Apparatus and method of transferring video data of a moving picture

DETAILED DESCRIPTION An object of the present invention is to execute a high-speed transfer of video data to a VRAM to thereby display a smooth moving picture.
The present invention is directed to an apparatus, for use in a computer system comprising a processor for performing logical operation and a video memory controlled by the processor for storing video data, for transferring moving-picture video data representing a moving picture to a desirable memory area in the video memory, comprising: a first memory for storing an offset address indicating a start position of the desirable memory area in the video memory; a second memory for storing an adding address indicating a difference between addresses of two scanning lines adjacent to each other in the video memory; first operation means for calculating a vertical address as a function of vertical and horizontal synchronizing signals synchronous with the moving-picture video data, the vertical address being equal to a value of the adding address multiplied by a scanning line number indicating an ordinal number of a scanning line in the moving picture, the scanning line number being specified by the number of pulses of the horizontal synchronizing signal given to the first operation means; a horizontal counter for generating a horizontal address indicating a difference of an address between an initial position of each scanning line in the moving picture and each pixel on the each scanning line; second operation means for adding the vertical address, the horizontal address, and the offset address to obtain a transfer address indicating an address in the video memory corresponding to a position of the each pixel on the each scanning line in the moving picture, and outputting the transfer address onto an address bus connected to the video memory; and data output means for outputting the moving-picture video data to be transferred to the video memory according to the transfer address, onto a data bus connected with the video memory.
Since the transfer address is calculated by arithmetic operation in the first and second operation means, the transfer address can be computed at a high speed