JPS63125073A - Characteristic correcting device - Google Patents

Abstract

PURPOSE:To easily obtain a level transforming table for correcting a characteristic by recording and reproducing a staircase wave and obtaining a corrected value according to the recording and reproducing level of the respective steps of the staircase wave. CONSTITUTION:At the time of recording, a stircase waveform is recorded in a part including no video signal such as a vertical blanking period. A reproduced signal is supplied to a waveform memory 2 and a change over switch 6, a microcomputer 3 obtains the level of the respective steps of a reproduced staircase waveform, a reproduced signal level is made an address according to the corresponding relation of the recording and reproducing signal level and a recording signal level corresponding thereto is written in a transforming table memory A4 or B5 as data. Accordingly, when reproduced signal data is inputted to the address of the memory A4 or B5, an output in which the characteristic of a recording and reproducing system is corrected is obtained in the data output. In order to avoid the interruption of the reproduced signal data during an updating of data, the two systems of the transforming table memories are used.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention automatically corrects distortion caused by nonlinearity of a signal processing system during recording and playback and corrects the playback signal level in a signal recording device. The present invention relates to a characteristic correction device for performing correction.

[Conventional technology]

In signal recording devices such as VTRs, channel division recording is a method for recording wideband signals by dividing one signal into multiple channels to reduce the bandwidth required for each channel. There is a method.

In such a method, if the signal to be recorded is a televised signal, the signal is divided into one horizontal scanning period and distributed to a plurality of channels1, and the distributed signal is expanded on the time axis and recorded. is used.

An example of this method is shown in FIG. 4, and in this example, the input video signal is distributed to two channels (A, B). , . . , (a) shows input signals, and numbers are given in chronological order as Hl, H2, H3, . . . for each horizontal scanning period. The input signal is divided into channel A and channel B for each horizontal scanning line, and is subjected to time axis expansion and converted into the recording signal format shown in FIG. 4 (a).

When the time axis of the signal is expanded by channel division in this way, the band for each channel decreases, but
Since one signal will be recorded and played back in two systems,
If there is a difference in characteristics between the channels, this leads to deterioration of the reproduced image quality, such as scanning lines becoming conspicuous in the above example. Therefore, a device that automatically corrects the characteristic difference between channels is required.

V that performs channel division and records and plays back as described above.
An example of a characteristic correction device used in a TR is [Kiyoshi Sasaki et al.: Band Compression High-Vision VTR, National Technical Report Vol. 32 No.
, 4J. FIG. 6 is a block diagram showing the configuration of this device. In the figure, 20 is a memory for recording the reproduced lamp signal, 21 is an averaging and checking circuit for averaging and checking the reproduced lamp signal, and 22 is a level correction circuit. 23 is a reference lamp signal data memory; 24 is a data processing circuit; 25 is a switch for switching the address of the level correction table memory 22; 26 is a table memory;
is a reproduction signal input terminal, 27 is a reproduction lamp signal input terminal,
2nd is a time axis data terminal, and 29 is a correction output terminal.

The conventional characteristic correction device is configured as described above, and records a ramp signal that changes from the black level to the white level within the vertical blanking period of the video signal, and reproduces this to make the correspondence between the recording level and the playback level. I try to add . When the ramp waveform shown in FIG. 5(a) is recorded, if a distorted waveform shown in FIG. 5(b) is obtained as a reproduced signal, this reproduced ramp signal is passed through a time base collector (TBC). By correcting the time axis and matching the timing with the ramp signal during recording, the correspondence between the input signal level and the reproduction output level can be found.

To explain this operation in detail, the reproduced lamp signal is first inputted to the averaging and checking circuit 21, where a plurality of reproduced lamp signals are added together to improve the S/N ratio, and the reproduced lamp signal obtained by adding and averaging the Check the shape of the signal and remove effects such as dropouts. The averaged and shape-checked reproduced lamp signal is stored in the reproduced lamp data memory 20 using the time axis data as an address.

Next, the data and address of the reproduction lamp data memory 20 are reversed and stored in the level correction table memory 22. The reference ramp signal data memory 23 stores the shape of the ramp signal at the time of recording, and if reproduced video signal data inputted via the switch 25 as the address of the level correction table memory 22 is given, the reference ramp signal data memory 23 stores the shape of the ramp signal at the time of recording. 23 is determined, and level-corrected video signal data is obtained as the output of the reference lamp signal data memory 23.

[Problem that the invention seeks to solve]

The conventional characteristic correction device is configured as described above, and determines the correspondence between the recorded signal level and the reproduced signal level by recording and reproducing a reference ramp waveform. However, according to such a method, it is necessary to accurately correct the time axis of the reproduced ramp signal in advance using a time base collector device, etc., and it is also necessary to have time axis data that matches the timing of the ramp waveform at the time of recording. Become.

This invention has been made in view of the above, and is a characteristic correction that eliminates the need to perform time axis correction of the reproduced signal in advance using a time 1 base collector device etc. when determining the correspondence between the recorded signal level and the reproduced signal level. The purpose is to obtain equipment.

[Means for solving problems]

The characteristic correction device according to the present invention reproduces a reference signal, such as a staircase waveform, whose waveform data is known in advance, and
a storage means for storing the converted data; a calculation means for calculating a level after characteristic correction corresponding to the playback signal level based on the data stored in the storage means; and a calculation means after the characteristic correction corresponding to the playback signal level. and a conversion table storage means for storing the level of the conversion table as a conversion table.

[Effect]

In this invention, the reproduced reference signal level is detected, the correspondence relationship between the reproduced level of this reference signal and the reference signal level at the time of recording is determined, and this is stored as a conversion table for the reproduced signal, and this conversion table is For example, output a reproduced signal after characteristic correction for each reproduced signal based on
When the above reference signal is a staircase waveform, the level at each step of the reproduced staircase wave is detected, the correspondence relationship between the level of each step during playback and the level of each step during recording is determined, and the level at each step is determined. For levels in between, the correspondence is determined by interpolation from the correspondence at each step, and these correspondences are used as a conversion table to determine the signal level of the reproduced signal after characteristic correction.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an A/D converter, 2 is a waveform memory for storing reproduced signal waveforms, 3 is a microcomputer, 4, 5 are level conversion table memories A, B, 6, . 7 is a changeover switch, 8 is a reproduction signal input terminal, and 9 is a correction signal output terminal.

Next, the operation will be explained using FIGS. 2 and 3.

In the following description, a case where the present invention is applied to a video signal magnetic recording/reproducing apparatus (VTR) will be explained.

First, during recording, a step waveform that changes from a black level to a white level as shown in Figure 2 (a) is generated in a part that has a certain timing with respect to a vertical synchronization signal and does not contain a video signal, such as a vertical blanking period. The reproduced signal recorded is converted into digital data by an A/D converter 1, and is supplied to a waveform memory 2 having a capacity to store data for one horizontal scanning period or more and a changeover switch 6. The micro combinator 3 monitors the input of the waveform memory 2, detects the data series corresponding to the vertical synchronization signal, finds the timing at which the staircase waveform is reproduced, and writes the staircase waveform data into the waveform memory 2. control like this. After the staircase waveform data is written into the waveform memory 2, the microcomputer 3 determines the level of each step of the reproduced staircase waveform.

The level detection method for each step is to sequentially read the staircase wave data into the microcomputer 3 and detect that a constant level continues for more than a certain number of samples, or to detect the part corresponding to the synchronization signal level. It is conceivable to find the level of each step and collect data at regular time intervals from there.

When the level of each step of the reproduced staircase wave can be detected, the correspondence relationship between the recorded signal level and the reproduced signal level at each step can be found. That is, in the graph showing the relationship between the recorded signal level and the reproduced signal level in FIG. 3, the points indicated by black circles are determined. The correspondence between the recorded signal level and the reproduced signal level at levels other than each step of the staircase wave can be calculated by the microcomputer 3 from the values at each step of the staircase wave using an appropriate interpolation method.

The correspondence between the recorded and reproduced signal levels obtained as described above is stored in the conversion table memory A (4) using the reproduced signal level as an address and the corresponding recording signal level as data.
Alternatively, it is written to conversion table memory B(5).

Therefore, when the reproduced signal data is input to the address of conversion table A (4) or conversion table B (5),
The data output has the characteristics of the recording and reproducing system corrected.

When the above series of operations is completed and a conversion table is created, the reproduced staircase wave is read into the waveform memory 2 again and creation of a new conversion table is started. At this time, in order to avoid interruption of the reproduced signal data during the period when the data in the conversion table memory is changed, two systems of conversion table memory, conversion table memory A (4) and conversion table memory B (5), are used. The data is written alternately to the switch 6 and the switch 7 alternately to correct the reproduced signal data.

Note that since the reproduced staircase wave contains noise, it is necessary to remove the influence of noise when creating the conversion table. Therefore, the microcomputer 3 performs signal processing such as filtering on the data stored in the waveform memory 2 to remove the influence of noise. An example of this signal processing is to average data of several consecutive samples. Furthermore, the influence of noise can be suppressed by calculating the average value of the levels of each step of a plurality of reproduced staircase waves using the microcomputer 3 and creating a conversion table based on this.

In this embodiment, the staircase wave is recorded and played back, and the correction value is determined based on the recording and playback level of each step of the staircase wave. Therefore, the time base correction using a time base collector device, etc., as in conventional devices is not possible. A level conversion table for characteristic correction can be obtained without performing.

In the above embodiment, the case where the characteristic correction device of the present invention is applied to a VTR has been explained, but it goes without saying that this characteristic correction device can also be applied to a video signal recording and reproducing device such as a disk device. .

Also, if the position of the staircase wave can be detected, other signals can be recorded,
It can also be applied to playback devices.

〔Effect of the invention〕

As described above, according to the present invention, a reference signal such as a staircase waveform whose waveform data is known in advance is recorded and reproduced, and the level of the reproduced signal is adjusted based on the recorded and reproduced waveform data of the reference signal. The level after characteristic correction is determined by calculation, and this calculation value is used as a conversion table to output a reproduction signal after characteristic correction for each reproduction signal, so that time base correction using a time base collector device, etc., as in conventional devices is possible. This has the effect that a level conversion table for characteristic correction can be easily obtained without performing the above steps.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a characteristic correction device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the shape of a staircase wave recorded and reproduced in the device, and FIG. 3 is similar to FIG. FIG. 4 is a diagram illustrating the correspondence between recording signal levels and reproduced signal levels to explain the operation of the characteristic correction device shown in FIG. FIG. 6 is a waveform diagram of a ramp wave used in a conventional characteristic correction device, and is a block diagram showing the configuration of the conventional characteristic correction device. l...A/D converter, 2...waveform memory, 3...
Microcomputer, 4.5... Conversion table memory, 62,7... Changeover switch.

Claims (3)

[Claims] (1) A characteristic correction device that corrects the characteristics of a signal processing system when recording and reproducing a signal, which converts a reproduced signal containing a reference signal at a predetermined position whose signal waveform data at the time of recording is known in advance into digital data. Convert A to
/D conversion means; waveform data storage means for storing at least reproduced waveform data of the reference signal out of the output of the A/D conversion means; and waveform data of the reference signal stored in the waveform data storage means; calculation means for determining the correspondence between the signal level during recording and the signal level during reproduction based on the waveform data of the reference signal during recording; A characteristic correction device comprising conversion table storage means for outputting converted reproduced digital data on which characteristics of a signal processing system have been corrected. (2) The characteristic correction device according to claim 1, wherein the waveform of the reference signal is a stepped waveform. (3) The characteristic correction device according to claim 1 or 2, wherein the calculation means is a microcomputer.