JPH11112941A - Interpolation method in vertical direction of television signal, aspect ratio conversion method, and frame image picture configuration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain reduction of dispersion in vertical frequency characteristics by deciding a position of each scanning line of an inter-line image and interpolating, so that a position of a scanning line after interpolation and a corresponding position and distance of each scanning line before the interpolation become almost constant. SOLUTION: A television signal inputted from an input terminal 10 of a device is transmitted to a synchronizing separation circuit 70 and is applied for a time shift for a one horizontal scanning period by a line memory 30. The number of line of a picture after interpolation is counted, based on the horizontal and a vertical synchronizing signal obtained at the synchronizing separation circuit 70. A coefficient control circuit 90 generates values, in which coefficients (p) and (q) become (7/8, 1/8), (1/8,7/8), (3/8, 5/8) and (5/8, 3/8), so that a distance to a scanning line to which an original image corresponds becomes 1/8, 1/8 and 3/8. Constant multipliers 40 and 50 multiply the coefficients to a signal before the one horizontal scanning period of the original picture corresponding to each and the present signal, and an adder 60 performs an output addition of the constant multipliers 40 and 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical interpolation method of a television signal suitable for application to AV equipment such as a television receiver and an optical disk reproducing apparatus.
The present invention relates to a technique for obtaining a high-quality frame image from an aspect ratio conversion and a field image.

[0002]

2. Description of the Related Art A conventional method for vertically interpolating television signals will be described below with reference to FIGS. 1, 2, 3 and 4. FIG. In the following, interpolation is performed in the vertical direction from a letterbox image having an aspect ratio of 4: 3 (an image having an effective image area having an aspect ratio of 16: 9 in which a non-image portion exists in the vertical direction by 1/8 of the entire vertical direction). An example will be described in which a squeeze image having an aspect ratio of 4: 3 (an image which is viewed vertically on a television having an aspect ratio of 4: 3) is obtained.

FIG. 1A shows a line position of an original image. In the conventional method, as shown in FIG. 1B, a specific line of the interpolated image is matched with the corresponding line of the original image, and the line interpolation is sequentially performed from the corresponding upper and lower lines of the original image. It was common to go.

FIG. 2 shows a typical circuit configuration for performing the interpolation operation shown in FIG. 1 using linear interpolation. The television signal input from the input terminal 10 of the apparatus is sent to the sync separation circuit 70 and the line memory 30 performs a time shift of one horizontal scanning period. The line counter 80 counts the line numbers of the interpolated image based on the horizontal and vertical synchronization signals obtained by the synchronization separation circuit 70. The count control circuit 90 generates a coefficient according to the line number from the line counter 80, and controls the constant multipliers 40 and 50. Each of the constant multipliers 40 and 50 multiplies the signal of the corresponding original image one horizontal scanning period before and the current signal by a coefficient and outputs the result. The adder 60 adds and outputs the outputs of the constant multipliers 40 and 50, and outputs the result from the output terminal 20 of the device as an output signal.

FIG. 3A shows a coefficient control circuit 9 shown in FIG.
FIG. 9 is a diagram illustrating the order in which coefficients of 0 occur. In the coefficient control circuit 90, as shown in FIG. 1B, the coefficients p and q are set so that the distance from the corresponding scanning line of the original image is 1/4, 1/2, 3/4, 0. 1/4, 3/4), (1/2, 1
/ 2), (3/4, 1/4), (1, 0).

[0006]

FIG. 1 (b) and FIG.
The vertical interpolation method shown in FIG. 3A and FIG. 3A is an aspect ratio conversion method conventionally used.
However, in such a configuration, since the frequency characteristics differ depending on the distance from the line of the original image corresponding to the interpolation line, the high-frequency component in the vertical direction differs significantly depending on the interpolation line. That is, the resolution in the vertical direction is sufficiently increased as the interpolation line is closer to the line of the original image, but the resolution is deteriorated as the interpolation line is farther from the line of the original image. FIG. 4 is a diagram illustrating a vertical frequency characteristic when interpolation is performed in the vertical direction using linear interpolation. When the line of the original image is output as it is, the frequency characteristic of the original image is maintained as shown in FIG. 9A, but as the distance from the line of the original image increases, as shown in FIG. When the vertical frequency characteristic is degraded and the center between the original images is obtained by linear interpolation, the vertical frequency characteristic becomes the worst as shown by the line C in FIG.

[0007] As shown in FIG. 1B, when the positions at which the distances from the original image are 1/4, 1/2, 3/4, and 0 are obtained by interpolation, FIG. Lines having various frequency characteristics indicated by lines A to C shown in FIG. 4A are periodically obtained as interpolation lines repeatedly. That is, an interpolated image whose frequency characteristic changes greatly from A to C in FIG. As a result, the screen after interpolation, such as when panning the screen in which the entire screen contains many high-frequency components such as lawn or sand, in the vertical direction,
Since the frequency characteristics in the vertical direction are different for each line, there is a problem that the image quality is remarkably degraded such that the screen looks jerky in the vertical direction.

In order to solve such a problem,
There are methods such as polynomial interpolation to increase the accuracy of interpolation to prevent the deterioration of the vertical frequency after interpolation.However, the number of taps of the interpolation filter necessary for interpolation in the vertical direction and the length of operation words are increased. Growth was a challenge.

[0009]

In the vertical interpolation method of a television signal according to the present invention, the position of each line after interpolation is selected so that the distance from the corresponding line of the original image is substantially constant, and the position after interpolation is selected. Interpolation is performed such that the vertical frequency characteristics of each line are substantially constant.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is such that the distance between each line position after interpolation and the position of each corresponding line before interpolation is substantially constant. Since the interpolation is performed by determining the relative position, it is possible to minimize the variation of the vertical frequency characteristics between the respective lines after the interpolation, and when the screen having many high frequency components is panned, etc. However, it has an effect that a high-quality image free from roughness can be obtained.

According to a second aspect of the present invention, when a squeezed image having an aspect ratio of 4: 3 is formed by performing vertical interpolation from a letterbox image having an aspect ratio of 4: 3, Since the positions of the scanning lines of the interpolated image are configured so that the distance between the position of the line and the position of each corresponding line before interpolation is substantially constant, variations in the vertical frequency characteristics of each line after interpolation are minimized. It is possible to obtain a high-quality image with no roughness even when a screen having many high-frequency components is panned.

According to a third aspect of the present invention, when a frame image is constructed by performing vertical interpolation from a field image of a television signal, the position of each line after interpolation corresponds to the position before interpolation. Since the positions of the lines of the interpolated image are configured so that the distance from the position of each line is constant, it is possible to make the variation of the vertical frequency characteristic between the lines after interpolation constant, and there are many high frequency components. This has the effect that a high-quality image free from roughness can be obtained even when the screen is panned.

An embodiment of the present invention will be described below with reference to FIG. (Embodiment 1) FIG. 1C shows an embodiment of the present invention. In the television signal interpolation method according to the present invention, the positions of the scanning lines of the interpolated image are arranged so as to be shifted from the original image (in FIG. 1C, the scanning line is set upward by 1/8).
With this configuration, the distance between each scanning line of the interpolation image and the corresponding scanning line of the original image is 1/8, as shown in FIG.
1/8, 3/8, and 3/8, and the change in the distance between each scanning line and the scanning line of the original image can be reduced to (3 / 8-1 / 8 = 1/4). FIG. 4B is a diagram showing the vertical frequency characteristics of each line at this time, and a change in the vertical frequency characteristics can be reduced as indicated by the lines D and E shown in FIG. 4B. As a result, it is possible to obtain a high-quality image free from roughness even when a screen having many high-frequency components is panned.

The circuit configuration according to the present invention also includes:
Since the present embodiment can be implemented only by changing the coefficient control method as in the conventional example, the configuration can be exactly the same as the configuration shown in FIG. FIG. 3B is a diagram showing the order in which the coefficients are generated by the coefficient control circuit 90 in FIG. In the coefficient control circuit 90, FIG.
As shown in (c), the coefficients p and q are set to (7/8, 1) so that the distance from the corresponding scanning line of the original image becomes 1/8, 1/8, 3/8, and 3/8. / 8), (1/8, 7/8),
The values (3/8, 5/8) and (5/8, 3/8) are generated.

(Embodiment 2) FIG. 5 shows another embodiment of the present invention, which is applied to a case where a frame image is formed from a field image. FIG. 5A shows lines constituting a field image, FIG. 5B shows a method of constructing a frame image according to a conventional method, and FIG. 5C shows a method of constructing a frame image according to the present invention. . Conventionally, as shown in FIG.
It has been common practice to output the same lines as the original image and obtain the center of each line by interpolation to form a frame image. However, as described in FIG. Notable among. Therefore, the interpolation method according to the present invention is configured not to directly output the lines of the original image, but to obtain lines shifted by 1/4 by interpolation. At this time, another line to be obtained by interpolation is １ ／ of the original image as shown in FIG.
At a distance of Accordingly, in this case, all the lines of the interpolation image are equidistant from the original image, and the vertical frequency characteristics are always constant. As a result,
Even when a screen having many high-frequency components is panned, it is possible to obtain a high-quality image without any noise.

In the above embodiment, the case where the frame image is formed from the conversion of the aspect ratio and the field image has been described as an example. However, when the number of lines is increased by performing the interpolation in the vertical direction, for example, the NTSC system is used. It goes without saying that the applicable range such as conversion to the PAL system or the HDTV system is naturally included. In the present invention, the case where the number of lines is increased by performing interpolation in the vertical direction has been described. However, the present invention can be similarly applied to the case where the number of lines is reduced while performing interpolation in the vertical direction. It is self-evident.

[0017]

As described above, according to the present invention, even when a television signal is vertically interpolated to convert the aspect ratio, or when a frame image is constructed from a field image by vertical interpolation, Since the distance between the position of each line after interpolation and the position of the corresponding line before interpolation is almost constant, the relative position of each line is determined and interpolation is performed. The advantage that the variation of the vertical frequency characteristic between lines can be minimized, and a high-quality image without roughness can be obtained even when a screen having many high-frequency components is panned. Can be Further, since the position of the interpolation line can be determined only by changing the coefficient at the time of interpolation, an advantageous effect that it can be realized with the same circuit configuration as in the related art is obtained.

[Brief description of the drawings]

FIG. 1 is a comparative explanatory diagram showing an operation according to a first embodiment of the present invention and an operation according to a conventional method.

FIG. 2 is a block diagram of a circuit configuration used for a vertical interpolation method.

FIG. 3 is a diagram showing a coefficient generation order of a coefficient control circuit 90 shown in FIG. 2;

FIG. 4 is a frequency characteristic diagram showing deterioration of vertical frequency characteristics caused by vertical interpolation.

FIG. 5 is an explanatory diagram showing an operation according to the second embodiment of the present invention and an operation according to a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Input terminal 20 Output terminal 30 Line memory 40, 50 Constant multiplier 60 Adder 70 Synchronization separation circuit 80 Line counter 90 Coefficient control circuit

Claims (3)

[Claims] When the number of lines is increased by vertically interpolating scanning lines of an original image, the distance between the position of each scanning line after interpolation and the position of each corresponding scanning line before interpolation is substantially constant. A method of vertically interpolating a television signal, wherein a position of each scanning line of an interpolated image is determined and interpolated. 2. When a vertical squeeze image having an aspect ratio of 4: 3 is formed by performing vertical interpolation from a letterbox image having an aspect ratio of 4: 3, the position of each scanning line after interpolation and the corresponding position before interpolation are provided. A method for converting the aspect ratio of a television signal, wherein a position of a scanning line of an interpolation image is configured such that a distance from the position of each scanning line is substantially constant. 3. When a frame image is constructed by performing vertical interpolation from a field image of a television signal, the distance between the position of each scanning line after interpolation and the position of each corresponding scanning line before interpolation is determined. A method of constructing a frame image of a television signal, wherein the positions of scanning lines of an interpolation image are configured to be constant.