JP2861273B2 - Waveform distortion detection circuit - Google Patents

Description

The present invention relates to a circuit for removing waveform distortion of a video signal.

[Summary of the Invention]

According to the present invention, for example, in a ghost elimination circuit, the cost is reduced by using a transversal filter in a time-division manner for ghost elimination and correlation calculation.

[Conventional technology]

To remove a ghost wave component from a received video signal in a television receiver, the following may be performed.

That is, on the transmission side, a ghost canceling reference signal (hereinafter, referred to as a GCR signal) is added to the video signal.

Then, on the receiving side, the received video signal
The GCR signal (including the ghost wave component) and the GCR signal formed on the receiving side are compared in waveform to extract the ghost wave component, and pass through a transversal filter so that the extracted ghost wave component disappears. Control characteristics.

Then, a signal SGCR as shown in FIG. 5 is considered as the GCR signal at this time.

That is, in the figure, HD is the horizontal synchronization pulse, BRST
Represents a burst signal, and the first GCR signal GCR has a bar waveform located at the rear side of the horizontal period as shown in FIG. 2A, a width of 44.7 μsec, and a level of 70 IRE. . The rising characteristic is a ringing characteristic of sinX / X.

Further, the second GCR signal PDS is, as shown in FIG.
A pedestal waveform (0 level) is set.

Then, as shown in FIG. 6A, an eight-field period of the video signal is set as a repetition period, and the eighteenth line or the eighteenth field period of the first, third, sixth, and eighth field periods is used.
The GCR signal GCR is inserted into the 281st line, and the signal PDS is inserted into the 18th line or the 281st line in the remaining second, fourth, fifth, and seventh field periods.
The video signal with the GCR inserted is transmitted.

Then, the first to eighth GCR signals SGCR are transmitted to the signals S _{1 to} S _8.
Then, if the receiving side performs an operation as shown in FIG. B, the operation result becomes a signal GCR. If there is a ghost, the calculation result also includes the ghost wave component Sg of the signal GCR.

Therefore, the ghost can be removed from the signal GCR (and Sg) of the operation result.

In this case, 4 Fi - field period apart the burst signal BRST, the color signal and the horizontal synchronization pulses HD, since each of phase with each other, when calculating the signal S ₁ to S _8, the burst signal BRST, the color signal and the horizontal sync The pulses HD are each canceled.

Therefore, since the signal GCR (and the ghost wave component Sg) of the operation result does not include the burst signal BRST, the color signal, and the horizontal synchronization pulse HD, the so-called front ghost and rear ghost removal and waveform equalization are performed. Up to 45 μs can be handled. In addition, erroneous detection does not occur even for a long ghost up to about 80 μsec.

FIG. 7 shows an example of a ghost removal circuit using the GCR signal SGCR.

That is, (1) shows a video detection circuit of a television receiver, from which the above-mentioned color composite video signal SY to which the GCR signal SGCR is added is extracted from this detection circuit (1), and this signal SY is converted into an A / D converter. One sample is supplied to (2) and converted into a digital video signal SY of, for example, 8 bits. This signal SY is transmitted to a D / A converter (4) through a transversal filter (3) of, for example, 640 stages (640 taps). The supplied analog video signal SY is converted into the original analog video signal SY, and this signal SY is taken out to the terminal (5).

At this time, a ghost wave component is detected from the GCR signal SGCR in the detection circuit (10), and the pass characteristic of the filter (3) is controlled by the detection output to remove the ghost wave component.

That is, the operation shown in FIG. 6B can be rewritten as shown in FIG.
This indicates that the R signal SGCR should be accumulated in order.

Then, the digital video signal SY from the A / D converter (2) is supplied to the gate circuit (11) and the GCR signal SGCR
(Including the preceding and following detection periods) is taken out and this signal SGCR
Is supplied to the buffer memory (12), and the GCR signal SGCR in the field period is held for each field period.

Then, the GCR signal SGCR of the memory (12) is supplied to the arithmetic circuit (21). The arithmetic circuit (21) and the following circuits (22) to (28) are actually constituted by a microcomputer (20) and software, but are represented by hardware here.

That is, in the arithmetic circuit (21), the memory (12)
The GCR signal SGCR held in the above is sequentially added or subtracted in accordance with the formula of FIG. 6C for each field period, and as shown in FIG. 8A, is the operation result of the eight field period. The signal GCR (including the ghost wave component Sg) is extracted. And since this signal GCR is a bar waveform,
To make a pulse response, this signal GCR is used as a differentiation circuit (22)
Is supplied to the differential pulse Pp as shown in FIG.
This pulse Pp is supplied to the correlation operation circuit (23).

Further, the video signal SY from the filter (3) is supplied to the gate circuit (13) to extract the GCR signal SGCR (including the preceding and following detection periods), and this signal SGCR is supplied to the buffer memory (14). The field every one field period
The GCR signal SGCR for the first period is held.

Then, the GCR signal SGCR of the memory (14) is supplied to the arithmetic circuit (24), and the arithmetic result in the eight field period is obtained as shown in FIG. 9A in the same manner as the arithmetic in the arithmetic circuit (21). GCR (including its ghost wave component Sg)
The signal GCR is supplied to a differentiating circuit (27) and then supplied to a subtracting circuit (25).
A reference waveform signal GCR (FIG. 5C) is extracted from the GCR signal forming circuit (26), and the signal GCR is supplied to a subtraction circuit (26). Therefore, as shown in FIG. 9B, the ghost wave component Sg of the received signal GCR is output from the subtraction circuit (26).
The differential pulse Pq shown in FIG. 9C is extracted (this ghost wave component Sg is also an error that could not be removed).

Then, the pulse Pq is supplied to the correlation operation circuit (23).

This correlation operation circuit (23) obtains ghost information by performing a product-sum operation of the pulse Pp and the pulse Pq. In this operation circuit (23), a routine (30) shown in FIG. Processing is performed.

However, as shown in FIG. 8B, the number of samples of the pulse Pp is 64 samples. I: Tap number of filter (3). i = 0 to 639 m: a sampling point for the pulse Pq in a ghost removal period (for example, −2 μs to +45 seconds) n: a sampling point of the pulse Pp. n = 0 to 63 Xn: Quantized value of pulse Pp Ym: Quantized value of pulse Pq RSLT: Calculation result

Further, the arithmetic circuit (23) only equivalently illustrates the processing of the microcomputer (20) as hardware, and the processing of the routine (30) is actually executed by the microcomputer (20).

When the processing of this routine (30) is executed,
In the step (32), the operation result RSLT is output from the operation circuit (23) and supplied to the conversion circuit (28), and the operation result RSLT is a tap coefficient (tap) for the i-th tap of the filter (3). Gain) converted to Ti.

Then, the coefficient Ti is supplied to the filter (3), and the pass characteristic of the filter (3) is controlled such that the ghost wave component Sg of the GCR signal SGCR extracted from the filter (3) is canceled and removed. .

Therefore, at this time, the ghost wave component of the video signal SY is also removed by the filter (3), and the video signal SY containing no ghost wave component is extracted from the terminal (5).

Reference: The 1989 National Convention of the Institute of Television Engineers of Japan "Ghost cancellation reference signal system" [Problems to be solved by the invention] However, as described above, when the correlation operation in the arithmetic circuit (23) is executed by the routine (30) As is clear from the figure, the multiplication in step (31) must be performed 40960 times (= 640 taps × 64 samples) which is the product of the number of taps of the filter (3) and the number of samples of the pulse Pp.

However, multiplication is one of the most time-consuming processes for the microcomputer (20).
Running more than ten thousand times would require a lot of time and would be impractical.

In this regard, if the correlation calculation circuit (23) is configured by hardware, high-speed calculation can be performed. However, this requires a dedicated correlation operation circuit, which increases the cost.

The present invention seeks to eliminate these problems.

[Means for solving the problem]

Now, considering the transversal filter (3), in the case of a standard type (output addition type), it is implemented as an IC with a configuration as shown in FIG.

However, D _{0 to} D ₆₃₉ are unit period delay circuits, M _{0 to} M ₆₃₉ are multiplier circuits, A ₀ is an adder circuit, SR is a shift register, T _IN is a signal input terminal, T _OUT is a signal output terminal, T _TAP Is a tap coefficient input terminal. Then, the tap coefficient is converted from serial data to parallel data by the register SR, and the multiplication circuit M ₀
~ _M639 is loaded.

The present invention focuses on the fact that the transversal filter (3) is configured as described above, and uses the transversal filter (3) in a time-division manner for removing a ghost wave component and performing a correlation operation. It was done.

[Action]

The multiplication is executed by hardware, the correlation operation is executed at high speed, and the cost is hardly increased by the hardware.

〔Example〕

In FIG. 1, a video signal SY from an A / D converter (2) is supplied to a switch circuit (41), and a value Xn described later is extracted from a microcomputer (20) and supplied to the switch circuit (41). , the switch output is supplied to the signal input terminal T _iN of the transversal filter (3).

The video signal SY from the video detection circuit (1) is supplied to the switch circuit (42), and the video signal SY from the D / A converter (4) is supplied to the switch circuit (42), and the switch output Is taken out to the terminal (5).

Further, the microcomputer (20) the value Ti or Ym taken from these values Ti, the Ym are supplied to the tap input terminal T _TAP.

Also, switch circuits (41), (4)
During the period when these control signals are supplied to 2) and the tap coefficient Ti of the filter (3) is set, the switch circuit (41) alternates between the state shown in the figure and the state opposite to the figure. The switching is performed, and the switch circuit (42) is switched to the state opposite to the state shown in the figure. When the setting of the tap coefficient Ti of the filter (3) is completed, the switch circuits (41) and (42) are switched to the states shown in the figure.

In such a configuration, first, the switch circuit (41)
Are connected to the state shown in the figure for eight field periods.

Therefore, in this state (8-field period), the removal circuit is equivalently configured as shown in FIG. 2, so that the microcomputer (20) uses the GCR signal SGCR to generate the pulses Pp and _Pq as described above. Xn and Ym are extracted. At this time, the tap coefficient Ti obtained so far is calculated by the microcomputer (20)
To the filter (3).

Then, after the lapse of eight field periods, the switch circuit (41) is connected in a state opposite to that of FIG. 1, and thus has the equivalent configuration of FIG.

Subsequently, as shown in FIG. 4A, the values Y ₀ to Y ₆₃₉ are set in the multiplication circuits M _{0 to} M ₆₃₉ of the filter (3) by the microcomputer (20) (actually, the value Y is stored in the register SR). _{0 to} Y ₆₃₉ are set. Here, for convenience of illustration, a multiplication circuit is set.
M _{0 to} M ₆₃₉ ).

Next, “0” is supplied as an input signal to the filter (3) by the microcomputer (20) to clear the delay circuits D _{0 to} D ₆₃₉ as shown in FIG. The values X _{63 to} X ₀ are supplied to the filter (3) as input signals, and the values X _{0 to} X ₆₃ are set in the delay circuits D _{0 to} D ₆₃ as shown in FIG.

Further, as shown in FIG. D, the values of the delay circuits D _{0 to} D ₆₃₉
And X ₀ to X _639, along with the values Y ₀ to Y ₆₃₉ of the multiplier circuit M ₀ ~M ₆₃₉ are multiplied, the multiplication result is added in adder circuit A _0, outputs the addition result from the filter (3) It is extracted as a signal.

In this case, this output signal has values X _{0 to} X when i = 0.
₆₃ and the result of the product-sum operation of the values Y _{0 to} Y ₆₃₉ , i
This is the value RSLT when = 0.

Then, this value RSLT is taken into the microcomputer (20) from the filter (3) through the gate circuit (13) and the memory (14), converted into the _0th tap coefficient T0, and stored.

Next, as shown in FIG. 4E, the values of the delay circuits D _{0 to} D ₆₃₉ are determined.
X _{0 to} X ₆₃₉ are shifted to the output side by one delay circuit, and then the values X _{0 to} X ₆₃₉ of the delay circuits D _{0 to} D ₆₃₉ as shown in FIG.
When, along with the values Y ₀ to Y ₆₃₉ of the multiplier circuit M ₀ ~M ₆₃₉ are multiplied, the multiplication result is added in adder circuit A _0, the filter as a value RSLT when the addition result is i = 1 ( 3). Then, this value RSLT is converted into the _first tap coefficient T1 in the microcomputer (20) and stored.

Further, as shown in FIG. _9F , the values of the delay circuits D _{0 to} D ₆₃₉
X _{0 to} X ₆₃₉ are shifted to the output side by one delay circuit, and then, as shown in FIG. H, the values X _{0 to} X ₆₃₉ of the delay circuits D _{0 to} D ₆₃₉ are shifted.
When, along with the values Y ₀ to Y ₆₃₉ of the multiplier circuit M ₀ ~M ₆₃₉ are multiplied, the multiplication result is added in adder circuit A _0, the filter as a value RSLT when the addition result is i = 2 ( 3). Then, this value RSLT is converted into the _second tap coefficient T2 in the microcomputer (20) and stored.

Thereafter, the shift operation of the values X _{0 to} X ₆₃₉ of the delay circuits D _{0 to} D ₆₃₉ and the product-sum operation by the multiplication circuits M _{0 to} M ₆₃₉ and the addition circuit A ₀ are alternately repeated, and the filter (3 ) Outputs the i-th value RSLT, and this value RSLT
Is converted into a tap coefficient Ti in the microcomputer (20) and stored.

Thus, from the filter (3), the 0th value RSLT
To the 639th value RSLT are output in order, and all the tap coefficients T _{0 to} T ₆₃₉ are obtained by the microcomputer (20).

Then, when all the tap coefficients T ₀ through T ₆₃₉ is determined, the switch circuit (41) is switched again to the state of FIG. 2, 8 Fi - the GCR signal SGCR over field period pulse Pp, pulse Pq values Xn , Ym are taken out. At this time, the tap coefficient Ti obtained so far is the microcomputer (2
0) to the filter (3).

When the eight field period has elapsed, the switch circuit (41) is switched to the state shown in FIG.
Is required.

Thereafter, the operation in the state shown in FIG. 2 and the operation in the state shown in FIG. 3 are alternately repeated, and the tap coefficient Ti of the filter (3) is set so that the ghost wave component Sg of the GCR signal SGCR disappears. It is being converged.

Then, when sufficiently converged, the switch circuit (41)
The video signal SY from which the ghost wave component has been removed is taken out at the terminal (5), which is fixed to the state shown in FIG.

During the period when the characteristics of the filter (3) are being set, the switch circuit (42) is switched in the opposite direction as shown, and the video signal SY from the detection circuit (1) is supplied to the terminal (5).
And the unstable video signal SY during the setting is prevented from being output.

〔The invention's effect〕

Thus, according to the present invention, the ghost wave component is removed. In this case, particularly, according to the present invention, since the correlation operation is performed by hardware, the operation can be performed at high speed, and the operation can be sufficiently performed. The ghost wave component can be removed within a practical time.

Moreover, when the correlation calculation is performed by hardware, a dedicated correlation calculation circuit is not provided, and the transversal filter (3) is used for time-division elimination of ghost wave components and correlation calculation. Therefore, there is almost no increase in cost due to hardware.

[Brief description of the drawings]

FIG. 1 is a system diagram of an example of the present invention, and FIGS. 2 to 11 are diagrams for explanation thereof. (1) is a video detection circuit, (2) is an A / D converter,
(3) is a transversal filter, (4) is a D / A converter, (10) is a detection circuit, (11) and (13) are gate circuits, (12) and (14) are buffer memories, and (20) is It is a microcomputer.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takayu Nagamine 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 5 / 14-5/217

Claims (1)

(57) [Claims] 1. A received video signal is supplied to a transversal filter, a GCR signal is extracted from an output signal of the transversal filter, a waveform distortion component is extracted from the extracted GCR signal, and based on the extracted waveform distortion component. In the waveform distortion component removal circuit, which controls the pass characteristics of the transversal filter to extract the video signal from which the waveform distortion component has been removed from the transversal filter, The GCR signal is extracted, the extracted GCR signal and the extracted waveform distortion component are supplied to the transversal filter to perform a correlation operation, and the result of the correlation operation is transmitted to the transversal filter to control the pass characteristics. Waveform distortion detection circuit that is supplied as a signal .