Displaying a subsampled video image on a computer display

Apparatus for displaying digital video image data for an image that is changing in real time on the display of a host computer, the display having a memory-mapped display memory with a predetermined protocol for representing the color and brightness value of a pixel on the display, the apparatus comprising:

• a peripheral processor that receives a directive from the host processor indicating a target display area of the host's display and thereafter autonomously takes as input blocks of said digital video image data and stores them into memory cells of the display memory corresponding to said target display area, said digital video image data being grouped in frames, each frame including the data for an image in said target display area;
• wherein the peripheral processor decodes the digital image data from one encoding to the predetermined protocol required by the display before storing said digital video image data in said display memory;
• such that active real-time video is displayed on the host's display with intervention required from the host processor less often than once per frame.

A method for displaying a reduced-size video image in a window of a display of a host computer, the reduced-size image displaying subsampled digital image data for an image that is changing in real time, the host computer including a central processing unit (CPU), a display, a display memory connected to said display, and a system bus connected to said central processing unit and said display memory, the method comprising the steps of:

• issuing a command from said host CPU to a peripheral controller, said command indicating the location on said display for said window;
• and
• thereafter receiving blocks of source image data for an image that is changing in real time at said peripheral controller, and autonomously subsampling said image data to result in subsampled data and writing said subsampled data through said system bus into said display memory at addresses corresponding to said window, said receiving, subsampling, and writing being carried out without intervention by said host CPU.