|Publication number||USRE42656 E1|
|Application number||US 12/801,725|
|Publication date||Aug 30, 2011|
|Filing date||Jun 22, 2010|
|Priority date||Oct 20, 1995|
|Also published as||US5874937, USRE41522, USRE43641|
|Publication number||12801725, 801725, US RE42656 E1, US RE42656E1, US-E1-RE42656, USRE42656 E1, USRE42656E1|
|Original Assignee||Seiko Epson Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (54), Non-Patent Citations (10), Classifications (15)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is one of four reissue applications of U.S. Pat. No. 5,874,937. The first reissue is application Ser. No. 10/224,477 filed Aug. 21, 2002. The second reissue is application Ser. No. 11/905,507, filed Oct. 1, 2007. The third is application Ser. No. 12/222,127, filed Aug. 1, 2008. The fourth is this application, filed Jun. 22, 2010. This application also is a continuation of Reissue application Ser. No. 12/222,127, which is a continuation of Reissue application Ser. No. 11/905,507, which is a continuation of Reissue application Ser. No. 10/224,477.
1. Field of the Invention
The present invention relates to a method of and an apparatus for scaling up and down an input video image and displaying the resultant video image on a display device.
2. Description of the Related Art
In some cases, it is required to display video images generated by a computer on another display device, such as a liquid-crystal projector. In such a case, the computer should generate video signals according to the resolution of the display device. In the description of this specification, the term “resolution” implies both a number of dots (that is, a number of pixels) in a horizontal direction of a video image and a number of lines (that is, a number of scanning lines) in a vertical direction. The number of dots in the horizontal direction is referred to as the horizontal resolution, whereas the number of lines in the vertical direction is referred to as the vertical resolution.
The resolution and the number of tones of a video image generated by a computer are restricted by the capacity of a video RAM (VRAM) in the computer. The number of tones is reduced for a display with a greater resolution (that is, a larger screen size), and increased for a display with a smaller resolution. When the display device has a significantly large screen size, it may be impossible to make the resolution of a video signal generated by the computer coincident with the resolution of the display device. The similar problem arises when a video image generated by a device other than the computer (for example, a television image) is displayed on a display device other than a television receiver.
Accordingly, an object of the present invention is to convert any resolution of an input video image to a resolution of a display device and display the video image with the converted resolution.
The present invention is directed to a video image scaling apparatus for scaling up or down an input video image and displaying the scaled video image on a display device. The apparatus comprises: resolution determination means for analyzing an input video signal to determine a resolution of the input video signal; and scaling means for expanding or contracting a video image expressed by the input video signal so that the resolution of the video signal is made equal to a resolution of the display device.
Since the resolution of a display device is known, a ratio of the resolution of the input video signal to the resolution of the display device can be obtained if the resolution of the input video signal is determined. Expansion or contraction of a video image by the ratio will make the resolution of a video signal equal to the resolution of the display device.
In a preferred embodiment of the present invention, the resolution determination means comprises: resolution storage means for storing relations between the resolution of the input video signal and frequencies of synchronizing signals of the input video signal; frequency determination means for determining frequencies of the synchronizing signals of the input video signal; and means for reading out a resolution corresponding to the frequencies of the synchronizing signals from the resolution storage means.
When the relations between the resolutions of a video signal and frequencies of synchronizing signals are stored in the resolution storage means, the resolution can be readily determined according to the frequencies of the synchronizing signals.
In accordance with an aspect of the present invention, the apparatus further comprises: means for displaying a sign indicating that a resolution is unknown when the frequencies of the synchronizing signals of the input video image are not stored in the resolution storage means; and resolution setting means for setting a value of the unknown resolution of the input video signal and registering a relation between the resolution and the frequencies of the synchronizing signals of the input video signal in the resolution storage means.
This aspect allows to convert the resolution of an input image signal even if the input video signal has synchronizing signals of unknown frequencies.
The scaling means comprises: a first buffer memory for temporarily storing the input video signal; a frame memory in which a video signal read out of the first buffer memory is written; a second buffer memory for temporarily storing a video signal read out of the frame memory; and memory control means for giving a write address to the frame memory while successively reading out video signals from the first buffer memory to write the video signal read out of the first buffer memory into the frame memory, and for giving a read address to the frame memory to read out the video signal from the frame memory and transfer the video signal to the second buffer memory, and wherein the memory control means comprises: means for expanding or contracting a video image read out of the frame memory by adjusting the read address given to the frame memory.
The present invention is also directed to a method of scaling up or down an input video image and displaying the scaled video image on a display device. The method comprises the steps of: (a) analyzing an input video signal to determine a resolution of the input video signal; and (b) expanding or contracting a video image expressed by the input video signal so that the resolution of the video signal is made equal to a resolution of the display device.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.
The CPU 20 functions as a frequency determination unit 26 for determining a frequency of a synchronizing signal SYNC given by the personal computer 100 and as a resolution determination unit 28 for determining a resolution corresponding to the frequency of the synchronizing signal SYNC. The CPU 20 executes computer program codes stored in the main memory 22 to implement these functions.
The A-D converter 32 converts an analog video signal VPC generated by the personal computer 100 to a digital video signal DPC and transmits the digital video signal DPC to the video scaler 36. The video scaler 36 receives the digital video signal DPC as well as the synchronizing signal SYNC output from the personal computer 100. In the description of this specification, the term “video signals” may represent video signals in a narrow sense that do not include synchronizing signals, and also those in a broad sense that include synchronizing signals.
The video scaler 36 writes the input digital video signal DPC into the frame memory 34 while reading out a video signal from the frame memory 34 and supplying the video signal to the LCD driver 38. In the course of writing or reading procedure, the video scaler 36 expands or contracts a video image, so as to make the resolution of the video signal coincident with a standard resolution of the LCD panel 40. The LCD driver 38 reproduces a video images that is transmitted from the video scaler 36 on the LCD panel 40. The video images reproduced on the LCD panels 40 are finally projected as a color image on the screen by means of an optical system including the light source 42.
The digital video signal DPC output from the A-D converter 32 shown in
The synchronizing signal SYNC generated by the personal computer 100 includes a horizontal synchronizing signal HSYNC1 and a vertical synchronizing signal VSYNC1. The write synchronizing signal generator 52 has an internal PLL circuit (not shown), which multiplies the frequency of either the horizontal synchronizing signal HSYNC1 or the vertical synchronizing signal VSYNC1 by N0 to generate a dot clock signal DCK1. The dot clock signal DCK1 indicates an update timing of a dot position in the horizontal direction. The dot clock signal DCK1 as well as the horizontal synchronizing signal HSYNC1 and the vertical synchronizing signal VSYNC1 are supplied to the address controller 58.
The video signal converted by the first color conversion unit 50 is temporarily stored in the FIFO buffer 54 and written into the frame memory 34 by the DRAM controller 56. The FIFO buffer 54 works to adjust the timing of the writing operation. The writing operation into the frame memory 34 is carried out synchronously with the write synchronizing signals (DCK1, HSYNC1, and VSYNC1) output from the write synchronizing signal generator 52. Each dot position (or horizontal address) is updated synchronously with the dot clock signal DCK1, while each scanning line position (vertical address) is updated synchronously with the horizontal synchronizing signal HSYNC1. Each frame or each field is updated synchronously with the vertical synchronizing signal VSYNC1. The DRAM controller 56 also reads out video signals stored in the frame memory 34 and writes the input video signals alternately into the two FIFO buffers 61 and 62. The reading-out operation from the frame memory 34 is carried out synchronously with read synchronizing signals (DCK2, HSYNC2, and VSYNC2) generated by the read synchronizing signal generator 68. The read synchronizing signals (DCK2, HSYNC2, and VSYNC2) are also supplied to the LCD driver 38 to be used as display synchronizing signals for the LCD panel 40. The address controller 58 is a circuit for generating a write address and a read address and supplying the write and read addresses to the DRAM controller 56. The address controller 58 further includes a scaling unit 70 for expanding or contracting (or scaling up or down) a video image.
One line of video signals read out from the frame memory 34 are written alternately into the two output FIFO buffers 61 and 62. In the mean time, video signals are read out from the buffer which is not under the writing operation, to be supplied to the filter unit 64. The filter unit 64 is a circuit for carrying out a variety of filtering processes, such as γ correction (conversion of input/output tones) and left-to-right and top-to-bottom inversions of video images. The filtered video signal undergoes the color conversion in the second color conversion unit 66, if necessary, to be converted to an output video signal DOUT. The output video signal DOUT is then supplied to the LCD driver 38 (see
The CPU 20 shown in
As shown in
The resolution of the input video signal VPC may be determined on the basis of not only the frequencies of the horizontal synchronizing signal and the vertical synchronizing signal but on period widths HH and HV of the horizontal and vertical synchronizing signals and on the kind of interlacing.
The horizontal resolution and the vertical resolution determined by the resolution determination unit 28 are given to the address controller 58 via the CPU access controller 60 (see
The PLL circuit 142 receives the horizontal synchronizing signal HSYNC2, which is generated for the reading-out operation, and generates a second dot clock signal DCKX having the frequency of N times the frequency of HSYNC2. The frequency divider 144 receives the dot clock signal DCK2, which is also generated for the reading operation, and divides the frequency of DCK2 by M to generate a line increment signal LINCX. The preset values N and M in the PLL circuit and the frequency divider 144 are used to convert the resolution of the input video signal VPC to the resolution of the LCD panel 40, and are respectively determined by the CPU 20. A concrete process of determining the preset values N and M will be described later.
The output signal DKFF of the EXNOR circuit 172 is supplied to a clock input terminal of the flip-flop 174, while the second dot clock signal DCKX is given to a D-input terminal of the flip-flop 174. The third dot clock signal DCKXX output from the flip-flop 174 thus represents the level of the second dot clock signal DCKX at a rising edge of the output signal DKFF of the EXNOR circuit 172 as shown in
After being reset by the pulse of the horizontal synchronizing signal HSYNC2, the first counter 152 of the horizontal address generator 146 (
The tables of
As discussed above, the horizontal address HADD depends upon the relation between the frequencies of the two dot clock signals DCK2 and DCKX. A video image can thus be expanded or contracted in the horizontal direction by adjusting the frequencies of these dot clock signals DCK2 and DCKX. A magnification MH2 of a video image in the horizontal direction is given as the ratio of the frequency fDCK2 of the first dot clock signal DCK2 to the frequency fDCKX of the second dot clock signal DCKX as shown in the bottom of
The reason why the latch error elimination circuit 150 is used to generate the signal DCKXX is as follows. As shown in
As discussed above, the magnification MH2 in the horizontal direction and the magnification MV2 in the vertical direction can be set independently as shown in the bottom of
The video signal selection unit 200 receives two television signals STV1 and STV2 as well as video signals (VPC, SYNC) generated by a personal computer, and selects one of the received signals. The television signals STV1 and STV2 are composite video signals including synchronizing signals. When the video signal selection unit 200 selects a composite video signal, a decoder (not shown) in the video signal selection unit 200 generates component video signals VIN and a synchronizing signal SYNC from the selected composite video signal.
The video encoder 202 generates a composite video signals from a digital video signal DOUT and the reading-out synchronizing signals (DCK2, HSYNC2, and VSYNC2) output from the video scaler 36. The composite video signal thus generated is supplied to the television receiver 204 and the video player 206. In order to write a video image into the CD-RAM 208 (write-enable compact disk unit), the video encoder 202 does not generate a composite video signal but directly supplies the digital video signal DOUT and the reading-out synchronizing signals to the CD-RAM 208. The video scaler 36 can change the resolution of a video image to a desired resolution as discussed previously. When the user specifies a desired resolution, the video scaler 36 can output video images with the desired resolution corresponding to the various output devices. The apparatus of
The present invention is not restricted to the above embodiments or applications. There may be many modifications, changes, and alterations without departing from the scope and spirit of the main characteristics of the inventions follows.
(1) The functions of the frequency determination unit 26 and the resolution determination unit 28 (see
(2) In the above embodiments, image expansion and contraction are carried out when video images are read out from the frame memory 34. The image expansion and contraction may, however, be executed when video images are written into the frame memory 34.
(3) Any technique other than the frequency control discussed above may be applied to the image expansion and contraction. For example, they can be attained by multiplying the read address or the write address by a predetermined coefficient to change the addresses so that the image is expanded or contracted according to the changed addresses. FIGS. 12A and 12B1-12B3 show a process of expanding and contracting a video image by multiplying read address by a predetermined coefficient K.
In the example of FIGS. 12A and 12B1-12B3, it is assumed that a memory resolution is defined by Mx (dots) by My (lines) and a display resolution Nx (dots) by Ny (lines). The coefficients K(Kx,Ky) by which the addresses are multiplied are given as follows:
A read address (XADD,YADD) used for reading out video data from the frame memory 34 is converted to a new read address (XADD,YADD) by the following equations:
wherein the operator INT( ) represents an operation of taking an integral portion of the value in parentheses.
FIG. 12B1 shows an example of the displayed image when the coefficients Kx and Ky are greater than 1.0 (for example, Kx=Ky=2.0). When the original horizontal address XADD is increased one by one, such as 0,1,2, . . . , the converted horizontal address XADD is varied as 0,2,4, . . . according to Equation (2a) given above. The vertical address YADD is converted in the same manner. Video data are read out from the frame memory 34 according to the converted read addresses XADD and YADD, so that a contracted video image is displayed as shown in FIG. 12B1. The horizontal magnification and the vertical magnification in this contracting process are respectively equal to 1/Kx and 1/Ky.
When the coefficients Kx and Ky are equal to 1.0, a video image in the frame memory 34 is displayed without any expansion or contraction as shown in FIG. 12B2.
FIG. 12B3 shows an example of the displayed image when the coefficients Kx and Ky are smaller than 1.0 (for example, Kx=Ky=0.7). When the original horizontal address XADD is increased one by one as 0,1,2,3, . . . , the converted horizontal address XADD is varied as 0,0,1,2, . . . The vertical address YADD is converted in the same manner. Video data are read out from the frame memory 34 according to the converted read addresses XADD and YADD, so that an expanded video image is displayed as shown in FIG. 12B3.
It is possible to set arbitrary values to Kx and Ky independently.
(4) When a high-speed read/write memory, such as a synchronous DRAM, is used for the frame memory 34, high-speed reading and writing of video signals can be carried out.
Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
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|U.S. Classification||345/428, 345/3.3|
|International Classification||G06T17/00, G09G5/00, H04N3/223, G09G5/36, G09G5/391, G09G3/20, G09G5/12|
|Cooperative Classification||G09G2360/02, G09G5/006, G09G2340/0407, G09G5/391, G09G5/005|