. At this time, the write and read clocks are generated by the address reset section 9, which captures one edge of the input TO multiplied signal burst signal, obtains a pulse with the same synchronization as the horizontal synchronization signal, and generates the respective clock generators 63.
Create by multiplying by 64.

The TC signal is FM modulated and then recorded on magnetic tape.
During playback, it is FM demodulated and becomes a TC signal. Figure 4a shows the playback signal waveform when carrier leak occurs at the falling edge of the horizontal synchronization signal H8 and jitter occurs (bold line section). ). FIG. 3 shows the internal configuration of the address reset section 9. Figure 4 shows the waveforms of each part in Figure 3.
The output of the synchronization separation circuit 8 becomes as shown in FIG. 3, and by the pulse delay circuit 91 becomes the output as shown in FIG.

On the other hand, the TC signal passes through a bandpass filter 94 to extract only the burst wave, as shown in FIG. 4d, passes through a waveform shaping circuit 95, and becomes as shown in FIG. to go into. Therefore, the output of the shift register 92 is as shown in FIG. 4f. This pulse is further converted into a reset pulse with a one-clock pulse width by the synchronous differentiator 93 (Fig. 4q), and as a result,
The address generation circuit 73 is reset and is used as a reference input for the clock generation circuit 63. As a result, the reset pulse shown in FIG. 4 coincides with the edge of the burst wave, regardless of the jitter shown in FIG. 4, and by using this pulse, the jitter can be reduced.

As described above, according to this embodiment, by superimposing a burst signal at a predetermined level higher than the horizontal synchronization signal between the horizontal synchronization signal and the time axis compression signal, and using this burst signal during reproduction, The jitter of the restored signal can be reduced. Further, by matching a predetermined level like pl with the achromatic color level, it is possible to reduce the time margin between each level and lengthen the effective time.

Further, in the embodiment, digital processing such as A/D conversion, memory, and D/A conversion is performed, but analog processing can also be performed using a charge transfer element or the like.

Effects of the Invention As described above, the present invention superimposes an expansion synchronization signal at a predetermined level higher than the pedestal level between the horizontal synchronization signal lower than the pedestal level and the time axis compression signal, so that the horizontal synchronization signal is lower than the pedestal level. When FM modulated so that the frequency becomes
The decompression synchronization signal has a high frequency, causes less carrier leak during demodulation, and obtains a high S/N ratio. By using this decompression synchronization signal, the jitter of the restored signal can be reduced. Furthermore, by using a sine wave burst signal as the expansion synchronization signal, a higher SN ratio can be obtained and jitter can be reduced. Furthermore, by making the predetermined level coincide with the achromatic color level, there is an effect that the time margin between the achromatic color level and the decompression synchronization signal can be reduced.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram according to an embodiment of the present invention, FIG. 2 is a configuration diagram of a restoration device for implementing an embodiment of the present invention, and FIG.
Figure 4 is a diagram of the configuration of the address reset section, Figure 4 is a waveform diagram of each part in Figure 3, Figure 5 is a diagram of the configuration of a waveform synthesizer for implementing an embodiment of the present invention, and Figure 6 is a diagram of its waveform synthesis device. FIG. 3 is a waveform diagram of an input signal. H5...Horizontal synchronization signal, BS...Burst signal, CI, C2...Time axis compressed color difference signal, Y...Time axis compressed luminance signal , Y′・
...Brightness signal, 01'. C2'...Color difference signal. Name of agent: Patent attorney Toshio Nakao and 1 other person - Figure 3 Figure 4 Figure 5 Figure 6

Claims (4)

[Claims] (1) In a video signal, two color difference signals and a luminance signal are time-axis compressed and arranged in one horizontal period, and an expansion synchronization signal is inserted between the horizontal synchronization signal and the time-axis compressed signal. A video signal processing method characterized by: (2) The video signal processing method according to claim 1, in which a sine wave burst signal is used as the decompression synchronization signal. (3) If the horizontal synchronization signal is at a level lower than the pedestal level, a predetermined level is provided at a level higher than the pedestal level, and an expansion synchronization signal is superimposed on the predetermined level. Video signal processing method described. (4) The video signal processing method according to claim 3, wherein the predetermined level is made to match the achromatic color level.