JP2000137802A - Filter arithmetic unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a filter arithmetic unit which can suppress the video disturbance that is caused when a coefficient is updated. SOLUTION: A filter part 3 applies a filter operation using a prescribed coefficient to the input data and then output the data. A coefficient storage part 2 consists of a RAM and writes the coefficients Cn and Dn to be supplied to the part 3 in response to plural addresses. An auxiliary coefficient generation part 5 generates the fixed auxiliary coefficients Cn' and Dn'. A selection part 4 supplies the coefficients Cn' and Dn' received from the part 5 to the part 3 in place of the coefficients Cn and Dn received from the part 2 while the coefficients Cn and Dn stored in the part 2 are rewritten and updated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a filter operation device used for scaling an image.

[0002]

2. Description of the Related Art In recent years, a television receiver or a projection display device (projector device) performs a multi-screen display in which a plurality of images are displayed on one screen,
Image display methods are diversifying, such as displaying a part of an image in an enlarged manner. In addition, not only television signals but also personal computer signals (personal computer signals) have been displayed. Further, in addition to a display device using a cathode ray tube, a matrix type display device using a non-raster type display panel such as a plasma display device (PDP) or a liquid crystal display device (LCD) has appeared.

With such diversification of image display methods and input video formats and diversification of image display devices,
An image scaling device for scaling a television image or a computer image by digital signal processing using hardware is an essential component. The image enlargement / reduction device enlarges or reduces an image using a filter operation device that is a digital signal processing device.

FIG. 3 is a block diagram showing an example of a conventional filter operation device. In the example of FIG. 3, the number of taps of the filter operation device is two. 3, a start signal indicating a start position of a filter operation, that is, a start position when an image is enlarged or reduced is input to the address generator 1. The address generator 1 generates an address based on the start signal and inputs the address to the coefficient storage unit 2.

[0005] The coefficient storage unit 2 stores a plurality of coefficient sets, and is composed of a random access memory (RAM) whose storage contents can be updated. RAM
Usually share a data write terminal and a data read terminal. The coefficient storage unit 2 receives coefficient data to be stored in the coefficient storage unit 2, a write address for specifying an address for writing the coefficient data, and a write control signal (write enable signal) for permitting writing of the coefficient data. You. When an address is input from the address generator 1 after the coefficient data is written into the coefficient storage unit 2, the coefficient storage unit 2 generates the coefficient data specified by the address and inputs the coefficient data to the filter unit 3. In this example, since the number of taps of the filter operation device is 2, the coefficient storage unit 2 generates two coefficients, a coefficient Cn and a coefficient Dn.

[0006] To the filter section 3, a video signal to be subjected to a filter operation is input as input data. The filter unit 3 uses the two coefficients Cn and Dn input from the coefficient storage unit 2 to perform a filter operation on the input video signal and output the result. The specific configuration and operation of the filter unit 3 are as follows.
It will be described later.

Here, the operation of the interpolation operation by the filter operation device will be described with reference to FIG. 4A illustrates an input video signal (hereinafter, input data), and FIG. 4B illustrates an output video signal (hereinafter, output data). The input data is pixels A0, A1, A2, A
3, A4, A5..., And the output data is B1, B
2, B3, B4, B5, B6,... X in FIG. 4A indicates a distance (phase) to a pixel of output data obtained by interpolation from a pixel of input data.

The output data is B1, B2, B3, B4
B5... Are obtained by the following calculation. B1 = A0 × C1 + A1 × D1, B2 = A1 × C2 + A2
× D2, B3 = A2 × C3 + A3 × D3, B4 = A3 ×
C4 + A4 × D4, B5 = A4 × C5 + A5 × D5 ...
(This is referred to as Expression (1).) C1, C2, C3... Are coefficients Cn generated by the coefficient storage unit 2.
, And D1, D2, D3,... Are coefficients Dn generated by the coefficient storage unit 2.

The coefficients Cn and Dn have a great correlation with the pixel interpolation position. When three cycles of the input data and four cycles of the pixel of the output data are generated, the coefficients Cn and Dn are represented as position information as follows. Is done. (C1, D1) = (1, 0), (C2, D2) = (0.2
5, 0.75), (C3, D3) = (0.5, 0.
5), (C4, D4) = (0.75, 0.25), (C
(5, D5) = (0, 1) (this is called equation (2))

From the equation (2), the actual coefficients Cn, Dn
Although there are various methods for obtaining, the simplest example is a linear interpolation method. In the linear interpolation method, position information is used as a filter coefficient. When weighted by a distance x from a pixel of input data to a pixel of output data, the following is obtained. (C1, D1) = (0, 1), (C2, D2) = (0.7
5, 0.25), (C3, D3) = (0.5, 0.
5), (C4, D4) = (0.25, 0.75), (C
(5, D5) = (1, 0) (this is called equation (3))

Output data can be obtained from the above equations (1) and (3). FIG. 5 is an example of the coefficients Cn and Dn stored in the coefficient storage unit 2. In the above example, for the sake of simplicity, a case has been described in which four cycles of pixels of output data are generated with three cycles of pixels of input data. However, in actuality, coefficients are determined by further subdividing pixel intervals. In the example of FIG. 5, the coefficients Cn and Dn when the pixel interval of the input data is divided into 32 are shown. By giving the position information of the output data for generating the interpolation pixel as an address, the coefficients Cn and Dn required for the filter operation can be generated. At this time, the coefficients Cn and Dn need to be normalized, and Cn + Dn must always be 1. This is because if Cn + Dn is not 1, a change in the DC component occurs in the result of the filter operation, causing interference in the output video.

The filter section 3 in FIG. 3 is configured as shown in FIG. 6, input data is input to a D flip-flop (hereinafter, DFF) 31 and a multiplier 32. The DFF 31 delays the input data by one pixel and inputs the data to the multiplier 33. When the input data is An (n = 0, 1, 2,
..), The output of the DFF 31 is A (n + 1). The multiplier 32 multiplies the input data An by the coefficient Cn and outputs a signal M1. Multiplier 33 receives input data A
(N + 1) is multiplied by the coefficient Dn to output a signal M2. The adder 34 adds the signal M1 and the signal M2, and outputs a signal M3. This signal M3 is the output data of the filter operation device.

[0013]

As described above, when the coefficient storage unit 2 is composed of a RAM, since the RAM shares a data write terminal and a read terminal, the data is stored in the coefficient storage unit 2. When updating the coefficients Cn and Dn, the coefficients Cn and Dn being written into the coefficient storage unit 2 are output to the filter unit 3 as they are. Usually, the writing of the coefficients Cn and Dn into the coefficient storage unit 2 is performed according to an instruction from an external microcomputer or the like, but the speed is much slower than the sample rate of the image.

As described above, when updating the coefficients Cn and Dn stored in the coefficient storage unit 2, if the coefficients Cn and Dn being written into the coefficient storage unit 2 are output to the filter unit 3 as they are. , While updating the coefficients Cn and Dn, erroneous coefficients Cn and Dn are sequentially switched and input to the filter unit 3.

Then, the interpolation phase in the filter unit 3 is disturbed, and the image is displayed as shaking on the screen. As described above, since the time required to update the coefficients Cn and Dn is much slower than the sample rate of the image, this is a serious problem visually. To avoid this, the coefficient C
When updating n and Dn, the image is not displayed or the coefficients Cn and Dn from the outside are temporarily stored in the buffer memory, and the coefficients Cn and Dn are stored in the coefficient storage unit 2 during a non-display period such as a video blanking period. There is a method of transferring Dn at high speed. However, in the former method, the video is interrupted and it is difficult to see, and in the latter method, a buffer memory is required and the control thereof is complicated.

The present invention has been made in view of such a problem, and provides a filter operation device having a rewritable coefficient storage unit, which can suppress disturbance of video at the time of updating a coefficient. The purpose is to do.

[0017]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, the present invention provides a filter unit (3) for performing a filter operation using a predetermined coefficient on input data and outputting the result. And a rewritable coefficient storage unit (2) for writing a coefficient to be supplied to the unit in correspondence with a plurality of addresses, wherein an auxiliary coefficient generation unit for generating a fixed auxiliary coefficient not stored in the coefficient storage unit And (5) a selection unit (4) that supplies the auxiliary coefficient from the auxiliary coefficient generation unit to the filter unit instead of the coefficient from the coefficient storage unit while rewriting and updating the coefficient stored in the coefficient storage unit. ) Is provided to provide a filter operation device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A filter operation device according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of a filter operation device according to the present invention.
FIG. 2 is a block diagram illustrating a specific configuration example of a filter operation device according to the present invention. In FIG. 1, the same portions as those in FIG. 3 are denoted by the same reference numerals, and the description thereof may be omitted as appropriate.

In FIG. 1, a start signal indicating a start position of a filter operation, that is, a start position when an image is enlarged or reduced is input to an address generator 1. The address generator 1 generates an address based on the start signal and inputs the address to the coefficient storage unit 2. The coefficient storage unit 2 stores a plurality of coefficient sets, and is composed of a random access memory (RAM) whose storage contents can be updated. The coefficient storage unit 2 shares a data write terminal and a data read terminal.

The coefficient storage unit 2 stores coefficient data to be stored in the coefficient storage unit 2, a write address for specifying an address for writing the coefficient data, and a write control signal (write enable signal) for permitting writing of the coefficient data. Is entered. When an address is input from the address generator 1 after the coefficient data is written into the coefficient storage unit 2, the coefficient storage unit 2 generates coefficient data specified by the address and inputs the coefficient data to the selection unit 4. In this example, since the number of taps of the filter operation device is 2, the coefficient storage unit 2 generates two coefficients, a coefficient Cn and a coefficient Dn.

The selector 4 receives two coefficients Cn 'and Dn' from the auxiliary coefficient generator 5. A write control signal input to the coefficient storage unit 2 is also input to the selection unit 4. The selection unit 4 keeps the coefficients Cn and Dn in the coefficient storage unit 2 while the write control signal is being input.
Is updated, the coefficient Cn 'is selected instead of the coefficient Cn, and the coefficient Dn' is selected instead of the coefficient Dn. If the high level is a write control signal (write enable signal) and the low level is a read control signal (read enable signal) as the control signals to be input to the coefficient storage unit 2, the selection unit 4 will be able to operate while the high level is being input. Medium, coefficient C
What is necessary is just to comprise so that n 'and Dn' may be output.

As described above, the selection unit 4 normally inputs the coefficients Cn and Dn from the coefficient storage unit 2 to the filter unit 3 and only updates the coefficients Cn and Dn in the coefficient storage unit 2 Inputs the coefficients Cn 'and Dn' to the filter unit 3. The coefficients Cn 'and Dn' need to be normalized, and Cn '+ Dn' is 1.

The video signal to be subjected to the filter operation is input to the filter unit 3 as input data. The filter unit 3 uses the two coefficients Cn and Dn or Cn 'and Dn' input from the coefficient storage unit 2 to perform a filter operation on the input video signal and output it. The specific configuration and operation of the filter unit 3 are as described with reference to FIG.

Here, a specific configuration example of the selection unit 4 and the auxiliary coefficient generation unit 5 will be described with reference to FIG. The auxiliary coefficient generator 5 includes an auxiliary coefficient generator 5 for generating a coefficient Cn '.
1 and an auxiliary coefficient generator 52 for generating a coefficient Dn '. The selector 4 includes a selector 41 for selecting the coefficient Cn and the coefficient Cn ', and a selector 42 for selecting the coefficient Dn and the coefficient Dn'.

As described above, the coefficients Cn, D in the coefficient storage unit 2
While n is being updated, fixed coefficients Cn 'and Dn' are input to the filter unit 3, so that the interpolation phase is constant. Therefore, the image is not displayed as shaking (image distortion) on the screen, and the adverse effect on the visual can be greatly reduced. The coefficients Cn 'and Dn' may be arbitrary as long as they are normalized, but may be 0 and 1 or vice versa. Setting the coefficients Cn 'and Dn' to 0 or 1 simply requires a low level (ground level) or a high level. Therefore, the auxiliary coefficient generators 51 and 52 may have an extremely simple configuration. it can. Further, since no rounding error occurs in the arithmetic processing in the filter unit 3, it can be said that the coefficient is a preferable coefficient. The coefficients Cn 'and Dn' may be changed as appropriate.

The present invention is not limited to the above-described embodiment, and can be variously modified without departing from the gist of the present invention. In the present embodiment, an example is shown in which the filter operation device is used for a scaling device. However, the filter operation device may be used for other purposes.

[0027]

As described above in detail, the filter operation device of the present invention rewrites the coefficient stored in the coefficient storage section and the auxiliary coefficient generation section for generating a fixed auxiliary coefficient not stored in the coefficient storage section. During the update, a selector is provided to supply the auxiliary coefficient from the auxiliary coefficient generator to the filter instead of the coefficient from the coefficient storage, so that the disturbance of the video image at the time of updating the coefficient can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration example of the present invention.

FIG. 3 is a block diagram showing a conventional example.

FIG. 4 is a diagram for explaining an operation of an interpolation operation by the filter operation device.

FIG. 5 is a diagram showing an example of filter coefficients stored in a coefficient storage unit 2 in FIGS. 1 and 3;

FIG. 6 is a block diagram showing a specific configuration of a filter unit 3 in FIGS. 1 and 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Address generator 2 Coefficient storage part 3 Filter part 4 Selection part 5 Auxiliary coefficient generation part 41,42 Selector 51,52 Auxiliary coefficient generator

Claims (1)

[Claims] 1. A filter unit for performing a filter operation using a predetermined coefficient on input data and outputting the result, and a rewritable coefficient storage unit for writing a coefficient to be supplied to the filter unit in correspondence with a plurality of addresses. An auxiliary coefficient generating unit that generates a fixed auxiliary coefficient that is not stored in the coefficient storage unit, and replaces a coefficient stored in the coefficient storage unit with a coefficient from the coefficient storage unit while updating the updated coefficient. And a selector for supplying an auxiliary coefficient from the auxiliary coefficient generator to the filter unit.