JPH04261286A - Level correction device for video signal - Google Patents

Abstract

PURPOSE:To improve the response speed as the entire device by correcting a level based on a correction data generated from a pseudo reproduction reference signal data subjected to arithmetic processing before a normal reproduction reference signal is generated. CONSTITUTION:A pseudo reproduction reference signal generating circuit 11 generates a pseudo reproduction reference data by implementing arithmetic processing based on an amplitude data in a reproduction reference signal data to be inputted and sends the data to a reproduction reference signal data selector circuit 5. The circuit 5 selects either the reproduction reference signal data inputted from an addition mean circuit 3 or the pseudo reproduction reference signal data inputted from the circuit 11. Then the pseudo reproduction reference data from the circuit 11 is selected and it is outputted to a level correction data generating circuit 6 at the time of start of reproduction or the rising of the level correction device. The circuit 6 based on the data generates a level correction table to correct the level of the reproduction video signal.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION The present invention relates to a level correction device for a video signal that corrects the level of a reproduced video signal based on a reference signal inserted into a part of a recorded video signal. Used in playback equipment.

0002

[Prior Art] Video recording and reproducing devices such as VTRs mainly use analog transmission systems such as FM modulation/demodulation circuits and tape head systems to apply DC offset, non-linear distortion, and multi-channel recording methods to reproduced video signals. Waveform distortion may occur due to gain differences between channels.

[0003] Conventionally, therefore, as a means of correcting such waveform distortion, a reference signal is inserted into a part of the recorded video signal sequence (for example, during the blanking period of the video signal) and then recorded. A method has been proposed in which a level correction table is generated in memory to perform level conversion to return a reference signal, that is, a reproduced reference signal, to the original reference signal, and the waveform distortion of the reproduced video signal is corrected based on this table. There is. In this method, when a level correction table is generated based on a playback reference signal on which noise is superimposed, the playback video signal whose level is corrected by the level correction table has a higher S/N than when the level is not corrected. deterioration cannot be avoided.

[0004] Therefore, the S/N of the reproduction reference signal is improved by averaging a plurality of reproduction reference signals, moving average within the data series of reproduction reference signals, etc.
There is a level correction device shown in FIG. 2 that generates a level correction table based on the improved reproduction reference signal and minimizes the deterioration of the S/N of the level-corrected reproduced video signal. In the figure, an input terminal 12 receives a reproduced video signal obtained by converting an analog reproduced video signal into a digital signal. This reproduced video signal data is transmitted to the reference signal gate circuit 1.
3, the digital data of the reproduction reference signal is extracted as reproduction reference signal data. This reproduction reference signal data is input to the averaging circuit 14, which performs averaging of a plurality of reproduction reference signals, moving averaging within the data series of the reproduction reference signal, etc. N
is improved. This reproduction reference signal data is checked by the inspection circuit 15 from time to time, and the reproduction reference signal data is determined to be unusable due to reasons such as the S/N exceeding the allowable range. In this case, a reset signal is sent to the averaging circuit 14, and new processing such as averaging of reproduction reference signal data is started. The reproduction reference signal data (hereinafter referred to as regular reproduction reference signal data) whose shape has been checked by the inspection circuit 15 is as follows.
The level correction data is inputted to the level correction data generation circuit 16 as level data on which the level correction is based, and is temporarily stored in the memory of the level correction data generation circuit 16. The level correction data generation circuit 16 performs level correction by determining the level difference between the reference signal and the reproduction reference signal from the stable reference signal data output from the reference signal generation circuit 17 and the reproduction reference signal data. Data is generated.

During the blanking period in which the reproduction reference signal of the reproduced video signal exists, the data changeover switch 1
8 is connected to the level correction data generation circuit 16 side, the address signal output from the level correction data generation circuit 16 is input to the level correction memory 19 via the changeover switch 18. This address signal is generated such that each level correction data corresponds to each reproduced video signal data. Therefore, in the level correction memory 19, the level correction data is written to the address corresponding to the address signal, thereby generating a level correction table in which the reproduced video signal data and the level correction data correspond.

On the other hand, during the non-blanking period (video signal period) of the reproduced video signal, the reproduced video signal data is input to the level correction memory 19 via the switch 18 whose connection is switched to the input terminal 12 side. Using the input reproduced video signal data as an address signal, data corresponding to this address is read out of the level correction data held in the level correction memory 19 and sent to the output terminal 20.
is output to. The level correction data of the reproduced video signal is added to the reproduced video signal data and converted into an analog signal, thereby correcting the level of the reproduced video signal.

[0007]

[Problems to be Solved by the Invention] In the conventional technique shown in FIG. There has been a problem in that it takes time to start normal level correction operations, such as when the correction device is started up. SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide a level correction device for a video signal that can increase the response speed of the entire device when the level correction device starts operating.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a playback method in which a reference signal inserted into a part of a recorded video signal string to be recorded is taken out as a playback reference signal when playing back a video signal. a reference signal extraction means, a data processing means for improving the S/N of the reproduction reference signal obtained from the reproduction reference signal extraction means, and a reference signal and reproduction standard that are the same as the reference signal inserted into the video signal sequence to be recorded. level correction data generating means for generating level correction data for correcting the level of the reproduced video signal by determining a level difference between the level correction data and the reproduced video signal data obtained from the level correction data generating means; In the video signal level correction device, the video signal level correction device is equipped with a level correction data holding means for holding the data in a corresponding state, and the pseudo reproduction generates pseudo reproduction reference signal data from the reproduction reference signal data obtained from the reproduction reference signal extraction means. A reproduction reference signal that selects one of the reproduction reference signal obtained from the reference signal generation means and the data processing means and the reproduction reference signal obtained from the pseudo reproduction reference signal generation means and then sends it to the level correction generation means. data selection means.

[0009]

[Operation] When starting playback or starting up the level correction device, level correction is performed based on pseudo level correction data generated from amplitude data at at least two points on the playback reference signal, and the level correction device Increases the response speed of the entire device when starting up operations, etc.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described with reference to the drawings. As shown in FIG. 1, a reference signal gate circuit 2 serving as reproduction reference signal extraction means is connected between an input terminal 1 and an output terminal 10.
, an averaging circuit 3, a pseudo reproduction reference signal generation circuit 11, a reproduction reference signal data selector circuit 5, an inspection circuit 4 as a control means, a level correction data generation circuit 6 as a level correction means, and a reference signal generation circuit 7. , a data changeover switch 8, and a level correction memory 9 as a level correction data holding means.

As shown in FIG. 1, reproduced video signal data is inputted from an input terminal 1 of the level correction device.
Reference signal gate circuit 2 and data changeover switch 8
is input to one terminal of The above reproduced video signal data is obtained by reproducing a recorded video signal recorded on a magnetic tape, and at the time of recording, a reference signal is inserted in advance into the blanking period of the recorded video signal. Therefore,
The reproduced video data includes a reference signal, that is, a reproduction reference signal.

The reference signal gate circuit 2 extracts reproduction reference signal data from the blanking period of reproduced video signal data and sends it to the averaging circuit 3 and the pseudo reproduction reference signal generation circuit 11. The averaging circuit 3 is
After improving the S/N of the reproduction reference signal data by averaging multiple reproduction reference signals or moving average within the reproduction reference signal data series, inspect the averaged reproduction reference signal data. The signal is sent to the circuit 4 and the reproduction reference signal data selector circuit 5.

The pseudo reproduction reference signal generation circuit 11 generates pseudo reproduction reference signal data by performing arithmetic processing based on the amplitude data of at least two points in the reproduction reference signal data inputted by the reference signal gate circuit 2. The reproduction reference signal is generated and sent to the reproduction reference signal data selector circuit 5. A simple example of the arithmetic processing performed by the pseudo reproduction reference signal data generation circuit 11 is a linear interpolation method. If a waveform that changes linearly, such as a ramp signal, is selected as the reference signal, the data between the two ends of the reproduced reference signal is interpolated by linear approximation to create a pseudo reproduced reference signal. Generate data.

The reproduction reference signal data selector circuit 5 includes:
reproduction reference signal data input from the averaging circuit 3;
One of the two pieces of pseudo reproduction reference signal data inputted from the pseudo reproduction reference signal generation circuit 11 is selected. Normally, the averaging circuit 3
However, when starting playback or starting up the level correction device, the pseudo playback reference signal data input from the pseudo playback reference signal generation circuit 11 is selected. You get to choose. The reproduction reference signal data selected by the reproduction reference signal data selector circuit 5 is inputted to the level correction data generation circuit 6 as level data on which level correction is based.
The data is temporarily stored in the memory of the level correction data generation circuit 6. A level correction data generation circuit 6 serving as a level correction data generation means sequentially writes reproduction reference signal data to appropriate addresses in a built-in memory, and also outputs stable reproduction reference signal data and a reference signal generation circuit 7. Level correction data is generated by determining the level difference between both signals from the reference signal data.

During the blanking period in which the reproduction reference signal of the reproduced video signal exists, the data changeover switch 8
are the level correction data generation circuit 6 and level correction memory 9
The address signal output from the level correction data generation circuit 6 is input to the level correction table. As a result, the reproduced video signal data output from the level correction data generation circuit 6 is written to the address corresponding to the above-mentioned address of the level correction memory 9, and a level correction table is created.

On the other hand, during the non-blanking period (video signal period) of the reproduced video signal, the data changeover switch 8 is switched to connect the input terminal 11 and the level correction memory 9, and the reproduced video signal is transferred to the level correction memory. 9 as an address signal. As a result, the level correction data held in the level correction memory 9 is sequentially read out and outputted from the output terminal 10. The level correction data obtained in this manner is added to the reproduced video signal data, thereby correcting the level of the reproduced video signal.

By the way, as mentioned above, the reproduction reference signal data selector circuit 5 generates reproduction reference signal data with improved S/N by the averaging circuit 3 at the time of starting reproduction or starting up the level correction device. If it is expected that it will take a long time for the reproduction reference signal data obtained from the reference signal gate circuit 2, a pseudo reproduction reference signal generated by processing amplitude data at at least two points in the reproduction reference signal data obtained from the reference signal gate circuit 2. Data is selected and output to the level correction data generation circuit 6. Therefore, the level correction data generation circuit 6 generates a level correction table based on this data, and performs level correction of the reproduced video signal.

In this embodiment, the controlled circuit of the test circuit 4 is the averaging circuit 3; however, the invention is not limited to this, and the reproduction reference signal data output from the reproduction reference signal data selector circuit 5 It is sufficient that the reproduction reference signal data selector circuit 5 can be switched as required, and the reproduction reference signal data selector circuit 5 can also be a controlled circuit of the inspection circuit 4.

[0019]

Effects of the Invention As explained above, the present invention enables the detection of at least two or more points on the reproduction reference signal before the regular reproduction reference signal data is generated, such as at the start of reproduction or when starting up the level correction device. By performing level correction based on level correction data generated from pseudo-reproduction reference signal data that has been calculated from amplitude data, the response speed of the entire device when starting up the level correction device, etc. is increased. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main part configuration of a video signal level correction device according to the present invention.

FIG. 2 is a block diagram showing the configuration of main parts of a conventional video signal level correction device.

[Explanation of symbols]

2 Reference signal gate circuit 3 Adding and averaging circuit 4 Inspection circuit 5 Reproduction reference signal data selector circuit 6 Level correction data generation circuit 7 Reference signal generation circuit 8 Data changeover switch 9 Level correction memory 11 Pseudo reproduction reference signal generation circuit

Claims (1)

[Claims] 1. Reproduction reference signal extraction means for extracting a reference signal inserted into a part of a recorded video signal sequence to be recorded as a reproduction reference signal when reproducing a video signal, and a reproduction reference obtained from the reproduction reference signal extraction means. Data processing means for improving the S/N of the signal, and correcting the level of the reproduced video signal by determining the level difference between the same reference signal as the reference signal inserted into the video signal sequence to be recorded and the reproduced reference signal. and a level correction data holding means for holding the level correction data obtained from the level correction data generating means and the reproduced video signal data in a corresponding state. A video signal level correction device includes a pseudo reproduction reference signal generation means for generating pseudo reproduction reference signal data from the reproduction reference signal data obtained from the reproduction reference signal extraction means, and a reproduction reference signal obtained from the data processing means. A level of a video signal characterized by comprising reproduction reference signal data selection means for selecting one data of the reproduction reference signal obtained from the pseudo reproduction reference signal generation means and sending the selected data to the level correction generation means. correction device.