JPH0787524A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To obtain a very stable reproduced signal by controlling the reproduced signal so that the reproduced signal obtained by reproducing a recorded signal is reproduced in a prescribed reference level and completely excluding the level deviation of the reproduced signal from a reference signal level. CONSTITUTION:The signal reproduced by magnetic heads 1A and 1B is supplied to a first deemphasis circuit 22 through a frequency demodulation means 21, and a reproduced TCI signal 22a obtained by attenuation of high-band frequency components is supplied to an ID detection means 25 and a control means 37 through an A/D converter 23. The signal 22a is clamped by the level of 501RE before A/D conversion if necessary. The control means 37 performs digital AGC control of the digitized signal 22a and outputs the signal 22a, whose peak level is a digital value corresponding to 1001RE, to a first TCI inverse conversion means 24. A digital value as the reference level is preset in a reference level circuit constituting the control means 37. As the result, the signal 22a can be reproduced in the P-P level of digital values corresponding to 0 to 1001RE in the overall reproducing period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal reproducing device.

[0002]

2. Description of the Related Art Conventionally, as a method of high-density magnetic recording / reproducing, a segment recording system is known in which one screen is divided and recorded / reproduced on a plurality of tracks. This system has a plurality of systems of signal processing means because one screen is recorded and reproduced by a plurality of heads, but has a drawback that line flicker or field flicker occurs due to the difference in characteristics among these signal processing means. It was

Therefore, as a magnetic recording / reproducing apparatus that solves the above-mentioned drawbacks, "UNI", which is one of the high definition VTR systems.
HI "(National) or high-definition VTR (" high-definition VTR for consumer use "Television Society Technical Report VO
L.15 NO.50) has been proposed. These conventional VTRs
In order to solve the above-mentioned drawback, in the above, a plurality of correction signals for correcting the characteristics between the signal processing means of a plurality of systems are recorded at the beginning of the track formed on the magnetic tape, and the plurality of correction signals are reproduced at the time of reproduction. The characteristics between the signal processing means of a plurality of systems were corrected by reproducing.

[0004]

However, if a predetermined period is required to record a plurality of correction signals unrelated to the pattern, there is a drawback that the utilization efficiency of the recording medium decreases. If the types of correction signals are limited, there is a drawback that the characteristics that can be corrected between the signal processing means are limited.

Therefore, in the present invention, as will be described later, a reproduction signal obtained by reproducing a recording signal composed of a time division multiplex video signal and a time division multiplex correction signal has a predetermined reference level (for example, 100 IRE which is a peak value. , When the clamp level is set to 50 IRE, AGC control (auto gain control) is performed on the gain of this reproduction signal so that the reproduction signal (reproduction TCI signal 22a) can be reproduced within the range of 0 to 100 IRE). As a result, even if amplitude distortion occurs in the reproduction signal due to transmission distortion in the reproduction transmission system in which the reproduction signal is transmitted, this can be completely eliminated, and the amplitude of the reproduction signal can always be reproduced at a value according to the reference level described above. As a result, by making this reference level the same as the reference level during recording, the time-division multiplexed video signal and the same amplitude as during recording can be obtained. It becomes possible to reproduce the time division multiplex correction signal, and as a result, it is possible to perform this at a stable reproduction signal level during demodulation signal processing when dividing the time division multiplex video signal into a plurality of types of video signals. The purpose is to enable reproduction of extremely high quality video signals.

[0006]

In order to solve the above problems, the present invention provides the following two configurations.

A time-division multiplexed video signal in which a plurality of types of video signals are time-division-multiplexed for each horizontal period and a plurality of types of correction signals corresponding to the plurality of types of video signals are time-axis-multiplexed to obtain the time-division multiplexed video. A video signal reproducing apparatus for reproducing a recording signal composed of a time division multiplex correction signal inserted within a predetermined horizontal period of a signal, wherein the reproduced signal obtained by reproducing the recording signal is reproduced at a predetermined reference level. A video signal reproducing apparatus having a control means for controlling the reproduction signal.

The video signal reproducing apparatus described above, wherein the control means controls the gain of the reproducing signal according to a level difference between the reproducing signal and the reference level.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A video signal reproducing apparatus according to the present invention will be described below with reference to the drawings. 1 and 2 are block diagrams of a video signal reproducing device according to first and second embodiments of the present invention, FIG. 3 is a block diagram of a video signal recording device, and FIG. 4 is a conceptual diagram for explaining a dividing means. 5 is a waveform diagram of the first to fourth correction signals, FIG. 6 is a waveform diagram of the TCI signal, FIG. 7 is a plan view for explaining the arrangement of the magnetic head on the rotating drum,
8 is a conceptual diagram for explaining a magnetic tape pattern, FIGS. 9 and 11 are block diagrams of an AGC circuit, FIG. 10 is a block diagram of an analog AGC circuit, and FIG. 12 is a diagram showing the AGC operation and the number of updates of multiplication coefficients. A graph showing the relationship, FIG. 13 shows A
It is a flow chart for explaining a GC algorithm.

A video signal reproducing apparatus according to the present invention is a time-division multiplexed video signal (first video signal recorded by time-division-multiplexing a plurality of types of video signals (compressed line sequential color signal, compressed luminance signal) for each horizontal period. , The second TCI signals 5a and 6a) and a plurality of types of correction signals (first to fourth correction signals 11a to 14a) respectively corresponding to the plurality of types of video signals described above are time-axis-multiplexed and A video signal reproducing apparatus for reproducing a recording signal (first and second recording TCI signals 7a, 8a) consisting of a time division multiplex correction signal inserted in a predetermined horizontal period of a division multiplex video signal, The reproduced signal (reproduced TCI signal 22a) obtained by reproducing the recorded signal is a predetermined reference level (for example, 100 IRE which is a peak value. Thus, when the clamp level is 50 IRE, 0 to 100 IR
The video signal reproducing apparatus is characterized by having control means (AGC circuit) for controlling the signal level of the reproduction signal so that the reproduction signal can be reproduced within the range of E).

First, a magnetic recording apparatus for recording a high-definition signal will be described with reference to FIG. In the figure, a Y signal aa (luminance signal) and PB, PR signals bb, cc (color signal) are supplied to the dividing means 4 via A / D converters 1 to 3 from a transmission line (not shown). Here, the Y, PB, and PR signals are signals conforming to the domestic high-definition signal standard,
It is a signal converted from the R, G, B signals by the following equation.

Y = 0.7154G + 0.0721B + 0.2125R PB = 0.5389 (-0.7154G + 0.9279B-0.2125R) PR = 0.6349 (-0.7154G-0.0721B + 0.7875R) The dividing means 4 uses the Y signal aa, PB and PR signals. bb, c
It has a role of compressing c and dividing it into two systems. This division processing will be described with reference to FIG. 4. Y, PB, PR signals aa, bb, cc (HDTV signals) shown in the upper left part of FIG.
Of these, a signal corresponding to the number of effective scanning lines of the MUSE signal in which the sync signal and the lines related to the upper and lower sides of the screen are deleted is generated, and this signal is divided into the two signals shown in the lower left and lower right of the figure. ing. The first Y signal 4a, the first PB signal 4b, the first PR signal 4c, the second Y signal 4d, the second PB signal 4e, and the second PR signal 4f, which are obtained by dividing in this way, Is supplied to the first and second TCI processing means 5 and 6.

The first and second TCI processing means 5,
A line-sequential color signal 6 converts the first and second PB signals 4b and 4e and the first and second PR signals 4c and 4f into a line-sequential color signal, and a time-axis-compressed compressed line-sequential color signal, A time-axis multiplex of a compressed luminance signal obtained by time-compressing the first and second Y signals 4a and 4d and a discrimination signal for discriminating whether the compressed line-sequential color signal is a signal relating to the PB signal or the PR signal. The first and second TCI signals 5a and 6a obtained in this way are supplied to the first and second selecting means 7 and 8.

The first and second selecting means 7 and 8 and the first and second TCI signals 5a and 6a and the first to fourth ROs, respectively.
First to fourth correction signals 11 supplied from M11 to 14
a to 14a, a data signal 50a supplied from the data generation circuit 50, a horizontal / vertical synchronization signal 51a supplied from the synchronization signal generation circuit 51, and a switching signal 52a supplied from the switching signal generation circuit 52. ，
It selectively outputs based on the second selection signals 10a and 10b. Here, the data signal 50a is an additional information signal such as a signal representing a program content to be recorded, a character multiplex signal, or a signal representing an absolute address for editing. Further, the switching signal 52a is a signal for securing a margin for switching the magnetic head, and the compressed line sequential color signal is ± 0% of 50 IRE, and the compressed luminance signal is 0% level of 0IR.
This signal is at the E level. The timings of the first and second selection signals 10a and 10b are generated based on the horizontal / vertical synchronization signal 9a separated by the horizontal / vertical synchronization signal separation circuit 9 from the luminance signal aa via the A / D converter 1. It is generated by the circuit 10.

Here, the first to fourth correction signals 11a to 1
4a will be described in detail. These signals are correction signals common to the compressed luminance signal and the compressed line sequential color signal, or correction signals provided separately. Here, the latter case will be described. The first correction signal 11a is a ramp signal and is a signal for correcting the linearity between the two systems. Also,
The second correction signal 12a is 0, 25, 50, 75, 100
The gray scale signal has five levels of IRE, and is for adjusting the DC level and the amplitude level between the two systems during reproduction. Further, the third correction signal 13a is a multi-burst signal and is a signal for correcting the frequency characteristic between the two systems. Furthermore, the fourth correction signal 14a is in the form of SIN2 and its half width is 1 /
It is a 2T pulse signal that matches the cycle of the frequency corresponding to 2, and is a signal for correcting the phase characteristic between the two systems.

Now, the contents of the correction signal will be described by taking the first correction signal 11a (ramp signal) shown in FIG. 5 as an example. In FIG. 5, the period T1 is a synchronizing signal period and the period T2 is 1st with 2-bit identification information
Is an identification signal period representing the types of the fourth correction signals 11a to 14a, a period T3 is a correction signal period relating to a compressed line sequential color signal, and a period T4 is a correction signal period relating to a compressed luminance signal. The period T2 is the above-mentioned discrimination signal period,
The period T3 corresponds to the period in which the compressed line sequential color signal is inserted, and the period T4 corresponds to the compressed luminance signal period. Therefore, it is possible to simplify the configuration of the correction unit in the reproducing apparatus described later. The correction signal is a time-division multiplex correction signal obtained by time-division-multiplexing a plurality of types of correction signals corresponding to the line-sequential color signal and the luminance signal, respectively, and a PB signal and a PR signal that are not line-sequentially converted. It may be applied to a compressed compressed PB signal, a compressed PR signal, and a compressed luminance signal. In such a case, time-division multiplex correction obtained by time-division-multiplexing three types of correction signals respectively corresponding to three types of video signals Of course, it is sufficient to use signals.

In this way, the first and second selection means 7 and 8 shown in FIG.
The second recording TCI signals 7a and 8a are transferred to the D / A converter 15,
Via the first and second emphasis circuits 17 and 18
Is being supplied to. Then, in the first and second emphasis circuits 17 and 18, the first and second recording TCI signals 7a and 8
The high frequency component of a is emphasized and supplied to the first and second modulation circuits 19 and 20 for performing a predetermined modulation such as FM modulation. Then, these output signals are amplified to a predetermined level by a recording amplifier (not shown) and recorded on the magnetic tape TT via the magnetic heads 1A and 1B and the magnetic heads 2A and 2B, respectively.

Here, the first and second recording TCI signals 7
The relationship between a, 8a, the magnetic heads 1A, 1B, 2A, 2B and the magnetic tape pattern will be described in detail with reference to FIGS.
It should be noted that the numbers in FIGS. 6 and 7 represent line numbers, "SW" is a switching signal, "V" is a vertical synchronization signal, and "CAL" is a first to fourth correction signal. , "D
"A" represents a data signal, respectively.

Then, the first recording TCI signal 7a relating to the even-numbered line is "SW" shown in FIG. 8A by using the magnetic head 1A arranged on the rotary drum shown in FIG. To "556 (1/2)" on the tracks, and the magnetic head 1B is used to record on tracks "556 (1/2)" to "1118" shown in FIG. 8A. It On the other hand, the second recording TCI signal 8a relating to the odd-numbered line is output from "SW" to "557" shown in FIG. 8A by using the magnetic head 2A arranged on the rotary drum shown in FIG. 8 is recorded on the track related to (1/2) ”and using the magnetic head 2B.
From "557 (1/2)" to "111" shown in FIG.
9 ”. In addition, the magnetic heads 1A and 2A or the magnetic heads 1 that are arranged close to each other
B and 2B perform simultaneous recording, but the audio tracks A and B in FIG. 8A are formed by the audio magnetic heads 3A and 3B preceding this. The magnetic heads 1A, 2A, 1
It goes without saying that the magnetic tape pattern shown in FIG. 8B can be obtained by appropriately setting the mounting heights of the B and 2B and the audio magnetic heads 3A and 3B.

In this way, one frame period is recorded, and this is repeated. Here, the first to fourth correction signals 11a to 14a are represented by "C" in FIGS.
The correction signal of the same type is recorded during this one frame period, and another correction signal is recorded in the next frame. Then, this is repeated thereafter, and the first to fourth correction signals 11a to 14a are recorded in four frame periods.
As a result, during the one frame period which constitutes one screen, the correction at the time of reproduction for the same characteristic is performed.

Next, a first embodiment of the video signal reproducing apparatus according to the present invention will be described with reference to FIG. Note that the configuration related to the magnetic heads 2A and 2B surrounded by the dotted line in the figure is the same as the configuration related to the magnetic heads 1A and 1B, and therefore the description thereof is omitted. In the figure, a signal reproduced from the magnetic tape TT by using the magnetic heads 1A and 1B is amplified to a predetermined level by a preamplifier (not shown), and then FM.
The reproduced TCI signal 22a, which is supplied to the first de-emphasis circuit 22 through the demodulation means 21 for performing demodulation such as demodulation and obtained by attenuating the high frequency component, is the A / D converter 2
It is supplied to the ID detection means 25 and the control means 37 via the control unit 3. The above-mentioned reproduced TCI signal 22a is the A / D converter 2
Clamping is performed at the level of 50 IRE as required prior to A / D conversion of No. 3.

The control means 37 is a digitized reproduction TCI.
The signal 22a is digitally AGC-controlled, and the digitized reproduced TCI signal 22a whose peak level is set to a digital value (reference level) corresponding to, for example, 100IRE is first
To the TCI inverse conversion means 24. Here, a digital value corresponding to 100 IRE serving as a reference level is preset in a reference level circuit 37f, which will be described later, which constitutes the control means 37. As a result, the digitized reproduced TCI signal 22a has a PP level of 0 to 10 over the entire reproduction period.
It becomes possible to reproduce with a digital value according to 0IRE.

The above-mentioned first TCI inverse conversion means 24 is P
A first luminance signal 2 obtained by expanding the compressed luminance signal and the compressed line-sequential color signal in the reproduced TCI signal 22a having a digital value corresponding to a P level of 0 to 100 IRE, respectively.
4a and the first line-sequential color signal 24b are supplied to one input of correction means 30, 31 and comparison control means 28, 29, respectively, which will be described later.

The ID detecting means 25 separates the vertical synchronizing signal and the horizontal synchronizing signal in the digitized reproduced TCI signal 22a, and inserts the first to fourth correction signals 11a to 14a from the vertical synchronizing signal. Identify the line
The insertion timing of the identification signal in the line is specified from the horizontal synchronization signal. Then, the discrimination signal 25a obtained by discriminating the discrimination signal at this insertion timing and discriminating the type of the correction signal of the line is supplied to the ROMs 26 and 27.
The ROM 26 is the first to fourth ROMs 11 to 1 described above.
Which has the contents relating to the compressed luminance signal in 4,
On the other hand, the ROM 27 is the above-mentioned first to fourth ROMs 11 to 11.
The content of the compressed line sequential color signal in FIG. Then, the ROMs 26 and 27 generate a correction signal of the same type as the correction signal in the line represented by the discrimination signal 25a, and supply this signal to the other inputs of the comparison control means 28 and 29, respectively.

The comparison control means 28, 29 are ROMs 26, 2
7 and the first to fourth correction signals 11a to 14 in the first luminance signal 24a and the first line-sequential color signal 24b.
The control signals 28a and 29a obtained by comparing the level with a are supplied to the correction means 30 and 31.

When the signal on the line is the first correction signal (ramp signal), the comparison control means 28, 29 determines the difference between the two input signals for each sample by the control signals 28a, 2a.
9a and outputs these signals as a complementary signal at the level specified for each sample described above,
The linearity is corrected by the correction means 30 and 31 by storing in the memory circuit in 31 and adding and subtracting the first luminance signal 24a and the first line-sequential color signal 24b and the complementary signal. .

When the signal on the line is the second correction signal (gray scale signal), the comparison control means 28,
At 29, the level difference between the black level (0IRE) and the white level (100IRE) of the second correction signal is detected, and the difference between this signal and the reference level difference output from the ROM 26, 27 is controlled by the control signal 28a, 29a, these signals are stored in the memory circuits in the correction means 30 and 31, respectively, and the correction means 30 and 31 are stored based on the control signals 28a and 29a.
The VCA in 31 is controlled to correct the amplitude levels of the first luminance signal 24a and the first line-sequential color signal 24b.
Further, the comparison control means 28, 29 outputs the difference between the black level (0IRE) of the second correction signal and the black reference level output from the ROMs 26, 27 as control signals 28a, 29a, and these signals are output. The first luminance signal 24a and the first line-sequential color signal 24b are stored in the memory circuits in the correction means 30 and 31, respectively, and the DC shifters in the correction means 30 and 31 are controlled based on the control signals 28a and 29a. The DC level of is corrected.

Further, when the signal on the line is the third correction signal (multiburst signal), the comparison control means 2
The levels of burst signals of a plurality of frequencies in the third correction signal are detected at 8, 29, and this signal and the ROM 26, 27 are detected.
The difference from the reference burst signal level output from each of the plurality of frequencies is detected and output as control signals 28a and 29a. These signals are stored in the memory circuits in the correction means 30 and 31, respectively, and the control signals 28a and 29a are stored. The frequency equalizer in the correcting means 30 and 31 is controlled based on 29a to
The frequency characteristics of the luminance signal 24a and the first line-sequential color signal 24b are corrected.

Further, when the signal of the line is the fourth correction signal (2T pulse signal), the comparison control means 2
8 and 29 detect the temporal positions and levels of the preshoot and the overshoot, and detect this signal and the ROM 26,
The difference from the reference 2T pulse signal output from 27 is detected and output as control signals 28a and 29a, and these signals are stored in the memory circuits in the correction means 30 and 31, respectively,
Correction means 30, 31 based on the control signals 28a, 29a
The phase shifter therein is controlled to correct the phase characteristics of the first luminance signal 24a and the first line-sequential color signal 24b.

In this way, from the correction means 30 and 31,
The first corrected Y signal 30a and the first corrected transmission signal
The corrected line-sequential color signal 31a is supplied to the synthesizing means 33 and the line-sequential demodulating means 32, respectively, and the line-sequential demodulating means 32 can perform the known line-sequential demodulation to obtain the first corrected PB and PR signals 32
The a and 32b are supplied to the synthesizing means 33.

The synthesizing means 33 has a complementary relationship with the above-mentioned dividing means 4, and the first correction Y, PB, PR signals 30a, 32a, 32b relating to the magnetic heads 1A, 1B.
Second correction Y, PB, PR relating to the magnetic heads 2A, 2B
Outputs Y, PB, PR signals dd, ee, ff obtained by synthesizing the signals 300a, 320a, 320b are supplied to a transmission line (not shown) via the A / D converters 34-36.

Now, a second embodiment of the video signal reproducing apparatus according to the present invention will be described with reference to FIG. The video signal recording device (shown in FIG. 3) and the video signal reproducing device (shown in FIG. 1) described above record / reproduce the first to fourth correction signals 11a to 14a, and perform signal processing relating to the magnetic heads 1A and 1B. The system and the signal processing system related to the magnetic heads 2A and 2B are separately and independently corrected so as to eliminate the characteristic difference between the two signal processing systems. On the other hand, the second embodiment of the video signal reproducing apparatus is to make a relative correction between both signal processing systems to eliminate the characteristic difference. That is, the characteristic of the signal processing system relating to the magnetic heads 2A and 2B is corrected with reference to the characteristic of the signal processing system relating to the magnetic heads 1A and 1B.

The video signal reproducing apparatus according to the present invention will be described with reference to FIG. 2. The video signal recording apparatus corresponding to this video signal reproducing apparatus has the same configuration as that shown in FIG. The same configurations as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Here, the difference between the configuration of FIG. 2 and the configuration of FIG.
The point that the ID coincidence detecting means 40 is used instead of the detecting means 25, the point that control means 38 and 380 are used instead of the control means 37, and the signal processing system relating to the magnetic heads 1A and 1B instead of the ROMs 26 and 27. The second luminance signal 240a and the second line-sequential color signal 240b related to the signal processing system relating to the magnetic heads 2A and 2B are corrected using the first luminance signal 24a and the first line-sequential color signal 24b relating to That is the point. The differences will be described in detail below.

The ID coincidence detection means 40 compares the identification signals in the output signals of the A / D converters 23 and 230 and detects whether or not they coincide with each other. 29. Two reproduced TCI signals having the same signal structure as the above-mentioned reproduced TCI signal 22a output from the first and second de-emphasis circuits 22 and 220 are A / D.
Prior to the A / D conversion of the converters 23 and 230, clamping is performed at a level of 50 IRE if necessary. The comparison control means 28 and 29 control signals 28a and 29 only when they match.
a is supplied to the correction means 30 and 31. In this way, the coincidence detection of the identification signals is performed because the first magnetic tape recorded in a fixed order when the edited magnetic tape is reproduced.
This is because it is considered that the order of the fourth correction signal may lose continuity at the editing point.

The control means 38 and 380 perform digital AGC control on the digitized reproduced TCI signal, and the first digitized two reproduced TCI signals whose peak level is a digital value (reference level) corresponding to 100 IRE, for example. , To the second TCI inverse conversion means 24 and 240, respectively. Here, a digital value corresponding to 100 IRE serving as a reference level is preset in a reference level circuit (not shown) having the same configuration as the reference level circuit 37f and configuring the control means 38 and 380, respectively. As a result, the digitized reproduced TCI signal has a PP level of 0 to 1 over the entire reproduction period.
It becomes possible to reproduce with a digital value according to 00IRE.

The comparison control means 28 uses the first luminance signal 24a.
The control signal 28a obtained by comparing the first to fourth correction signals 11a to 14a related to the second luminance signal 240a with the first to fourth correction signals 11a to 14a according to However, here, the characteristic of the second luminance signal 240a is corrected so as to match the characteristic of the first luminance signal 24a. Similarly, the comparison control means 29 controls the first to fourth correction signals 11a to 1 related to the first line-sequential color signal 24b.
The control signal 29a obtained by comparing the first to fourth correction signals 11a to 14a related to the second line-sequential color signal 240b on the basis of 4a is supplied to the correction means 30, where the second line-sequential color is generated. The characteristic of the signal 240b is corrected so as to match the characteristic of the first line-sequential color signal 24b.

In this way, the characteristics of one signal processing system are relatively corrected so as to match the characteristics of the other signal processing system, so that there is no characteristic difference between both signal processing systems, and there is no line flicker or field flicker. Output Y, P
B, PR signals dd, ee, ff can be obtained.

Now, the control means 37, 3 constituting the video signal reproducing apparatus according to the present invention shown in FIGS. 1 and 2 described above.
The configuration and operation of the No. 8,380 will be described. A digital AGC circuit is used for the control means 37, 38, 380. For convenience of description, the control means 37, 38, 380
Have the same configuration, only the configuration and operation of the control means 37 will be described, and description of the other control means 38 and 380 will be omitted.

As shown in FIG. 9, the control means 37 comprises a digital AGC circuit composed of a multiplier 37a, a hold circuit 37b, an adder 37c, a frequency divider 37d, a subtractor 37e and a reference level circuit 37f. The multiplier 37a multiplies the digitized reproduced TCI signal 22a supplied from the A / D converter 23 shown in FIG. 1 by the multiplication data held and updated by the hold circuit 37b at regular intervals (one field period). The output is supplied to the minus side input terminal of the subtractor 37e.

The output side of the reference level circuit 37f is connected to the plus side input terminal of the subtractor 37e, and the reference level data (for example, data corresponding to 100IRE) is output from this side. Here, a digital value corresponding to 100 IRE serving as the reference level is preset in the reference level circuit 37f. Then, the subtractor 37e is the reference level circuit 37.
The subtraction data obtained by subtracting the multiplication output output from the multiplier 37a from the reference level data output from f is the frequency divider 37d.
Output to. The frequency divider 37d frequency-divides the subtracted data by A (A = 2 ⁿ ) and outputs the frequency-divided data to one plus side input terminal of the adder 37c. The adder 37c outputs the addition data obtained by adding the divided data to the multiplication data output from the hold circuit 37b to the other plus side input terminal, to the hold circuit 37b.

Such a series of AGC operations is performed by the subtractor 37.
Until the subtraction data output from e becomes 0 (that is, the multiplication output output from the multiplier 37a and the reference level circuit 37f
From the same as the reference level data output from).

The above digital AGC circuit is based on the configuration of the analog AGC circuit 37g shown in FIG. 10, and has a gain adjusting unit VCA 37h and a level detecting unit A.
A multiplier 37a is used in place of the VCA 37h composed of the GC detector 37i, and a hold circuit 37b, an adder 37c, a frequency divider 37d, a subtractor 37e, and a reference level circuit 37f are used in place of the AGC detector 37i. It is equivalent to using the combined configuration.

In this way, the multiplication data obtained by successively and continuously accumulating the reproduction signal level of the reproduction TCI signal 22a digitized by the multiplier 37a and the hold circuit 37b is input to the minus side of the subtractor 37e. It is output to the terminal. As a result, the multiplication data output from the multiplier 37a gradually converges to the same level as the reference level data every one field period.

Now, the digital AG shown in FIG.
The C circuit is further embodied in the digital A shown in FIG.
This is the GC circuit 37j. As shown in the figure, this AGC
The circuit 37j includes a multiplier 37k, a subtractor 37l, and a frequency divider 3
The digital AGC circuit is composed of 7 m, an adder 37 n, and a coefficient circuit 37 o. The multiplier 37k is a digitized reproduction T supplied from the A / D converter 23 shown in FIG.
A multiplication output obtained by multiplying the CI signal 22a by the multiplication data updated and held by the coefficient circuit 37o every fixed period (one field period) is supplied to the minus side input terminal I inverse conversion means 24 of the subtractor 37l. Reference level data (for example, data corresponding to 100 IRE) is always output to the plus side input terminal of the subtractor 37l. Then, the subtractor 37l outputs subtraction data obtained by subtracting the multiplication output output from the multiplier 37k from the reference level data to the frequency divider 37m. The frequency divider 37m divides this subtracted data by 256 and outputs the divided frequency data to one plus side input terminal of the adder 37n.
The adder 37n outputs the addition data obtained by adding the divided data to the multiplication data output from the coefficient circuit 37o to the other plus side input terminal, to the coefficient circuit 37o.

Such a series of AGC operations is performed by the subtractor 37.
It continues until the subtraction data output from l becomes 0 (that is, until the multiplication output output from the multiplier 37k and the reference level data become the same).

Here, the multiplier 37 which is the gain adjusting unit
The AGC detection unit composed of k, the subtractor 37l, the amplifier 37m, the adder 37n, and the coefficient circuit 37o operates as shown in the following (1) to (5) for each field period. (1) The reproduction TCI signal 22a digitized by the multiplier 37k is multiplied by the initial value "1.0" of the multiplication data. (2) The subtractor 37l subtracts the multiplication output of the multiplier 37k from the reference level data. (3) The divider 37m divides the subtraction data of the subtractor 37l by 256. (4) The adder 37n adds the division data to the multiplication data of the coefficient circuit 37o. (5) One field period (ID section) The above operations (1) to (4) are repeated every time) until the subtraction data of the subtractor 37l in (2) above is no longer output.

FIG. 12, which is a graph showing the number of updates (the number of accumulations) of the multiplication data, has the configuration A shown in FIG.
As a result of the multiplication data obtained by successively multiplying (accumulating) the reproduction signal level of the reproduction TCI signal 22a digitized by using the GC circuit 37j every one field period, to the minus side input terminal of the subtractor 37l, It is shown that the multiplication data output from the multiplier 37k gradually converges to the same level as the reference level data every one field period. Here, the reproduction signal level of the digitized reproduction TCI signal 22a is the 17th. After the field period, it is almost equal to the reference level data.

The above-described detection operation of the AGC detection section is specifically performed by the AGC algorithm shown in FIG. -Flow AA ... Digitized reproduction TCI signal 2 of (1 field period (ID period)) in the multiplier 37k
The reproduction level data of 2a is multiplied by the multiplication data (coefficient) from the coefficient circuit 37o, and the multiplication output (correction value) is obtained from the multiplier 37k. Flow BB ... Measuring one field period (ID period) Flow CC ... Subtractor 3 after one field period
The above correction value is subtracted from the reference level data in 7 l, and subtraction data (ΔID) is obtained from the subtractor 37 l. Flow DD ... This subtraction data (ΔID) is divided by 256 in the frequency divider 37 m and divided. Divided data (ΔID / 256) is obtained from the frequency divider 37m. Flow EE ... The frequency divided data is added to the coefficient of the immediately preceding one field period by the adder 37n, and the added data (new coefficient) is obtained from the adder 37n. The above flow AA to flow EE is repeated until the subtraction data (ΔID) in the flow CC that obtains is obtained.・ First field period K ₁ = K ₀ + (ID-ID _pb1 × K ₀ ) / 256 S _AGC1 = K ₁ × S _pb・ Second field period K ₂ = K ₁ + (ID-ID _pb2 × K ₁ ) / 256 S _AGC2 = K ₂ × S _{pb ····} nth field period K _n = K _n-1 + (ID-ID _pbn × K _n-1 ) / 256 S _AGCn = K _n × S _pb (here , ID: reference level data supplied to the plus side of the subtractor 37l ID _pb : multiplication data from the multiplier 37k supplied to the minus side of the subtractor 37l _Spb : data of the digitized reproduced TCI signal 22a K: coefficient circuit multiplying output from 37o (coefficient) data K _0: multiplying (coefficient) data initial value (K ₀ = 1.0) thus, AGC operation as multiplication in the digital AGC circuit 37j described above (coefficient) data Figure 1 showing the number of updates
In the graph of 2, when K ₀ = 1.0, the vertical axis represents the signal level data error amount D [dB] from the reference level, the horizontal axis represents the field period, and the field period “0” is the first deviation amount, It can be seen that the AGC operation converges toward the reference level data “0”.

[0049]

The video signal reproducing apparatus according to the present invention has the time-division multiplexed video signal in which a plurality of types of video signals are time-division-multiplexed for each horizontal period, and the plurality of types of video signals. , A reproduction signal reproduced from a recording signal composed of a time-division-multiplexed correction signal obtained by time-division-multiplexing a plurality of types of correction signals respectively corresponding to Since it is possible to reproduce at the level, it is possible to completely eliminate the level deviation of the reproduction signal with respect to the reference signal level generated by transmission distortion in the reproduction transmission system, and reproduce the reproduction signal having an extremely stable level. As a result, it becomes possible to perform this at a stable level even during demodulation signal processing for separating this reproduction signal into a plurality of types of video signals and correction signals, respectively. , There is an effect that can be reproduced very high quality of the video signal.

Further, the video signal reproducing apparatus according to the present invention, for example, according to the structure described in claim 2, controls the reproduction signal according to the level difference between the reference signal level and the reproduction signal level. It is possible to extremely quickly and completely eliminate the level deviation of the reproduction signal with respect to the reference signal level caused by transmission distortion in the system, and as a result, this reproduction signal is divided into a plurality of types of video signals and correction signals. Even when the demodulation signal processing to be separated is performed, this can be performed rapidly at a stable level in a short period of time, and therefore, there is an effect that an extremely high quality video signal can be reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of a video signal reproducing apparatus according to the present invention.

FIG. 2 is a block diagram of a second embodiment of a video signal reproducing device according to the present invention.

FIG. 3 is a block diagram of a video signal recording device.

FIG. 4 is a conceptual diagram for explaining a dividing unit.

FIG. 5 is a waveform diagram of first to fourth correction signals.

FIG. 6 is a waveform diagram of a TCI signal.

FIG. 7 is a plan view for explaining the arrangement of magnetic heads on a rotating drum.

FIG. 8 is a conceptual diagram for explaining a magnetic tape pattern.

FIG. 9 is a block diagram of an AGC circuit.

FIG. 10 is a block diagram of an analog AGC circuit.

FIG. 11 is a block diagram of an AGC circuit.

FIG. 12 is a graph showing the relationship between the AGC operation and the number of times the multiplication coefficient is updated.

FIG. 13 is a flowchart for explaining an AGC algorithm.

[Explanation of symbols]

5a, 6a 1st, 2nd TCI signal (time division multiplex video signal) 7a, 8a 1st, 2nd recording TCI signal (recording signal) 11a-14a 1st-4th correction signal (time division multiplex correction) Signal) 22a reproduction TCI signal (reproduction signal) 30, 31, 37, 38, 380 correction means 37g, 37j AGC circuit aa Y signal (video signal) bb, cc PB, PR signal (video signal) TT magnetic tape

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 9/47 Z

Claims (2)

[Claims] 1. A time-division multiplexed video signal in which a plurality of types of video signals are time-division-multiplexed for each horizontal period, and a plurality of types of correction signals respectively corresponding to the plurality of types of video signals are time-axis-multiplexed to perform the time division. A video signal reproducing apparatus for reproducing a recording signal composed of a time division multiplex correction signal inserted in a predetermined horizontal period of a multiplex video signal, wherein the reproduction signal reproduced from the recording signal is reproduced at a predetermined reference level. And a control means for controlling the reproduction signal. 2. The video signal reproduction apparatus according to claim 1, wherein the control means controls the gain of the reproduction signal according to a level difference between the reproduction signal and the reference level.