JP2758973B2 - Ghost removal device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ghost removal device installed in a television receiver.

(Prior Art) A ghost removing device is scheduled to be installed in a high-definition television receiver or the like in order to enhance the effect of high image quality.

The ghost removal apparatus detects a ghost included in the received television signal, generates a pseudo ghost that simulates the detected ghost, and subtracts the generated pseudo ghost from the received television signal to thereby reduce the received ghost. The ghost is removed from the television signal. The above-mentioned ghost detection and removal processing is performed by digital operation, and therefore, the received television signal is converted into a digital television signal at a stage before the ghost detection unit.

The generation of the pseudo ghost is performed by a transversal filter, and the detection of the ghost is performed as a process of generating a tap coefficient to be set in the transversal filter. The tap coefficient generation process extracts a reference waveform set at a predetermined location in the received television signal, and calculates a reference waveform distorted by the ghost and an undistorted reference waveform held in advance by a predetermined algorithm. The calculation is performed according to the following. Various calculation methods are known.

Empirically, the tap coefficients generated by the ghost detection unit are distributed in groups while being discrete on the time axis, as illustrated in FIG. That is, assuming that the position of the video signal of interest is the reference point “0”, first, the first coefficient group (that is, the detected ghost) appears near this reference point “0”. Next, the second tap coefficient group (ghost) appears with a delay of time τa, and the third tap coefficient group (ghost) appears with a delay of τb. Appear in shape. A group of tap coefficients (ghost) generated in the vicinity of the reference point “0” is called a nearby ghost, which is considered to be completely integrated with transmission distortion caused by band limitation of a transmission path. For this reason, the process of removing the proximity ghost is also called waveform equalization. On the other hand, a typical ghost appearing in an area separated from the reference point “0” by several tens of taps or more is called a normal ghost, and an appearance area of the normal ghost is abbreviated as a normal area. However, the tap interval of the transversal filter is set to a sampling period (for example, 1/4 fsc) at the time of A / D conversion.

As described above, ghosts appear in groups over a width of several taps to several tens of taps, and appear discretely about several tens of taps between each group. For this reason, if a transversal filter having several hundred taps (ideally, 910 taps that can cover an entire line) is installed, a large number of unused taps appear at each time point, resulting in waste of efficiency.

Therefore, as exemplified in the block diagram of FIG. 5, a small-sized sub-transversal filter having several tens taps is used.
21a is a variable delay circuit 22a, 22b ... 22n
Pairs are installed in pairs. The ghost detection section includes variable delay circuits 22a to 22n and transversal filters 21a to 21n.
By setting the delay time and the tap coefficient via the input terminal 26 for each of the above, the small-scale transversal filters 21a to 21n are adaptively allocated to the ghost removal of each group.

In the “ghost removing device” (Japanese Patent Application No. 1-109784) related to the earlier application of the present applicant, when a plurality of pairs of the sub-transversal filter and the variable delay circuit are provided, each transversal filter is provided. An invention has been disclosed in which the amount of hardware is reduced by dividing the pseudo ghost generation into a large-level pseudo ghost having a large bit width and a small-level pseudo ghost having a small bit width.

(Problem to be Solved by the Invention) In the above-mentioned "ghost removing apparatus", the transversal filter is divided into two groups according to the level of the pseudo ghost to be generated. For this reason, a pseudo ghost of an intermediate level is generated by a large-level transversal filter having a large bit width, and waste is generated in the bit width.

Further, the above-mentioned "ghost removing apparatus" does not consider the diversion between the transversal filters grouped according to the level of the pseudo ghost to be generated. For this reason, when small-level ghosts occur frequently, there is a waste that even if the large-level transversal filter is in an unused state, it is not diverted for small-level ghost removal.

(Means for Solving the Problems) According to the ghost elimination device of the present invention, the ghost elimination unit usually includes a transversal pseudo ghost generation unit.
The filters are divided into three groups, large, medium, and small, and the ghost detection unit includes means for setting tap coefficients and delay times at levels corresponding to the three groups of transversal filters.

According to the ghost elimination device of one embodiment of the present invention, a bit shifter is added to the output side of the transversal filter for generating an intermediate level pseudo ghost, so that the bit shifter can be used as a transversal filter for generating a small level pseudo ghost. It is configured to be diverted.

 Hereinafter, the operation of the present invention will be described in detail with examples.

(Embodiment) FIG. 1 is a block diagram showing a configuration of a ghost removing apparatus according to an embodiment of the present invention, where IN is an analog television signal input terminal, 1 is an A / D converter, and 2 is ghost detection.・
Control unit 3, proximity ghost removal unit 4, normal ghost removal unit 5, synchronization separation unit 5, timing signal generation unit 6,
Is a D / A converter, and OUT is an output terminal of an analog television signal from which ghost has been removed.

The normal ghost removing unit 4 includes a transversal filter 11 for generating a large-level pseudo ghost, a transversal filter 12 for generating an intermediate-level pseudo ghost, a transversal filter 13 for generating a low-level pseudo ghost, a level shifter 14, and an adder 15, It consists of 16 parts.

The horizontal and vertical yellow signals included in the analog television signal supplied to the input terminal IN are separated by the sync separation unit 5. Various timing signals are generated by the timing signal generator 6 based on the separated synchronization signals,
It is supplied to each unit such as the D conversion unit 1 and the ghost detection unit 2. The analog television signal supplied to the input terminal IN is converted into a digital signal in the A / D conversion unit 1,
It is supplied to the ghost detection / control unit 2 and the proximity ghost removal unit 3.

The ghost detection and control unit 2 extracts a reference waveform set at a predetermined location such as a vertical synchronization pulse of a digital television signal, removes noise by time averaging, and retains a distortion-free reference waveform that is previously stored. By performing a predetermined arithmetic operation between and, a tap coefficient group having a distribution as shown in FIG. 3 is generated. The portion of the tap coefficient group that exists in the proximity area is supplied to the proximity ghost removal unit 3.

On the other hand, the generated tap coefficient group that exists in the normal region is divided into three stages of a large level, an intermediate level, and a small level, and the corresponding pseudo ghost in the normal ghost removing unit 4 together with the corresponding delay time. The transversal filters for generation 11, 12, and 13 are set.

That is, as illustrated in FIG. 2, the generated tap coefficient group is as shown in FIG. 2A, and these tap coefficient groups are classified into a large level above the dashed line, a small level below the dotted line, and It is assumed that the image is divided into three stages according to the level, such as an intermediate intermediate level. However,
For simplicity, only the positive polarity portion of the tap coefficient group is shown. In this case, the large-level tap coefficient group is as shown in FIG. 7B, the intermediate-level tap coefficient group is as shown in FIG. 6C, and the small-level tap coefficient group is as shown in FIG. It will be as shown. As shown in the figure, the appearance frequency generally increases as the ghost level decreases. For this reason, it is sufficient to prepare a larger number of transversal filters with a smaller pseudo ghost level to be generated.

The transversal filters 11, 12, and 13 for generating pseudo ghosts in the normal ghost removing section 4 are all composed of a plurality of small-scale sub-transversal filters as shown in FIG. However, the number of sub-transversal filters increases as the level of the pseudo ghost to be generated decreases. In addition, each transversal
The bit width of the processed data in the filters 11 to 13 is larger for a higher level.

According to the present embodiment, the calculation of the 8-bit coefficient and the 8-bit television signal is performed in the large-level pseudo-ghost generating transversal filter 11. The transversal filters 12 and 13 for generating the intermediate-level pseudo ghost and the small-level pseudo ghost calculate the 4-bit coefficient and the upper 4 bits of the 8-bit television signal.

That is, as shown in FIG. 3, the tap coefficients of the intermediate level and the small level are represented by 5 bits from b1 to b5 at the time of detection. Upper 4 bits b2 to b5 of these 5 bits
Are set in the intermediate level pseudo ghost generation transversal filter 12 as intermediate level tap coefficients.
On the other hand, the lower 4 bits b1 to b4 of the 5-bit tap coefficient
Are set in the small-level pseudo ghost generation transversal filter 13 as small-level tap coefficients.

Due to the frequent occurrence of small-level ghosts, the number of sub-transversal filters in the small-level pseudo ghost generating transversal filter 13 is insufficient, while the number of sub-transversal filters in the intermediate-level pseudo ghost generating transversal filter 12 is small. It is assumed that there are extra filters.

In this case, the ghost detection / control unit 2 sets the small-level tap coefficients b1 to b4 in the intermediate-level pseudo ghost generation transversal filter 12, and operates the bit shifter 14 to lower the output data by one bit. By shifting in the direction, this is diverted to the transversal filter 13 for generating a small-level pseudo ghost.

The configuration in which the level shift 14 is provided outside the intermediate-level pseudo ghost generation transversal filter 12 to convert the entirety to the small-level pseudo ghost generation has been described above. However, by installing this level shifter at the output side of each of the sub-transversal filters in the intermediate-level pseudo-ghost generating transversal filter 12, only some of the sub-transversal filters are used for generating the small-level pseudo-ghost. It can also be configured to be diverted to.

In addition, a bit shifter to the upper bit side is added to the output side of each sub-transversal filter in the transversal filter for generating small-level pseudo-ghosts, and a part of these sub-transversal filters is used for generating intermediate-level pseudo-ghosts. A configuration that is diverted to a transversal filter is also possible.

Further, if there is no large-level ghost, the large-level pseudo-ghost-generating transversal filter can be used as an intermediate-level or small-level-generating transversal filter.

(Effects of the Invention) As described above in detail, the ghost removing apparatus of the present invention groups the transversal filters of the normal ghost removing unit into three groups according to the three levels of pseudo ghosts to be generated. Since the ghost detection unit is configured to set tap coefficients having different bit widths in the corresponding transversal filters in accordance with the level, the transversal filter can be simplified.

Further, according to the ghost removing apparatus of one embodiment of the present invention, since the bit shifter is added to the output side of the transversal filter for generating the pseudo ghost of the intermediate level and the small level, these are diverted to each other. It is possible to achieve the effect that the utilization efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of a ghost removing apparatus according to one embodiment of the present invention, and FIG. 2 explains the state of grouping according to the level of a tap coefficient group generated and set by the apparatus of FIG. FIG. 3 is a conceptual diagram for explaining an example of a bit arrangement of tap coefficient groups of an intermediate level and a small level, and FIG. 4 is a diagram for explaining a general distribution of tap coefficient groups. FIG. 5 is a block diagram showing a general configuration of a pseudo ghost transversal filter. IN: Input terminal for analog television signal, 1 ... A /
D conversion unit, 2 ghost detection / control unit, 3 proximity ghost removal unit, 4 normal ghost removal unit, 5 synchronization separation unit, 6 timing signal generation unit, 7 D / A Conversion unit, OUT: Output terminal for analog television signals from which ghosts have been removed.

Claims (6)

(57) [Claims] A reference waveform set at a predetermined location is extracted from a digital television signal, a ghost is detected from the reference waveform, and a tap coefficient and a delay time to be set in a transversal filter for generating a pseudo ghost are determined. A ghost detection / control unit that generates and controls the setting of the generation result; and a proximity ghost removal unit that receives the setting of the tap coefficient from the ghost detection / control unit and removes the proximity ghost in the digital television signal. And a normal ghost removing unit that removes a normal ghost by receiving the setting of the tap coefficient and the delay time from the ghost detection and control unit, wherein the normal ghost removing unit includes a predetermined bit. Large-level pseudo-ghost that is composed of arithmetic circuits with a width and generates a large-level pseudo-ghost A transversal filter for generation, an arithmetic circuit having a bit width smaller than the predetermined bit width, and an intermediate level pseudo ghost generation transversal filter for generating a pseudo ghost at an intermediate level; A low-level pseudo ghost generating transversal filter configured to generate a low-level pseudo ghost, the ghost detection / control unit being configured by a small bit width arithmetic circuit; A ghost eliminator comprising a level and small-level pseudo ghost generation transversal filter, and a setting control means for setting tap coefficients and delay times of a large level, an intermediate level and a small level. 2. The transversal filter for generating each of the large-level, intermediate-level, and small-level pseudo ghosts,
2. The ghost eliminator according to claim 1, wherein the ghost eliminator comprises a plurality of sub-transversal filters. 3. A transversal filter for generating pseudo-ghosts at the intermediate and small levels, comprising a bit shifter for outputting generated data while bit-shifting the data downward and upward in accordance with a shift command. The ghost removing device according to claim 1 or 2. 4. The setting control means of the ghost detection / control section, wherein if there is no intermediate level ghost, the tap coefficient of the small level pseudo ghost generating transversal filter is set to the intermediate level pseudo ghost generating transversal. 4. The ghost eliminator according to claim 1, further comprising a unit that supplies the shift command to the bit shifter and supplies the shift command to the filter. 5. The setting control means of the ghost detection / control section, wherein if there is no small-level ghost, the tap coefficient of the intermediate-level pseudo-ghost generating transversal filter is set to the small-level pseudo-ghost generating transversal. 4. The ghost eliminator according to claim 1, further comprising a unit that supplies the shift command to the bit shifter and supplies the shift command to the filter. 6. The ghost detection / control section controls the large-level pseudo ghost generation transversal filter as an intermediate level or small level pseudo ghost generation transversal filter unless a large level ghost exists. The ghost removing device according to claim 1 or 2, wherein