Method and apparatus for scaling up and down a video image

Abstract

An input video image having an arbitrary resolution is converted to another video image having a predetermined resolution of a display device to display the video image with the converted resolution. The frequencies of the synchronizing signals of the input video signal are measured, and then a resolution of an input video signal is determined from the measured frequencies of the synchronizing signals. The video image represented by the input video signal is expanded or contracted, so as to make the resolution of the input video signal coincident with a resolution of the display device. A resulting video image with the converted resolution is displayed on the display device.

What is claimed is:  
     
       1. A video image scaling apparatus for receiving a video image output as a video signal in a first format for a first display device and outputting the video image in a second format for a second display device, said apparatus comprising:
 frequency determination means for analyzing the video signal to determine a frequency of synchronizing signals when the video signal is output in the first format;    image size determination means for determining an image size of the video signal by analyzing the frequency of the synchronizing signals of the video signal output in the first format; and    scaling means for scaling the video image expressed by the video signal in the first format by utilizing the synchronizing signals and the determined image size so that the video signal is output in the second format of said second display device.    
     
     
       2. A video image scaling apparatus in accordance with  claim 1 , wherein said image size determination means comprises:
 image size storage means for storing relationships which identify the image size of the video signal in the first format based on the frequency of the synchronizing signals of the video signal; and    means for determining the image size of the video signal in the first format by referencing said image size storage means according to the frequency of the synchronizing signals of the video signal.    
     
     
       3. A video image scaling apparatus in accordance with  claim 2 , said apparatus further comprising:
 means for displaying a sign indicating that an image size is unknown when the frequencies of the synchronizing signals of the video image are not stored in said image size storage means; and    image size setting means for setting a value of the unknown image size of the video signal and registering a relation between the image size and the frequencies of the synchronizing signals of the video signal in said image size storage means.    
     
     
       4. A video image scaling apparatus in accordance with  claim 1 , wherein said 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 said first buffer memory is written;    a second buffer memory for temporarily storing a video signal read out of said frame memory; and    memory control means for giving a write address to said frame memory while successively reading out video signals from said first buffer memory to write the video signal read out of said first buffer memory into said frame memory, and for giving a read address to said frame memory to read out the video signal from said frame memory and transfer the video signal to said second buffer memory, and wherein 
 said memory control means comprises: 
 means for expanding or contracting a video image read out of said frame memory by adjusting the read address given to said frame memory.  
 
   
     
     
       5. A method for receiving a video image output as a video signal in a first format for a first display device and outputting the video image in a second format for a second display device, said method comprising the steps of:
 (a) analyzing the video signal to determine a frequency of synchronizing signals when the video signal is output in the first format;    (b) determining an image size of the video signal by analyzing the frequency of the synchronizing signals of the video signal output in the first format; and    (c) scaling the video image expressed by the video signal in the first format by utilizing the synchronizing signals and the determined image size so that the video signal is output in the second format of said second display device.    
     
     
       6. A method in accordance with  claim 5 , wherein said step (b) comprises the steps of:
 storing, in a memory, relationships which identify the image size of the video signal in the first format based on the frequency of the synchronizing signals of the video signal; and    determining the image size of the video signal in the first format by referencing said memory according to the frequency of the synchronizing signals of the video signal.    
     
     
       7. A method in accordance with  claim 6 , further comprising the steps of:
 displaying a sign indicating that an image size is unknown when the frequencies of the synchronizing signals of the video image are not stored in said memory; and    setting a value of the unknown image size of the video signal and registering a relation between the image size and the frequencies of the synchronizing signals of the video signal in said memory.    
     
     
       8. A method in accordance with  claim 5 , wherein said step (b) comprises the steps of:
 writing the input video signal into said frame memory; and    giving a read address to said frame memory to read out the video signal from said frame memory while adjusting the read address to expand or contract a video image read out of said frame memory.    
     
     
       9. A video image scaling apparatus for receiving a video image output as a video signal in a first format for a first display device and outputting the video image in a second format for a second display device, said apparatus comprising:
 a video signal input for receiving a video signal, in the first format, including synchronizing signals;    a synchronizing signal frequency analyzer receiving the video signal from the video signal input and determining a frequency of the synchronizing signals when the video signal is output in the first format;    an image size determination unit for determining an image size of the video signal by analyzing the frequency of the synchronizing signals being applied to the video signal input; and    a scaling unit for scaling the video image expressed by the video signal in the first format by utilizing the synchronizing signals and the determined image size so that the video signal is output in the second format of said second display device.    
     
     
       10. A video image scaling apparatus in accordance with  claim 9 , wherein the image size determination unit comprises:
 a memory unit for storing relationships which identify the image size of the video signal in the first format based on the frequency of the synchronizing signals of the video signal; and    a lookup unit for looking up frequencies in the memory unit to determine the image size of the video signal output in the first format.    
     
     
       11. A video image scaling apparatus in accordance with  claim 10 , further comprising:
 an indicator for indicating that an image size is unknown when the frequency of the synchronizing signals are not stored in the memory unit; and    a memory unit updating unit for setting in the memory unit (1) a value of the unknown image size of the video signal and (2) a relation between the unknown image size and the frequency of the synchronizing signals.    
     
     
       12. A video image scaling apparatus in accordance with  claim 9 , wherein said scaling unit comprises:
 a first buffer memory for temporarily storing the video signal;    a frame memory in which a video signal read out of said first buffer memory is written;    a second buffer memory for temporarily storing a video signal read out of said frame memory; and    a memory controller for applying a write address to said frame memory while successively reading out video signals from said first buffer memory to write the video signal read out of said first buffer memory into said frame memory, and for applying a read address to said frame memory to read out the video signal from said frame memory and transfer the video signal to said second buffer memory, and wherein    said memory controller includes a read address updating unit which expands or contracts a video image read out of said frame memory by adjusting a read address given to said frame memory.    
     
     
       13. A video image scaling apparatus for scaling a video image by receiving a video signal in a first format and outputting a video signal in a second format, the video signal in the second format having a predetermined number of pixels in a scanning line in a horizontal direction and a predetermined number of scanning lines in a vertical direction, the apparatus comprising:
   a video signal input for receiving the video signal in the first format, including synchronizing signals;        a synchronizing signal frequency analyzer receiving the video signal in the first format from the video signal input and determining a frequency of the synchronizing signals;        an image size determination unit for determining a number of pixels in a horizontal direction of the video signal in the first format and a number of scanning lines in a vertical direction of the video signal in the first format by analyzing the frequency of the synchronizing signals; and        a scaling unit for calculating a horizontal magnification from the number of pixels in the horizontal direction of the video signal in the first format and the number of pixels in the horizontal direction of the video signal in the second format and a vertical magnification from the number of scanning lines in a vertical direction of the video signal in the first format and the number of scanning lines in the vertical direction of the video signal in the second format, and scaling the video image expressed by the video signal in the first format by utilizing at least one of the horizontal magnification and the vertical magnification so that the video signal is output in the second format.     
     
     
       14. The video image scaling apparatus according to  claim 13 , further comprising:
   a memory to store the video image,        wherein the scaling unit performs scaling when the video image is written into the memory.     
     
     
       15. The video image scaling apparatus according to  claim 13 , further comprising:
   a memory to store the video image,        wherein the scaling unit performs scaling when the video image is read out from the memory.     
     
     
       16. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling in the horizontal and vertical directions. 
     
     
       17. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling only in the horizontal direction. 
     
     
       18. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling only in the vertical direction. 
     
     
       19. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling when the number of pixels in the horizontal direction of the video signal in the first format is larger than the number of pixels in the horizontal direction of the video signal in the second format. 
     
     
       20. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling when the number of pixels in the horizontal direction of the video signal in the first format is less than the number of pixels in the horizontal direction of the video signal in the second format. 
     
     
       21. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling when the number of scanning lines in the vertical direction of the video signal in the first format is larger than the number of scanning lines in the vertical direction of the video signal in the second format. 
     
     
       22. The video image scaling apparatus according to  claim 13 , wherein the scaling unit performs scaling when the number of scanning lines in the vertical direction of the video signal in the first format is less than the number of scanning lines in the vertical direction of the video signal in the second format. 
     
     
       23. A projector comprising:
   a light source;        a video image scaling apparatus for scaling a video image by receiving a video signal in a first format and outputting a video signal in a second format, the video signal in the second format having a predetermined number of pixels in a scanning line in a horizontal direction and a predetermined number of scanning lines in a vertical direction; and        a light modulation panel for modulating light from the light source in response to the video signal in the second format supplied from the video image scaling apparatus,        the video image scaling apparatus comprising:      a video signal input for receiving the video signal in the first format, including synchronizing signals;        a synchronizing signal frequency analyzer receiving the video signal in the first format from the video signal input and determining a frequency of the synchronizing signals;        an image size determination unit for determining a number of pixels in a horizontal direction of the video signal in the first format and a number of scanning lines in a vertical direction of the video signal in the first format by analyzing the frequency of the synchronizing signals; and        a scaling unit for calculating a horizontal magnification from the number of pixels in the horizontal direction of the video signal in the first format and the number of pixels in the horizontal direction of the video signal in the second format and a vertical magnification from the number of scanning lines in a vertical direction of the video signal in the first format and the number of scanning lines in the vertical direction of the video signal in the second format, and scaling the video image expressed by the video signal in the first format by utilizing at least one of the horizontal magnification and the vertical magnification so that the video signal is output in the second format.       
     
     
       24. The projector according to  claim 23 , further comprising:
   a memory to store the video image;        wherein the scaling unit performs scaling when the video image is written into the memory.     
     
     
       25. The projector according to  claim 23 , further comprising:
   a memory to store the video image;        wherein the scaling unit performs scaling when the video image is read out from the memory.     
     
     
       26. The projector according to  claim 23 , wherein the scaling unit performs scaling in the horizontal and vertical directions. 
     
     
       27. The projector according to  claim 23 , wherein the scaling unit performs scaling only in the horizontal direction.