JPS619086A - Video signal processing system - Google Patents

Abstract

PURPOSE:To attain correct AGC at reproduction by normalizing a synchronizing signal level after a video level is optimized even when a video level of an input signal to be recorded and the synchronizing signal level are deviated from the specified value to bring the video level to a level constant to the synchronizing signal level at all times. CONSTITUTION:A so-called non-composite signal without any synchronizing signal is given to terminals 15-17. The recording level is adjusted so that the peak level of the video signal reaches 100% while the waveform at video monitor terminals 24-26 is observed by a waveform monitor. The level of the synchronizing signal inputted from a synchronizing signal input terminal 30 is normalized by a sync processor 31 and the same synchronizing signal is added to the blanking portion of each video signal of Y, R-Y and B-Y. After the signal added with the synchronizing signal is modulated into an FM signal by modlators 32- 34, the result is amplified by record amplifiers 35-37, and recorded on a recording medium 41 via recording heads 38-40.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a signal processing method for a device for recording and reproducing video signals. Regarding improvements.

[Technical Background of the Invention and Four Problems] Due to the difference in means of transmitting the luminance component and chrominance component of the video, video signals are divided into composite signals having subcarriers and Y, R-Y, B-Y, or Y, R-Y, B-Y, or It can be roughly divided into component signals such as R, G, and B.

Both signals express the glow component and two chromaticity components as the level of the video signal, and if the signal levels are different, a correct image cannot be displayed.

A device for recording and reproducing video signals is usually equipped with a video level adjustment during recording and a video level adjustment during reproducing in order to correctly record and reproduce the video signal.

The automated version of these adjustments is called video AGC.
An example of this will be explained using FIG.

FIG. 2 is a signal system block diagram of a magnetic recording/reproducing apparatus equipped with a manual level adjustment trimmer on the recording (full) side and an AGC on the reproduction side.

A trimmer 2 attached to the input video amplifier 1 is used for recording level adjustment, and is adjusted to vary the level of the video signal input to the input terminal 3 to obtain an optimum video level. This record signal level adjustment is performed at input video monitor terminal 4. The peak level of the video signal is mainly adjusted to a specified value while looking at the waveform.

The video signal adjusted to the optimum level is modulated by a modulator 5, amplified by a recording amplifier 6, and then recorded on a recording medium by a recording head 7.

On the other hand, during reproduction, the reproduction node 8 reads the reproduction signal from the recording medium. The read signal is amplified by a preamplifier 9, subjected to characteristic compensation by an equalizer 10, and then sent to a demodulator 11.
demodulated into a video signal.

The AGC amplifier 12 and the sync level detector 13 constitute a feedback loop for always keeping the video level at the output terminal 14 at an optimum level.

The sync level detector 13 detects the level of the sync signal in the video signal, and the error voltage is fed back to the AGC amplifier 12, thereby correcting the sync signal level so that it always remains at a constant value.

In this way, the synchronization signal level is detected and the AGC is set to 1.
This method is also common in video signal recording and reproducing devices.

The drawback of this method is that since the synchronization signal level is detected and corrected, if the ratio between the optimum image level and the synchronization signal level deviates, correct correction cannot be made. For example, in the case of a 525/60 NTSC television signal, the ratio between the image level and the synchronization signal level is 10:
4, but if this proportional relationship breaks down and the level of the synchronizing signal becomes relatively small, the image level will become higher than the optimum value due to AGC. Conversely, if the synchronization signal level becomes relatively large, the video level will become lower than the optimum value.

In addition, even if a video signal with the correct synchronization signal level is input to the input terminal 3 in Figure 2, the amplification factor of the input video amplifier 1 is changed by the trimmer 2 in order to optimize the recorded video level. This results in a change in the synchronization signal level, and when such a signal is recorded and played back, the AGC may make incorrect corrections, making it impossible to obtain the optimal video level.
This problem is the same in devices equipped with AGC on the recording side as well.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a video signal processing system that improves the above-mentioned drawbacks of the prior art and allows recording and playback at an optimal video signal level at all times.

[Summary of the invention]

The present invention is characterized in that before recording a video signal, a synchronization signal level serving as a reference for AGC is normalized.
Image 1'8 of the input signal to be recorded! By optimizing the video level and then normalizing the synchronization signal level, even if the level and synchronization signal level deviate from the specified values, the video level and synchronization signal level can be kept constant and recorded.
This is a video signal processing method that allows correct AGC during playback.

Methods for normalizing the synchronization signal level include (1) calibrating the level of only the synchronization signal section, (2) replacing the synchronization signal with a synchronization signal having a normalized level, and (3) using the normalized synchronization signal. There are three ways to add.

[Practice of the invention, examples]

[Rin] The figure is a block diagram of the signal processing system when implemented in the present invention 7i-1 magnetic recording and reproducing apparatus, and the figure (a
) indicates a recording system, and (b) indicates a reproduction system.

The device separately records the luminance and chromaticity components of the image. This is a so-called component recording type magnetic recording/reproducing apparatus, and the signal system basically has a three-channel configuration of a luminance signal (tY) and a chromaticity signal (RY and BY).

15 is an input terminal for the Y signal, 16 is an input terminal for the Roux Y signal, and 17 is an input terminal for the BY signal. A so-called non-composite signal without a synchronizing signal is connected to these Q; movers. 18°19.20 is an input video amplifier, and a trimmer 21.20 for adjusting the memory level.
This is an amplifier for adjusting the video level to the optimum level according to 22.23.

The recording level is adjusted so that the peak level of the video signal is 1.0 (1/1) while viewing the waveform of the video monitor terminal 24.25°26 on the waveform monitor.

27, 28, 29 is a sync adder, which converts the level of the synchronization signal input from the synchronization signal input terminal 30 into positive m (by % Y tR-Y, B-Y
The same synchronization signal is added to the blanking portion of each ferric acid signal.

Here, the signal to which the synchronization signal has been added is a signal whose image level is optimal [hi], and the ratio of the video level and the same level is the normal level ratio of 10:4, which will be discussed later. With AGC @ production, it is possible to accurately reproduce the level of the movie at the time of recording.

The signal to which the synchronization signal has been added is sent to transformers 32 and 33°3.
After being modulated into FM signal by 4, record amplifier 35°36
, 37 and the recording heads 38 , 39 , 40
The four pieces are inserted into the buttock recording medium 41 through.

The above is the signal processing during recording. Next, the signal processing operation during reproduction will be explained with reference to the 11th bacterium (bl).

The FM signal read from the recording medium 45 by the playback heads 42, 43, 44 is amplified by the preamplifier 46°47.48, the characteristics are compensated by the equalizer 49°50.51, and the demodulator 52° ! >Video 1 at 3.54
It is demodulated into the word (Y, 11%-Y, B-Y).

55, 56, 57 are AGC amplifiers for automatically controlling the level of the output signal, and sync level detectors 58, 5
Output terminals 61, 62, 63 detected by 9.60
By feeding back the error voltage of the Domei signal level in the output signal, the synchronization signal level of the output signal is always maintained at a constant value.

In the signal processing method of the present invention, since the synchronization signal level is normalized during recording as described above, the AG
Set the level of the same, cut 1 word to a constant value by C.
This makes it possible to accurately reproduce the video level at the time of recording.

In particular, in the equipment of this real gun array, recording of component signals,
Y, because it is playing! It is necessary to correctly adjust the levels between L-Y and B-Y, but by adding the same normalized synchronization signal during recording,
Recording is performed with the same Φ condition for all three channels, and the recorded signal can be faithfully reproduced during playback.

[Brief explanation of drawings]

FIG. 1 is a block diagram explaining the present invention in detail, and FIG. 2 is a diagram explaining the conventional system. 15.16.17...Video input terminal, 18.1.9
. 20...Input video amplifier, 21, 22.23...
Record level adjustment trimmer, 24, 25', 26...
Video monitor terminal, 27, 28, 29...Sync adder% 30...Sync signal input terminal, 31...Sync processor, 32.33.34...FM modulator, 35
゜j6, 37...Record amplifier, 38, 39.4
0...Record head, 41.45...5 Self-recording medium, 42°43.44...Playback head, 46,47,4
8...Preamplifier, 49,50,51...Equalizer, 52°53.54...F'M demodulator, 55,56
．． 57...AGC amplifier, 58,59.60...Sync level detector, 61,62.63...Video output terminal. Representative Patent Attorney Nori Chika Kan (ti(η) 1 person) No.
1 figure

Claims (1)

[Claims] 1. A video signal processing system for recording and reproducing video signals, characterized in that a synchronizing signal level is normalized before recording, and the synchronizing signal level is detected during reproduction to perform automatic gain control.