JP3003786B2 - Waveform equalization system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform equalizing system for compensating transmission distortion in a device for transmitting a video signal.

[0002]

2. Description of the Related Art FIG. 12 is a conceptual diagram of a transmission system for transmitting a video signal.

As shown in FIG. 1, a video signal is transmitted through a transmission processing system A, a transmission path B, and a reception processing system C, respectively. As this transmission system, for example, VT
R, package media, CATV, etc.

More specifically, in a VTR, a transmitting side processing system A corresponds to a recording signal processing unit, a transmission line B corresponds to a tape head system, and a receiving side processing system C corresponds to a reproduction signal processing unit. In package media such as video software, the transmission-side processing system A corresponds to the recording signal processing means at the time of master disc creation and master tape creation, the transmission path B corresponds to various package media, and the reception-side processing system C corresponds to reproduction signal processing means.
In CATV, the transmission side processing system A is a transmission signal processing means, the transmission path B is a wired (optical cable or the like), and the reception side processing system C
Corresponds to the received signal processing means in the repeater or the terminal, respectively.

In these various transmission systems, various waveform equalization systems have been proposed for compensating transmission characteristics, that is, compensating for distortion generated in the transmission system.

As an example of a waveform equalizing system for compensating for distortion generated in this transmission system, the following (1) and (2) used in a VTR or the like will be described.

That is, as the compensating means (1), at the time of recording, a video signal in which a reference signal having a frequency near the upper limit of the reproduction frequency bandwidth is inserted in a part of the vertical blanking period of the video signal is reproduced. At this time, a magnetic recording / reproducing apparatus that supplies a reference signal extracted from a reproduced signal to a frequency characteristic variable unit and reproduces the reference signal so that the reproduction level of the reference signal becomes constant, and adjusts the frequency characteristics during reproduction to compensate for the deterioration of the transmission characteristics. It is known (for example, JP-A-61-41284).

The compensating means (2) records a video signal in which a ramp signal is inserted in a part of a blanking period of the video signal during recording, and a reproduction lamp signal extracted from the reproduction signal and a reference signal during reproduction. There is known a video signal recording / reproducing method in which the level of a video signal is compared with a ramp signal to detect a correction amount, and the level of the reproduced video signal is corrected based on the detected level to compensate for the deterioration of transmission characteristics (for example, see Japanese Patent Application Laid-Open Publication No. HEI 9-163191). 61-46681).

[0009]

However, the above-mentioned conventional compensation means (1) and (2) have the following problems.

That is, in the compensating means (1), since the object of compensation is only the frequency characteristic, other deteriorations (ringing, smear, etc.) cannot be compensated. Can be properly compensated only when the frequency characteristic is linear, and it may be inconvenient to use it for other frequency characteristics.

Further, in the compensating means (2), since only linearity and gain are to be compensated, other degradation cannot be compensated for yet, and non-linear distortion (distortion due to white / dark clip, emphasis, etc.) is not possible. Could not respond.

[0012]

In order to solve the above problems, the present invention provides a waveform equalization system having the following configuration.

A waveform equalizing system for compensating for transmission distortion of a transmitted video signal, which is provided at a preceding stage of a transmission side processing system, and transmits a luminance reference signal to a specific position in a luminance signal relating to a video signal to be transmitted. A reference signal inserting unit for inserting a color reference signal whose phase is inverted in synchronization with a predetermined position of the luminance reference signal at a specific position in a color signal related to the video signal to be transmitted; The reproduction luminance reference signal is captured from the luminance signal transmitted through the receiving side processing system, and the reproduction color reference signal is captured from the color signal transmitted through the receiving side processing system, and the reproduction luminance reference signal and the reproduction color reference signal are Detecting means for detecting distortion received during transmission,
Filter means for canceling each of the transmission distortion components of the luminance signal transmission system and the chrominance signal transmission system detected by the detection means, and detecting the synchronization shift between the reproduction luminance reference signal and the reproduction color reference signal by the detection means A waveform equalizing means comprising: a synchronizing means for removing the synchronization deviation based on the detection signal obtained as described above.

[0014]

FIG. 1 is a block diagram showing an embodiment of a waveform equalizing system according to the present invention.

As shown in FIG. 1, a waveform equalizing system 1
Has the same configuration as that of the transmission system shown in FIG. 12 in which a reference signal insertion unit D is provided in a stage preceding the transmission side processing system A and a waveform equalization unit E is provided in a stage subsequent to the reception side processing system C. The waveform equalizing means E includes a detecting means 10, digital filter means 13 and 20, and a synchronizing means 43, as described later.

The waveform equalization system 1 is a waveform equalization system for compensating for transmission distortion of a transmitted video signal. The waveform equalization system 1 is provided at a stage prior to the transmission side processing system A and has a luminance related to a video signal to be transmitted. A luminance reference signal is inserted at a specific position in the signal, and a color reference signal whose phase is inverted in synchronization with a predetermined position of the luminance reference signal is inserted at a specific position in the color signal related to the video signal to be transmitted. Reference signal insertion means D
A reproduction luminance reference signal from the luminance signal transmitted via the receiving side processing system C,
Detecting means 10 for fetching a reproduced color reference signal from the color signal transmitted via the CPU and detecting distortions received by the reproduced luminance reference signal and the reproduced color reference signal during transmission, respectively. Filter means 13 and 20 for canceling transmission distortion components of a luminance signal transmission system and a chrominance signal transmission system, respectively.
Waveform equalization comprising: a synchronization unit 43 that removes a synchronization shift between the reproduced luminance reference signal and the reproduced color reference signal based on a detection signal obtained by detecting the synchronization shift by the detection unit 10. This means that each of the luminance signal transmission system and the chrominance signal transmission system can perform optimal and any distortion correction corresponding to each transmission system and can easily detect a timing shift between the transmission systems. Timing can be adjusted accurately and easily.

Hereinafter, a VTR will be described as an example.

FIG. 2 is a block diagram of an embodiment of the reference signal inserting means D which is a main part of the waveform equalization system according to the present invention. FIG. 3 is a waveform diagram of the reference signal, and FIG. signal,
4B is a waveform diagram of a color reference signal, and FIGS. 4 and 10 are waveform diagrams of a recording luminance signal and a recording color signal into which a luminance reference signal and a color reference signal are inserted, respectively. D) is the first
FIG. 5 is a configuration diagram of a comb filter provided in the receiving side processing system C of the waveform equalization system according to the present invention, and FIG. 6 is a diagram of the comb filter. FIGS. 3A, 3B and 3E are input / output signal waveform diagrams, wherein FIGS. 3A, 3C, and 3E are waveforms of an input reproduction luminance signal of a comb filter, and FIGS. 3B, 3D, and 3F;
7 and 8 show the first and second embodiments of the waveform equalizing means E which is a main part of the waveform equalizing system according to the present invention. 9A and 9B are explanatory diagrams for compensating for deterioration of transmission characteristics. FIG. 9A shows a signal waveform at the time of recording, FIG. 9B shows a reproduced signal waveform, FIG. 9C shows a main signal path waveform, and FIG. D) is an anti-phase pseudo distortion waveform, (E) is an addition waveform of the main signal path waveform and anti-phase pseudo distortion, and FIG. 11 is a configuration diagram for explaining a timing circuit.

In FIG. 2, 2 is a reference signal insertion circuit, 2A is a synchronization separation circuit, 2B is a timing generation circuit,
2C is a clock generation circuit, 2D and 2E are reference signal storage circuits (ROM1 and ROM2), 2F and 2G are D / A converters (DAC), and 2H and 2I are low-pass filter circuits (LP).
F), a, b, d, e, g, h, j, k are fixed contacts,
c, f, i, l are movable contacts, SW1, SW2, SW3,
SW4 is a changeover switch, and 3 is a Y / C separation circuit.

The reference signal insertion circuit 2 shown in FIG. 2 is a recording signal processing means (luminance (Y) signal recording processing means and color (C)) of a VTR corresponding to the transmission side processing system A of the waveform equalization system 1.
Signal recording processing means).

Although not described in detail here, the aforementioned V
The luminance signal recording processing means of the TR sequentially goes to the video head via an AGC circuit, a clamp circuit, a pre-emphasis circuit, a clip circuit, an FM modulator, a high-pass filter, a recording amplifier, a rotary transformer, and the like. The signal recording processing means sequentially reaches the recording amplifier of the luminance signal recording processing means via an ACC circuit, a frequency converter, a low-pass filter, a killer circuit, and the like.

By the way, as an input signal of the VTR, an S terminal (separate terminal, S input, a luminance signal input terminal and a color signal input terminal for separate input of a luminance signal (Y) and a color signal (C) are integrally formed. Terminals) and a composite video signal input terminal (composite video input) for composite signal input.

This S terminal is connected to the reference signal insertion circuit 2 described above.
Switch SW1, SW2 provided on the input side of
And the composite video signal input terminal is connected to the other input terminals of the signal changeover switches SW1 and SW2 via the Y / C separation circuit 3.

The changeover switches SW1 and SW2 are interlocked through control means (not shown) according to an input signal supplied from the S terminal or the composite video signal input terminal via the Y / C separation circuit 3 as described later. Is switched. Y
The / C separation circuit 3 outputs a luminance signal (Y) and a chrominance signal (C) obtained by separating the composite video signal.

When a signal is applied only to the composite video signal input terminal, the changeover switches SW1 and SW2 are used to separate the composite video signal by the Y / C separation circuit 3 into a luminance signal (Y) and a chrominance signal (C). (I.e., the movable contact c of the changeover switch SW1).
Is switched to the fixed contact b side, and the movable contact f of the changeover switch SW2 is switched to the fixed contact e side.

When a signal is simultaneously applied to the composite video signal input terminal and the S terminal, the changeover switch SW
1 and SW2 are switched so as to select a luminance signal and a chrominance signal on the S terminal side (that is, in a switching state shown in the drawing), the movable contact c of the changeover switch SW1 is moved to the fixed contact a side, and the movable switch SW2 is moved. The contact f is switched to the fixed contact d side in conjunction with each other).

When a signal is applied only to the S terminal input signal The changeover switches SW1 and SW2 are switched so as to select a luminance signal and a chrominance signal of the S terminal.

As described above, of the luminance signal and the chrominance signal supplied to the input side of the reference signal insertion circuit 2 via the changeover switches SW1 and SW2, the luminance signal is the synchronizing separation circuit 2A and one input terminal h of the changeover switch SW3. Supplied to

The luminance signal supplied to the synchronization separation circuit 2A is separated here by synchronization, and then a horizontal synchronization signal and a vertical synchronization signal are output to the timing generation circuit 2B.

The color signal is supplied to the clock generation circuit 2C and one input terminal k of the changeover switch SW4.

The timing generation circuit 2B generates a burst gate pulse for extracting a color burst signal from a color signal supplied thereto to the clock generation circuit 2C based on the horizontal and vertical synchronization signals supplied from the synchronization separation circuit 2A. It generates and outputs, and also sends to the storage circuits 2D and 2E a luminance reference signal and a color reference signal (FIG. 3A,
(B), and generates and outputs an address signal for reading out a data signal corresponding to each of them (shown in (B)), and further generates and outputs a signal switching control signal to the above-mentioned changeover switches SW3 and SW4.

The clock generation circuit 2C extracts a color burst signal from the supplied color signal based on the burst gate pulse supplied from the timing generation circuit 2B, and generates a color burst frequency synchronized with the burst gate pulse. A clock having an integer multiple (for example, four times the frequency) is generated and output.

This clock serves as a master clock for all circuits constituting the reference signal insertion circuit 2.

The storage circuit 2D stores data corresponding to the luminance reference signal, and the storage circuit 2E stores data corresponding to the color reference signal. These data are stored in accordance with the address signal supplied from the timing generation circuit 2B. Are output respectively.

Each data signal output from the storage circuits 2D and 2E is converted into an analog data signal by the D / A converters 2F and 2G, and then supplied to the low-pass filter circuits 2H and 2I. After the high frequency component is removed, the changeover switches SW3 and SW4 are used as a luminance reference signal and a color reference signal.
Are supplied to the other input terminals g and j, respectively.

The changeover switch SW3 passes through the movable contact c of the changeover switch SW1 and is applied to the fixed contact h and the luminance signal applied to the fixed contact g via the low-pass filter circuit 2H. The reference signal and the reference signal are alternately switched in accordance with the timing of the switching control signal supplied from the timing generation circuit 2B. The alternately switched input luminance signal or luminance reference signal is formed as one serial signal via the movable contact i. It is output to, for example, an AGC circuit of a luminance signal recording system (Y signal recording system) not shown.

The changeover switch SW4 passes through the movable contact f of the changeover switch SW2 and is applied to the fixed contact k, and the input color signal is applied to the fixed contact j via the low-pass filter circuit 2I. The reference signal and the reference signal are alternately switched according to the timing of the switching control signal supplied from the timing generation circuit 2B, and the alternately switched input color signal or color reference signal is converted into one serial signal via the movable contact l. Color signal recording system not shown (C signal recording system)
For example, to the ACC circuit.

Here, the above-mentioned luminance reference signal will be described.

The luminance reference signal is used to compensate for transmission distortion (deterioration of transmission characteristics) in a luminance signal transmission system (luminance signal recording processing means → tape head system → luminance signal reproduction processing means). It is a signal that has features and can reliably detect this transmission distortion.

FIG. 3A shows an example of a waveform of the luminance reference signal. The luminance reference signal is a bar waveform having a rising characteristic of SINX / X, and is a bar waveform having a rising characteristic of a specific line in a vertical blanking period (for example, 12th line).

The characteristics of the SINX / X used here have a flat frequency characteristic up to the system transmission band (for example, S-VHS) in order to compensate the entire band of the waveform equalization system.
If the frequency is higher than that, the characteristic is a characteristic obtained by applying an appropriate window function such that the signal attenuates with an appropriate curve (for example, raised cosine characteristic).

The above-described color reference signal will be described.

The color reference signal is used for the purpose of compensating for transmission distortion in a color signal transmission system (color signal recording processing means → tape head system → color signal reproduction processing means), and has characteristics as a color signal. This signal can reliably detect transmission distortion.

FIG. 3B shows an example of a color reference signal in a quadrature two-phase modulated color signal transmission system. The color reference signal is, for example, a lower limit frequency of a color signal band (for example, 3.
This is a sine sweep signal whose frequency linearly increases from 08 MHz) to an upper limit frequency (for example, 4.08 MHz), and a signal whose phase is inverted at the position of the color subcarrier frequency (for example, 3.58 MHz) which is the center frequency.

In FIGS. 3A and 3B, the timing positional relationship between the luminance reference signal and the color reference signal is such that the time of 50% of the rise of the bar waveform of the luminance reference signal and the time at which the phase of the color reference signal is inverted. Are synchronized so that coincides with each other.

The reason for this is that, as will be described later, the synchronization deviation between the reproduction luminance reference signal and the reproduction color reference signal caused by transmission can be easily detected by the detection means 10. The timing circuit 43 removes this synchronization shift based on a detection signal obtained by detecting the synchronization error.

In order to easily detect a timing shift between the luminance signal transmission system and the color signal transmission system from the luminance reference signal and the color reference signal, a time 50% of the rise of the bar waveform of the luminance reference signal is used. Although the time when the phase of the color reference signal is inverted is set to coincide, for example, when the luminance reference signal is a T pulse or a 2T pulse signal,
The time at the peak position and the time at which the phase of the color reference signal is inverted need not be the same time.

Further, a predetermined time is predetermined from a predetermined position of the luminance reference signal (50% of the rising time in the case of the bar waveform, and a time of the peak position in the case of the T pulse or 2T pulse signal). If it does, it does not necessarily have to be the same time.

FIG. 4 shows the waveforms of a recording luminance signal and a recording color signal into which the luminance reference signal and the color reference signal have been inserted.
FIG. 3 shows timing positions of a luminance reference signal and a color reference signal in a TSC video signal.

As shown in FIGS. 3A to 3D, FIG.
The luminance reference signal shown in (A) is the twelfth line (12H) of each luminance signal in the first to fourth fields.
And the video signal periods of the eleventh line and the thirteenth line adjacent to the video signal period in which the luminance reference signal is inserted are blanked.

Also, the color reference signal shown in FIG. 3B is inserted in the video signal period of the twelfth line of each color signal in the first to fourth fields, similarly to the above-described insertion timing of the luminance reference signal. And the eleventh line and the thirteenth line adjacent to the video signal period in which the color reference signal is inserted.
Each video signal period of the line is blanked, but in order to match the color sequence, the color reference signals of the odd field (first and third fields) and the color reference signal of the even field (second and fourth fields) are used. The signals are recorded such that the hues are inverted from each other (the phases are reversed).

In this state, the first field is "C +" and the second field is "C +" in FIGS.
"-", The third field is represented by "C-", and the fourth field is represented by "C +", and the relationship with the color burst phase makes one cycle every four fields (frames A and B).

The receiving-side processing system C of the waveform equalizing system 1 may include a line-correlation-type comb filter 4 shown in FIG. 5 as a noise canceller.

For example, when the two-line correlation type comb filter 4 shown in FIG.
When a luminance signal in which one line before and after the luminance reference signal shown in FIG. 6A is not blanked is input to this filter 4, the signal shown in FIG. 6B is output.

As shown in FIG. 6B, the reproduced luminance reference signal is disturbed by an unspecified signal of one line before (or one line after), and unspecified distortion irrelevant to the transmission characteristics is generated. Therefore, the characteristics cannot be compensated satisfactorily.

To solve the above, FIG.
A luminance signal in which only one line before the luminance reference signal shown in (C) is blanked is input to the filter 4.

Alternatively, a luminance signal in which one line before and after the luminance reference signal shown in FIG.

As a result, the signals shown in FIGS. 9D and 9F are output, and the 12 lines are １ ／ of the luminance reference signal.
Only the reproduced luminance reference signal having the amplitude of ## EQU1 ## appears, and this signal can be compensated for characteristics without receiving unspecified interference.

The above-mentioned comb filter 4 comprises a delay circuit (1H delay) 5, an adder circuit 6, and an attenuation circuit (1/2) 7.

When a three-line correlation type comb filter is used as the noise canceller, similarly, FIG.
When the luminance signals shown in (A) and (C) are input, the reproduction luminance reference signal is disturbed and unspecified distortion irrelevant to the transmission characteristics is generated.
When the luminance signal shown in FIG. 8E is input, the signal shown in FIG. 7F is output, and it goes without saying that the reproduced luminance reference signal is not disturbed and the characteristics can be well compensated.

Here, the operation of the noise canceller may be stopped at least only during the luminance reference signal insertion period (the twelfth line), so that the interference by the noise canceller does not occur, and FIG. As shown, the amplitude does not become １ ／.

Since the color signal system may use a noise canceller such as CNR (color noise reduction), in such a case, the color reference signal insertion period (the period corresponding to the luminance reference signal insertion period (line 12)) It is necessary to stop this operation by cutting the loop for a period only).

Although the above description of FIGS. 6A to 6F is for a luminance signal, it will not be described in detail here, but the chrominance signal is the same as the luminance signal shown in FIG. Then, when a color signal in which one line before and after the color reference signal is blanked is input to this filter 4,
As in the case of the signal shown in FIG. 9F, only the reproduced color reference signal having an amplitude of の of the color reference signal appears here. It goes without saying that you can do it.

The luminance signal into which the luminance reference signal is inserted and the color signal into which the color reference signal is inserted by the reference signal insertion means D (reference signal insertion circuit 2) shown in FIG.
In R, each is supplied to a transmission side processing system A, which is a recording signal processing means, and through each recording process, is converted into a recording luminance signal and a recording chrominance signal, and is recorded via a tape head system as a transmission path B. Then, at the time of reproduction, the VT
In R, the recording luminance signal and the recording color signal are supplied to the receiving side processing system C, which is a reproduction signal processing unit, and reproduced through the respective reproduction processes to obtain the reproduction luminance signal and the reproduction color signal. The waveform equalizing means E reproduces and outputs the reproduced luminance signal and reproduced color signal obtained by waveform equalization based on the reproduced luminance reference signal and reproduced color reference signal extracted from the reproduced luminance signal and reproduced color signal.

The above-mentioned waveform equalizing means E is a receiving side processing system C
Detecting means 10 for fetching a reproduction reference signal based on a reference signal from a video signal transmitted via a transmission line, and detecting distortion received by the reference signal during transmission, and filter means 13 for canceling a transmission distortion detected from the transmitted video signal , 20 are provided.

FIGS. 7 and 8 are block diagrams of first and second embodiments of the waveform equalizing means which is a main part of the waveform equalizing system according to the present invention.

7 and 8, reference numerals 8A and 24A denote reproduction luminance signal transmission characteristic compensation circuits, reference numerals 8B and 24B denote reproduction color signal transmission characteristic compensation circuits, reference numeral 9 denotes a clock generation circuit, and reference numeral 10 denotes a CP.
U (detection means), 11 and 18 are A / D converters (AD
C), 12, 19, 26 and 28 are delay circuits (DLY),
13, 20 are transversal filters (digital filter means), 14, 21, 25, 27 are adders, 15
Is a variable delay circuit (VDL), 16 and 22 are D / A converters (DAC), 17 and 23 are low-pass (LPF) filters, C
Is a receiving side processing system, and E is a waveform equalizing means.

The luminance signal transmission system includes an A / D converter 11, a reproduced luminance signal transmission characteristic compensation circuit 8A, a variable delay circuit 15,
It outputs a reproduced luminance signal composed of an / A converter 16 and a low-pass filter 17 from which transmission distortion has been removed. The color signal transmission system includes an A / D converter 18, a reproduced color signal transmission characteristic compensation circuit 8B,
A reproduced color signal composed of a D / A converter 22 and a low-pass filter 23 from which transmission distortion has been removed is output.

The reproduction luminance signal transmission characteristic compensating circuit 8A includes a delay circuit 12, a transversal filter 13, and an adder 14.
The reproduction color signal transmission characteristic compensating circuit 8B is a feedback control system composed of a delay circuit 19, a transversal filter 20, and an adder 21, and the reproduced luminance signal transmission characteristic compensating circuit 2
4A is a feedforward control system including a transversal filter 13, an adder 25, and a delay circuit 26;
The reproduction color signal transmission characteristic compensating circuit 24B is a feedforward control system including the transversal filter 20, the adder 27, and the delay circuit 28.

The waveform equalizing means E shown in FIGS. 7 and 8 is a VTR reproduced signal processing means (luminance (Y) signal reproducing processing means and color (C)) corresponding to the receiving side processing system C of the waveform equalizing system 1. Signal reproduction processing means).

Although not described in detail here, the aforementioned V
The luminance signal reproduction processing means of the TR is supplied from a rotary transformer or the like via a video head to a preamplifier circuit, a channel switcher, a high-pass filter circuit, a dropout compensation circuit (DO)
C), a limiter circuit, an FM demodulator, a de-emphasis circuit, a low-pass filter circuit, and the like. The above-described color signal reproduction processing means passes through a pre-amplifier circuit of the luminance signal reproduction processing means, and a low-pass filter, The ACC circuit, the frequency converter, the band-pass filter circuit, the killer switch, etc. are sequentially reached.

Now, as shown in FIG. 7, the reproduced luminance signal (reproduced Y) supplied from the luminance signal reproducing processing means
Is supplied to the clock generation circuit 9 and the A / D converter 11, respectively. The reproduced color signal (reproduced C) supplied from the color signal reproduction processing means is supplied to the clock generation circuit 9 and the A / D converter 11.
Each is supplied to the D converter 18.

The clock generation circuit 9 generates and outputs a clock similar to the clock generated from the clock generation circuit 2C in the reference signal insertion circuit 2 shown in FIG.

That is, the clock generation circuit 9 generates a burst gate pulse from the reproduced chrominance signal based on the horizontal and vertical synchronizing signals extracted from the reproduced luminance signal, and uses this burst gate pulse to generate a color burst signal from the reproduced chrominance signal. A clock is generated and output at an integer multiple (for example, four times) of the color burst frequency synchronized with the burst gate pulse.

The clock output from the clock generation circuit 9 includes a reproduction luminance signal transmission characteristic compensation circuit 8A, a reproduction color signal transmission characteristic compensation circuit 8B, A / D converters 11 and 18, a variable delay circuit 15, and a D / A converter. 16 and 22, respectively.

Here, the waveform equalization of the waveform equalization means E shown in FIG. 7 will be described with reference to FIG.

Here, for the sake of explanation, the waveform equalization is described only for the reproduced luminance signal, but it is needless to say that the waveform equalization can be performed for the reproduced color signal in the same manner.

The recording luminance signal output from the reference signal insertion circuit 2 and having the luminance reference signal inserted therein (FIG. 9).
The waveform aa) shown in (A) is converted into a recording luminance signal through each recording process in the recording signal processing means, and is then recorded on a tape.
Recorded via the head system.

At the time of reproduction, a reproduced luminance signal (waveform bb shown in FIG. 7B) reproduced through each reproduction process in the reproduced signal processing means is supplied to the A / D converter 11 of the waveform equalizing means E.
Are supplied to the delay circuit 12 composed of multi-stage shift registers and the transversal filter 13 as A / D-converted digital data signals.

The delay signal from the delay circuit 12 ((C) in FIG.
A digital signal corresponding to the waveform cc shown in FIG. 7 is output, and a compensation signal (digital signal corresponding to the waveform dd shown in FIG. 10D) is output from the transversal filter 13.

The transversal filter 13 has a CP
Under the control of U10, the above-described compensation signal having a phase opposite to that of the signal component is output so as to cancel the signal component corresponding to the deterioration of the transmission characteristic in the above-described delayed signal.

In this way, the adder 14 adds the compensation signal from the transversal filter 13 to the delay signal from the delay circuit 12, and the delay signal (from which the signal component corresponding to the deterioration of the transmission characteristic is canceled) A digital signal corresponding to the waveform ee shown in FIG.

The delay circuit 12 is composed of a shift register so that the adder 14 matches the timing with the compensation signal from the transversal filter 13. This is for realizing a delay amount that is uniquely determined.

The reproduction luminance signal including the reproduction luminance reference signal output from the adder 14 and having compensated for the deterioration of the transmission characteristics is supplied to the variable delay unit 15.

The variable delay unit 15 is, for example, a variable-length shift register whose delay amount is variable according to a control signal (detection signal) from the CPU 10. The variable delay unit 15 roughly adjusts the timing of the reproduced luminance signal supplied thereto to the timing of the reproduced chrominance signal in units of a half clock, and then outputs the reproduced luminance signal in units of a half clock. After being supplied to the / A converter 16 and subjected to D / A conversion here, it becomes a final reproduced luminance signal via the low-pass filter circuit 17, and the other output is directly supplied to the CPU 10.

As described above, the variable delay unit 15 can adjust the timing of the reproduced luminance signal in units of a half clock of the reproduced chrominance signal in units of a half clock of the timing of the reproduced chrominance signal.
Further, the minute timing within a half clock (small delay amount) can be adjusted within a half clock by using the timing circuit 43 described later.

Here, although the reproduced luminance reference signal is inserted in the reproduced luminance signal output from the low-pass filter circuit 17, this insertion position is within the vertical blanking period of the reproduced luminance signal. By supplying the reproduction luminance signal to reproduction means such as a TV receiver (not shown) together with the reproduction color signal from the low-pass filter circuit 23, a good reproduction image can be obtained. However, this reproduction luminance reference signal is extracted. In order to obtain a reproduced luminance signal, a signal between the variable delay unit 15 and the D / A converter 16 (variable delay unit 15 and C
It is sufficient to insert a reference signal extracting circuit complementary to the above-described reference signal inserting circuit 2 shown in FIG.

The reproduced luminance signal output from the variable delay unit 15 to the CPU 10 and including the reproduced luminance reference signal is converted by the CPU 10 from the reproduced luminance signal according to the timings of the luminance signal and the chrominance signal shown in FIGS. A control signal corresponding to a difference obtained by comparing the extracted reproduced luminance reference signal waveform (the above-mentioned waveform bb) with the same regular waveform as the recording luminance signal waveform (the above-mentioned waveform aa) is transmitted to the transversal filter 13.
, And the coefficient of the transversal filter 13 is varied so that this difference does not occur.

The CPU 10 takes in the reproduction luminance reference signal reproduced every field, and gradually updates the coefficient of the transversal filter 13 so that the reproduction luminance reference signal waveform becomes the same as the recording luminance reference signal waveform. Go. The reproduced waveform used for the calculation at this time is used after performing synchronous addition for several field periods in order to improve S / N.

Although the above description has been made on compensating for the deterioration of the transmission characteristics in the luminance signal transmission system, the waveform equalization of the reproduced color signal can be performed similarly to the reproduced luminance signal. In the same manner as described above, it is possible to compensate for the deterioration of the transmission characteristics, thereby compensating for the deterioration of the transmission in both the luminance signal and the chrominance signal transmission systems.

That is, in the color signal transmission system, the recording color signal output from the reference signal insertion circuit 2 and into which the color reference signal is inserted is converted into a recording color signal through each recording process in the recording signal processing means. Is recorded via a tape head system.

At the time of reproduction, the reproduced color signal reproduced through each reproduction process in the reproduction signal processing means is converted into a digital data signal A / D-converted by the A / D converter 18 of the waveform equalizing means E in a multi-stage. The signals are supplied to a delay circuit 19 composed of a shift register and a transversal filter 20, respectively.

A delay signal is output from the delay circuit 19,
The transversal filter 20 outputs a compensation signal. This transversal filter 20 has a CPU
By the control of 10, the above-mentioned compensation signal having a phase opposite to that of the signal component is output so as to cancel the signal component corresponding to the deterioration of the transmission characteristic in the above-mentioned delayed signal.

In this manner, the adder 21 adds the compensation signal from the transversal filter 20 to the delay signal from the delay circuit 19, and the delay signal from which the signal component corresponding to the deterioration of the transmission characteristic has been canceled is added. Is output.

The reason why the delay circuit 19 is composed of a shift register is to adjust the timing with the compensation signal from the transversal filter 20 in the adder 21. This is for realizing a delay amount that is uniquely determined.

One of the reproduced color signals including the reproduced color reference signal output from the adder 21 and having compensated for the deterioration of the transmission characteristic is
After being supplied to the D / A converter 22 and subjected to D / A conversion, it becomes a final reproduced color signal via the low-pass filter circuit 23, and the other output is directly supplied to the CPU 10.

Here, although the reproduced color reference signal is inserted in the reproduced color signal output from the low-pass filter circuit 23, since this insertion position is within the vertical blanking period of the reproduced color signal, it is practically used. Although there is no problem, in order to obtain a reproduced color signal extracted from the reproduced color reference signal, in FIG.
Between the adder 21 and the D / A converter 22 (adder 21 and C
It is sufficient to insert a reference signal extracting circuit complementary to the above-described reference signal inserting circuit 2 shown in FIG.

The CPU 10 takes in the reproduced color reference signal reproduced every field, and gradually updates the coefficient of the transversal filter 13 so that the reproduced color reference signal waveform becomes the same as the color reference signal waveform at the time of recording. Go.

The reproduced waveform used for the calculation at this time is S / N
In order to improve, the synchronous addition is performed for several field periods.

By the way, the steepest descent method is used as a basic algorithm for updating the coefficients of the transversal filters 13 and 20, and a tap update equation such as the following equation (1) is used.

Cn ^* = Cn-αen
Equation (1) where Cn is the current n-th tap coefficient Cn ^* , the current n-th tap coefficient after updating, and the n-th error signal α is the correction coefficient (<1). It is performed during the ranking period, and is not performed during the effective scanning period of the luminance signal and the color signal, the color burst signal period, and the horizontal / vertical synchronization signal period.

The waveform bb shown in FIG. 9B is obtained by reproducing the waveform aa shown in FIG. 9A.
Ringing occurs due to distortion of transmission characteristics.

A waveform dd in FIG. 9D is a filter output whose coefficient is controlled by the CPU 10, and a waveform b
b has a negative phase component of the distortion included in the distortion.

The above-mentioned luminance reference signal and color reference signal are
In the vertical blanking period of the luminance signal and the chrominance signal, the eleventh line to the thirteenth line are used when the blanking lines of the eleventh and thirteenth lines are included, and the eleventh to thirteenth lines are used. 10th line to 13th line
The period may be set arbitrarily within the period of the 17th to 20th lines.

However, the fourteenth line to the sixteenth line, the second line
Since one line is used in teletext, this line may be used if it does not need to coexist with it.

Although the above-described luminance reference signal and color reference signal have been described as a one-field / four-field sequence, a two-line / field four-field sequence as shown in FIGS. good.

In this case, a total of four lines including the two lines before and after the blanking are applied, the same luminance reference signal is recorded on the eleventh and twelfth lines of each field, and the same color reference signal is recorded on the same line At the same timing as the luminance signal.

The color reference signal is set so that the hue is inverted between consecutive lines and the same line of the even field next to the odd field.

This is because when the transmission system has an arithmetic circuit (Y / C separation circuit, noise reduction, etc.) utilizing the correlation between fields or frames, the arithmetic circuit erroneously uses the color reference signal as the luminance reference signal. This is to prevent detection and malfunction.

FIG. 10 is a waveform diagram of a recording luminance signal and a recording color signal in which the luminance reference signal and the color reference signal are inserted.
FIG. 6 shows timing positions of a luminance reference signal and a color reference signal in an NTSC video signal.

As shown in FIGS. 3A to 3D, FIG.
The luminance reference signal shown in (A) is the eleventh and twelfth lines (1) of each luminance signal in the first to fourth fields.
1H, 12H), respectively.
Each video signal period of the tenth line and the thirteenth line (10H, 13H) is blanked.

The color reference signal shown in FIG. 3B has the eleventh and fourth color signals in the first to fourth fields in the same manner as the above-described timing of inserting the luminance reference signal.
Each is inserted in the video signal period of 12 lines,
Although the video signal periods of the 0th line and the 13th line are blanked, in order to match the color sequence, the color reference signal of the odd field (first and third fields) and the even field (second and fourth fields) are used. The field and the color reference signal are recorded such that the hues are mutually inverted (the phases are reversed).

In this state, the color reference signals of the eleventh and twelfth lines in the first field are "C +" and "C-", respectively, and the second field is "C-" in FIGS.
− ”And“ C + ”, and the third field is“ C− ”and“ C
The "+" and the fourth field are indicated by "C +" and "C-", respectively, and the relationship with the color burst phase makes one cycle every four fields (frames A and B).

Since the color reference signal is not a signal for viewing on the screen, it is not always necessary to satisfy the color sequence unless there is an arithmetic circuit utilizing the field / frame correlation in the transmission system.

For example, it does not matter if the same signal is inserted in each field.

Each of the reproduction luminance signal transmission characteristic compensating circuits 8A and 8B shown in FIG. 7 is of the FIR type, and the above description has been made in accordance therewith. Instead, the reproduction shown in FIG. Luminance signal transmission characteristic compensation circuits 24A and 24B
The IIR type may be used as shown in FIG. Further, both may be combined.

The waveform equalizing means E shown in FIG. 8 removes the reproduced luminance signal transmission characteristic compensating circuits 8A and 8B from the waveform equalizing means E shown in FIG. 7, and replaces the reproduced luminance signal transmission characteristic compensating circuit 24A. , 24B, and the other components are the same as the components shown in FIG. 7, so the same components are denoted by the same reference numerals.
Although the description is omitted, it goes without saying that the waveform equalization of the reproduced luminance signal and the reproduced color signal can be performed in the same manner as the waveform equalizing means E shown in FIG.

In this case, since the reproduced luminance signal transmission characteristic compensating circuits 24A and 24B are of the IIR type, the tap updating formula using the above formula (1) cannot be used, but is performed under the control of the CPU 10. Updating of taps for the transversal filters 13 and 20 is performed every several fields within a vertical blanking period, and an effective scanning period of a luminance signal and a chrominance signal, a color burst signal period, and the like.
Of course, it is not performed in the horizontal / vertical synchronization signal section.

The clock generation circuit 9 shown in FIGS. 7 and 8 generates and outputs a clock of an integral multiple (for example, four times) of the color burst frequency synchronized with the burst gate pulse. Instead of the clock, it is synchronized with the horizontal synchronizing signal included in the reproduced luminance signal and is an integral multiple thereof (for example, 910 for an NTSC video signal).
A clock that is synchronized with the color burst signal included in the reproduced color signal and that is an integral multiple thereof (for example, four times the color subcarrier frequency in the case of an NTSC video signal) may be used. May be used.

Now, in a home VTR without a TBC (time base collector), the phase relationship between the color subcarrier frequency and the frequency of the horizontal / vertical synchronization signal is not always constant and fluctuates on the time axis. If a clock generated from a signal (or a reproduced luminance signal) is used in common for both the chrominance signal and luminance signal transmission systems, there is a problem that an error on the time axis occurs between the two signal transmission systems.

To solve this, the timing circuit 43 having the configuration shown in FIG.
5 and a D / A converter 16, and a variable delay 15
After the timing of the reproduction luminance reference signal and the reproduction color reference signal is roughly adjusted in half clock units from the clock generation circuit 9, the phase is slightly different (for example, shifted by 1 to 2 nsec) under the control of the CPU 10. The clock closest to this timing shift is selected by the multiplexer 39 from the clocks, and the flip-flop circuit 42
The D / A converter 16 performs D / A conversion on the reproduced luminance signal output from the variable delay unit 15 in synchronization with this clock, thereby enabling timing adjustment within half a clock.

Clocks having different phases have delay times of 1-2.
Buffer circuits 40a, 40b, 40c,.
40n are connected in cascade by an appropriate number of stages, and each output side of the buffer circuits 40a, 40b, 40c,..., 40n is connected to the parallel input side of the multiplexer 39.

Thus, the timing circuit 43
By changing the clock selection signal supplied from the PU 10 to the multiplexer 39, the multiplexer 3
The phase of the clock output from 9 is varied, and this variable control is updated every several fields until the timing of the reproduced luminance signal and the reproduced color signal matches (convergence).

The timing circuit 43 having the structure shown in FIG. 11 is interposed between the variable delay unit 15 and the D / A converter 16 of the luminance signal transmission system, and outputs the reproduced luminance signal at the timing of the reproduced color signal. Although the timing is adjusted, although not described in detail here, the timing circuit 43 is provided with a reproduction color signal transmission characteristic compensation circuit 8B (24B) of a color signal transmission system and a D / A.
It is needless to say that the timing of the reproduced chrominance signal is adjusted to the timing of the reproduced luminance signal in the same manner as described above.

When performing the characteristic compensation on the two transmission systems shown in FIGS. 7 and 8, respectively, the reproduction reference waveform is taken in immediately before the D / A converters 16 and 22 to obtain the transmission characteristics. Find the timing deviation between the compensation and each transmission system,
The configuration is such that the timing between the transmission systems is adjusted by controlling the delay amount of each transmission system. Therefore, the A / D converter is not required in the characteristic compensation circuit, so that the operation can be performed at low cost and the temperature characteristics can be reduced. , Conversion accuracy (quantization error, A
/ D conversion linearity error) does not occur.

Although the above description has been given of the case where the system of the present invention is applied to a VTR having a known configuration, the present invention can be applied to other recording / reproducing means such as a magnetic disk and an optical disk.

Further, even when there is no recording process on the user side, as in the case of a package medium such as a video disk or video software, the same effect can be obtained by recording a reference signal when creating the package medium.

Not only in the case of recording / reproducing, but also in a system for transmitting a signal, for example, a CATV or a wireless communication, including a reference signal on the transmission side and a waveform equalization on the reception side. The same effect can be obtained.

It is also possible to insert the above-mentioned reference signal continuously for at least two horizontal synchronizing periods of the video signal. In this case, interference is prevented by a comb filter for Y / C separation. No (Even with a 2-line comb filter,
The H-th reference signal can be completely separated.)

The above-mentioned reference signal can be inserted in a four-field sequence. In this case, an arithmetic circuit (Y / C separation circuit, Even when noise reduction or the like is included, the arithmetic circuit can prevent a color reference signal from being erroneously detected as a luminance reference signal, thereby preventing malfunction.

[0131]

As described above, the waveform equalization system according to the present invention inserts a luminance reference signal into a luminance signal to be transmitted, inserts a color reference signal into a color signal to be transmitted, and Since the synchronization error is removed based on the detection signal obtained by detecting the synchronization error between the signal and the reproduction color reference signal by the detection means, the transmission form of the video signal is plural as a combination of a plurality of signals. (For example, a device that performs Y / C separation processing such as a VHS VTR for direct recording / reproduction of a composite video signal or a VTR of a system other than this system). Component recording / reproducing), the luminance signal transmission system and the chrominance signal transmission system can perform optimal and any distortion correction according to each transmission system. Since easily detect the timing shift between, it is possible to perform the timing alignment accuracy better yet easily able to reduce the computational error due to jitter occurring between the transmission system, furthermore,
Any distortion such as frequency characteristic linearity or gain, ringing and smear can be removed, and when the system of the present invention is applied to a transmission device such as a VTR having a recording / reproducing transmission system variation for each product, This has the effect of stably providing a transmission device having a constant quality without being affected by variations in transmission characteristics between the transmission devices.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a waveform equalization system according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a reference signal inserting means which is a main part of the waveform equalization system according to the present invention.

FIG. 3 is a waveform diagram of a reference signal.

FIG. 4 is a waveform diagram of a recording luminance signal and a recording color signal into which a luminance reference signal and a color reference signal are inserted.

FIG. 5 is a configuration diagram of a comb filter provided in a reception-side processing system of the waveform equalization system according to the present invention.

FIG. 6 is an input / output signal waveform diagram of a comb filter.

FIG. 7 is a block diagram of a first embodiment of a waveform equalizing means which is a main part of the waveform equalizing system according to the present invention.

FIG. 8 is a configuration diagram of a second embodiment of the waveform equalization means which is a main part of the waveform equalization system according to the present invention.

FIG. 9 is an explanatory diagram for compensating for deterioration of transmission characteristics.

FIG. 10 is a waveform diagram of a recording luminance signal and a recording color signal in which a luminance reference signal and a color reference signal are inserted.

FIG. 11 is a configuration diagram illustrating a timing circuit.

FIG. 12 is a conceptual diagram of a transmission system for transmitting a video signal.

[Explanation of symbols]

Reference Signs List 1 waveform equalization system 10 CPU (detection means) 13, 20 transversal filter (filter means) 29 sampling frequency converter (sampling frequency conversion means) 43 timing circuit (synchronization means) A transmission processing system B transmission path C reception side Processing system D Reference signal insertion means E Waveform equalization means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/79-9/898 H03H 17/00 H04N 5 / 04,5 / 21 H04N 5/91-5 / 956 H04N 7/10

Claims (1)

(57) [Claims] 1. A waveform equalizing system for compensating for transmission distortion of a transmitted video signal, wherein the system is provided in a preceding stage of a transmission side processing system, and a luminance reference is provided at a specific position in a luminance signal relating to a video signal to be transmitted. A reference signal insertion unit for inserting a signal and inserting a color reference signal whose phase is inverted in synchronization with a predetermined position of the luminance reference signal at a specific position in a color signal relating to the video signal to be transmitted; A reproduction luminance reference signal is fetched from a luminance signal transmitted through a processing system, and a reproduction color reference signal is fetched from a color signal transmitted through the reception processing system, and the reproduction luminance reference signal and the reproduction color reference Detection means for respectively detecting distortion received by the signal during transmission,
Filter means for canceling each of the transmission distortion components of the luminance signal transmission system and the chrominance signal transmission system detected by the detection means, and detecting the synchronization shift between the reproduction luminance reference signal and the reproduction color reference signal by the detection means A waveform equalizing means comprising: a synchronizing means for removing the synchronization deviation based on the detection signal obtained as described above.