JPH01151382A - Video signal correcting device - Google Patents

Abstract

PURPOSE:To correct a video noise picture-displayed at an almost constant position on a screen by extracting a time base error component from a video signal, storing it, generating data for correction and correcting the time base error component based on this. CONSTITUTION:The video signal outputted from a regenerating signal processing circuit is supplied to a time base correcting circuit 18. A horizontal synchronizing signal outputted from a horizontal synchronizing signal separating circuit out of this is inputted to a phase comparator 19a, extracted residual phase error signal is converted by an A/D converter 20 and after that, multiplied by (1-k) by a coefficient multiplier 21. This output signal is added by an adder 24 to a signal that the residual phase error signal of one field before read out of a memory 22 is multiplied by (k) by a coefficient multiplier 23. Next, it is converted by a D/A converter 25 and added to the output signal of LPF 19b by an adder 26. Thus, a jitter component to cause the video noise picture- displayed in the almost constant position on the screen can be corrected.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a video signal reproducing system such as a rotary head type video tape recorder, and particularly relates to a video signal reproducing system such as a rotary head type video tape recorder. The present invention relates to a video signal correction device that performs correction.

(Prior Art) As is well known, in a rotary head type video tape recorder, dedicated heads are provided for each of the SP (standard recording and playback) mode and the EP (3x recording and playback) mode in the VH8 system. Increasingly, the number of heads has been increased by installing audio heads and flying erase heads for higher sound quality.

For example, as shown in FIG.
Head for mode 12. Some devices are equipped with two heads 13 and two audio heads 14 for EP mode.

In addition, the use of multi-head systems that use cylinders with a smaller diameter than the standard and sequentially switch between multiple heads for recording and playback is being promoted. has been done.

However, when such a multi-head system is used, in the middle of the television screen, one head comes into contact with and separates from the tape while the other head is tracing the tape, so there is a so-called impact caused by the head hitting the tape. There is a problem in that jitter occurs, and as shown in FIG. 4, image noise such as curved vertical lines and color unevenness occurs at approximately fixed positions on the screen.

In order to reduce this impact jitter, it has been considered to form a hill-shaped protrusion at the position where the head on the rotating cylinder leaves the tape, but this has not been shown to be sufficiently effective in practice. Moreover, when reproducing a tape that has already been recorded with impact jitter, there is an inconvenience that there is no effect at all.

(Problems to be Solved by the Invention) As described above, in conventional multi-head video tape recorders, it is difficult to reduce image noise caused by impact jitter to a practical level. have.

Therefore, this invention was made in consideration of the above circumstances, and it reduces the image noise caused by the time axis error component in the video signal, which is displayed at a substantially fixed position on the screen, to the extent that it can be put to practical use. It is an object of the present invention to provide an extremely good video signal correction device that can perform correction.

[Structure of the Invention] (Means for Solving the Problems) That is, the video signal correction device according to the present invention corrects the time axis error component that causes video noise that is displayed as an image at a substantially fixed position on the screen from the video signal. is extracted, and a storage means for storing the extracted time axis error component is used to generate correction data for correcting the time axis error component, and based on this correction data, the time axis in the video signal is It is configured to correct error components.

(Function) According to the above configuration, correction data for correcting the time axis error component is generated using the storage means for storing the time axis error component in the video signal, and this correction data is used to generate correction data for correcting the time axis error component. Since the time axis error component in the video signal is corrected based on the above, it is possible to put into practical use the image noise that is displayed at a substantially fixed position on the screen due to the time axis error component in the video signal. This makes it possible to correct up to a wide range.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. In FIG. 1, reference numeral 15 denotes an input terminal to which a tape reproduction signal obtained from a rotary head (not shown) is supplied. The tape reproduction signal supplied to this input terminal 15 is guided to a reproduction signal processing circuit 16 and demodulated into a video signal.

The video signal output from the reproduced signal processing circuit 16 is supplied to a horizontal synchronization separation circuit 17 to extract a horizontal synchronization signal, and is also supplied to a time axis correction circuit 18. Of these, the horizontal synchronization signal output from the horizontal synchronization separation circuit 17 contains minute noise components, so
Phase comparator 19a.

LPF (0-Hasufui/l/evening) 19b and vCO
(Voltage control generator) A PLL (phase locked loop) circuit 19 consisting of 19C converts it into a horizontal synchronization signal with a stable flywheel effect.

Then, a residual phase error signal corresponding to high-frequency jitter is extracted from the phase comparator 19a, and after this residual phase error signal is converted into digital data by an A/D (analog/digital) conversion circuit 20, (1-k) in the coefficient unit 21
be multiplied.

The output signal of the coefficient multiplier 21 is added to the signal obtained by multiplying the residual phase error signal of one field before by the coefficient multiplier 23 by the adder 24, which is read from the memory 22.

Therefore, the output signal of the adder 24 is obtained by averaging the residual phase error signal between fields, and only the jitter component that causes image noise that is displayed at a substantially fixed position on the screen is extracted, resulting in uneven images. Noise components will be removed.

The output signal of the adder 24 is converted into analog data by a D/A (digital/analog) conversion circuit 25, and added to the output signal of the LPF 19b by an adder 26. Then, the output signal of the adder 26 becomes correction data that has an enhanced ability to correct jitter components that cause image noise that is displayed at a substantially fixed position on the screen.

Therefore, this correction data is supplied to the time axis correction circuit 18, and the video signal output from the reproduction signal processing circuit 16 is
By performing correction processing based on the correction data, the output terminal outputs a video signal that corrects the impact jitter component, which causes video noise that is displayed at approximately the same position on the screen, and also removes minute noise components. It can be obtained from 27.

FIG. 2 shows signal waveforms of various parts during one field period. First, the horizontal synchronization signal output from the horizontal synchronization separation circuit 17 is shown in FIG. 2(a) in one field period.
Suppose that it contains a jitter component as shown in . Then,
The LPF 19b of the PLL circuit 19 extracts only the low-frequency component of jitter, as shown in FIG. 2(b), and the phase comparator 19a extracts the high-frequency component of jitter, as shown in FIG. The components are extracted.

Then, the high-frequency components of the jitter shown in FIG. 2(C) are averaged between fields using the memory 22, so that
The output of the D/A conversion circuit 25 has noise removed, as shown in FIG. 2(d). After that, the output shown in FIG. 2(d) from the D/A conversion circuit 25 and the L P F
The output from the adder 26 shown in FIG.
As a result, the adder 26 outputs the result as shown in FIG.
As shown in FIG. 3A, correction data that is close to the original jitter waveform shown in FIG. 3A, but with noise removed, is output.

Here, since the memory 22 only needs to store error component values for each horizontal scanning period, for example, the capacity thereof is much smaller than that of the field memory of the imager.

Further, the address of the memory 22 can be generated by using a horizontal synchronization signal, a signal obtained by phase-synchronizing the horizontal synchronization signal using a PLL, an angle signal of a rotating cylinder, or the like.

Furthermore, if a frame memory is used as the memory 22,
Correction can be made every revolution of the rotating cylinder.

For this reason, the head is for SP mode.

Correction can be made even if the 82 jitter generating stones, such as the EP mode head and the audio head, are different.

Here, in the above embodiment, a horizontal synchronization signal is used, but for example, if a pilot signal is recorded, it may be used, or a color burst signal, etc. may be used. .

Furthermore, if a TBC (time base corrector) is used as the time axis correction circuit 18, it is possible to correct even the curvature of the image, but by applying the output of the adder 26 only to the color signal processing circuit of the video tape recorder, the color It is also possible to perform only correction of the residual chroma phase error that causes unevenness.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications without departing from the gist thereof.

[Effects of the Invention] As described in detail above, according to the present invention, video noise caused by a time axis error component in a video signal, which is displayed as an image at a substantially fixed position on the screen, can be reduced within a practical range. It is possible to provide an extremely good video signal correction device capable of correcting up to

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the video signal correction device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the same embodiment, and FIG. 3 is a multi-head video tape recorder. FIG. 4 is a plan view for explaining the curvature of vertical lines on the screen due to impact jitter. 11...Rotating cylinder, 12-14...Head, 1
5... Input terminal, 16... Playback signal processing circuit, 17
...Horizontal synchronization separation circuit, 18...Time base correction circuit,
19... PLL circuit, 20... A/D conversion circuit, 2
DESCRIPTION OF SYMBOLS 1... Coefficient unit, 22... Memory, 23... Coefficient unit, 24... Adder, 25... D/A conversion circuit, 26
...Adder, 27...Output terminal. Applicant's agent Patent attorney Takehiko Suzue No. 20 No. 30 Figure 4

Claims (1)

[Claims] Extraction means for extracting from a video signal a time axis error component that causes video noise that is displayed as an image at a substantially fixed position on the screen, a storage means for storing the time axis error component extracted by the extraction means, and the memory. generation means for generating correction data for correcting the time axis error component using a means; and correction for correcting the time axis error component in the video signal based on the correction data generated by the generation means. 1. A video signal correction device comprising: means.