JPH0471397B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video tape recorder (hereinafter simply referred to as
It's called a VTR. The present invention relates to a time axis correction device that uses a digital memory to correct the time axis error of a reproduced video signal obtained by a video signal reproduction device such as ), and particularly relates to a time axis correction device that also has a dropout correction function for a reproduced video signal.

[Background technology and its problems]

In general, the reproduced video signal obtained by a VTR includes time axis errors due to uneven rotation of the video head, changes in tape running speed, etc., and errors due to defects in the magnetic recording medium of the magnetic tape. It is widely known that signal loss, or so-called dropout, occurs. Therefore, in order to obtain a high-quality reproduced image from the reproduced video signal, it is necessary to correct the time axis error and dropout of the reproduced video signal.

Conventionally, time axis errors in reproduced video signals have been corrected by converting the reproduced video signals into digital signals, writing them into a digital memory, and reading out the digital signals written in the memory using a reference signal. There is. In addition, the dropout correction of the reproduced video signal uses the vertical correlation of the image to correct the dropout video signal for one horizontal scanning period (1H).
This is done by replacing the previous video signal.

FIG. 1 is a block diagram showing a general configuration of a signal processing system for correcting time axis errors and dropouts in a reproduced video signal obtained by a VTR 1. As shown in FIG.

In the conventional example shown in FIG. 1, the VTR 1 has the function of outputting a reproduced video signal and a dropout signal indicating a dropout of the reproduced video signal.

The reproduced video signal output from the above VTR1 is
The signal is supplied to the analog-to-digital A/D converter 2, and converted into an n-bit digital signal by the A/D converter 2. Then, the n-bit digital signal is written to the n-bit digital memory 3 by a write clock (CK _WR ) containing a time axis error, which is generated based on the synchronization signal in the reproduced video signal.
written to. The digital signal written in the digital memory 3 is read out from the digital memory 3 using a read clock (CK _RE ) formed based on a reference signal that does not include a time axis error. is corrected and supplied to the dropout correction circuit 4. Also, above
The dropout signal output from VTR1 is
The signal is supplied to the dropout correction circuit 4 via a 1-bit memory 5 having the same address amount as the n-bit digital memory 3.

In addition, the dropout correction circuit 4 has a 1H
A 1H memory having a storage capacity of 1H is provided, and dropout correction is performed by outputting a 1H previous digital signal from the 1H memory during the dropout period in response to the dropout signal. This dropout correction circuit 4 directly outputs the digital signal read out from the n-bit digital memory 3 for time axis correction during periods other than the dropout period.

The digital signal whose time axis error and dropout have been corrected in this manner is converted into an analog signal by a digital-to-analog D/A converter 6, and outputted from a signal output terminal 7 as a corrected reproduced video signal. .

By the way, in the conventional example having the above configuration, in order to make the dropout correction circuit 4 work, in addition to the n-bit digital memory 3 for time axis correction of the video signal, the above-mentioned digital memory is used for time axis correction of the dropout signal. A 1-bit memory 5 having the same number of addresses as 3 must be used, resulting in a problem that the memory becomes large-scale.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention is designed to perform the function of correcting the time axis of a dropout signal using the memory without increasing the storage capacity of the memory for time axis correction of the video signal. The present invention provides a time axis correction device with a novel configuration.

[Summary of the invention]

In order to achieve the above-mentioned object, a time axis correction device according to the present invention converts a reproduced video signal obtained by a video signal reproducing device into a digital signal, writes this digital signal into a memory, and writes the digital signal into a memory. A time axis correction device that corrects time axis errors by reading out a digital signal using a reference signal detects a dropout period of the reproduced video signal, and replaces the digital signal of this dropout period with a code signal indicating dropout. The present invention is characterized in that the information is written into the memory using the data.

That is, since the information of the reproduced video signal during the dropout period is replaced with other information in the dropout correction processing, there is no need to write it into the memory for time axis correction. By replacing the information of the reproduced video signal with a code signal indicating that the dropout period is in progress, a time axis correction memory dedicated to the dropout signal is omitted.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a time axis correction device according to the present invention will be described in detail below with reference to the drawings.

In the embodiment shown in the block diagram of FIG.
The VTR 10 outputs a reproduced video signal and
It is assumed that the device has a function of outputting a dropout signal indicating dropout of the reproduced video signal.

In this embodiment, a reproduced video signal output from the VTR 10 is first supplied to an A/D converter 21, and converted by this A/D converter 21 into an n-bit digital signal. The n-bit digital signal obtained by the A/D converter 21 is supplied to a dropout code replacement circuit 23 via a prohibition code replacement circuit 22.

The prohibited code replacement circuit 22 replaces the data corresponding to the dropout code with other code data in the digital signal supplied from the A/D converter 21. Here, as the dropout code, a code indicating the upper limit or lower limit of data of the digital signal is used. Further, the other code data replaced by the prohibition code replacement circuit 22 is set to a code indicating data before one quantization of the upper limit or lower limit of the data of the digital signal. The digital signal obtained by the prohibited code replacement circuit 22 is a continuous signal in which the upper or lower limit data is replaced with data before quantization, and the above data, that is, the dropout code is removed. Become.

In addition, the dropout code replacement circuit 23
A dropout signal is supplied from the VTR 10, and based on this dropout signal, the digital signal during the dropout period is replaced with a dropout code signal. The digital signal outputted from the dropout code replacement circuit 23 is written into an n-bit digital memory 24 and subjected to time axis correction processing. That is, the digital signal is written into the digital memory 24 using a write clock (CK _WR ) that includes a time axis error and is generated based on the synchronization signal in the reproduced video signal, and is written as a reference signal that does not include a time axis error. The time base error is removed by reading the data from the digital memory 24 using the read clock (CK _RE ) formed based on the data.

The digital signal read from the digital memory 24 is supplied to a dropout correction circuit 25 and a dropout code detection circuit 26.

The dropout code detection circuit 26 detects a dropcode in the digital signal read from the digital memory 24 and supplies a detection output signal indicating that the dropout period is in progress to the dropout correction circuit 25. The dropout correction circuit 25 performs dropout correction processing based on the detection output signal.

Then, the digital signal whose time axis error and dropout have been corrected in this way is converted into a D/A
The converted signal is converted into an analog signal by a converter 27 and outputted from a signal output terminal 28 as a corrected reproduced video signal.

Here, in the above embodiment, assuming that the A/D converter 21 outputs a 4-bit digital signal, the specific configurations of the prohibition code replacement circuit 22 and the dropout code replacement circuit 23 will be described below. It is shown in Figure 3.

In the specific example shown in FIG. 3, the upper limit code of the 4-bit digital signal output from the A/D converter 21, that is, [1, 1, 1, 1] is used as the dropout code, and the dropout the code
By inhibiting the output of the least significant bit ²⁰ of the digital signal from the AND gate 32 which is detected by the NAND gate 31 and gate-controlled by the output of the NAND gate 31, the upper limit code of the digital signal "1, 1, 1, 1'' to ``1, 1, 1,''
0”. Then, each bit 2 ⁰ , 2 ¹ , 2 ² , 2 ³ of the above digital signal is ORed.
Each of the above OR gates 33, 34, 3 is outputted via the gates 33, 34, 35, 36.
By supplying a dropout signal from the VTR 10 to bits 5 and 36, each bit 2 ⁰ , 2 ¹ , 2 ² , and 2 ³ is replaced with a logic "1", that is, a dropout code, during the dropout period. Note that the dropout signal output from the VTR 10 normally maintains logic "0" and becomes logic "1" during the dropout period.

Note that in the above embodiment, a VTR having a function of outputting a playback video signal and a dropout signal is used.
10 is used, but a dropout detection circuit is provided to detect a dropout period by performing envelope detection of a reproduced video signal output from a VTR, and the dropout code conversion circuit 23 is activated. It's okay. Furthermore, if the A/D converter 21 performs digitization processing that does not include dropout codes, the above-mentioned prohibited code replacement circuit 22 may not be provided.

〔Effect of the invention〕

As is clear from the description of the embodiments described above, the time axis correction device according to the present invention replaces the code signal indicating the dropout of the reproduced video signal with the information of the reproduced video signal during the dropout period, writes it in the memory, and calculates the time. Since axis correction processing is performed, the dropout correction circuit installed in the subsequent stage can be used without providing a memory for time axis correction of the dropout signal, which was required in the past, and the desired purpose can be achieved sufficiently. can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional time axis correction device. FIG. 2 is a block diagram showing an embodiment of the time axis correction device according to the present invention. FIG. 3 is a circuit diagram showing specific configurations of the prohibition code replacement circuit and the dropout code replacement circuit in the above embodiment. 10...VTR, 21...A/D converter, 22
...Prohibition code replacement circuit, 23...Dropout code replacement circuit, 24...Memory.

Claims (1)

[Claims] 1 Converting a reproduced video signal obtained by a video signal reproducing device into a digital signal, writing this digital signal into a memory, and correcting the time axis error by reading out the digital signal written in the memory using a reference signal. The time axis correction device is characterized in that the dropout period of the reproduced video signal is detected, the digital signal of the dropout period is replaced with a code signal indicating dropout, and the code signal is written in the memory. Device.