JPH02162883A - Picture signal recording and reproducing device - Google Patents

Abstract

PURPOSE:To correctly restore an original picture signal by comparing the central value of a ternary signal added at the time of recording with the sample value of the center part of the ternary signal obtained at the time of regeneration, and correcting the phase of a recovered sampling clock at the time of regeneration according to a result. CONSTITUTION:The ternary signal is added to a Y signal and a C signal at the time of starting a picture (immediately after back porching) by ternary signal adding circuits 3 and 3', a sampling pulse in synchronization with a pilot signal recorded together with the picture signal at the time of recording is formed at the time of reproduction, and based on the sampling pulse, the regenerative picture signal is sampled. Thereafter, by an error signal obtained by comparing the sampling value near the center part of the ternary signal added at the time of recording with a prescribed level by means of a comparator 12, the phase of the sampling pulse is corrected. Thus, the picture signal recorded on a recording medium can be correctly restored with the use of the analog transmission of the sample value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an image signal recording and reproducing apparatus that records and reproduces image signals via a recording medium.

[Prior Art] Conventionally, there is a still video (hereinafter referred to as Sv) system as a recording and reproducing device for still image signals. This Sv system converts current TV signals into FM 2-inch magnetic disks.
It modulates and records. The image resolution achieved by this system is only comparable to that of current TV systems, but in systems that handle still images, such as the Sv system, the final output may be printed out using a printer. In that case, the problem is that the image quality (especially resolution) is lower than that of silver halide photography.

On the other hand, recently HD TV (High Definition)
New TV systems are being considered, such as HDTV, which has about 1,000 scanning lines, which is about twice the number of the current NTSC system, and a corresponding horizontal signal band. have. Therefore, S
Even in the V system, the 10
It has become essential to develop a still image recording and reproducing system with an image quality of about 00x 1000 pixels (when a square screen is taken out).

In view of this situation, in the Sv system, the recording format for the recording medium is made high band (wide band). However, when viewed as an Sv system, it is necessary to achieve high image quality while maintaining compatibility with conventional systems to some extent.

Therefore, as a method to improve image quality while maintaining compatibility with conventional systems, the applicant proposed the CHSV method (C
Compatible High Definition
SV) can be considered.

An outline of the CHSV method will be described below.

First, a method for recording a luminance (Y) signal based on the CHSV method will be described. FIG. 5 shows sample points of the Y signal recorded based on the CHSV method. The sample points of the Y signal are sub-sampled at a sampling period Ts, for example, so as to be arranged offset as shown in the figure.

There are 650 sample points in a row (1300/2), and -
There are 500 (10 mouths 0/2) in the row. And A8 in the figure. A2.

. . . sample f1 included in the line B, , B2 .・・・・・・
The sample values included in the line are recorded on another track, and so on, all sample values are recorded using a total of four tracks. Furthermore, recording is performed on each track in accordance with the format of the conventional Sv system.

Next, the reproduction method will be described. FIG. 6 shows the reproduction process based on the CHSV method. A signal reproduced by a magnetic head 1502 from a magnetic disk 1501, which is a recording medium, is amplified by a reproduction amplifier 1503 and then input to an Sv reproduction process circuit 1504. Here, separation of the luminance signal Y and color difference line sequential signal C, FM demodulation, de-emphasis, etc. are performed, and a reproduced Y signal and a reproduced C signal are output. Then, those two signals are γ-inverted in a γ-inverter 1506 or 1507, and L P F 15
After being band-limited at 08 or 1509, the signals are input to the image memory via an analog-to-digital (A/D) converter 1513 or 1514, respectively. This A/D converter! The sampling clocks 513 and 1514 are obtained by extracting a pilot signal, which has been frequency multiplexed in advance from the signal reproduced from the magnetic disk 1501 into the recording medium, using a band pass filter (BPF) 1505, and extracting the pilot signal from the signal reproduced from the magnetic disk 1501 using a synchronization separation circuit 1510. This clock is generated by the sampling clock generation circuits 1511 and 1512 using the synchronized and separated synchronization signals.

The above process is performed for four tracks on the magnetic disk 1501, and the sample data output from the A/D converters 1513 and 1514 is sent to the address generator 1517.
．． The image is stored at the address on the image memory 1515 designated by 1518. Then, the image processing circuit 1516 uses the sample data stored in the image memory 1515.
After performing interpolation processing etc., the high component of the Y signal (Y□)
, low frequency component of Y signal (YL), color difference signal (C11, Ca
) are read out in a separated state, and YL, C, and C□ are supplied to the matrix circuit 1519 as shown in the figure, and the three primary color signals (R
L, GL, BL), then the high frequency component of the Y signal (
Y□) are added in adders 1520, 1521.
523,1524.1525 converted to analog signal,
It is output as an RGB signal.

The above is the reproduction process.Next, we will discuss the analog transmission of sample values performed in the CHSV method.

FIG. 7 shows a conceptual diagram of a CH3V transmission system.

As shown in the figure, the input analog signal is sampled at a period T. Then, the sample value is band-limited, FM modulated, and recorded on a magnetic disk. Then, the signal reproduced from the magnetic disk is FM demodulated, band-limited, resampled, and a sample value signal as shown in FIG. 7 is output.

In analog transmission of sample values, it is extremely important that the time axis of the sampling pulse be transmitted without fluctuation. FIG. 8 shows an explanatory diagram for explaining the importance of the time axis of the sampling pulse. Let us consider the case where a sample value sequence obtained by sampling at period T is recorded and reproduced as shown in FIG. 8(a). The transmission path consisting of FM modulation/demodulation and electromagnetic conversion system exhibits LPF characteristics, and the transmission path output signal is as shown in (b) in the same figure.This signal is converted into a sampling pulse at the time of input as shown in (c) in the same figure. By resampling with a sampling pulse having the same period or T and the correct phase, the original input sample value sequence can be restored as shown in FIG. 4(d).

However, if this reproduced sampling pulse is out of phase as shown in FIG. 12(e), a sample value sequence as shown in FIG. 12(f) is output, and the sample value sequence is not reproduced correctly and ringing occurs. Furthermore, it goes without saying that the data will not be played back correctly even if the sampling period is different.

Therefore, during reproduction, a resampling pulse with the correct frequency (period) and correct phase is required. There is also one more condition for completely transmitting sample values. This is because the transmission path characteristics are linear phase (group delay flat) and the amplitude characteristics are symmetrical roll-off characteristics centered on the frequency t, (-'/2T), which is shown in the figure. The characteristics shown in the figure are required.

[Invention or problem to be solved] CHSV using sample value analog transmission as described above
In the case of this method, in order to generate a correct reproduction sampling clock, the reproduced image signal is sampled using a sampling clock that is phase-synchronized with the pilot signal reproduced from the magnetic disk, thereby absorbing the jitter that occurs during reproduction. So, TBC circuit (Ti■e
Ba5eCorrector) forms a sampling clock, but although this sampling clock absorbs jitter that occurs during playback, there is a problem in that the sampling phase is not necessarily correct, so resampling is not performed correctly. The problem arises that there is no such thing.

The present invention has been made to solve this problem, and an object of the present invention is to provide an image signal recording and reproducing device that can correctly restore the original image signal by obtaining sampling pulses with the correct phase.

[Means for Solving the Problems] In order to achieve the first objective of item L, the device of the present invention adds a ternary signal to the beginning of the image signal (immediately after the back porch) and records it, and during playback, After forming a sampling pulse synchronized with the pilot signal recorded together with the image signal and sampling the reproduced image signal based on the sampling pulse, the sampling value near the center of the ternary signal added at the time of recording is The phase of the sampling pulse is corrected using an error signal obtained by comparing it with a predetermined level.

[Operation] With the above configuration, it is possible to resample the image signal reproduced from the magnetic disk using a sampling pulse having the correct phase.

[Example] FIG. 1 shows the configuration of a first embodiment of the present invention.

In the same figure, an image signal input from an image signal input terminal l is processed by a recording signal processing circuit 2 to receive a luminance (Y) signal and a color (C) signal.
) signals are separated. Then, two of these Y signal and C signal
A ternary signal as shown in FIG. 2 is added to the signal by a ternary signal adding circuit 3°3'. This ternary signal is the beginning of the video signal immediately after the hack pouch of the synchronization signal section, and the center point of the ternary signal, that is, point a in FIG. The position to be added is determined so that the interval has elapsed.

Furthermore, in the case of a C signal without a synchronization signal section, it is added at the same timing as the Y signal. The Y and C signals to which the ternary signals have been added are frequency-multiplexed by an FM modulator 4°4', continuous pilot signals are added by a pilot signal addition circuit 5, and then transferred to a magnetic disk 7 by a magnetic head 6. recorded. At this time, the recording/reproducing switch 48 is on the recording side (side a).
Make it so.

When playing back, set the recording/playback switch 8 to the playback side (b side).
The magnetic head 6 reads out the recorded signal. The read signal is subjected to Y/C separation in the reproduced signal processing circuit 9, FM demodulated, and outputted as a Y signal and a C signal. Further, from the reproduced signal, the pilot signal extraction circuit 10 extracts the pilot signal added at the time of recording, and extracts the pilot signal added at the time of recording, P L L (Ph
(LockedLoop) circuit 11 generates a clock pulse for resampling that is phase-synchronized with the pilot signal.

Next, the comparison circuit 12 compares the median values of the ternary signals added to the Y signal output from the reproduced signal processing circuit 9. Here, the value obtained when sampling is performed near the center of the ternary signal is compared with the median value in recording (the pedestal level in the example of FIG. 2). The sampling performed at this time is performed by applying a sampling gate within the comparator circuit 12. As shown in FIG. 3, this sampling gate is located at a point where a predetermined time has elapsed from the rise of the horizontal synchronizing pulse, and is performed by a sampling gate pulse whose pulse width is one sampling interval. Note that the predetermined time is adjusted so as to include the sampling point of the resampling clock pulse that is closest to the center of the gate pulse or the ternary signal. Then, the sample value obtained when sampling is performed using the sampling gate pulse is compared with the median value of the ternary signal (pedestal level in the example of the ffi2 diagram) at the time of recording, and the result is used as an error signal. The signal is sent to the variable delay line 13 as a signal. Then, the delay amount of the variable delay line 13 is changed according to the sent error signal. As this variable delay line 13, for example, a CMO
The amount of delay is changed by changing the power supply voltage of an IC as a buffer of an S integrated circuit. In addition, the variable range of the amount of delay at this time is the period of the sample clock, 70 to 80n, e
c, and the phase difference in the first stage PLL circuit ll is 35~
Since it is set to 40nmea, it is possible to realize a maximum delay amount of 40n@ec. Like this delay fi13
A clock pulse outputted from the sample value forming circuit 14, 14' whose phase is correctly matched is used as a resampling clock in the sample value forming circuit 14, 14'. This results in correct resampling in the sample value forming circuit 14.14'.

Furthermore, the C signal is subjected to the same processing as the Y signal by applying a sampling gate at the same timing as the Y signal.

Also, whether it is the position of the ternary signal, this is a pixel arrangement, or a local pixel offset as shown in Figure 5, so the positional relationship is shifted by a local pixel for every l line, that is, by a local phase of the sampling clock pulse. become.

An example of the ternary signal in this embodiment is the signal shown in Fig. 4(a), but if there is an amplitude centered around the pedestal level, this amplitude will be used when detecting the synchronization pulse. It is necessary to set the threshold level so that it does not exceed the threshold level. As another possible signal, the one shown in FIG. 4(b) is effective. The amplitude center of this signal is not set to the pedestal level, but is set to a predetermined positive level. In this way, it is not necessary to set the amplitude small, so it is possible to set the phase difference with high precision. Further, both signals (a) and (b) may be monotonically increasing or monotonically decreasing over one hour, or either signal may be used.

In addition, in the first embodiment, one ternary code is added to every horizontal scanning period, and the phase of the resampling clock is corrected every one horizontal scanning period, or this phase correction is performed every one vertical scanning period. The phase correction may be performed by adding the ternary value code to one vertical scanning period so as to perform the phase correction every time. In this way, in the first embodiment, there is a limit to the level width of the ternary value code, and in order to solve the problem that the accuracy of phase difference detection cannot be achieved very high, a ternary value code with a large level width is used. becomes possible.

[Effects of the Invention] As explained above, the present invention adds a three-value code to an image signal and records it on a recording medium, and calculates the median value of the three-value code added at the time of recording and the three-value code obtained at the time of playback. By comparing the sample value obtained by sampling the central part of the signal, and correcting the phase of the resampling clock during playback according to the result, resampling the image signal using the phase-corrected resampling clock. This has the advantage that an image signal recorded on a recording medium can be correctly restored using analog transmission of sample values.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the main configuration of the first embodiment of the present invention, and FIG. 2 is a diagram showing the time relationship between the ternary code added to the image signal during recording and the sampling clock pulse. The figure shows the time relationship between the three-value code obtained during reproduction, the resampling clock pulse, and the sampling gate pulse. Figure 4 shows an example of the three-value code, and Figure 5 shows the CH3.
FIG. 3 is a block diagram showing a sample point arrangement of a Y signal of the V method. Fig. 6 is a block diagram showing the configuration of the reproduction process of the CHSV method, Fig. 7 is a system diagram of analog transmission of sample values,
Figure 8 is a diagram showing the relationship between the sampling clock and the output signal, and Figure 9 is the transmission line LP for analog transmission of sample values.
FIG. 3 is a diagram showing F characteristics. In the figure. l: Image signal input terminal 2: Recording signal processing circuit 3.3°: Three-value signal addition circuit 4.4': FM modulator 5: Pilot signal addition circuit 6: Magnetic head 7: Magnetic disk 8: Recording/reproduction switch 9 : Reproduction signal processing circuit 10 : Pilot signal extraction circuit 11 : PLL circuit 12 : 3-value code median comparison circuit 13 : Variable delay line 14.14' : Sample value formation circuit 15, image signal output terminal agent Patent attorney 1) Haru Kitatake Figure 3 IJ! The signal now shows the rift pull point arrangement of Y4 which is δq on CH5V! Sanfu Tsushiki no 7 Pro 2 “Fu-Mana 2’s First Thought Diagram”

Claims (1)

[Claims] A device for recording and reproducing an image signal via a recording medium, the first level being the same as or higher than the pedestal level within the prescribed level of the image signal, and the second level being set at the time of detection of the synchronization signal. and the third level is set to be higher than the first level by the level difference between the first level and the second level. The second period is the third level, and the third period is the level that changes linearly from the third level to the first level.
A fourth period, which is the same period as the third period, shows a level that changes linearly from the first level to the second level, and a fifth period, which is the same period as the second period, shows the level that changes linearly from the first level to the second level. The sixth period, which is the same period as the first period, takes the first level.
, 6 consecutive periods in this order, or the first period is the first level, the second period is the second level, and the third period is the third level. The level changes linearly from the second level to the first level, and the fourth period, which is the same period as the third period, changes linearly from the first level to the third level. level during the fifth period, which is the same period as the second period.
The first, second, third, fourth, fifth and sixth periods are at the third level, and the sixth period, which is the same period as the first period, is at the first level. Replace the continuous ternary waveform in this order for the same period as each of the above-mentioned periods of the image signal, FM modulate the replaced image signal,
a recording means for continuously adding a pilot signal having a predetermined frequency and recording it on the recording medium; and a recording means for reproducing the signal recorded on the recording medium from the recording medium and adding the pilot signal to the FM demodulated signal. A sampling clock formed by the pilot signal is delayed by a variable delay line according to a signal output by comparing a value near the center of the ternary waveform with the first level, and the delayed sampling clock is generated. 1. An image signal recording and reproducing apparatus comprising: a reproducing means for sampling the FM demodulated image signal based on the FM demodulated image signal and outputting a sample value signal.