JPS63211984A - Video signal recording and reproducing system - Google Patents

Abstract

PURPOSE:To obtain a time base signal having a correct time position and a good S/N, while an interchangeability between a customary system is maintained as well by recording a video signal after superimposing the code of a strong autocorrelativity on it, and forming the time base reference signal by means of giving a convolution operation to the code, at the time of a reproduction. CONSTITUTION:A burker code generation circuit 14 receives a timing signal from a previous step, and generates the burker code of n=7, for instance, during a horizontal synchronizing period, and it is recorded, being superimposed on the video signal. In a reproducing system, a code detection circuit 36 detects the burker code of the horizontal synchronizing period from a demodulated signal. A convolution circuit 38 gives the convolution operation to the detected code signal. By the above-mentioned operation, an impulse, having an amplitude of n-time and the S/N of n-times, is formed. The output of the circuit 38 is used as the time reference signal by impressing it to a time base correction circuit 34. Because the time position of the output of the circuit 38 is extremely correct, in the circuit 34, the time base error of the reproduced signal can be detected by a high precision, in cooperation with the good S/N, and also the time base correction in the circuit 34 comes highly precise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording and reproducing method for video signals, and more specifically to a recording and reproducing method in which a video signal includes a signal serving as a time reference.

[Conventional technology and its problems]

Conventional video recording and reproducing devices that record video signals on magnetic tape use horizontal synchronization signals as time reference signals. However, if the S/N ratio deteriorates in either the recording system or the playback system, jitter will occur due to noise, making it difficult to identify the shifter generated in the mechanical system, making it difficult to obtain an accurate time reference signal during playback. There are certain problems.

Therefore, the present invention aims to solve this problem and to present a recording and reproducing method that can obtain a time reference signal with accurate time position and good S/N ratio while maintaining compatibility with conventional systems. purpose.

[Means for solving problems]

The recording and reproducing method according to the present invention is characterized in that a highly autocorrelated code is superimposed on a video signal and recorded on a recording medium, and upon reproduction, a time axis reference signal is formed by subjecting the code to a composure operation. shall be.

[Effect]

By convolution calculation of codes with strong autocorrelation, it is possible to form an impulse with n times the amplitude and n times the S/N ratio, where the length of the code is n.

Since this impulse has an accurate time position, it is most suitable as a time axis reference signal, and therefore accurate time axis correction can be performed.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1A shows a schematic block diagram of the recording system of an embodiment of a system for FM-modulating a video signal and recording it on a magnetic tape, and FIG. 1B shows a schematic block diagram of the playback system. , a par force sequence of length n=7 will be explained as an example.

In FIG. 1A, the signal processing circuit 10 includes a timing generation circuit 12 that performs predetermined signal processing on an input video signal.
receives the synchronization signal of the video signal to be recorded,
Generates a timing signal and includes a bar force/code generation circuit 14
receives the timing signal and generates a bar force/code during the horizontal synchronization period.For example, when n=7, the bar force sequence is (1, 1, 1, -1, -1, 1, -N It is.

The superimposition position of this bar force/code may be any period as long as it appears periodically, such as a pedestal period, but in the following explanation, the horizontal synchronization period will be used. Adder 1
6 adds the bar force/code from the bar force/code generation circuit 14 to the output of the signal processing circuit 10, and adds the bar force/code from the bar force/code generation circuit 14 to the FM modulation circuit 1
Send to 8. FIG. 2 shows a signal waveform in which the bar force and code are added during the horizontal synchronization period by the adder 16. The signal FM modulated by the FM modulation circuit 18 is applied to the recording head 22 via the recording amplifier 20. It is recorded on the magnetic tape 24.

In a recording/reproduction system for luminance signal FM modulation and color signal low-frequency conversion, in which the color signal is low-frequency converted and recorded while being superimposed on the FM-modulated luminance signal, in addition to the FM modulation circuit 18, there is also a A frequency conversion circuit and the like are provided. However, the recording format itself is not related to the present invention, so
Detailed explanation will be omitted.

In the reproduction system shown in FIG. 1B, the recorded signal on the magnetic tape 24 is converted into an electric signal by the reproduction head 26 and applied to the FM demodulation circuit 30 via the reproduction amplifier 28. The signal demodulated by the FM demodulation circuit 30 is sent to the video signal processing circuit 32.
The signals are subjected to various known processes such as level adjustment and sent to a time base correction (TBC) circuit 34. The zero time base correction circuit 34 corrects the time base of the reproduced video signal and outputs the corrected signal.

The method of time axis correction in the time axis correction circuit 34 itself is not related to the present invention, so detailed explanation will be omitted.

On the other hand, the code detection circuit 36 detects the bar force/code during the horizontal synchronization period from the demodulated signal by the FM demodulation circuit 30. This code detection circuit 36 is comprised of, for example, a voltage comparator that compares the input signal with a comparison voltage Vtl1, and as shown in FIG.
If it is smaller, the code is detected as -1. The convolution circuit 38 performs a convolution operation on the code signal detected by the code detection circuit 36 to form a time reference signal.

A specific example of this convolution circuit 38 is shown in FIG. In FIG. 3, 40 to 50 are delay elements having the same delay time. This delay time is designed to match the period of each symbol of the bar force code superimposed on the horizontal synchronization period of the recording video signal. The input signal to this convolution circuit 38 and each delay element 40 to 50 are connected to gate circuits 52 to 64 (i.e., gate circuits 52 to 64 (i.e., gate circuit 52,
58. 58 is an inverter circuit, and the other gate circuit 5
4, 60, 62, and 64 are circuits that allow the signals to pass through as is. ) to the integration circuit 66. Integration circuit 66
integrates the signals from each gate direction path 52-64. Specifically, the code string from the code detection circuit 38 is converted into (aO+a
l+8! +a3+a4+as+ai), the output P of the integration circuit 66 is given by the following equation.

Figure 4 shows the value of P versus k. As shown in FIG. 4, when k-0, P becomes 7, but when k is other than 0, P becomes 0 or -1, resulting in an impulse waveform with an amplitude of 7. That is, the horizontal axis in FIG. 4 corresponds to time.

In this example, the impulse waveform with an amplitude of 7 is
It can be understood that during recording, a pulse train of amplitude l is distributed in the time direction. Generally, when a sequence of length n is used, the amplitude will be multiplied by n, but the noise will be multiplied, so
The S/N ratio will be improved by a factor of 5.

The output of this convolution circuit 38 is applied to the time axis correction circuit 34 and used as a time reference signal. Since the time position of the output of the convolution circuit 38 is extremely accurate, combined with its good S/N ratio, the time axis correction circuit 34 can accurately detect the time axis error of the reproduced video signal. The time axis correction in the axis correction circuit 34 also becomes highly accurate.

In the above embodiment, a bar force sequence is used as an example, but codes with strong autocorrelation such as a pseudo-noise sequence (PN sequence) may also be used. Also, as a recording medium,
It is not limited to a magnetic tape, but may have a disk shape or other shapes. Furthermore, recording to a recording medium and reproducing from a recording medium can be associated with transmission to a transmission path and reception from a transmission path, respectively.In this sense, a video signal recording and reproducing system is a video signal transmission system. It can also be understood as a system. Therefore, in the above embodiment, a recording/reproducing system using a VTR is taken as an example, but the meaning of the recording/reproducing method or recording/reproducing system in the present invention should be broadly understood as such.

VTR devices generally have a limited dynamic range, but the present invention makes it possible to increase the S/N ratio of the synchronizing signal portion, and also maintains compatibility with conventional devices.

〔Effect of the invention〕

As can be easily understood from the above description, according to the present invention, it is possible to obtain a time reference signal with an extremely accurate time position and a high S/N ratio, and therefore, it is possible to extremely accurately correct the time axis error of a reproduced video signal. It can be corrected.

[Brief explanation of the drawing]

FIG. 1A is a schematic block diagram of the recording system according to an embodiment of the present invention, FIG. 1B is a schematic block diagram of the reproduction system, and FIG. 2 is a waveform diagram in which bar force and code are superimposed on the horizontal synchronization period. FIG. 3 is a diagram showing an example of the configuration of the convolution circuit 38, and FIG. 4 is a diagram showing an impulse waveform obtained by convolving a bar force/code having a length of 7 using the convolution circuit 38. 10--Signal processing circuit 12--Timing generation circuit 14-Bar power/code generation circuit 16--Adder 1B-
-FM modulation circuit 20-recording amplifier 22...-recording head 24--magnetic tape 26--reproducing head 28
-Reproduction amplifier 30--FM demodulation circuit 32--Video signal processing circuit 34--Time axis correction circuit 36-Code detection circuit 38--Composure circuit 40
~50...-Delay element 52-64...-Gate circuit 66-Integrator circuit Fig. 1B

Claims (3)

[Claims] (1) Recording and reproducing of a video signal characterized in that a highly autocorrelated code is superimposed on the video signal and recorded on a recording medium, and upon reproduction, a convolution operation is performed on the code to form a time axis reference signal. method. (2) The method according to claim (1), wherein the code with strong autocorrelation is a Barker sequence code. (3) The system according to claim (1), wherein the code with strong autocorrelation is a pseudo-noise sequence code.