JPS6215983A - Signal processor for video signal - Google Patents

Abstract

PURPOSE:To prevent the deterioration of picture quality in a level correcting and reproducing video signal by inserting and recording a reference index signal within the vertical blanking period of a video signal when recording, taking out a reproducing index signal within the vertical blanking period of a reproducing video signal when reproducing, and converting it to a digital quantity for processing. CONSTITUTION:A device consists of a means 1 which inserts and records the reference index signal within the vertical blanking period of the video signal when recording, and takes out the reproducing index signal within the vertical blanking period of the reproducing video signal when reproducing, and processes a data string obtained by the conversion of the signal to the digital quantity, in the recording and the reproducing of the video signal, a means 2 which generates a level correction data string that relates the data string obtained by the means 1 and the data string representing the reference index signal, a storing means 4 which stored the level correction data string and a means 5 which performs the level correction of above started reproducing video signal based upon the level correction data string stored at the storing means 4. Thereby, the non-linear distortion of a recording and reproducing device, or gain fluctuation or DC fluctuation is automatically corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to converting video signals into FM when recording and reproducing video signals.
Non-linear distortion of the playback level, gain fluctuations and DC
The present invention relates to a signal processing device having a function of automatically correcting fluctuations.

Conventional Technology When a video tape recorder (hereinafter referred to as a VTR) records and reproduces video signals on a magnetic tape, it generally converts at least a luminance signal into an FM signal and records and reproduces it, so the signal is transmitted through an FM modulator, FM demodulator, etc. It turns out. These FM modulators and FM demodulators are required to have a proportional or inversely proportional relationship between signal level and frequency, but in reality, nonlinear distortion of several orders of magnitude often occurs. Also, DC fluctuations due to amplifier gain fluctuations and clamp potential fluctuations occur. However, in conventional VTRs, few measures have been taken to proactively eliminate the above-mentioned problems, which has been an obstacle to improving the quality of reproduced images.

Problems to be Solved by the Invention In actual FM modulators and FM demodulators, as described above, non-linear distortion of several degrees often occurs, resulting in white or dark patches in the luminance signal. This poses a problem in broadcasting VTRs where dubbing is performed several times during editing, as the non-linear distortion accumulates and deteriorates the image quality each time dubbing is performed. Furthermore, when recording and reproducing a video signal divided into multiple channels of video signals using methods such as frequency division 9 time axis expansion, Hadamard transform, and dot division, not only the above-mentioned nonlinear distortion but also the amplifier characteristics caused by the division occur. It is said that the characteristics between channels may be unbalanced due to gain fluctuations due to variations in voltage, DC fluctuations due to shifts in clamp potential, etc., and line crawling and changes in frequency characteristics may occur in the reproduced video signal, greatly deteriorating the image quality of the reproduced video. There's a problem.

Means for Solving the Problems The present invention solves the above-mentioned problems.In the recording and reproduction of video signals, a reference index signal is inserted and recorded within the vertical blanking period of the video signal at the time of recording, and is reproduced at the time of reproduction. Means for extracting a reproduced index signal within a vertical blanking period of a video signal and processing a data string obtained by converting it into a digital quantity, and associating the data string with a data string representing the reference index signal. means for generating a level correction data string, storage means for storing the level correction data string, and means for level correcting the reproduced video signal based on the level correction data string stored in the storage means. This is a signal processing device for video signals.

According to the present invention, the level of the reproduced video signal is corrected so that the level of the reproduced index signal becomes equal to the level of the reference index signal, and the level of the reproduced video signal is corrected so that the level of the reproduced index signal is equal to the level of the reference index signal. automatically corrects nonlinear distortion, gain fluctuations, and DC fluctuations.

When a level correction data string is created, the S/N is improved by averaging multiple rows of ζ-lower reproduction index signal data strings, or by performing smoothing processing within one data string, or by performing both. This prevents the S/N of the reproduced video signal from deteriorating by adjusting the level and correcting the level.
When the reproduction index signal data string is inspected and determined to be unsuitable for creating level correction data, and furthermore, during the initial operation of the level correction circuit until the level correction data string is created. By performing the level correction using the initial value of the level correction data string prepared in advance, deterioration in the image quality of the level-corrected reproduced video signal during the initial operation of the circuit is prevented.

Example In this example, for each level of the reproduced index signal converted into a digital quantity, the address data that corresponds to the level of the reference index signal is used as level correction data, and the level correction data is stored. The level correction data corresponding to the level of the reproduced video signal is stored in the device, and upon level correction, the level correction data corresponding to the level of the reproduced video signal is outputted from the storage device, and the reference index signal data determined thereby is used as the level-corrected reproduced video signal. Further, as the reference index signal, a ramp signal covering the levels from the black level to the white level of the video signal is used.

A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a level correction circuit in a first embodiment. FIG. 2 is a waveform diagram showing the level correction process in this embodiment. In FIG. 2, 7 is a reference index signal, and 6 is a reproduced index signal obtained by inserting the reference index signal 7 into the vertical blanking period of the video signal, recording it on a recording medium, and reproducing it again.

In FIG. 1, a reproduction index signal data string converted into a digital quantity undergoes data processing for S/N improvement in a data processing circuit 1, and then is transmitted to a level correction data creation circuit 2. The details of the above data processing will be explained later. In synchronization with this transmission, the address generator 3
Address data is output from. Then, the reproduction index signal data string after the above data processing is set as an address,
The above address data is stored in the storage circuit 4.

The above operations complete the level correction data setup.

Next, when reproduced video signal data whose level is to be corrected is input to the storage circuit 4 as an address, address data corresponding to the level of the reproduced video signal data is output. A reference index signal data string is stored in advance in the reproduced video signal level correction circuit 6 using the above address data as an address, and when the output of the storage circuit 4 is input to the reproduced video signal level correction circuit 5, the reference index signal data string is stored at that address. Corresponding reference index signal data is output. Level P of reproduction index signal 6 in Fig. 2
Address A is determined for the reproduced video signal at the same level as , and the reference index signal 7 is determined according to address A.
The level R1, that is, the level-corrected reproduced video signal is output. The level correction data is calculated based on the consideration that the reproduction index signal fluctuates due to changes over time in the amplification degree due to temperature characteristics of the amplifier in the recording and reproduction circuit.
Please make sure to update it at a suitable time.

Here, the processing contents of the data processing circuit 1 will be described. If the video signal recording and reproducing device is a VTR or the like, it is inevitable that the S/N of the video signal will deteriorate due to recording and reproducing, but the S/N of the level correction data is the same as the S/N of the reproduced video signal. If it is at or below this level, level correction will actually significantly deteriorate the reproduced image quality. Therefore, it is necessary to improve the S/N ratio of the reproduction index signal from which level correction data is generated in advance. Therefore, by inserting a plurality of reference index signals within a plurality of vertical blanking periods of a video signal during recording, and averaging the plurality of reproduction index signals in the data processing circuit 1 shown in FIG. 1 during reproduction,
Improve S/N. The averaging must be performed at least several times.

Next, a second embodiment of the present invention will be described.

In this embodiment, the S/N improvement of the reproduction index signal described in the first embodiment is performed using only one reproduction index signal. That is, the data processing circuit 1 of FIG.
By applying this, the S/N of the reproduced index signal is improved.

Thereafter, level correction is performed using the procedure described in the first embodiment. By using the above method, the S/N of the reproduction index signal can be improved in a shorter time than in the first embodiment, which adds and averages multiple reproduction index signals inserted for each field of the video signal. , Therefore, level correction data can be updated in short cycles. If both the first embodiment and the second embodiment are adopted, it will be more effective in improving the S/N.

Next, a third embodiment of the present invention will be described.

When the video signal recording/reproducing device is a VTR or the like, level correction data may not be created properly due to factors such as deterioration of the S/N of the reproduction index signal, data loss due to dropout, and error in detecting one phase. Therefore, a situation arises in which the level correction actually deteriorates the reproduced image quality. Therefore, the data processing circuit 1 shown in FIG. 1 inspects the reproduction index signal data, and if the reproduction index signal data string becomes unsuitable for use due to the above problem, the corresponding reproduction index signal data string or By discarding the level correction data string created using the level correction data string and replacing it with a level correction data string created previously and already stored in the storage device 4, deterioration in the image quality of the level correction reproduced video signal is avoided.

Thereafter, level correction is performed using the procedure described in the first embodiment.

FIG. 3 shows a block diagram of the data processing circuit. Fourth
The figure shows a reproduced index signal waveform on which noise is superimposed.

The shape of the reproduction index signal is roughly ramp-shaped, and the time and signal level are roughly in direct proportion to each other in minute intervals, so the signal levels at two points are sampled at appropriate time intervals and the difference in level between them is monitored. This allows you to discover defects in the signal waveform. In other words, in FIG. 4, the level s (t) of the reproduction index signal at time t
With respect to the signal level 5(t-T) a time T before that, the comparator 9 in FIG. 3 calculates 5(t)-8(t-T
)〉m or n': 2S(t)-S (t-T)
〉m. Then, the level correction data creation circuit 2 and storage circuit 4 shown in FIG. 1 are controlled according to the results. The above m, n, and T can be set to arbitrary values, and it is possible to decide with what degree of accuracy the level correction data is created. For example, when the reference index signal data increases with a slope of 1 relative to the data transmission lock, T=4 clock width, m=0, and n=about 8 are selected. Since the above inspection circuit effectively utilizes the waveform of the index signal, it does not simply inspect the contents of the index signal data string, but uses the address data generated by the address generator 3 in Figure 1 in the reproduced index signal data string. The same thing will happen if you create a level correction data string by associating them and then inspect its contents.

Next, a fourth embodiment of the present invention will be described. In the level correction circuit described so far, at the initial operation of the circuit,
The time it takes to create the first level correction data string is:
It depends on the processing content of the data processing circuit 1 in FIG.
When the first embodiment is adopted 1. The above time is equivalent to several frames of the video signal, and since there is no level correction data until then, the reproduced image quality will be significantly degraded by the level correction. Furthermore, when the third embodiment is adopted, depending on the content state of the reproduction index signal, the generation of the level correction data sequence may be delayed, or in the worst case, it may not be generated forever. Therefore, at the same time as the level correction circuit starts operating, first the initial value of the level correction data string prepared in advance is stored in the storage circuit 4 shown in FIG. By doing so, deterioration in the image quality of the level-corrected reproduced video during the initial operation of the level correction circuit is avoided.

As mentioned at the beginning of the embodiment, in this embodiment, the address data for making the reproduction index signal data and the reference index signal data correspond to each other is used as level correction data. According to the present invention, non-linear distortion caused by FM modulation and FM demodulation when recording and reproducing a video signal, and amplifier gain fluctuation and clamping that occur when recording and reproducing a video signal by dividing it into a plurality of channels can be avoided. DC fluctuations caused by potential deviations can be removed, so white and dark areas in the video signal can be removed, and when multiple channels of playback video signals are combined to restore the original single-channel playback video signal, the channel It is possible to obtain a high-quality reproduced video signal free from line crawling caused by unbalanced characteristics.

To solve the problem that the S/N of the reproduced video signal deteriorates due to level correction, the reproduction index signal data sequence that creates the level correction data sequence can be averaged over multiple columns, or smoothing can be performed within one data sequence. The problem can be solved by improving the S/N ratio by performing one or both of the above.

If the playback index signal becomes inappropriate due to S/N deterioration of the playback video signal, data loss due to dropout, phase detection error, etc., and there is a risk that the level correction data sequence cannot be created correctly, By substituting the previously created level correction data string, it is possible to avoid deterioration in the image quality of the level-corrected reproduced video signal.

To solve the problem that the image quality of the level-corrected playback video signal deteriorates because the level correction data string is not created at the time of initial operation of the level correction circuit, it is necessary to prepare in advance until the level correction data string is created. This can be solved by replacing it with a certain level correction data string initial value.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the basic operation of the present invention,
FIG. 3 is a block diagram of a data processing circuit in the third embodiment, and FIG. 4 is a waveform diagram showing a part of a reproduced index signal data string on which noise is superimposed. 1... Data processing circuit, 2... Level correction data creation circuit, 3... Address generator,
4... Memory circuit, 5... Playback video signal level correction circuit, 6... Playback index signal waveform, 7... Reference index signal waveform, 8...
...Delay circuit, 9...Comparator. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure 2 Figure L= --, -J Figure 3

Claims (5)

[Claims] (1) During recording, a reference index signal is inserted and recorded within the vertical blanking period of the video signal, and during playback, the playback index signal within the vertical blanking period of the playback video signal is extracted, and the level of the playback index signal is above A signal processing device for a video signal that corrects the level of the reproduced video signal so as to be equal to the level of a reference index signal, comprising means for converting the reproduced index signal into a digital quantity and creating a first data string; data processing means for processing the first data string to produce a second data string; and a third data processing means representing the reference index signal.
and a fourth data string that associates the data string with the second data string.
a storage means for storing the fourth data string; and a means for level-correcting the reproduced video signal based on the fourth data string. Device. (2) A signal processing device for a video signal as set forth in claim 1, further comprising means for averaging the first data string over a plurality of columns. (3) The signal processing device for a video signal according to claim 1, further comprising means for smoothing the first data string within one data string. (4) A signal processing device for a video signal according to claim 1, further comprising means for inspecting the data in the process of creating the fourth data string and controlling the storage means according to the inspection result. . (5) The content of the storage means is initialized, and level correction is performed using the initial setting data until the first generation of the fourth data string is completed. A signal processing device for video signals according to scope 1.