JP2001210018A - Device for controlling reproducing envelope level - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an amplitude controller so that a signal level of a input to an A-D converter may not exceed an input dynamic range of the A-D converter due to variations in coercivity of a magnetic tape and variations in a reproduced output caused by aging of a magnetic head. SOLUTION: This reproducing envelope level control device detects a loading state from loading of a cassette by a cassette detector 20 and a loading position detector 21; samples an envelope level by an envelope data sampling unit 23 until the loading has been completed; obtains a maximum value of the envelope level during sampling when the loading is completed; calculates to optimize an amplitude adjustment value from the maximum value by an amplitude adjustment value arithmetic processor 25; and supplies the value to an amplitude variable unit 6 via an amplitude controller 12. In such a manner, the envelope level of the input to the A-D converter 7 is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital VTR equipped with a rotating drum and the like, and performs an A / D conversion on a reproduction signal reproduced from a magnetic tape by an A / D converter and then performs an equalization process. The present invention relates to a reproduction envelope level control device for controlling the input level to the A / D converter at the time. In the description, envelope is an abbreviation for envelope.

[0002]

2. Description of the Related Art FIG. 10 is a circuit block diagram of a main part of a digital VTR including a conventional reproduction envelope level control device.

Reference numeral 1 denotes a magnetic tape for recording digital signals, and 2a denotes a magnetic head which has a positive azimuth angle and is arranged on a rotating drum and reproduces signals from the magnetic tape 1.
b has a negative azimuth angle, is disposed at a position 180 degrees opposite to the magnetic head 2a on the rotating drum, and has a magnetic tape 20b.
A magnetic head 3a for reproducing a signal from 1 is a rotary transformer for transmitting a reproduction signal from the magnetic head 2a from the rotor side to the stator side, and a 3b is for transmitting a reproduction signal from the magnetic head 2b from the rotor side to the stator side. It is a rotary transformer. 4 is a magnetic head 2a or 2
A head switch generator 5 for generating a control signal indicating which of the reproduction signals b is reproducing the reproduction signal, and a switch 5 for alternately switching the reproduction signal from each of the rotary transformers 3a and 3b by the head switch generator 4. .

[0004] Reference numeral 6 denotes an amplitude varying device that varies the amplitude of the reproduction signal from the switching device 5 under the control of the amplitude controller 12.
Reference numeral 7 denotes an A / D converter for converting a reproduction signal from the amplitude variable unit 6 into a digital value. Reference numeral 8 denotes an automatic equalizer that optimally equalizes intersymbol interference generated in the electromagnetic conversion system from the reproduction signal data from the A / D converter 7, and outputs a required reproduction signal from the automatic equalizer 8. Is done.

Reference numeral 9 denotes a tracking information detector for detecting tracking information from the reproduction signal data from the A / D converter 7. The tracking information detector 9 determines which magnetic heads 2a and 2b are on the magnetic tape 1. Tracking information such as whether the track number is being tracked is output. Reference numeral 10 denotes an envelope level detector for separately sampling the reproduction signal levels from the reproduction signal data from the A / D converter 7 under the control of the head switch generator 4.
Data such as which position on the track of the magnetic tape 1 the a and 2b track is output.

Reference numeral 11 denotes an amplitude adjustment value storage for separately storing the amplitude variation of the reproduced signals from the magnetic heads 2a and 2b.
Reference numeral 12 denotes an amplitude controller for level-converting the amplitude adjustment value from the amplitude adjustment value storage 11 under the control of the head switch generator 4.

Here, the variable amplitude unit 6, the amplitude controller 12, and the amplitude adjustment value storage unit 11 constitute a conventional reproduction envelope level control device, and the input level of the reproduction signal to the A / D converter 7 Is controlled so as not to exceed its input dynamic range.

[0008]

In such a conventional apparatus, unless the amplitude adjustment value is set properly, the reproduction output of the magnetic tape 1 due to the variation of the coercive force and the change of the magnetic heads 2a and 2b with the lapse of time. The input level of the reproduction signal may exceed the dynamic range of the input to the A / D converter 7 due to variations or the like. Therefore, in the conventional device,
In consideration of such variations, for example, the storage value of the amplitude adjustment value in the amplitude adjustment value storage unit 11 is set by the manufacturer at the time of factory shipment or the like.

However, in the conventional apparatus, the use condition and environment assumed at the time of factory shipment differ depending on the subsequent use conditions and environment changes on the user side, and in some cases, the input level of the reproduced signal. Is A / D
If the input dynamic range of the converter is exceeded, the amplitude adjustment value is a fixed value and there is no way to deal with it.

Therefore, the amplitude adjustment value for the amplitude controller 12 is controlled so that the input level of the reproduced signal does not exceed the input dynamic range of the A / D converter even when the use conditions and the environment change on the user side. It is required to be able to do so.

According to the present invention, the level of the input signal to the A / D converter is changed by the variation of the coercive force of the magnetic tape, the variation of the reproduction output due to the aging of the magnetic head, and the like.
An object of the present invention is to appropriately control an amplitude adjustment value for an amplitude controller so as not to exceed an input dynamic range of a converter.

[0012]

A reproduction envelope level control device according to the present invention is a reproduction envelope level control device for controlling an input level when a reproduction signal reproduced from a recording medium is input to an A / D converter. By changing the amplitude of the reproduced signal reproduced from the recording medium,
Amplitude variable means for input to the D converter, amplitude control means for controlling the amplitude variable means according to the input of the amplitude adjustment value,
And an arithmetic control means for calculating an appropriate amplitude adjustment value from the envelope level of the reproduction signal from the A / D converter, and inputting the calculated value to the amplitude control means as the amplitude adjustment value.

According to the present invention, when the recording medium is a magnetic tape, there are variations in coercive force of the magnetic tape and variations in reproduction output due to aging of the magnetic head.
When the envelope level of the reproduction signal of the A / D converter changes, an appropriate amplitude adjustment value is calculated according to the change,
Since the calculated value is used as the amplitude adjustment value, the input level of the reproduced signal can be adjusted to the input dynamic range of the A / D converter even if there is a change in the use condition or its environment beyond the initial prediction on the user side after the factory shipment. , And the level of the reproduced signal can be stably controlled.

In a preferred embodiment of the present invention, the calculation is performed by calculating a difference between a maximum value of an envelope of a reproduction signal from the A / D converter and an input level target value of an input dynamic range of the A / D converter. Is used to calculate the amplitude adjustment value.

In such a case, since the amplitude adjustment value can be accurately calculated so that the reproduction envelope level becomes the target value of the input level of the converter, the resolution performance of the A / D converter can be sufficiently obtained. Thus, the level of a stable reproduction signal can be controlled.

As a preferred embodiment of the present invention, a table for correcting the amplitude adjustment value according to a difference between the maximum value and the target value is provided, and the calculation is performed with reference to the table.

In such a case, the correction amount of the amplitude adjustment value for setting the reproduction envelope level to the target value of the input level of the A / D converter is determined in advance, thereby shortening the calculation processing time for obtaining the amplitude adjustment value. Thus, the level of a stable reproduction signal can be instantaneously controlled.

As a preferred embodiment of the present invention, the table is a table in a case where the reproduction signal level is not subjected to an in-track average value processing of a recording medium.

In such a case, the maximum value of the envelope value is the maximum value of the input level to the A / D converter regardless of whether the reproducing head is performing on-track reproduction of the recording track of the recording medium. By preliminarily determining the correction amount of the amplitude adjustment value according to the difference between the maximum value of the envelope value and the input level target value, the calculation processing time for obtaining the amplitude adjustment value can be shortened, and the operation can be instantaneously stabilized. The level of the reproduced signal can be controlled.

As a preferred embodiment of the present invention, the table is a table in a case where the level of the reproduced signal is subjected to an in-track average value process on a recording medium.

In such a case, the maximum value of the envelope value differs depending on whether or not the reproducing head is performing on-track reproduction of the recording track of the recording medium. Calculation processing time for level conversion required when calculating the difference between the input level target value and the maximum value of the envelope value by determining in advance the correction amount of the amplitude adjustment value from the maximum value of the envelope during off-track playback Can be shortened,
It is possible to instantaneously control the level of a stable reproduction signal.

As a preferred embodiment of the present invention, the arithmetic control means includes an amplitude adjustment value initial value memory for storing an initial value of the amplitude adjustment value, and a reproduction for measuring a level of a reproduction signal from the A / D converter. Signal level measuring means, and the table in which a correction amount for the initial value is determined according to a difference between the maximum value and the target value for the calculation, and the amplitude adjustment value initial value memory And an amplitude adjustment value calculation processing means for inputting the amplitude adjustment value initial value and the reproduction signal level of each of the reproduction signal level measurement means and performing the calculation according to the table at a predetermined timing.

In such a case, the level of the reproduced signal input to the A / D converter using the reference recording medium in the amplitude adjustment value initial value memory is 1/1 / the input dynamic range.
2 is stored as an initial value, and the amount of correction from the initial value can be easily calculated for the difference between the maximum value and the target value, and the amplitude adjustment value can be determined accurately. can do.

As a preferred embodiment of the present invention, the arithmetic control means includes an insertion detecting means for detecting an inserted state of the recording medium, and a position detecting means for detecting a state until the recording medium reaches a position where reproduction is possible. The apparatus further controls the timing of calculating the amplitude adjustment value based on the state of the recording medium detected by the insertion detection unit and the position detection unit.

In such a case, for example, after the insertion of the recording medium is detected, the reproduction signal envelope level is measured until the recording medium reaches a proper position where reproduction is possible. The average value and peak value of the reproduction signal envelope level are obtained, and a more optimal amplitude adjustment value is obtained by comparing the average value and the peak value with the data in the table.

As a preferred embodiment of the present invention, the arithmetic control means includes an insertion detecting means for detecting an inserted state of the recording medium, a position detecting means for detecting a state until the recording medium reaches a position at which reproduction can be performed, Mode information detecting means for detecting mode information such as reproduction, recording, stop, and the like, and a recording format detecting means for detecting a format of the recording medium, wherein the recording medium is detected by the insertion detecting means and the position detecting means. The timing of the calculation of the amplitude adjustment value is controlled based on the state, the mode information by the mode information detecting means, and the recording format information by the recording format detecting means.

In such a case, for example, in the case of a VTR capable of reproducing a plurality of formats, the relative speed between the reproducing head and the recording medium changes depending on the format. After detecting the insertion of the recording medium, the recording medium comes to an appropriate position where it can be reproduced,
Furthermore, the recording format of the recording medium is correctly detected, and when the relative speed between the reproducing head and the recording medium is stabilized, the reproducing signal level data is measured for a certain period of time, and the average value or peak value of the measured reproducing signal envelope level is obtained. Compared with the data in the table, a more optimal amplitude adjustment value can be obtained based on the mode information during the measurement period, and the amplitude variable means can be controlled.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 shows a circuit block diagram of a main part of a digital VTR including a reproduction envelope level control device according to Embodiment 1 of the present invention. The same reference numerals are given, and only the parts corresponding to the same reference numerals are listed, and detailed description thereof is omitted.

In FIG. 1, 1 is a magnetic tape, 2a,
2b is a magnetic head, 3a and 3b are rotary transformers, 4 is a head switch generator, 5 is a switch, 6
Is an amplitude varying device as amplitude varying means capable of varying the amplitude of a reproduction signal reproduced from the magnetic tape 1 as a recording medium.

7 is an A / D converter, 8 is an automatic equalizer,
9 is a tracking information detector, 10 is an amplitude variator 6
An envelope level detector 12 as a reproduced signal level detecting means for detecting the level of the reproduced signal from the controller 12 is an amplitude controller for controlling the amplitude variable device 6 according to the amplitude adjustment value.

The feature of the first embodiment is that the following operation control means A1 is used instead of the conventional amplitude adjustment storage unit 11.
That is to deploy.

That is, the calculation control means A1 in the first embodiment calculates a proper amplitude adjustment value from the envelope level of the reproduction signal from the A / D converter 6, and uses this calculation value as the amplitude adjustment value. Input to an amplitude controller, wherein the calculation is performed with a predetermined value, preferably a maximum value, of the envelope of the reproduction signal from the A / D converter 7;
The amplitude adjustment value is calculated from the difference between the input dynamic range of the A / D converter 7 and the input level target value.

In this case, the operation control means A1 includes a table for correcting the amplitude adjustment value according to the difference between the maximum value and the target value, and performs the operation with reference to the table. Has become.

Specifically, as shown in FIG. 1, the arithmetic control means A1 comprises a cassette detector 20, a loading position detector 21, a central controller 22, an envelope data sampler 23, an amplitude adjustment value, An initial value memory 24 and an amplitude adjustment value calculation processor 25 are provided.

The cassette detector 20 inserts a recording medium,
As insertion detection means for detecting each state of ejection, insertion of a cassette containing the magnetic tape 1 into a VTR at a predetermined position and ejection at a predetermined position are detected as cassette insertion information.

The loading position detector 21 serves as a position detecting means for detecting a state until the recording medium reaches an appropriate position where the recording medium can be played back. The loading position detector 21 performs loading and unloading in accordance with the state in which the magnetic tape 1 is wound around the rotating drum. Detected as loading position information.

The central controller 22 uses the cassette insertion information input from the cassette detector 20 and the loading position information input from the loading position detector 21 to calculate an envelope data sampler 23 and an amplitude adjustment value processor 25, respectively. , And generates timing signals for the envelope level sampling and the amplitude adjustment value calculation.

The envelope data sampling unit 23 starts the loading position detector 21 when the cassette insertion information detected by the cassette detector 20 indicates that the cassette is inserted.
Until it is detected from the loading position information by the CPU that the magnetic tape 1 has reached the appropriate position for reproduction (during loading), the envelope level detector 10 is controlled by the central controller 22 as a reproduction signal level measuring means. Is sampled for the reproduction signal level.

When the reference magnetic tape used for adjusting the amplitude adjustment value is reproduced on track, the amplitude adjustment value initial value memory 24 stores the level of the reproduction signal to the A / D converter 7 in each magnetic head 2a. , 2b, the initial value of the amplitude adjustment value that is の of the input dynamic range of the A / D converter 7 is stored.

The amplitude adjustment value arithmetic processor 25 is controlled by the central controller 22 to control the embedded data sampler 23.
Calculates the maximum value of the sampled envelope data, calculates the difference between the maximum value and the input level target value of the input dynamic range of the A / D converter 7, and calculates the amplitude adjustment value for eliminating the difference between the two values. Is calculated based on the initial value of the amplitude adjustment value from the amplitude adjustment value initial value memory 24 in accordance with the tables shown in FIGS.

The operation of the first embodiment will be described with reference to FIGS.

FIG. 2 shows an operation sequence of the reproduction envelope level control device of FIG. 1, and FIG. 3 shows a correction of the amplitude adjustment value when the envelope level detector 10 does not process the average value of the envelope level in the track. FIG. 4 shows a table used for the calculation. FIG. 4 shows a table used for the calculation of the correction of the amplitude adjustment value when the envelope level detector 10 processes the envelope level within the track.

In FIG. 2, a shows the timing of cassette insertion detection and cassette ejection detection, b shows the timings of unloading, loading, loading completed, unloading, and unloading,
d is sampling OFF (no sampling),
The timings of sampling ON (sampling) are shown, and e is each timing of initial setting of amplitude adjustment value, calculation of correction amount of amplitude adjustment value, correction amount setting of amplitude adjustment value, initial setting of amplitude adjustment value. Is shown.

3 and 4, the maximum value of the envelope of the reproduced signal−the target value of the input level of the input dynamic range = the envelope level difference X and the correction amount from the initial value of the corresponding amplitude adjustment value (correction from the initial value). The set value is set as the amplitude adjustment value). FIG.
In the table, when X> +6 dB, the value obtained by subtracting -6 dB from the initial value of the amplitude adjustment value is used as the amplitude adjustment value, and when +6 dB ≧ X> +3 dB, the value obtained by subtracting -3 dB from the initial value of the amplitude adjustment value is used as the amplitude. + 3dB ≧
In the case of X, the initial value of the amplitude adjustment value is 0 dB, that is, the initial value is used as the amplitude adjustment value. In the table of FIG. 4, when X> +3 dB, a value obtained by subtracting −6 dB from the initial value of the amplitude adjustment value is set as the amplitude adjustment value, and +3 dB ≧ X>
When +1.5 dB, the value obtained by subtracting -3 dB from the amplitude adjustment value initial value is set as the amplitude adjustment value. When +1.5 dB ≧ X, 0 dB from the amplitude adjustment value initial value, that is, the initial value is used as the amplitude adjustment value.

When the cassette detector 20 detects that the cassette has been ejected, the central controller 22 causes the amplitude adjustment value calculation processor 25 to correct and calculate the initial value of the amplitude adjustment value in the amplitude adjustment value initial value memory 24. Instead, the initial value is supplied to the amplitude controller 12 as it is as an amplitude adjustment value to control the amplitude variator 6.

When the cassette detector 20 detects that a cassette is inserted, the central controller 22 causes the envelope data sampler 23 to start sampling envelope data from the envelope level detector 10.

When the loading position detector 21 detects that the loading of the magnetic tape 1 has been completed, the central controller 22 causes the envelope data sampling unit 23 to stop sampling the envelope data from the envelope level detector 10.

Immediately thereafter, the central controller 22 searches the amplitude adjustment value arithmetic processing unit 25 for the maximum value sample from the envelope data sampled by the envelope data sampling unit 23, and the envelope level detector 10 detects the envelope level. Is not processed in the track, the envelope level difference X = (maximum value-1/2 of the input dynamic range of the A / D converter) is obtained, and the envelope level detector 10 processes the envelope level in the track. In this case, the envelope level difference X = (maximum value−１ ／ of the input dynamic range of the A / D converter) is obtained.

Since the on-track reproduction cannot be performed while the magnetic tape 1 is being loaded, the average of the envelope levels in the track is half the level during on-track reproduction.

The amplitude adjustment value arithmetic processing unit 25 performs the processing when the envelope level detector 10 does not perform the average processing of the envelope level in the track (the processing of obtaining the average value of the envelope level of each reproduction signal in the track of the magnetic tape). 3, and when the envelope level detector 10 processes the average of the envelope level in the track, according to the table of FIG.
The amplitude initial value of each head is corrected and the calculation result is supplied to the amplitude controller 25 as an amplitude adjustment value, and the amplitude
Control.

Thereafter, the corrected amplitude adjustment value is maintained until the cassette discharge state is detected by the cassette detector 20.

When the cassette discharge state is detected by the cassette detector 20, the central controller 22 does not perform a correction operation on the amplitude initial value of the amplitude adjustment value initial value memory 24 with respect to the amplitude adjustment value calculation processor 25. It is supplied to the amplitude controller 12 as an amplitude adjustment value to control the amplitude variator 6.

As described above, in the first embodiment, the input signal level to the A / D converter 7 becomes A due to the variation of the coercive force of the magnetic tape 1, the variation of the reproduction output due to the aging of the magnetic heads 2a and 2b, and the like. The amplitude adjustment value for the amplitude controller 12 can be controlled so as not to exceed the input dynamic range of the / D converter 7.

(Embodiment 2) FIG. 5 is a circuit block diagram of a main part of a digital VTR including a reproduction envelope level control device according to Embodiment 2 of the present invention.
The same reference numerals are given to the portions corresponding to and the detailed description of the portions related to the same reference numerals is omitted.

Operation control means A2 characterized in the second embodiment
Means that the mode switch detector 26 is added. The mode switch detector 26 detects mode information such as reproduction, recording, and stop as an example of mode information detection means.

The central controller 22 generates timing signals for envelope level sampling and amplitude adjustment value calculation from the cassette insertion information from the cassette detector 20 and the loading position information from the loading position detector 21, and generates timing signals for envelope level sampling. An amplitude adjustment value calculation method is selectively controlled based on mode information from the mode switch detector 26.

The operation will be described with reference to FIG. FIG.
FIG. 6 shows an operation sequence in the case where the mode information does not change from the time of cassette insertion to the completion of loading in the reproduction envelope level control device of FIG. FIG. 6a,
b, d, and e respectively correspond to a, b, d, and e in FIG. 2, and FIG. 6c shows mode information.

When the cassette detector 20 detects that the cassette has been ejected, the central controller 22 does not correct the amplitude initial value of the amplitude adjustment value initial value memory 24 to the amplitude adjustment value arithmetic processing unit 25 without correcting the amplitude adjustment value. To the amplitude controller 12 to control the amplitude variator 6.

When the cassette position is detected by the cassette detector 20 and the loading position detector 21 detects that the loading is completed, the central controller 22 holds the mode information from the mode switch detector 26 at this time and The envelope data sampling unit 23 causes the envelope data from the envelope level detector 10 to be sampled for a certain period of time. Immediately after the end of sampling, the central controller 1
09, the amplitude adjustment value calculation processor 25 searches for the maximum value sample from the envelope data sampled by the envelope data sampler 23, and the envelope level detector 10
If the envelope level is not processed in the track average value, the envelope level difference = (maximum value-1 / 2 of the A / D input dynamic range) is obtained, and the envelope level detector 10 processes the envelope level in the track average value. Is the envelope level difference = (maximum value−1 / A / D input dynamic range)
Find 4). Since the mode information has not changed from the cassette insertion detection until the loading is completed, the magnetic tape 1 is stopped when the loading is completed. Therefore, since on-track reproduction cannot be performed during sampling of the envelope data, the average of the envelope levels in the track is half the level of the on-track reproduction. The adjustment value arithmetic processing unit 25 follows the table in FIG. 3 when the envelope level detector 10 does not perform the average processing of the envelope level in the track, and when the envelope level detector 10 performs the average processing of the envelope level in the track. Is an amplitude adjustment value initial value memory 24 according to the table of FIG.
The amplitude initial value of each head is corrected and the calculation result is supplied to the amplitude controller 12 as an amplitude adjustment value, and the amplitude
Control.

Thereafter, the corrected amplitude adjustment value is maintained until the cassette detector 20 detects the cassette discharge state. When the cassette discharge state is detected by the cassette detector 20, the central controller 22 sends the amplitude adjustment value calculation processor 2
5, the amplitude initial value of the amplitude adjustment value initial value memory 24 is not corrected and calculated, and the amplitude initial value is supplied to the amplitude controller 12 as an amplitude adjustment value to control the amplitude variable device 6.

FIG. 7 is an operation sequence diagram in the case where the mode switch information changes to reproduction in the reproduction envelope level control device of FIG. 5 between the time of cassette insertion and the completion of loading. 7a, b, d, and e correspond to a, b, d, and e in FIG. 2, respectively, and FIG. 7c shows mode information.

When the cassette detector 20 detects that a cassette has been inserted, if the loading position detector 21 detects that loading has been completed, the central controller 22 retains the mode information from the mode switch detector 26 at this point and stores the information. When the data sampler 23 enters a stable on-track reproduction state, the envelope data from the envelope level detector 10 is sampled for a certain period of time. Immediately after the end of the sampling, the central controller 22 sends the envelope data sampler 2 to the amplitude adjustment value processor 25.
The sample of the maximum value is searched for from the envelope data sampled in step 3, and an envelope level difference = (maximum value-1 / 2 of A / D input dynamic range) is obtained. The adjustment value calculation processor 25 corrects and calculates the amplitude initial value of each head in the amplitude adjustment value initial value memory 24 according to the table of FIG.
The calculation result is supplied to the amplitude controller 12 as an amplitude adjustment value, and the amplitude variable device 6 is controlled.

As described above, also in Embodiment 2, Embodiment 1
Similarly to the above, the input signal level to the A / D converter 7 becomes A / D due to the variation of the coercive force of the magnetic tape 1, the variation of the reproduction output due to the aging of the magnetic heads 2a and 2b, and the like.
The amplitude adjustment value for the amplitude controller 12 can be controlled so as not to exceed the input dynamic range of the D converter 7, and further, the amplitude adjustment value calculation method can be selectively controlled based on the mode information, and a more preferable amplitude adjustment value is set. it can.

(Embodiment 3) FIG. 8 shows a digital V including a reproduction envelope control device according to Embodiment 3 of the present invention.
FIG. 10 is a circuit block diagram of a main part of the TR. Parts corresponding to those in FIG. 5 are denoted by the same reference numerals, and detailed description of the parts related to the same reference numerals is omitted. The arithmetic control means A3, which is a feature of the third embodiment, is a VTR capable of reproducing two recording formats, comprising an amplitude adjustment value memory 27 having an amplitude initial value for each format and an amplitude adjustment value memory 28, and further reproduced. A recording format detector 29 for detecting the recording format of the recording medium. The recording format detector 29 detects recording format information of a recording medium as recording format information detecting means. The amplitude adjustment value memory switch 30 receives the recording format information from the recording format detector 29, and the central processing unit 22 sends the amplitude adjustment value initial value from the amplitude adjustment value memory 27 or the amplitude adjustment value memory 28 according to the recording format of the recording medium. The value is selected and transmitted to the amplitude adjustment value calculation processor 25. A timing signal for envelope sampling and amplitude adjustment calculation from the central processing unit 22 and the cassette insertion information from the cassette detector 20, the loading position information from the loading position detector 21, and the recording format information from the recording format detector 29. Is generated, and an amplitude adjustment value calculation method is selectively controlled based on mode information from the mode switch detector 26 at the time of embedding sampling.

The operation will be described with reference to FIG. FIG.
FIG. 10 shows an operation sequence in the case where the mode information does not change from the time of cassette insertion to the completion of loading in the reproduction envelope level control device of FIG. FIG. 9a,
b, c, d, and e respectively correspond to a, b, c, d, and e in FIG. 6, and FIG. 9f shows recording format information. When the cassette detector 20 detects that the cassette has been ejected, the central controller 22 outputs an amplitude adjustment value calculation processor 25.
On the other hand, the amplitude initial value stored in the amplitude initial value memory 24 of the amplitude adjustment value initial value memory 24 is supplied to the amplitude controller 12 as an amplitude adjustment value without performing a correction operation to control the amplitude variable device 6.

When the cassette detector 20 detects that a cassette has been inserted, the loading position detector 21 detects that loading has been completed, and the recording format detector 29 detects that the loading has been completed.
Detects valid recording format information. afterwards,
The central processing unit 2 waits for A hours until the relative speed between the magnetic tape 1 and the magnetic heads 2a and 2b is stabilized by the change of the recording format. After the elapse of the standby time A, the central processing unit 22 holds the mode information from the mode switch detector 26 at this time and causes the envelope data sampler 23 to sample the envelope data from the envelope level detector 10 for a certain period of time. . After the sampling is completed, the central processing unit 22 searches the amplitude adjustment value calculation processing unit 25 for the sample of the maximum value from the envelope data sampled by the envelope data sampling unit 23, and the envelope level detector 10 averages the envelope level within the track. When the value processing is not performed, the envelope level difference = (maximum value−１ ／ of the A / D input dynamic range) is obtained. When the envelope level detector 10 processes the envelope level within the track, the envelope level difference = (maximum). Value-1/4 of the A / D input dynamic range).

Thereafter, the central processing unit 22 reads the amplitude initial value from the amplitude adjustment value initial value memory 27 or the amplitude initial value from the amplitude adjustment value initial value memory 28 according to the recording format information from the recording format detector 29,
The amplitude initial value is subjected to a correction operation to the envelope level difference, and the calculation result is supplied to the amplitude controller 12 as an amplitude adjustment value to control the amplitude variable device 6.

Thereafter, the corrected amplitude adjustment value is maintained until the cassette detector 20 detects the cassette discharge state. When the cassette discharge state is detected by the cassette detector 20, the central controller 22 sends the amplitude adjustment value calculation processor 2
5, the amplitude initial value of the amplitude adjustment value initial value memory 24 is not corrected and calculated, and the amplitude initial value is supplied to the amplitude controller 12 as an amplitude adjustment value to control the amplitude variable device 6.

As described above, also in the third embodiment, as in the first and second embodiments, the variation in the coercive force of the magnetic tape 1, the variation in the reproduction output due to the aging of the magnetic heads 2a and 2b, and the other factors. The amplitude adjustment value for the amplitude controller 12 can be controlled so that the input signal level to the A / D converter 7 does not exceed the input dynamic range of the A / D converter 7, and further, the amplitude adjustment calculation method based on the mode information. And the embedding data is not erroneously sampled in a transient state in which the relative speed between the magnetic tape 1 and the magnetic heads 2a and 2b changes according to the recording format information. Can be set.

[0071]

As described above, according to the present invention, when the recording medium is a magnetic tape, if the coercive force of the magnetic tape varies and the reproduction output varies due to the aging of the magnetic head, the A / D The envelope level of the reproduced signal of the converter changes, but an appropriate amplitude adjustment value is calculated in accordance with this change, and the calculated value is used as the amplitude adjustment value. The input level of the reproduced signal does not exceed the input dynamic range of the A / D converter even if there is a change in the use conditions or the environment, and therefore, the level of the reproduced signal can be controlled stably.

Accordingly, A / D conversion of a reproduced signal can be performed stably with respect to variations in coercive force of the magnetic tape and a change in reproduced output due to wear of the magnetic head, so that stable operation of the automatic equalizer and accurate servo control can be achieved. Thus, it is possible to obtain an effect that a stable tracking operation can be ensured and a stable error rate of the identification data can be ensured.

On the other hand, when the input level of the A / D converter is sampled after the magnetic tape is inserted and loading is completed, the contact state between the magnetic tape and the magnetic head becomes very stable, and the accurate information is obtained from the mode information during sampling. Since the amplitude can be controlled, the advantageous effect that the input level of the reproduction signal to the A / D converter can be more stably supplied is obtained.

Further, since the control of the input level of the reproduction signal to the A / D converter is performed only once when the magnetic tape is inserted, the servo tracking control in the magnetic tape reproduction state is not affected. There is.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a main part of a digital VTR including a reproduction envelope level control device according to a first embodiment of the present invention.

FIG. 2 is an operation sequence diagram of the reproduction envelope level control device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an amplitude adjustment value correction amount conversion table when the envelope level detector of the reproduction envelope level control device according to the first embodiment of the present invention does not process the average value of the envelope level in the track;

FIG. 4 is an amplitude adjustment value correction amount conversion table when the envelope level detector of the reproduction envelope level control device according to the first embodiment of the present invention processes the average of the envelope level in a track;

FIG. 5 is a circuit block diagram of a main part of a digital VTR including a reproduction envelope level control device according to a second embodiment of the present invention.

FIG. 6 is an operation sequence diagram when there is no change in mode switch information from the time of cassette insertion to the completion of loading in the reproduction envelope level control device according to the second embodiment of the present invention.

FIG. 7 is an operation sequence diagram in a case where mode switch information changes to reproduction in a reproduction envelope level control device according to a second embodiment of the present invention between the time of cassette insertion and the completion of loading.

FIG. 8 is a circuit block diagram of a main part of a digital VTR including a reproduction envelope level control device according to a third embodiment of the present invention.

FIG. 9 is an operation sequence diagram in a case where recording format information is determined by loading completion from the time of cassette insertion in the reproduction envelope level control device according to the third embodiment of the present invention.

FIG. 10 is a circuit block diagram of a main part of a digital VTR including a conventional reproduction envelope level control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 6 Amplitude variable device 7 A / D converter 10 Envelope level detector A1, A2 Arithmetic control means 20 Cassette detector 21 Loading position detector 22 Central controller 23 Embedded data sampler 24 Amplitude adjustment value initial value memory 25 Adjustment value calculation processor 26 Mode switch detector 29 Recording format detector

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5D031 AA03 DD02 DD09 HH20 5D044 BC01 CC03 FG04 FG05 5J022 AA01 BA08 CA10 CD02 CG01 5J030 CB03 CC11

Claims (9)

[Claims] 1. A reproduction signal reproduced from a recording medium is subjected to A / D conversion.
What is claimed is: 1. A reproduction envelope level control device for controlling an input level when inputting a signal to a converter, comprising: an amplitude variable means for changing an amplitude of a reproduction signal reproduced from a recording medium and inputting the amplitude to the A / D converter; An amplitude control means for controlling the amplitude varying means in accordance with the input of the adjustment value; and an appropriate amplitude adjustment value is calculated from an envelope level of the reproduction signal from the A / D converter, and the calculated value is used as the amplitude adjustment value. A reproduction envelope level control device, comprising: an arithmetic control means for inputting to the amplitude control means. 2. The reproduction envelope level control device according to claim 1, wherein the calculation is performed using a maximum value of an envelope of a reproduction signal from the A / D converter and an input level of an input dynamic range of the A / D converter. A reproduction envelope level control device for calculating the amplitude adjustment value from a difference from a target value. 3. The reproduction envelope level control device according to claim 2, further comprising a table for correcting the amplitude adjustment value according to a difference between the maximum value and the target value, wherein the calculation is performed by referring to the table. A playback envelope level control device. 4. The reproduction envelope level control device according to claim 3, wherein the table is a table in a case where the reproduction signal level is not processed in a track average value of a recording medium. Envelope level control device. 5. The reproduction envelope level control device according to claim 3, wherein the table is a table for a case where the level of the reproduction signal is subjected to an in-track average processing of the level of the reproduction signal. Control device. 6. The reproduction envelope level control device according to claim 3, wherein the arithmetic control means includes: an amplitude adjustment value initial value memory for storing an initial value of the amplitude adjustment value; and the A / D converter. Reproduction signal level measuring means for measuring the level of the reproduction signal, and a table in which a correction amount for the initial value is determined according to a difference between the maximum value and the target value for the calculation. Amplitude adjustment value calculation processing means for inputting an amplitude adjustment value initial value from the amplitude adjustment value initial value memory and a reproduction signal level of each of the reproduction signal level measurement means and performing the calculation according to the table at a predetermined timing; A playback envelope level control device, comprising: 7. The reproduction envelope level control device according to claim 6, wherein the arithmetic control means detects an insertion state of the recording medium, and detects a state until the recording medium reaches a position at which reproduction can be performed. A reproduction envelope level control device, further comprising a position detection unit, wherein a timing of calculating the amplitude adjustment value is controlled based on a state of the recording medium detected by the insertion detection unit and the position detection unit. 8. The reproduction envelope level control device according to claim 6, wherein the arithmetic control means detects an insertion state of the recording medium, and detects a state until the recording medium reaches a position at which the recording medium can be reproduced. A position detection unit; and a mode information detection unit that detects mode information such as reproduction, recording, and stop, and the state of the recording medium detected by the insertion detection unit and the position detection unit and a mode determined by the mode information detection unit. Controlling the timing of the calculation of the amplitude adjustment value based on the information and
A playback envelope level control device, characterized in that: 9. The reproduction envelope level control device according to claim 6, wherein the arithmetic control means detects an insertion state of the recording medium, and detects a state until the recording medium reaches a position at which the recording medium can be reproduced. A position detection unit; a mode information detection unit for detecting mode information such as reproduction, recording, and stop; and a recording format detection unit for detecting a recording format of a recording medium of the recording medium. A timing for calculating the amplitude adjustment value based on a state of the recording medium detected by the detecting means, mode information by the mode information detecting means, and recording format information by the recording format detecting means. Level control device.