JP2000050212A - Image display device and image display method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a converted image with high image quality when converting an interlace signal into a non-interlaced signal. SOLUTION: An interpolation system selection section 4 applies threshold level processing to an inter-frame difference for each pixel calculated by an inter-frame difference calculation section 2 and to an in-frame difference for each pixel calculated by an in-frame difference calculation section 3 respectively, and selects one system among three interpolation systems as inter-field interpolation 7, in-field interpolation 8 and median interpolation 9 depending on the processing result. A motion vector calculation section 5 calculates a motion vector in unit of blocks and provides an output of it to a threshold level control section 6. The threshold level control section 6 controls the threshold level used by an interpolation system selection section 4, depending on a magnitude of the motion vector in unit of blocks. A scanning line conversion section 10 uses the interpolation system selected by the interpolation system selection section 4 to interpolate the image and provides the output of a non-interlaced signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device and an image display method, and more particularly to an image display method for converting an interlaced image signal into a non-interlaced image and displaying the converted image signal.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing a configuration of an interlaced image. An image signal from a television or the like performs interlaced scanning called interlaced scanning, and one frame is composed of a set of an odd field and an even field. On a TV (television) monitor, odd and even fields are alternately scanned every 1/60 second, and the frame image changes every 1/30 second. On the other hand, a display monitor in an information processing system such as a PC (personal computer) has a frame structure by non-interlaced scanning as shown in FIG.

Therefore, when displaying a TV image or an interlaced image encoded by MPEG2 or the like on a monitor of a PC or the like, it is necessary to convert interlaced to non-interlaced. The simplest method for converting from interlace to non-interlace is an inter-field interpolation method in which two fields shown in FIG. 5 are combined into one frame. In this method, as shown in FIG. 7, a pixel Y to be interpolated (pixel to be interpolated) Y is replaced with a pixel value X24 one field before.

There is also known an intra-field interpolation method in which interpolation is performed using pixel values of upper and lower lines in the same field.
This means that, as shown in FIG. 8, the pixel Y to be interpolated is determined by the pixel value X33 of the upper line and the pixel value X
This method replaces the average value with 35. FIG. 9 illustrates median interpolation. In this method, the pixel Y to be interpolated is replaced with the median of the pixel values X33 and X35 of the upper and lower lines in the same field and the pixel value X24 of the previous field.

[0005] An interlace / non-interlace conversion method for adaptively selecting some interpolation methods is described in Japanese Patent Application Laid-Open No. 6-315140. As shown in FIG. 10, in this interlaced / non-interlaced conversion system, first motion detecting means 12 for detecting the motion of the current field and the previous field, and second motion detecting means for detecting the motion of the current field and the subsequent field. Means 13 for comparing the two motion detection signals with a predetermined still image level and a predetermined moving image level and outputting a control signal;
And an interpolation means 15 for selecting and interpolating an interpolation method based on the control signal obtained by the comparison means.

The conventional interlace / non-interlace conversion system having such a configuration operates as follows.
That is, three types of interpolation methods, that is, inter-field interpolation from either the previous field or the subsequent field, interpolation using the pixel average value of the previous field and the subsequent field, and interpolation from the pixel average values from the upper and lower two lines of the current field are used for motion detection. We select adaptively according to the results.

[0007]

The problem of the conventional system is that when the system for adaptively selecting the interpolation system is used, deterioration occurs due to switching of the interpolation system. The reason is that, since the interpolation method is independently selected for each pixel based on the amount of motion for each pixel, there is no continuity in the determination of the interpolation method. Another reason is that it is difficult to determine a threshold value as a criterion for switching, and an erroneous determination is made near the threshold value, so that an appropriate interpolation method cannot be selected.

An object of the present invention is to provide an image display apparatus and an image display method which can select an appropriate interpolation method without causing deterioration due to switching of the interpolation method.

[0009]

According to the present invention, there is provided an image display apparatus for converting an interlaced input image signal into a non-interlaced image signal and displaying the converted signal.
Inter-field interpolation means for interpolating with pixel data at the same position in the previous field, intra-field interpolation means for interpolating with pixel data of upper and lower lines of the same field, and pixel data of upper and lower lines of the same field and the same position of the previous field Median interpolation means for interpolating at the median of the data,
An inter-frame difference calculating means for calculating a difference value D1 from the pixel data of the previous frame, an intra-field difference calculating means for calculating a difference value D2 between upper and lower lines of the same field, and threshold processing of each of the difference values D1 and D2 And, according to the result, the inter-field interpolation means, the intra-field interpolation means, and the interpolation method selection means for selectively deriving each output of the median value interpolation means, and the threshold value used in the interpolation method selection means are An image display device characterized by including threshold control means for adaptively controlling according to a motion vector obtained for each block of the input image signal.

And a motion compensation type coded image decoding unit which receives the input image signal as an input, wherein the motion vector detection unit converts the motion vector in block units obtained by the motion compensation type coded image decoding unit into a motion vector. A vector detection output, and the threshold value control means is configured to generate first and second threshold values T1 and T2 that change in inverse proportion to the motion vector, and the interpolation method selection means includes: , D2> T2, the output of the median interpolation means is selected, and in the case of D2 ≦ T2, the output of the intra-field interpolation means if D1> T1, and the inter-field interpolation means if D1 ≦ T1. It is characterized in that it is configured to select the output of each means.

According to the present invention, there is provided an image display method for converting an interlaced input image signal into a non-interlaced image signal and displaying the converted image signal, wherein the frame calculates a difference value D1 from pixel data of a previous frame. Calculating the difference between the two, and the difference value D2 between the upper and lower lines of the same field
And a threshold value process for each of the difference values D1 and D2, and an interpolation method for selecting one of an inter-field interpolation method, an intra-field interpolation method, and a median value interpolation method according to the result. An image display method comprising: a selection step; and a threshold control step of adaptively controlling a threshold value used in the interpolation method selection step in accordance with a motion vector obtained for each block of the input image signal. .

And a motion compensation type coded image decoding step in which the input image signal is input, wherein the motion vector is a block unit motion vector obtained in the motion compensation type coded image decoding step. The threshold value controlling step includes generating first and second threshold values T1 and T2 that change in inverse proportion to the motion vector, and the interpolation method selecting step includes the step of selecting the median value when D2> T2. Selecting an interpolation method, and D2 ≦ T2
Wherein the step of selecting the intra-field interpolation method if D1> T1, and the step of selecting the inter-field interpolation method if D1 ≦ T1.

The operation of the present invention will be described. In the present invention, the interpolation method determination threshold is adaptively controlled according to the magnitude of the motion vector. More specifically, when it is determined that the motion is large by the motion vector obtained from the motion vector calculation result, the intra-field is determined. To make it easier to select the interpolation,
The threshold for selecting the interpolation method is changed. When selecting the interpolation method by performing threshold processing on the motion amount for each pixel, the threshold value is adaptively controlled for each block according to the magnitude of the motion vector, so that more accurate selection can be performed. In addition, since the threshold value is controlled in units of blocks, continuity occurs in the selection of the interpolation method as compared with the determination based only on the amount of motion in units of pixels, and deterioration due to frequent switching can be suppressed.

[0014]

Next, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG.
In the first embodiment of the present invention, a frame memory 1 and an inter-frame difference calculator 2 for calculating a difference from a previous frame are described.
An intra-field difference calculator 3 for calculating a difference between upper and lower lines in the same field, an interpolation method selector 4 for selecting an interpolation method on a pixel basis based on the intra-frame difference value and the inter-field difference value, A motion vector calculation unit 5 for calculating a motion vector in a block unit including a plurality of predetermined pixels; and an interpolation method selection unit 4 according to the size of the motion vector
Threshold control unit 6 that adaptively controls the threshold value used in each block, inter-field interpolation unit 7 that interpolates with pixel data at the same position one field before, and intra-field interpolation unit that interpolates with the average value of upper and lower lines of the same field 8, a median value interpolating unit 9 for interpolating the upper and lower lines of the same field with the median value of the pixel value one field before, and a scanning line converting unit 10 for performing scanning line conversion using the selected interpolation method. .

The interpolation method selection unit 4 performs threshold processing on the inter-frame difference calculated by the inter-frame difference calculation unit 2 and the intra-field difference calculated by the intra-field difference calculation unit 3, respectively. , Intra-field interpolation 8 and median value interpolation 9 are selected.

Now, assuming that the inter-frame difference calculated by the inter-frame difference calculation section 2 is D1, the intra-field difference calculated by the intra-field difference calculation section 3 is D2, and the thresholds used by the interpolation scheme selection section 4 are T1 and T2. When D1 ≦ T1 and D2 ≦ T2, it is determined that the region is a still region, and the inter-field interpolation 7 is selected. If D1 ≦ T1 and D2> T2, there is a possibility that a boundary exists even though the area is a stationary area, so the median interpolation 9 is selected. When D1> T1 and D2 ≦ T2, the intra-field interpolation 8 is selected as the moving area. When D1> T1 and D2> T2, median value interpolation is selected because it is a moving area and there is a possibility that a boundary exists.

The motion vector calculation unit 5 divides the image into blocks each including a plurality of pixels such as 8 × 8 pixels, calculates a motion vector for each block, and outputs the calculated motion vectors to the threshold control unit 6. When the interlace signal, which is an input image signal, is obtained by decoding an image subjected to motion compensation type image compression such as MPEG2, a motion vector obtained in a decoding process may be used.

The threshold value control unit 6 determines threshold values T1 and T2 used by the interpolation method selection unit 4 for each block according to the magnitude of the motion vector. As a method of determining the threshold values T1 and T2, for example, the relationship between the motion vector and the threshold value T1 is shown in FIG.
The threshold value T1 used in the interpolation method selection unit 4 is determined according to the magnitude of the motion vector as shown in FIG. That is, when the magnitude of the motion vector is large, the threshold value of T1 is reduced. The relationship between the thresholds T1 and T2 is determined as shown in FIG. 2B, and the value of the threshold T2 is determined according to the value of the threshold T1. Accordingly, when the motion vector is large, the threshold values T1 and T2 are controlled to be small. Therefore, when the motion vector is large, it is easy to select the intra-field interpolation.

If the relationship between the motion vector and the threshold values T1 and T2 is determined so as to make it easy to select intra-field interpolation when the motion vector is large, FIGS. 2 (a) and 2 (b)
Other relationships may be used. In addition, as a specific method of calculating the thresholds T1 and T2, the thresholds T1 and T2 can be calculated from a relational expression, and by indexing a table of the thresholds T1 and T2 prepared in advance according to the value of the motion vector, The thresholds T1 and T2 may be determined.

Next, the operation of the embodiment of the present invention will be described with reference to the flowchart of FIG. In step S1, the motion vector calculation unit 5 divides an input image signal into blocks each including a plurality of pixels and calculates a motion vector in block units. The calculated value of the motion vector is sent to the threshold controller 6. First, in step S2, the threshold control unit 6 obtains a threshold T1 according to the value of the motion vector calculated in step S1, from the relationship between the motion vector shown in FIG. 2A and the threshold T1. Next, in step S3, based on the relationship between the threshold values T1 and T2 shown in FIG.
The threshold value T2 is determined according to the threshold value T1 obtained in step S2.

Then, in step S4, the inter-frame difference value D1 is calculated in step S5.
2 are calculated by the inter-frame difference calculator 2 and the intra-field difference calculator 3 respectively. The interpolation method selection unit 4 determines an interpolation method based on the threshold values T1 and T2, the inter-frame difference value D1, and the intra-field difference value D2 calculated in steps S2 to S4.

That is, first, in step S6,
The in-field difference value D2 is compared with the threshold value T2. If D2 is equal to or smaller than T2, the process proceeds to step S7. Step S7
Then, the inter-frame difference value D1 is compared with the threshold value T1, and D
If 1 is greater than T1, the process proceeds to step S9 to perform intra-field interpolation. If D1 is equal to or less than T1, step S
Proceed to 8 to perform inter-field interpolation. Step S6
If D2 is greater than T2, the flow advances to step S10 to perform median value interpolation.

In step S11, it is checked whether or not the processing in units of blocks has been completed. If not, the flow returns to step S4, and the processing in units of blocks in steps S4 to S11 is repeated.

FIG. 4 is a block diagram showing another embodiment of the present invention, and the same parts as those in FIG. 1 are denoted by the same reference numerals. In this example, instead of the motion vector calculation unit 5 in FIG.
The motion vector obtained by the motion-compensated coded image decoding unit 11 is used. As a result, the calculation amount of the motion vector calculation can be significantly reduced.

[0025]

The first effect is that the outline of the moving object is doubled, the resolution is reduced, and the thin line disappears.
That is, a high-quality converted image can be obtained while suppressing deterioration due to the interpolation method. The reason is that a suitable interpolation method is selected from among inter-field interpolation, intra-field interpolation, and median value interpolation.

The second effect is that the interpolation method varies,
It does not cause deterioration due to improperness. The reason is that the threshold is controlled so that it is easy to select the intra-field interpolation in the moving area in consideration of not only the inter-frame difference value and the intra-field difference value in pixel units but also the size of the motion vector in block units as a means of motion judgment. It is because. Also, by performing control in accordance with the magnitude of the motion vector in block units other than the difference value in pixel units, continuity for each region occurs in the interpolation method.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of a control mode for a threshold T1 and a motion vector of T2 in a threshold controller 6;

FIG. 3 is a flowchart showing the operation of the block in FIG. 1;

FIG. 4 is a block diagram showing a configuration of another embodiment of the present invention.

FIG. 5 is a diagram showing interlaced scanning.

FIG. 6 is a diagram illustrating non-interlaced scanning.

FIG. 7 is a diagram showing inter-field interpolation;

FIG. 8 is a diagram showing intra-field interpolation.

FIG. 9 is a diagram showing median value interpolation.

FIG. 10 is a block diagram showing a configuration of a conventional system.

[Explanation of symbols]

 Reference Signs List 1 frame memory 2 inter-frame difference calculation unit 3 intra-field difference calculation unit 4 interpolation method selection unit 5 motion vector calculation unit 6 threshold control unit 7 inter-field interpolation unit 8 intra-field interpolation unit 9 median value interpolation unit 10 scan line conversion unit 11 Motion compensated coded image decoding unit

Claims (6)

[Claims] 1. An image display device for converting an interlaced input image signal into a non-interlaced image signal and displaying the converted image signal, wherein an inter-field interpolating means for interpolating with pixel data at the same position in a previous field, and the same field In-field interpolation means for interpolating with the pixel data of the upper and lower lines, median interpolating means for interpolating with the median of the pixel data of the upper and lower lines of the same field and the pixel data at the same position of the previous field, and pixel data of the previous frame. An inter-frame difference calculating means for calculating a difference value D1 of the same, an intra-field difference calculating means for calculating a difference value D2 of the upper and lower lines of the same field, and a threshold value process for each of the difference values D1 and D2. Output between the inter-field interpolation means, the intra-field interpolation means and the median value interpolation means. An image display comprising: an interpolation method selecting means for deriving; and a threshold control means for adaptively controlling a threshold value used in the interpolation method selecting means in accordance with a motion vector obtained for each block of the input image signal. apparatus. 2. The apparatus according to claim 1, further comprising a motion-compensated coded image decoding unit that receives the input image signal as an input, wherein the motion vector detecting unit operable to move a block-based motion vector obtained by the motion-compensated coded image decoding unit. 2. The image display device according to claim 1, wherein the output is a vector detection output. 3. The threshold value control means is configured to generate first and second threshold values T1 and T2 that change in inverse proportion to the motion vector.
> T2, the output of the median value interpolation means is selected and D
In the case of 2 ≦ T2, the output of the intra-field interpolation means is selected if D1> T1, and the output of the inter-field interpolation means is selected if D1 ≦ T1. Item 3. The image display device according to item 1 or 2. 4. An image display method for converting an interlaced input image signal into a non-interlaced image signal and displaying the converted image signal, the method comprising: calculating a difference value D1 from pixel data of a previous frame; An intra-field difference calculating step of calculating a difference value D2 between the upper and lower lines of the same field; a threshold value process for each of the difference values D1 and D2; An interpolation method selection step of selecting one of the interpolation methods, and a threshold value control step of adaptively controlling a threshold value used in the interpolation method selection step in accordance with a motion vector obtained for each block of the input image signal. An image display method characterized by the following. 5. A motion-compensated coded image decoding step which receives the input image signal as an input, wherein the motion vector is a block-unit motion vector obtained in the motion-compensated coded image decoding step. The image display method according to claim 4, characterized in that: 6. The threshold control step includes generating first and second threshold values T1 and T2 that change in inverse proportion to the motion vector, and the interpolation method selecting step includes:
Selecting the median interpolation method when> T2, and selecting the intra-field interpolation method if D1> T1 when D2 ≦ T2, and selecting the inter-field interpolation method if D1 ≦ T1 6. The image display method according to claim 4, further comprising the step of: