JPS61265993A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To reproduce properly the phase of the high frequency component of a luminance signal subjected to low frequency conversion and to improve a resolution by inverting the phase of a frequency-converting carrier or a high frequency luminance signal when the phase relationship between the synchronizing signal of a demodulated reproduction low frequency luminance signal and the high frequency component of a synchronous signal included in the high frequency luminance signal is reverse. CONSTITUTION:The titled device is provided with a phase detecting part 1 detecting the phases of the outputs of a synchronizing separator 6 and an YCF 8, a pulse width discriminating part 2 detecting that the width of the output pulse exists over the prescribed time in order to eliminate influence such as a noise, a state holding part 3, which inverts the state of the output when it is given. otherwise, holds the state as it is, and a phase control part 4 which converts reversely or normally the phase of a frequency converting carrier due to the output. Then the phase relation-ship between the synchronous signal of the demodulated reproduction low frequency luminance signal and the high frequency component of the synchronous signal included in the high frequency luminance signal is detected. When it is reverse, the phase of the frequency converting carrier is inverted. Thus the high frequency luminance signal is inverted accordingly, the the phases of the high and low frequency components of the luminance signal are made equal.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an apparatus for reproducing video signals recorded using a low frequency conversion method.

2. Description of the Related Art Conventional general low-frequency conversion video signal recording and reproducing apparatuses have configurations as shown in FIGS. 8 and 9, respectively. This will be explained using FIG. Figure 7 (al is NTSC or P in which luminance signal Y and chromaticity signal C are combined)
It shows a composite color video signal such as AI, but the following shows NT
This will be explained using the SC signal.

The NTSC signal is applied to input terminal 60 in FIG. Then, the output of the low-pass filter (hereinafter referred to as LPF) 61 of approximately sMHz is the luminance signal Y as shown in FIG. 7 (bl).
Only the low-frequency luminance signal YL, which is the low-frequency component of the signal, is input to a frequency modulator (FM modulator) 62 as a frequency modulation signal (hereinafter referred to as FM signal). On the other hand, the composite color video signal that has passed through a band pass filter (hereinafter referred to as BPF) 64 is a high-frequency component YH of the luminance signal Y, as shown in FIG. 7 (cl).
and the carrier color signal C are combined. If we consider the chromaticity signal C by dividing it into a subcarrier frequency f8 and a sideband component c, this can be expressed as f, 10fC+YH. From this signal, only the burst signal is extracted by a burst gate 65, and a continuous wave at the burst frequency, that is, subcarrier frequency f8, is generated by a PLL (phase locked loop) consisting of a phase comparator 66, an LPF 6, and a voltage controlled crystal oscillator (VXO) 68. Furthermore, from the horizontal synchronization signal fH extracted from the composite color video signal by the synchronization separator 71, a PLL consisting of a phase comparator element 2, an LPF 73, a voltage controlled oscillator (hereinafter referred to as VCO) 74, and a frequency divider 75 , the low-frequency subcarrier f1 is obtained, and the signal obtained by the balanced modulator (hereinafter referred to as BM) θ9 is
It becomes a continuous wave with a frequency of fs+f, so this and B
The output of the PF 64 is input to the BM 70 to obtain a low frequency converted signal centered on the low frequency subcarrier f1. This signal and FM
The combined signal is amplified by a recording amplifier 63 in FIG. 7 (dl), and recorded on a magnetic tape or the like by a head 61.

FIG. 9 is a block diagram of the reproduction side, in which the reproduction signal obtained by the head 51 is amplified by a preamplifier 52, and then filtered through a bypass filter (hereinafter referred to as HPF) 53 and an LPF.
6 into an FM signal and a low frequency conversion signal. FM signal.

The limiter 54 limits the amplitude, suppresses amplitude fluctuations, and
It is demodulated by an M demodulator 56 to obtain the original low-band luminance signal YL.

However, it includes jitter Δ in the drive system of the magnetic tape, etc.

On the other hand, the low frequency conversion signal is returned to the carrier color signal C centered on the original subcarrier f11 by the output of the local oscillator 96 and the chromaticity processing unit (APC) 9, and is combined with the low frequency luminance signal YL and output. At terminal 76, the original composite color video signal is obtained. At this time, the human PC 9 operates to stabilize the phase of the subcarriers, so that colors can be reproduced correctly on the receiver side. i.e.), in PO2, 8
From the signal that has undergone frequency conversion in M91 and passed through BPF92, only the burst portion is increased by burst gate 93,
The phase of the output of the subcarrier fixed oscillator 95 is compared with the phase comparator 94, and the obtained error signal is smoothed by the Lpyc4e and drives the VCO 97.

The output of the VCO 97 is the frequency of the low subcarrier f1 plus an error, which is the frequency of the subcarrier fixed oscillator 9.
The frequency is converted by the output of 5 and BM98, and the frequency is converted by the low frequency conversion signal and 8M91. Then, a conveyed color signal fs+fc+YH is obtained as shown in the following equation.

(to fs + f+ +) - (f+ -fC-YH+Δ
)=f5+fc+YH Since this loop performs a negative feedback operation to eliminate errors, a signal without jitter components is obtained as an output. This is generally called an APC loop. These are described in Japanese Patent Publication No. 50-14852.

Now, since the jitter of the carrier color signal has been removed, the colors are correctly reproduced, and the FM demodulated low-band luminance signal YL+Δ
Although it contains jitter, it can be tracked on the receiver side, so one image can be reproduced.

By the way, jitter has been removed from the high-frequency luminance signal YH, which is included in the carrier color signal band signal by frequency-converting the low-frequency conversion signal, but it is difficult for the receiver to follow the jitter of the low-frequency luminance signal YL+Δ. On the other hand, the reproduced high-frequency luminance signal YH appears to be distorted, as if there is jitter.
are not fully utilized. A method of making use of this high-range luminance signal YH is also described in JP-A-57-89387-8, but it requires setting the frequency of the carrier wave for frequency conversion to be an integral multiple of the synchronization signal. As described above, this method cannot be applied to cases where the subcarrier fs of the NTSC signal is used as the carrier wave.

Problems to be Solved by the Invention When using the subcarrier fs of the NTSC signal, (1
), there are two types of phase relationships with the synchronizing signal, so even if the phases of the high-range luminance signal YH and the low-range luminance signal YL are adjusted and matched.

In the case of the other phase relationship, the phases of YH and YL will be shifted by 1800 degrees.

The present invention has been made in view of the above points. 1. A video recording and reproducing device capable of obtaining a reproduced composite color video signal in which a high-frequency luminance signal YH and a low-frequency luminance signal YL are in phase with each other with a simple configuration. is intended to provide.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention always has a constant phase relationship between the synchronization signal and the luminance signal, and as described above, the phase relationship between the synchronization signal and the carrier wave for frequency conversion is twofold. Focusing on the fact that there are only two types, we have developed a phase detection unit that detects the phase relationship between the synchronization signal of the demodulated reproduced low-band luminance signal and the high-frequency component of the synchronization signal included in the high-band luminance signal, and its output pulse. a pulse width discriminator that detects that the width of the pulse width is longer than a predetermined time; a state holding section that inverts the state when there is an output, and maintains the same state when there is no output; Alternatively, a phase control unit that inverts or normalizes the phase of the high-frequency luminance signal is provided, so that the phase relationship between the synchronization signal of the demodulated reproduced low-frequency luminance signal and the high-frequency component of the synchronization signal included in the high-frequency luminance signal is reversed. In the case of phase, by inverting the phase of the carrier wave for frequency conversion or the high-frequency luminance signal, the luminance signal, which has a certain phase relationship with the synchronization signal, and its low-frequency and high-frequency components are also in phase. This is how it was done.

Effect of the Invention With the above-described configuration, the present invention can reproduce a composite color video signal without shifting the phase of the reproduced luminance signal and the high-frequency components of the low-frequency converted luminance signal, and the luminance signal included in the low-frequency converted signal can be reproduced. It is possible to effectively restore the high frequency components of the image and dramatically improve the resolution.

Embodiment FIG. 1 is a block diagram showing an embodiment of the video signal reproduction system of the present invention. In FIG. 1, the same components as in FIG. 9 are given the same numbers, and their explanations will be omitted.

The two in Figure 1 (DAPC901 and 902 are person P in Figure 9)
It has the same configuration as C9.

The case of an NTSG signal will be explained with reference to FIG.

The signal passing through LPF6 is sent to APC901 and APC9
02. In the APC 902, as in FIG. 9, the jitter component is removed by a fixed oscillator 95, the frequency is converted, and the chromaticity signal comb filter (CCF
) 7 outputs only the chromaticity signal. As is well known in this method, since the chromaticity signal and the luminance signal have a frequency inter-IJ-b relationship as shown in Figure 6 (bl), the chromaticity signal and the luminance signal have the frequency characteristics shown by the solid line in Figure 6(a). Comb filter (c
cF)7 can easily pass only the chromaticity signal.

On the other hand, in the APC901, from the output of the 7M demodulator 65,
PLL based on the horizontal synchronization signal obtained by the synchronization separator 66
The frequency of the subcarrier fs is 227.5 times that of the horizontal synchronization signal by the 456 multiplier 57° 1/2 frequency divider 58, which is composed of the following:
A luminance signal comb filter (Y
CF)8 extracts only the luminance signal. These two signals and the low frequency luminance signal Y which is the output of the 7M demodulator 65
By combining the signals L and L, a jitter-free carrier chrominance signal and a luminance signal with the same jitter in both the high and low frequency components of the luminance signal are obtained at the output terminal 76, which is then transmitted to the receiver. When viewed, colors are correctly reproduced because the chromaticity signal has no jitter, and since it follows the jitter of the luminance signal, even the high range of the luminance signal can be seen without fluctuation.

Furthermore, a phase detection section 1 that detects the phase of the output of the synchronous separator 56 and the output of the YCF 8, and a pulse width discrimination section that detects that the width of the output pulse is longer than a predetermined time in order to eliminate the influence of noise etc. 2, a state holding section 3 which inverts the state when there is an output, and maintains the same state when there is no output, and a phase control section 4 which inverts or normalizes the phase of the carrier wave for frequency conversion depending on the output. If the phase relationship between the synchronization signal of the reproduced low-frequency luminance signal provided and demodulated and the high-frequency component of the synchronization signal included in the high-frequency luminance signal is in reverse phase, the phase of the frequency conversion carrier wave is inverted. As a result, the high-frequency luminance signal is inverted, and the phases of the low-frequency and high-frequency components of the luminance signal can be matched.

This will be further explained with reference to FIGS. 2, 3 and 4. FIG. 2 shows an embodiment of the phase adjustment section of the present invention, and FIGS. 3 and 4 are waveform diagrams of each part in FIG. 2. Third
Figure b+ shows the output of the FM demodulator 55, which is sent to the sync separator 5.
6 (the output of 0YCF8, which becomes C1 and becomes the trigger input for the flip-flop 12, is shown in Figure 1), and passes through the time adjustment section 11 of Figure 2 to match the synchronization signal in time to Figure 3 (Figure 3). dl, and input the data to the flip-flop 12.The flip-flop 12 is a phase detector, and when it is normal, it is output from II O (as shown in el). ”, and when the phase is reversed, it becomes 1” as shown in the figure (b).

In FIG. 4, the output of the phase detection section 1 is el in the same figure. (fl. If the pulse width is long, or if the phase is out of phase or continues for a long time, the voltage of the integrating circuit will exceed the threshold voltage Vt of the Schmitt trigger circuit 25 and the output will be 1'', and the state of the state holding section 3 consisting of the exclusive or gate 31 and the flip-flop 32 is reversed.Then, the phase control section 4 consisting of the exclusive or gate 41 The phase of the carrier wave for frequency conversion is inverted and returned to the normal phase.Furthermore, even if the phase detection section 1 malfunctions due to noise etc., the voltage of the integrating circuit will not exceed the threshold voltage Vt, so the state holding section 3 The state of is not reversed.

In this way, the phase of the carrier wave for frequency conversion is maintained correctly, and the phases of the high-range luminance signal Yl (and the low-range luminance signal YL) match.

If the phase of the carrier wave for frequency conversion is inverted, the high-frequency luminance signal will be inverted as a result, so instead of inverting the phase of the carrier wave for frequency conversion, a phase control section is installed before or after the luminance signal comb filter (YCF) 8. A similar result can be obtained even if the phase of the high-frequency luminance signal itself is reversed by inserting

FIG. 5 shows an example using a time base collector 80 with a subcarrier feedback terminal, which is a method of inputting an external carrier wave to the APC 9 in a conventional circuit. In this case, both a luminance signal and a carrier color signal with jitter are outputted to the output terminal 76, and the jitter is removed by the connected time base collector 80 to obtain a jitter-free composite color video signal. Even in this case, since the carrier wave for frequency conversion can take two different phases, it is necessary to arbitrarily determine the phase, and the present invention can be applied.

The phase detection unit 1, pulse width discrimination unit 2, state holding unit 3, and phase control unit 4 have the same configuration as in FIG. can be combined.

Further, even if the phase control section 4 is inserted after the APC 9 as in FIG. 1, the same result can still be obtained.

Effects of the Invention As described above, according to the present invention, with an extremely simple configuration, the high-frequency components of the low-frequency converted luminance signal are reproduced with correct phase, and the resolution is dramatically improved, making it suitable for practical use. In particular,
Extremely useful.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a video recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a detailed block diagram of the - part in FIG. 11, and FIGS. 6 is a block diagram showing a video recording and reproducing apparatus in another embodiment of the present invention. FIG. 6 is a diagram showing the relationship between the characteristics of the comb filter and frequency interleaving, and FIG. FIG. 8 is a block diagram showing a conventional video signal recording device, and FIG. 9 is a block diagram showing a conventional video recording and reproducing device. DESCRIPTION OF SYMBOLS 1... Phase detection section, 2... Pulse width discrimination section, 3... State holding section, 4... Phase control section. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure 3 Figure 4 (h) Figure 5 Figure 6 @ Figure 7 Figure 8 Figure 9

Claims (2)

[Claims] (1) Frequency modulation of the carrier wave using a low-frequency conversion signal obtained by converting the frequency of the carrier color signal band signal separated from the composite color video signal to a low frequency band and a luminance signal separated from the composite color video signal using a low-pass filter. The reproduced low-pass conversion signal separated from the reproduced signal obtained by reproducing the same is multiplex-recorded with the frequency modulated signal obtained by the above process, and the reproduced carrier color signal band signal obtained by frequency converting the reproduced low-pass conversion signal to the original frequency band. , in a video recording and reproducing apparatus that obtains a reproduced composite color video signal by mixing a reproduced luminance signal obtained by demodulating a reproduced frequency modulation signal separated from the reproduced signal, a synchronization signal of the reproduced luminance signal and the reproduced carrier color; a phase detection unit that detects a phase difference with a high-frequency component of a synchronization signal included in a signal in a signal band; and a pulse width discrimination unit that detects that the pulse width of the output of the phase detection unit is longer than a predetermined time. , a state holding unit that inverts the state when there is an output from the pulse width discriminator and maintains the same state when there is no output; A video signal reproducing device characterized in that the high-frequency component of the luminance signal existing in the carrier color signal band is effectively restored by being equipped with a phase control section that rotates in the normal direction, and the phase also matches that of the reproduced luminance signal. . (2) A phase control section is inserted into the reproduced high-frequency luminance signal circuit after frequency conversion, and configured to invert or normal rotate the phase of the reproduced high-frequency luminance signal itself, rather than the phase of the carrier wave used for frequency conversion. A video signal reproducing device according to claim (1).