JP2001251591A - Aspect ratio conversion circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the deviation from circularity at a point near the center of an image, without having to change the aspect ratio (4:3) of the image as a whole and to reduce the impression of elongation of the image to an observer in regard to an image applied product that shows an image, that is acquired by converting a material image of 16:9 aspect ratio of an HDTV signal, etc., into an image of 4:3 aspect ratio of an NTSC signal, etc. SOLUTION: The aspect ratio of an image is selected stepwise, according to the horizontal areas of the image and these areas are converted so that they have different aspect ratios. The number of horizontal pixels is adjusted to secure a 16:9 aspect ratio equal to that of a material image at a point near the center of the screen of a displayed image, and the number of horizontal pixels is decreased to be close to the right and left ends of the screen. Thus, the 16:9 aspect ratio is converted stepwise into a 4:3 aspect ratio or smaller. As a result, the deviation from circularity is improved at a point near the center of screen, without having to change the aspect ratio of the overall image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to convert a TV signal having a given aspect ratio into a TV signal having a different aspect ratio in an image application product such as a television (hereinafter, TV) receiver or a TV conference system. And an aspect ratio conversion circuit.

[0002]

2. Description of the Related Art With the spread of HDTV, H
There is an increasing number of occasions in which a DTV signal is used for recording and then the material image is converted to an NTSC signal for use. in this case,
Since the aspect ratio of HDTV is 16: 9, N
If the display device that displays the TSC signal has an aspect ratio of 16: 9 such as a wide TV, the roundness of the image (expressed by the degree of distortion when a circle is displayed on the image) is maintained. However, when a conventional display device having an aspect ratio of 4: 3 is used, the image becomes a vertically long image as shown in FIGS. 1A and 1B, and the roundness is impaired.

In order to avoid this problem, in the prior art, both ends of an image are cut off (FIG. 1C) or the image is compressed in the vertical direction and converted to 16: 9, and there is no upper and lower part of the image. The roundness of the image is maintained by the method of adding an image portion (FIG. 1D) (see, for example,
-98354, JP-A-2-145882, and JP-A-5-316449).

A problem with this method is that a 4: 3 aspect ratio image obtained by converting a 16: 9 aspect ratio material image such as an HDTV signal into an NTSC signal is used in a 4: 3 aspect ratio display device. If the image is displayed without dropping the entire image or adding no image portion,
That is, the entire image becomes vertically long. The reason is that, in order to convert the image into a 4: 3 image without dropping the entire image or without adding a non-image portion, the aspect ratio conversion is performed uniformly over the entire region of the image. Is deteriorated.

Therefore, in the prior art, FIG.
As shown in FIG.
When converting the image into a 3 aspect ratio, the image is enlarged once to a normal 16: 9 aspect ratio image which is not a letterbox, and then thinned while increasing the thinning rate from the center to the both ends of the image. It has been proposed to maintain the roundness (Japanese Patent Application Laid-Open Nos. 8-331520 and 10-117295). According to this method, the roundness in the vicinity of the center of the image can be increased without changing the aspect ratio of the entire image of 4: 3, and the vertical feeling of the image perceived by the observer of the image can be reduced.

[0006]

However, the problem with this method is that the hardware scale must be increased and the operating clock must be speeded up. The increase in hardware scale is due to the need to temporarily convert the image to a 16: 9 aspect ratio. Also, it is necessary to increase the speed of the operation clock because the conversion increases the number of pixels included in one horizontal period, and it is impossible to perform actual processing without increasing the processing clock. Because it becomes.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method such as an HDTV signal.
In converting a material image having a 6: 9 aspect ratio into an image having a 4: 3 aspect ratio such as an NTSC signal, a 4: 3 aspect ratio is required.
Without changing the aspect ratio of the entire image, it is possible to increase the roundness near the center of the image, reduce the vertical feeling of the image perceived by the viewer of the image, and realize it with limited scale hardware It is an object of the present invention to provide an aspect ratio conversion circuit that can perform the conversion. An object of the present invention is to provide an aspect ratio conversion circuit capable of achieving the above object without increasing the speed of an operation clock.

[0008]

SUMMARY OF THE INVENTION Generally, the aspect ratio conversion circuit of the present invention changes the aspect ratio of the entire image by switching the aspect ratio stepwise from the center of the image to the horizontal direction of the image. Instead, the roundness in the vicinity of the center of the image is improved.

More specifically, the aspect ratio conversion circuit of the present invention comprises: input signal storage means for storing effective pixels of at least one horizontal period of a digitized and componentized television signal input; Counting means driven by a clock signal synchronized with a signal and operated based on a horizontal synchronization signal synchronized with a digital television signal; and writing control means for controlling a writing operation to the input signal storage means based on the counting means. Reading control means for controlling a read operation from the input signal storage means based on the counting means, and aspect ratio selection for selecting a desired aspect ratio from a plurality of aspect ratios based on the counting means. Means for reading digital data read from the input signal storage means based on the selection of the aspect ratio selection means. Aspect ratio conversion means for increasing or decreasing the number of pixels with respect to the vision signal, output signal storage means for storing an output signal of the aspect ratio conversion means, and writing operation to the output signal storage means based on the counting means Control means for controlling the read operation, read control means for controlling a read operation from the output signal storage means based on the counting means, and a digital television signal output from the output signal storage means based on the counting means. And a synchronizing signal generating means for outputting a horizontal synchronizing signal synchronized with.

The aspect ratio conversion circuit selects the aspect ratio of the image stepwise according to the horizontal area of the image, and converts each area to a different aspect ratio. The aspect ratio conversion circuit adjusts the number of horizontal pixels in the vicinity of the center of the screen of the display image so as to have the same aspect ratio of 16: 9 as that of the material image, and decreases the number of horizontal pixels as approaching the left and right ends. The aspect ratio is converted stepwise to 4: 3 or less. As a result, the roundness in the vicinity of the center of the screen is improved, and the sense of verticalness felt by the viewer of the image is reduced.

On the other hand, the roundness at both ends of the screen is lower than that when the image is simply displayed with the aspect ratio of 4: 3. However, depending on the application, the viewer may not be conscious of the deterioration, or may be at the both ends. It is conceivable that the merit of improving the roundness near the center is greater than the demerit due to deterioration, and the present invention is suitable for use in such an image application. For example, in the case of an application that displays an image of an aquarium containing fishes, etc., the deterioration of the roundness at both ends of the image reminds the observer of the image of the distortion on the curved glass surface seen in the actual aquarium. It does not make you feel relatively uncomfortable. Therefore,
The improvement of the roundness near the center of the image is a great merit. In addition, these processes are performed on the componentized luminance or color difference signals. In either case, there is no difference in the structural features, means, and operational features.

In a preferred embodiment, the aspect ratio selection means selects an aspect ratio determined according to the horizontal position of the digitized television signal input. In another preferred embodiment, the aspect ratio conversion means performs a plurality of expansion processes or a plurality of expansion processes in the horizontal direction of the digital television signal read from the input signal storage means based on the selection of the aspect ratio selection means. Either compression processing or no processing is performed.

[0013]

Referring to FIG. 2, an aspect ratio conversion circuit according to the present invention includes an input line memory circuit 4 acting as input signal storage means, a counter circuit 5 acting as counting means, and various control circuits. , A timing generation circuit 6 acting as control means for performing the operation, an aspect ratio conversion circuit 7, and an output line memory circuit 8 acting as output signal storage means.
Having.

The aspect ratio conversion circuit has a digital TV signal input terminal 1 for inputting digitized and componentized NTSC signals. This digital T
The digital TV signal a input from the V signal input 1 is
The digital TV signal a is input to an input line memory circuit 4 for storing valid data in a scanning line. Also,
From the horizontal synchronizing signal input terminal 2, a horizontal synchronizing signal b indicating the scanning line cycle of the digital TV signal a is input. The digital TV signal a and the horizontal synchronizing signal b are synchronized with the clock signal c input from the clock input terminal 3.

The counter circuit 5 is reset by the horizontal synchronizing signal b and operates as a counting circuit driven by the clock signal c. The output count value d of the counter circuit 5 is input to the timing generation circuit 6. In the aspect ratio conversion circuit 7,
The conversion input data e output from the input line memory circuit 4 is subjected to arithmetic processing for performing interpolation or thinning according to the selection signal h output from the timing generation circuit 6, and converted output data i is output.

The timing generation circuit 6 includes: an input write control signal f for storing valid pixel data of the digital TV signal a in the input line memory circuit 4;
An input read control signal g for reading out effective pixel data stored in the input line memory circuit 4 at a required timing; and a selection signal for selecting an aspect ratio according to an effective pixel area in a scanning line. h, a filter selection signal n for selecting a filter to be used for each pixel, and an output write signal j for storing conversion output data i output from the aspect ratio conversion circuit 7 in the output line memory circuit 8. -An output read signal k for reading data stored in the output line memory circuit 8;-a horizontal line indicating a scan line cycle of the output data k in synchronization with the output data 1 read from the output line memory circuit 8. And outputs a synchronization signal output m.

In the conversion of the aspect ratio, it is considered that the image quality is improved as the aspect ratio is subdivided. In this embodiment, as shown in FIG. 5, 16: 9, 4: 3, 8: 9. ,
This is realized by switching the four aspect ratios of 4: 9 by the selection signal h. The conversion to each aspect ratio is
This can be realized by horizontal expansion by simple repetition of pixels or horizontal compression by simple thinning out of pixels, but in this embodiment, filter processing is performed, and image quality degradation due to expansion and compression is reduced. Keep as low as possible.

FIG. 3 shows details of the aspect ratio conversion circuit 7. The aspect ratio conversion circuit 7 has delay circuits 7-1 and 7-2 and a filter circuit 7-3. The converted input data e is delayed by the delay circuit 7-1 and the delay circuit 7-2 by the clock signal c and output as a delay signal y and a delay signal z. The conversion input data e, the delay data o, and the delay data p are input to the filter circuit 7-3. The filter outputs q, r, s, and t output from the filter circuit 7-3 are output as filter selection outputs u, v, w, and x corresponding to the respective aspect ratios shown in FIG. . The filter selection outputs u, v, w, and x are selected by a selection signal h and output as converted output data i.

The filter circuit 7-3 includes a coefficient circuit 7-3-
1 and an addition circuit 7-3-2 and a selection circuit 7-3-3. The signals e, y, and z are multiplied by necessary coefficients in a coefficient circuit 7-3-1.
Add by -3-2. Selection circuit 7-
In 3-3, the result selected based on the filter selection signal n is used as the filter selection output u, v,
Output as w, x. By determining the coefficient values used here so that the output pixels are apparently at equal intervals as shown in FIG. 6, deterioration due to compression and expansion of horizontal pixels can be reduced.

Next, the operation of the aspect ratio conversion circuit will be described. First, referring to FIG. 4, it is possible to change the aspect ratio of the image without changing the aspect ratio of the entire image by dividing the image into a plurality of regions in the horizontal direction and expanding or compressing each region. Will understand.
As an example, FIG. 5 shows an example of horizontal area division and respective aspect ratios. In the embodiment shown in FIG. 5, the image is a central region IV, III and V on both sides thereof, and an outer region.
It is divided into four types of regions, II and VI, and regions I and VII at both ends. The number of effective pixels in one scanning line period in this embodiment is 720 pixels generally used in digital processing of an NTSC image signal.

Next, referring to the timing chart of FIG. 7, the digital TV signal a is written into the input line memory circuit 4 by the clock signal c when the input write signal f is active (Low). The input line memory circuit 4 outputs the converted input data e by the clock signal c. At this time, if the input read control signal g is active, the read is updated to the next data. Updating of the converted input data e is performed continuously in the case of horizontal pixel compression and no processing, and is performed in bursts in the case of expansion. The reason for performing the read operation in a burst manner is to extend the data in the horizontal direction by repeatedly using the data, as can be seen from the region IV in FIG.

The conversion input data e is processed by the aspect ratio conversion circuit 7 in accordance with each of the divided areas, and the processing results corresponding to the four types of areas are selected by the selection signal h, and the conversion output data i Is output as Conversion output data i
Is written to the output line memory circuit 8 when the output write signal j is active (Low) by the clock signal c. The output write signal j becomes active when valid data is output to the converted output data i as shown in FIG. The clock signal c from the line memory circuit 8
Outputs the output data l. The output data 1 is updated when the output read signal k is active, and is output together with the horizontal synchronizing signal output m to a circuit for performing image display and the like.

The operation of the aspect ratio conversion circuit 7 will be described with reference to FIGS. As described above, the horizontal / vertical conversion circuit 7 in this embodiment performs conversion corresponding to four types of regions. These conversions are performed by processing such as compression and decompression of horizontal pixels, and are realized by calculation by multiplication and addition of coefficients for successive pixels as shown in FIG. In this embodiment, since there are a plurality of types of operations in the regions II, V and IV, necessary output pixels can be obtained by selecting the result of the operation by the filter selection signal n. The result of the operation is shown in FIG.
As shown in the above, continuous effective data can be obtained by writing valid operation data to the output line memory circuit 8 by the output write control signal j.

[0024]

As described above, according to the present invention, a plurality of regions are provided from the center of the image to the left and right of the image, and the aspect ratio of 16: 9 near the center of the screen is the same as that of the material image. The number of horizontal pixels is adjusted so that the number of horizontal pixels is reduced toward the left and right ends to gradually convert the image into an aspect ratio of 4: 3 or less. In displaying the image converted to the three aspect ratios, the roundness near the center of the image can be improved without changing the aspect ratio of the entire image. FIG. 9 shows the effect of the present invention. 1 shown in FIG.
Assuming that a 6: 9 aspect ratio image is a material image, when a 16: 9 aspect ratio image is simply a 4: 3 aspect ratio image as in the related art (FIG. 9B), a perfect circle at the center of the image is obtained. 9C, it is confirmed that the roundness in the vicinity of the center of the image is improved without changing the aspect ratio of the entire image, as can be clearly understood from FIG. 9C. . Further, according to the present invention, once 16:
Since there is no need to convert the image into a 9 aspect ratio image, the circuit can be simplified. Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that the embodiments can be appropriately changed within the technical idea of the present invention. No.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a change in circularity due to a conventional aspect ratio conversion method, in which (A) a 16: 9 aspect ratio material image is compressed, and (B) is a horizontal image compressed by a conventional method. 4: C aspect ratio image, (C) a 4: 3 aspect ratio image with left and right ends deleted by the conventional method, and (D) a 16: 9 aspect ratio image by the conventional method in the vertical direction. (E) shows a case where the image is displayed on a 4: 3 aspect ratio image by the method disclosed in Japanese Patent Application Laid-Open No. 8-331520.

FIG. 2 is a block diagram of an aspect ratio conversion circuit according to the present invention.

FIG. 3 is a block diagram of the aspect ratio conversion circuit of the aspect ratio conversion circuit shown in FIG. 2;

FIG. 4 shows an outline of an aspect ratio conversion operation by the aspect ratio conversion circuit of the present invention.

FIG. 5 shows an example of horizontal area division and aspect ratio in the aspect ratio conversion circuit of the present invention.

FIG. 6 is a diagram showing the outline of the aspect ratio conversion in the aspect ratio conversion circuit of the present invention, in which figures such as 2/3 and 1/4 indicate coefficients by which input pixels are multiplied, and double circles indicate addition. Shows the pixels obtained by

FIG. 7 is a timing chart showing an aspect ratio conversion operation in the aspect ratio conversion circuit of the present invention.

FIG. 8 is a timing chart showing the aspect ratio conversion in the aspect ratio conversion circuit of the present invention.
The operation is the same as that of .about.III.

9A and 9B show effects of the present invention in comparison with a conventional method, wherein FIG. 9A shows a material image, and FIG.
(C) shows a processed image based on the present invention when a 6: 9 aspect ratio image is simply a 4: 3 aspect ratio image.

[Explanation of symbols]

1: Digital TV signal input 2: Horizontal synchronization signal input 3: Clock input 4: Input line memory circuit (input signal storage means) 5: Counter circuit (counting means) 6: Timing generation circuit (control means, aspect ratio selection means) 7: Aspect ratio conversion circuit 8: Output line memory circuit (output signal storage means)

Claims (3)

[Claims] An aspect ratio conversion circuit for converting a television signal of a given aspect ratio to a television signal of a different aspect ratio, comprising: at least one horizontal of a digitized and componentized television signal input. Input signal storage means for storing effective pixels of a period, counting means driven by a clock signal synchronized with a digitized television signal, and operating based on a horizontal synchronization signal synchronized with a digital television signal; and the counting means A write control unit that controls a write operation to the input signal storage unit based on the control unit; a read control unit that controls a read operation from the input signal storage unit based on the count unit; Aspect ratio selecting means for selecting a desired aspect ratio from the aspect ratios of Aspect ratio conversion means for increasing or decreasing the number of pixels for the digital television signal read from the input signal storage means based on the selection of the aspect ratio selection means, and an output for storing an output signal of the aspect ratio conversion means Signal storage means; write control means for controlling a write operation to the output signal storage means based on the counting means; read control means for controlling a read operation from the output signal storage means based on the count means And a synchronizing signal generating means for outputting a horizontal synchronizing signal synchronized with the digital television signal output from the output signal storing means based on the counting means. 2. The aspect ratio conversion circuit according to claim 1, wherein said aspect ratio selection means selects an aspect ratio determined according to a horizontal position of a digitized television signal input. 3. The digital video signal read from the input signal storage means based on a selection of the aspect ratio selection means, wherein the aspect ratio conversion means performs a plurality of expansion processes or a plurality of compression processes in a horizontal direction. The aspect ratio conversion circuit according to claim 1, wherein any one of non-processing is performed.