JPH04304087A - Waveform equalization system - Google Patents

Abstract

PURPOSE:To surely compensate the transmission distortion by inserting the reference signal at the prescribed position in the video signal to be transmitted and making the video signal period adjacent to the video signal period that the signal was inserted blanking state. CONSTITUTION:A luminance signal Y and a color signal C obtained in a Y/C separation circuit 3 are selected at SW1 and SW2. In a reference signal insertion circuit 2, the signal Y outputs burst gate pulse from the signal C to be supplied to a clock generation circuit 2C via a synchronizing separator circuit 2A and a timing generation circuit 2B. The circuit B outputs an address to ROMD, E and switches SW 3, 4. The output of ROM is supplied to SW 3, 4 via D/A converters G, LPF. By this constitution, when the reproduction reference signal is fetched from the transmitted video signal, this reference signal can be fetched without receiving obstruction from the line adjacent to the reference signal period and the fetch of adjacent unnecessary noise can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform equalization system for compensating for transmission distortion in equipment that transmits video signals.

0002

2. Description of the Related Art FIG. 11 is a conceptual diagram of a transmission system for transmitting video signals.

As shown in the figure, a video signal is transmitted via a transmitting side processing system A, a transmission path B, and a receiving side processing system C, respectively. As this transmission system, for example, VT
R, package media, CATV, etc. can be considered.

Specifically, in a VTR, the transmission side processing system A corresponds to the recording signal processing means, the transmission path B corresponds to the tape head system, and the reception side processing system C corresponds to the reproduction signal processing means. For package media such as video software, the transmitting side processing system A corresponds to the recording signal processing means when creating master discs and master tapes, the transmission line B corresponds to various package media, and the receiving side processing system C corresponds to the reproduction signal processing means. In CATV, the transmission side processing system A is a transmission signal processing means,
The transmission line B corresponds to a wire (optical cable, etc.), and the receiving side processing system C corresponds to a received signal processing means in a repeater or terminal, respectively.

[0005] In these various transmission systems, various waveform equalization systems have been proposed for compensating for each transmission characteristic, that is, for compensating for distortion occurring in the transmission system.

[0006] As an example of a waveform equalization system for compensating for distortion occurring in this transmission system, the following (1) and (2) used in VTRs and the like will be explained.

That is, the compensation means (1) records a video signal in which a reference signal having a frequency near the upper limit of the reproduction frequency bandwidth is inserted into a part of the vertical blanking period of the video signal during recording, and then reproduces the video signal. At the time, a magnetic recording and reproducing device supplies a reference signal extracted from a reproduced signal to a frequency characteristic variable means and reproduces the reference signal so that the reproduction level of the reference signal is constant, thereby adjusting the frequency characteristic during reproduction and compensating for deterioration of transmission characteristics. This method is known (for example, JP-A-61-41284).

Further, as compensation means (2), during recording, a video signal with a ramp signal inserted into a part of the blanking period of the video signal is recorded, and during playback, a reproduced ramp signal extracted from the reproduced signal and a reference are recorded. A video signal recording and reproducing method is known in which a correction amount is detected by comparing the level with a ramp signal, and based on this, the level of the reproduced video signal is corrected to compensate for deterioration in transmission characteristics (for example, as disclosed in Japanese Patent Application Laid-Open No. 61-466
No. 81).

[0009]

[Problems to be Solved by the Invention] However, the above-mentioned conventional compensation means (1) and (2) have the following problems.

That is, in compensation means (1), since the object of compensation is only the frequency characteristics, other deteriorations (ringing, smear, etc.) cannot be compensated for, and since the reference signal is a single frequency, reproduction is difficult. Appropriate compensation can only be achieved when the frequency characteristics of the signal are linear, and it may be inconvenient to use it for anything else.

Furthermore, in the compensation means (2), since the compensation targets are only linearity and gain, it is still not possible to compensate for other deterioration, and non-linear distortion (distortion due to white/dark clip, emphasis, etc.) I was also unable to respond.

0012

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a waveform equalization system having the following configuration.

[0013] A waveform equalization system that compensates for transmission distortion of a transmitted video signal, which includes a reference signal insertion means that is provided at a stage before the transmitting side processing system and inserts a reference signal at a predetermined position of the video signal to be transmitted. and a detection means for detecting a reproduction reference signal based on the reference signal from the video signal transmitted via the receiving side processing system and detecting the distortion that the reference signal has undergone during transmission; 1. A waveform equalization system comprising: a filter means for canceling transmission distortion; and a waveform equalization means provided with a filter means for canceling transmission distortion.

[0014] A waveform equalization system that compensates for transmission distortion of a transmitted video signal, comprising a reference signal insertion means that is provided upstream of the transmission side processing system and inserts a reference signal at a predetermined position of the video signal to be transmitted. and a detection means for detecting a reproduction reference signal based on the reference signal from the video signal transmitted via the receiving side processing system and detecting the distortion that the reference signal has undergone during transmission; A waveform equalization system comprising: a filter means for canceling transmission distortion; A waveform equalization system characterized in that a video signal period is in a blanking state.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of an embodiment of a waveform equalization system according to the present invention.

As shown in the figure, in the transmission system shown in FIG. 11, the waveform equalization system 1 is provided with reference signal insertion means D at the front stage of the transmitting side processing system A and at the rear stage of the receiving side processing system C. The configuration is the same as that in which a waveform equalization means E is provided, and the waveform equalization means E includes a detection means 10 and digital filter means 13 and 20, as will be described later.

The waveform equalization system 1 includes a reference signal insertion means D, which is provided before the transmitting side processing system A and inserts a reference signal at a predetermined position of the video signal to be transmitted, and a receiving side processing system C. detection means 10 for capturing a reproduced reference signal based on the reference signal from the transmitted video signal and detecting the distortion that the reference signal has undergone during transmission; and filter means 13 for canceling the transmission distortion detected from the transmitted video signal.
. The transmission characteristics of the entire transmission system are compensated by detecting the distortion of the video signal and processing the video signal to cancel the distortion.

[0018] Hereinafter, explanation will be given using a VTR as an example.

FIG. 2 is a block diagram of an embodiment of the reference signal insertion 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,
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
Each waveform of the recording luminance signal and the recording color signal in the field to the fourth field, FIG. 5 is a block diagram of the 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. This is an input/output signal waveform diagram, in which (A), (C), and (E) are the input reproduced luminance signal waveforms of the comb filter, and (B), (D), and (F) are the waveforms of the input reproduced luminance signal of the comb filter, respectively. Filter output reproduced luminance reference signal waveform, Figure 7
, FIG. 8 is a block diagram of the first and second embodiments of the waveform equalization means E, which is a main part of the waveform equalization system according to the present invention, and FIG. 9 is an explanatory diagram for compensating for deterioration of transmission characteristics. Figure (A) shows the signal waveform during recording, Figure (B) shows the reproduced signal waveform, and Figure (C) shows the signal waveform during recording.
) is the main signal path waveform, (D) is the pseudo-distortion waveform of the opposite phase,
(E) in the same figure is an added waveform of the main signal path waveform and the pseudo distortion having the opposite phase.

Now, 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, ROM2), 2F and 2G are D/A converters (DAC), and 2H and 2I are low-pass filter circuits (LPF).
, a, b, d, e, g, h, j, k are fixed contacts, c, f
, i, l are movable contacts, SW1, SW2, SW3, SW4
3 is a changeover switch, and 3 is a Y/C separation circuit.

The reference signal insertion circuit 2 shown in FIG. 2 is a VTR recording signal processing means (luminance (Y) signal recording processing means and color (C)
(signal recording processing means).

[0022]Although not detailed here, the above-mentioned V
The brightness signal recording processing means of the TR is sequentially connected 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, etc. The signal recording processing means successively 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, etc.

By the way, as an input signal for a VTR, there is an S terminal for separate input of a luminance signal (Y) and a color signal (C).
A terminal in which a luminance signal input terminal and a color signal input terminal are integrated) and a composite video signal input terminal for inputting a composite signal (composite video input).

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

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

- When a signal is applied only to the composite video signal input terminal, the changeover switches SW1 and SW2 select the luminance signal (Y) and chrominance signal (C) obtained by separating the composite video signal in the Y/C separation circuit 3. ) (that is, 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 signals are applied to the composite video signal input terminal and the S terminal at the same time, the changeover switches SW1 and SW2 are switched to select the luminance signal and color signal on the S terminal side (that is, the switching shown in the figure state, the movable contact c of the changeover switch SW1 is on the fixed contact a side, and the movable contact f of the changeover switch SW2 is on the side of the fixed contact a.
(are switched in conjunction with the fixed contact d side).

- When a signal is applied only to the S terminal input signal, the changeover switches SW1 and SW2 are switched to select the luminance signal and color signal of the S terminal.

Of the luminance signals and color signals supplied to the input side of the reference signal insertion circuit 2 via the changeover switches SW1 and SW2, the brightness signal is sent to one input terminal h of the sync separation circuit 2A and the changeover switch SW3. supplied to

The luminance signal supplied to the synchronization separation circuit 2A is synchronously separated here, and then outputted as a horizontal synchronization signal and a vertical synchronization signal to the timing generation circuit 2B. Further, the color signal is supplied to the clock generation circuit 2C and one input terminal k of the changeover switch SW4.

The above-mentioned timing generation circuit 2B generates a burst gate pulse for extracting a color burst signal from the color signal supplied to the clock generation circuit 2C based on the horizontal and vertical synchronization signals supplied from the synchronization separation circuit 2A. It also generates and outputs a luminance reference signal and a color reference signal (FIG. 3A, (
It generates and outputs an address signal for reading out the data signal according to each of the data signals shown in FIG.

The above-mentioned clock generation circuit 2C extracts a color burst signal from the color signal supplied here based on the burst gate pulse supplied from the timing generation circuit 2B, and generates a color burst frequency synchronized with this burst gate pulse. Generates and outputs a clock that is an integral multiple (for example, 4 times the frequency). This clock serves as a master clock for all the circuits making up the reference signal insertion circuit 2.

The above-described memory circuit 2D stores data corresponding to the luminance reference signal, and the memory circuit 2E stores data corresponding to the color reference signal, and these data are stored in accordance with the address signal supplied from the timing generation circuit 2B. Output each.

Each data signal output from the memory circuits 2D, 2E is converted into an analog data signal by the D/A converters 2F, 2G, and then supplied to the low-pass filter circuits 2H, 2I, where unnecessary After the high-frequency component is removed, the brightness reference signal and color reference signal are selected by switching switches SW3 and SW4.
are supplied to the other input terminals g and j, respectively.

The changeover switch SW3 receives the input luminance signal that passes through the movable contact c of the changeover switch SW1 and is applied to the fixed contact h, and the brightness that is applied to the fixed contact g via the low-pass filter circuit 2H described above. The input luminance signal or the luminance reference signal that has been alternately switched is outputted as one series signal via the movable contact i. The signal is output to, for example, an AGC circuit of a luminance signal recording system (Y signal recording system) not shown.

The changeover switch SW4 receives the input color signal which passes through the movable contact f of the changeover switch SW2 described above and is applied to the fixed contact k, and the color signal which is applied to the fixed contact j via the above-mentioned low-pass filter circuit 2I. The reference signal and the reference signal are alternately switched in accordance with the timing of the switching control signal supplied from the above-mentioned timing generation circuit 2B, and the alternately switched input color signal or color reference signal is transmitted as one serial signal via the movable contact l. Color signal recording system (C signal recording system) not shown
is output to, for example, an ACC circuit.

The above luminance reference signal will now be explained.

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

FIG. 3A shows an example of a luminance reference signal waveform, and this luminance reference signal is a bar waveform having a rising characteristic of SIN line 12).

The characteristics of SINX/X used here include, for example, a flat frequency characteristic up to the system transmission band in order to compensate for the entire band of the waveform equalization system (for example, approximately 5 MHz for S-VHS); At frequencies above, the characteristics are obtained by applying an appropriate window function such that the attenuation occurs with an appropriate curve (for example, a squared cosine characteristic).

The above color reference signal will be explained.

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

FIG. 3B shows an example of a color reference signal in a color signal transmission system subjected to quadrature two-phase modulation.
08MHz) to the upper limit frequency (e.g. 4.08MHz)
A sinusoidal sweep signal whose frequency increases linearly up to
The center frequency is the color subcarrier frequency (e.g. 3.58M
This is a signal whose phase is inverted at the position (Hz).

In FIGS. 3A and 3B, the timing positional relationship between the luminance reference signal and the color reference signal is the 50% time of the rise of the bar waveform of the luminance reference signal and the time when the phase of the color reference signal is reversed. Set so that they match.

The reason for this is that the timing deviation between the luminance reference signal and the color reference signal can be easily detected from the reproduced luminance reference signal and the reproduced color reference signal.

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

As shown in FIGS. 3(A) to 3(D), FIG.
The luminance reference signal shown in A) is inserted into the video signal period of the 12th line (12H) of each luminance signal in the first to fourth fields, and is adjacent to the video signal period in which the luminance reference signal is inserted. Each video signal period of the 11th line and the 13th line is in a blanking state.

Further, the color reference signal shown in FIG. 3B is inserted into the video signal period of the 12th line of each color signal in the first to fourth fields, similar to the insertion timing of the luminance reference signal described above. The 11th line and the 13th line adjacent to the video signal period in which the color reference signal is inserted are
Each video signal period of the line is blanked, but in order to match the color sequence, the color reference signals of the odd fields (first and third fields) and the color reference signals of the even fields (second and fourth fields) are blanked. The signals are recorded so that the hues are inverted (opposite) to each other.

In this state, the first field is "C+" and the second field is "C-" in (A) to (D) of the same figure.
", the third field is "C-", the fourth field is "C
+'' symbol, and the relationship with the color burst phase goes around every four fields (frames A and B).

Now, the receiving side processing system C of the waveform equalization system 1 may be equipped with 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. 5 is installed in the receiving side processing system C,
When a luminance signal in which blanking is not applied to one line before and after the luminance reference signal shown in FIG. 6(A) is input to this filter 4, the signal shown in FIG. 6(B) is output, and the luminance reference signal is inserted. On the twelfth line, a signal appears in which 1/2 the amplitude of the luminance reference signal and 1/2 the amplitude of the previous one line (or the next one line) having no line correlation are added.

In this way, the reproduced luminance reference signal is interfered with by the unspecified signal of the first line (or the next line), and unspecified distortion unrelated to the transmission characteristics occurs, so characteristic compensation is not possible. I can't do it well.

Furthermore, when the luminance signal shown in FIG. 6(C), in which only one line before the luminance reference signal is blanked, is input to this filter 4, the signal shown in FIG. 6(D) is output, and the luminance The 12th line into which the reference signal is inserted has an amplitude of 1/2 of the luminance reference signal and the previous 1st line with no line correlation.
A signal obtained by adding 1/2 the amplitude of the line (or the next line) may appear here.

In this way, the reproduced luminance reference signal is disturbed by the unspecified post-line signal, causing unspecified distortion unrelated to the transmission characteristics, so that good characteristic compensation cannot be achieved.

In order to solve the above problem, the same figure (E
) When a luminance signal in which one line before and after the luminance reference signal is blanked is input to this filter 4, the signal shown in FIG. Since only the reproduced luminance reference signal with an amplitude of appears, this signal is not subject to unspecified interference,
Characteristic compensation is possible.

The comb filter 4 described above includes a delay circuit (
1H delay) 5, an addition circuit 6, and an attenuation circuit (1/2) 7.

Similarly, when a 3-line correlation type comb filter is used as a noise canceller, FIG.
When the luminance signals shown in (A) and (C) are input, the signals shown in (B) and (D), respectively, are output, and the reproduced luminance reference signal is interfered with and unspecified unrelated to the transmission characteristics. As distortion occurs, good characteristic compensation cannot be achieved.
When the brightness signal shown in E) is input, the signal shown in FIG.

[0058] Here, the operation of the noise canceller may be stopped at least during the luminance reference signal insertion period (line 12), and by doing so, interference by the noise canceler will not occur, and also, as shown in Fig. 4(F). As shown, the amplitude never becomes 1/2.

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 (12th line)) ) It is necessary to stop this operation by cutting the loop for a period of time.

The above explanation of FIGS. 6(A) to 6(F) is about the luminance signal, but although it will not be explained in detail here, the color signal is also similar to the luminance signal shown in FIG. 6(E). When a color signal with blanking applied to one line before and after the color reference signal is input to this filter 4,
Similar to the signal shown in (F) of the same figure, since only the reproduced color reference signal with an amplitude of 1/2 of the color reference signal appears here, this signal is not subject to unspecified interference and the characteristics can be compensated. It goes without saying that it can be done.

By the way, the luminance signal into which the luminance reference signal is inserted and the chrominance 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, the signals are supplied to the transmission side processing system A, which is a recording signal processing means, and are processed through each recording process to become a recording luminance signal and a recording color signal, and then recorded via a tape head system, which is a transmission path B. Then, during playback, from this transmission path B to VT
In R, the signals are supplied to a receiving side processing system C which is a reproduction signal processing means, and after going through each reproduction process, reproduce the above-mentioned recorded luminance signal and recorded color signal to obtain a reproduced luminance signal and a reproduced color signal, which will be described later. The waveform equalization 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 waveform equalization means E described above is the receiving side processing system C.
Detection means 10 detects the distortion that the reference signal has undergone during transmission by receiving a reproduced reference signal based on the reference signal from the video signal transmitted through the video signal, and filter means 13 for canceling the transmission distortion detected from the transmitted video signal. , 20.

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

In FIGS. 7 and 8, 8A and 24A are reproduction luminance signal transmission characteristic compensation circuits, 8B and 24B are reproduction color signal transmission characteristic compensation circuits, 9 is a clock generation circuit, and 10 is a CP
U (detection means), 11 and 18 are A/D converters (ADC)
, 12, 19, 26, 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, 22 are D/A converters (D
AC), 17, and 23 are low-pass (LPF) filters, C is a receiving side processing system, and E is a waveform equalization means. The reproduction luminance signal transmission characteristic compensation circuit 8A is a feedback control system consisting of a delay circuit 12, a transversal filter 13, and an adder 14, and the reproduction color signal transmission characteristic compensation circuit 8B is a feedback control system consisting of a delay circuit 19, a transversal filter 20, and an adder 21. The reproduced luminance signal transmission characteristic compensation circuit 24A is a feedforward control system composed of a transversal filter 13, an adder 25, and a delay circuit 26, and the reproduced chrominance signal transmission characteristic compensation circuit 24B. are transversal filter 20, adder 27,
This is a feedforward control system composed of a delay circuit 28.

The waveform equalization means E shown in FIGS. 7 and 8 corresponds to the receiving side processing system C of the waveform equalization system 1.
) is provided at the subsequent stage of the signal reproduction processing means).

Although not detailed here, the above-mentioned V
The brightness signal reproducing processing means of the TR passes through the video head, from a rotary transformer, etc. to a preamplifier circuit, a channel switcher, a high-pass filter circuit, and a dropout compensation circuit (DOC).
), a limiter circuit, an FM demodulator, a de-emphasis circuit, a low-pass filter circuit, etc., and the above-mentioned color signal reproduction processing means passes through a preamplifier circuit of the luminance signal reproduction processing means, a low-pass filter, an ACC circuit, etc. This includes circuits, frequency converters, bandpass filter circuits, killer switches, etc.

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

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 color signal based on the horizontal and vertical synchronization signals extracted from the reproduced luminance signal, extracts a color burst signal from the reproduced color signal using this burst gate pulse, and generates a burst signal. A clock having an integral multiple (for example, four times the frequency) of the color burst frequency synchronized with the gate pulse is generated and output.

The clock output from the clock generation circuit 9 is transmitted to a reproduced luminance signal transmission characteristic compensation circuit 8A, a reproduced 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, waveform equalization by the waveform equalization means E shown in FIG. 7 will be explained using FIG. 9.

For convenience of explanation, waveform equalization will be explained only for the reproduced luminance signal, but it goes without saying that waveform equalization can also be performed for the reproduced chrominance signal in the same manner.

Now, the recorded luminance signal (FIG. 9(
The waveform aa) shown in A) is converted into a recording luminance signal through various recording processes in the recording signal processing means, and then recorded via the tape head system.

At the time of reproduction, the reproduced luminance signal (waveform bb shown in FIG. 3B) that is reproduced through each reproduction process in the reproduced signal processing means is sent to the A/D converter 11 of the waveform equalization means E.
A/D converted digital data signals are supplied to a delay circuit 12 consisting of a multi-stage shift register and a transversal filter 13, respectively.

The delay circuit 12 outputs a delay signal ((C) in the same figure).
The transversal filter 13 outputs a compensation signal (a digital signal corresponding to the waveform dd shown in FIG. 1D).

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

In this way, the adder 14 adds the compensation signal from the transversal filter 13 to the delayed signal from the delay circuit 12, thereby producing a delayed signal (from which the signal component corresponding to the deterioration of the transmission characteristics has been canceled). A digital signal corresponding to the waveform ee shown in FIG. 3(E) is output.

Here, the reason why the delay circuit 12 described above is constituted by a shift register is to synchronize the timing with the compensation signal from the transversal filter 13 in the adder 14. This is to realize a delay amount that is uniquely determined.

The reproduced luminance signal outputted from the adder 14 and containing the reproduced luminance reference signal that has been compensated for deterioration in transmission characteristics is supplied to the variable delay unit 15. The variable delay device 15 is the CPU 10
The amount of delay is varied according to the control signal from the D/R, and the reproduced luminance signal supplied here is output after matching the timing with the reproduced color signal, and one of the outputs is output from the D/
After being supplied to the A converter 16 and subjected to D/A conversion, it passes through the low-pass filter circuit 17 to become the final reproduced luminance signal,
Further, the other output is directly supplied to the CPU 10.

Here, although the reproduced luminance reference signal is inserted into the reproduced luminance signal outputted from the low-pass filter circuit 17, this insertion position is within the vertical blanking period of the reproduced luminance signal, so it is left as is. A good reproduced image can be obtained by supplying the reproduced luminance signal together with the reproduced color signal from the low-pass filter circuit 23 to reproduction means such as a TV receiver (not shown), but this reproduced luminance reference signal was extracted. In order to obtain the reproduced luminance signal, in FIG.
It is sufficient to insert a reference signal extraction circuit complementary to the reference signal insertion circuit 2 shown in FIG.

The reproduced luminance signal including the reproduced luminance reference signal outputted from the variable delay device 15 to the CPU 10 is converted from the reproduced luminance signal by the CPU 10 in accordance with the timing of the luminance signal and color signal shown in FIGS. 4(A) to 4(D). The transversal filter 13 outputs a control signal corresponding to the difference obtained by comparing the extracted reproduction brightness reference signal waveform (waveform bb above) and the recorded brightness signal waveform (waveform aa above) with the same regular waveform.
The coefficients of the transversal filter 13 are varied so that this difference does not occur.

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

[0082] What has been described above is about compensating for the deterioration of the transmission characteristics in the luminance signal transmission system, but it is also possible to compensate for the deterioration in the transmission characteristics in the color signal transmission system as well. Deterioration in the transmission system can be compensated for.

That is, in the color signal transmission system, the recorded color signal output from the reference signal insertion circuit 2 described above and into which the color reference signal has been inserted is converted into a recorded color signal through various recording processes in the recording signal processing means. , 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 by the A/D converter 18 of the waveform equalization means E, and is converted into a multi-stage digital data signal. The signal is supplied to a delay circuit 19 consisting of a shift register and a transversal filter 20, respectively.

A delay signal is output from the delay circuit 19,
Further, the transversal filter 20 outputs a compensation signal. This transversal filter 20 is
10 outputs the above-mentioned compensation signal having an opposite phase relationship with the signal component in the delayed signal so as to cancel out the signal component corresponding to the deterioration of the transmission characteristic.

In this way, by adding the compensation signal from the transversal filter 20 to the delay signal from the delay circuit 19 in the adder 21, a delay signal in which the signal component corresponding to the deterioration of the transmission characteristics has been canceled is obtained. Output.

Here, the reason why the above-mentioned delay circuit 19 is configured with a shift register is to synchronize the timing with the compensation signal from the transversal filter 20 in the adder 21, and the delay circuit 19 is configured with a shift register in order to synchronize the timing with the compensation signal from the transversal filter 20. This is to realize a delay amount that is uniquely determined.

One of the reproduced color signals outputted from the adder 21 and containing the reproduced color reference signal whose transmission characteristics have been compensated for is:
After being supplied to the D/A converter 22 and subjected to D/A conversion, it becomes the 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 into the reproduced color signal output from the low-pass filter circuit 23, this insertion position is within the vertical blanking period of the reproduced color signal, so it is not suitable for practical use. Although there is no problem, in order to obtain a reproduced color signal extracted from this reproduced color reference signal, the following steps in FIG.
Between the adder 21 and the D/A converter 22 (adder 21 and C
It is sufficient to insert a reference signal extraction circuit complementary to the reference signal insertion circuit 2 shown in FIG.

The CPU 10 takes in the reproduced color reference signal reproduced every field, and gradually updates the coefficients 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.

[0091] The reproduced waveform used for calculation at this time is S/N
In order to improve the performance, synchronous addition is performed over several field periods.

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

Cn*=Cn−αen
Formula (1)
However, Cn current n-th tap coefficient Cn*
Current nth tap coefficient after update en nth error signal α Correction coefficient (<1) Tap updating is performed every few fields within the vertical blanking period, and the effective scanning period of the luminance signal and chrominance signal , color burst signal section, and horizontal/vertical synchronization signal section.

Waveform bb shown in FIG. 9(B) described above is obtained by reproducing waveform aa shown in FIG. 9(A),
Ringing is caused by distortion in the transmission characteristics.

Waveform dd in the figure (D) is a filter output whose coefficients are controlled by the CPU 10, and waveform b
It has an antiphase component of the strain contained in b.

The above luminance reference signal and color reference signal are as follows:
It is inserted in the 12th line during the vertical blanking period of the luminance signal and color signal, and if the blanking lines of the 11th and 13th lines are included, the 11th to 13th lines are used, but the present invention is not limited to this. 10th line to 13th line
line, and the period from the 17th line to the 20th line may be set arbitrarily.

[0097] However, the 14th line to the 16th line, the 2nd line
Line 1 is used for teletext broadcasting, so if there is no need to coexist with teletext, this line may be used.

Although the luminance reference signal and color reference signal described above have been explained as a 4-field sequence with 1 line/field, they can also be expressed as a 4-field sequence with 2 lines/field as shown in FIGS. 10(A) to 10(D). good.

In this case, the field consists of a total of 4 lines including 2 lines before and after blanking, the same luminance reference signal is recorded on the 11th line and the 12th line of each field, and the color reference signal is recorded on the same line. is inserted at the same timing as the luminance signal.

The color reference signal is set so that the hue is inverted between successive lines and on the same line in an even field following an odd field.

[0101] If the transmission system has an arithmetic circuit (such as a Y/C separation circuit or noise reduction circuit) that utilizes the correlation between fields or frames, this arithmetic circuit may mistake the color reference signal for 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 into which a luminance reference signal and a color reference signal are inserted,
It shows the timing positions of a luminance reference signal and a color reference signal in an NTSC video signal.

As shown in FIGS. 3(A) to 3(D), FIG.
The luminance reference signal shown in A) corresponds to the 11th and 12th lines (11
The video signal periods of the 10th line and the 13th line (10H, 13H) are blanked.

Further, the color reference signal shown in FIG. 3(B) is similar to the insertion timing of the luminance reference signal described above, and the 11th,
The first line is inserted into each of the 12 lines of video signal period.
Each video signal period of the 0th line and 13th line is blanked, but in order to match the color sequence, the color reference signal of the odd field (first, third field) and the even field (second, fourth field) are blanked. The color reference signal of the field) is recorded so that the hue is inverted (opposite) to that of the color reference signal of the field.

In this state, the color reference signals of the 11th and 12th lines of the first field are "C+" and "C-", respectively, and the color reference signals of the second field are "C-", respectively, in (A) to (D) of the same figure.
", "C+", and the third field is "C-", "C+" respectively.
", and the fourth field is indicated by symbols "C+" and "C-", respectively, and the relationship with the color burst phase goes around every four fields (frames A, B).

Furthermore, since the color reference signal is not a signal to be viewed on a screen, it is not necessarily necessary to satisfy the color sequence unless there is an arithmetic circuit using field/frame correlation in the transmission system.

For example, there is no problem even if the same signal is inserted every field.

The reproduced luminance signal transmission characteristic compensation circuits 8A and 8B shown in FIG. Reproduction luminance signal transmission characteristic compensation circuit 2
A feedforward control system like 4A and 24B may be used. Furthermore, both may be combined.

The waveform equalization means E shown in FIG. 8 removes the reproduced luminance signal transmission characteristic compensation circuits 8A and 8B from the waveform equalization means E shown in FIG. , 24B, and the other components are the same as those shown in FIG. 7, so the same components are denoted by the same reference numerals.
Although the description thereof will be 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 equalization means E shown in FIG.

In this case, since the reproduced luminance signal transmission characteristic compensation circuits 8A and 8B are feedback control systems,
Although the tap update formula using equation (1) described above cannot be used, the tap update for the transversal filters 13 and 20, which is performed under the control of the CPU 10, is performed every few fields within the vertical blanking period,
Of course, this is not performed during the effective scanning period of the luminance signal and color signal, the color burst signal period, and the horizontal and vertical synchronization signal period.

In the above description, the system of the present invention is applied to a VTR having a well-known configuration, but it can also be applied to other recording/reproducing means such as a magnetic disk or an optical disk.

[0112] Furthermore, even when there is no recording process on the user's side, such as with package media such as video discs and video software, the same effect can be obtained by including and recording the reference signal when creating the package media.

[0113] Furthermore, not only in the case of recording/playback, but also in general signal transmission systems such as CATV and wireless communication, the transmitting side includes a reference signal and transmits it, and the receiving side equalizes the waveform of this signal. The same effect can be obtained by doing so.

[0114] Furthermore, the above-mentioned reference signal can be inserted continuously for at least two horizontal synchronization periods of the video signal, and in this case, interference can be prevented by a comb filter for Y/C separation. No (even with a 2-line comb filter, 2
The H-th reference signal can be completely separated).

[0115] The reference signal described above can also be inserted in a 4-field sequence, and in this case, an arithmetic circuit (such as a Y/C separation circuit or noise reduction, etc.), it is possible to prevent this arithmetic circuit from mistakenly detecting a color reference signal as a luminance reference signal and malfunctioning.

[0116]

Effects of the Invention The waveform equalization system according to the present invention can remove the transmission distortion components that the transmitted video signal received during transmission, so that the waveform equalization system according to the present invention can produce a video signal that is almost the same as the video signal before transmission, since it is possible to remove the transmission distortion component that the transmitted video signal received during transmission. It is possible to obtain a video signal, and it is particularly effective in eliminating all distortions such as linearity or gain in frequency characteristics, ringing, and smear, and it is also effective in transmitting the same video signal simultaneously using multiple different transmission systems. It has the effect of being able to transmit video signals with constant quality without variations in video signals caused by differences in the transmission characteristics of each transmission system, and especially when the video signal transmission form is a combination of multiple signals and is transmitted over multiple transmission paths. (e.g. direct recording of composite video signals/
(Even if the player performs Y/C separation processing for playback, such as a VHS system VTR, or performs component recording/playback, such as a VTR of a system other than this system),
It is possible to optimally correct all kinds of distortion according to each transmission system, and when the system of the present invention is applied to transmission equipment such as a VTR, which has variations in recording and playback transmission systems for each product, it is possible to correct distortions between each transmission equipment. This has the effect of stably providing transmission equipment with constant quality that is not affected by variations in transmission characteristics.

[0117] Furthermore, the waveform equalization system according to the present invention has the following features:
The reference signal insertion means in the above configuration is configured to insert the reference signal at a predetermined position in the video signal to be transmitted and to blank the video signal period adjacent to the video signal period in which this reference signal is inserted. Now that I have configured it, after transmission,
When capturing the playback reference signal from the transmitted video signal,
Since this reference signal can be captured during the reference signal period without interference from adjacent lines, even if a line correlation type signal processing circuit is used, unnecessary noise components adjacent to the reproduced reference signal can be captured. Since this can be prevented, in addition to the above-mentioned effect, there is an effect that transmission distortion of the transmitted video signal can be more reliably compensated for.

[Brief explanation of drawings]

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

FIG. 2 is a configuration diagram of an embodiment of reference signal insertion 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 the receiving 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 configuration diagram of a first embodiment of waveform equalization means, which is a main part of the waveform equalization system according to the present invention.

FIG. 8 is a configuration diagram of a second embodiment of 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 in transmission characteristics.

FIG. 10 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. 11 is a conceptual diagram of a transmission system for transmitting video signals.

[Explanation of symbols]

1 Waveform equalization system 10 CPU (detection means) 13, 20 Transversal filter (filter means) A Transmission side processing system B Transmission line C Receiving side processing system D Reference signal insertion means E Waveform equalization means

Claims (2)

[Claims] 1. A waveform equalization system that compensates for transmission distortion of a transmitted video signal, the system comprising: a reference signal that is provided before a transmitting side processing system, and that inserts a reference signal at a predetermined position of the video signal to be transmitted; an insertion means, a detection means for capturing a reproduction reference signal based on the reference signal from the video signal transmitted via the receiving side processing system and detecting distortion that the reference signal has undergone during transmission; 1. A waveform equalization system comprising: a filter means for canceling detected transmission distortion; and a waveform equalization means provided with a filter means for canceling detected transmission distortion. 2. The waveform equalization system according to claim 1, wherein when inserting the reference signal, a video signal period adjacent to a video signal period in which the reference signal is inserted is set in a blanking state. waveform equalization system.