Abstract: The present invention is directed towards a cache management system for a set top box that improves the loading speed of hypertext markup language (HTML) documents that are provided by web servers. The cache management system includes a set top box with a processor and memory that includes cache, where a plurality of HTML documents is stored in the cache. A cache manager manages the cache and calculates a removal factor for each of the HTML documents. The cache manager removes at least one of the HTML documents based on its removal factor until sufficient room is available for an additional HTML document. Additionally, the cache manager keeps the maximum number of relevant web pages in cache to maximize loading speed.

Abstract: A graphics blending feature for a terminal such as a home communication terminal (HCT) allows an overlay image to be selectively blended with a background image through the use of a chroma key function and one or more alpha control bits. The chroma key function is used to determine whether the overlay will be completely transparent or not, and the one or more alpha control bits are used to look up a larger alpha value used to blend the overlay and background images. By using a small number of alpha control bits to retrieve a larger alpha value for blending, memory requirements per pixel are reduced. The chroma key function may be implemented by comparing each overlay pixel value to a chroma value and, responsive to a match, making the overlay pixel transparent (i.e., no blending occurs). A dithering function is included in various embodiments to smooth out the resulting image.

Abstract: A system for downloading different versions of software or data modules into a plurality of terminals having different compatibility interfaces includes an authoring component for generating the different module versions, a downloading source including a descriptor table which associates each module version with a list of compatibility requirements needed to download the module, and a plurality of terminals coupled to the downloading source. The downloading source transmits the descriptor table to each terminal and also continuously transmits the modules over the network. Each terminal extracts the descriptor table and, based on a match between an entry in the descriptor table and an internally stored table determines which version of a particular module should be downloaded. The system avoids the need for two-way communication between each terminal and the downloading source.

Abstract: Interpolating a low or medium resolution image to a higher resolution image using a pixel replication and averaging technique. An overlay image having pixels of a first display resolution and a plurality of alpha blending values each indicating the degree of blending with a background image is interpolated to the resolution of the background image. In addition to interpolating pixel values, alpha blending values are themselves interpolated and multiplied by corresponding overlay pixel values prior to being blended with the background image.

Abstract: An improved graphical manipulation technique for a home communication terminal (HCT) includes a linked-list of commands controlling various video operations in an application specific integrated circuit (ASIC). After each command has been implemented by the ASIC, the ASIC proceeds to the next command without interrupting a host processor. Accordingly, the linked-list eliminates the need of the host processor to continually process interrupts at the completion of each instruction. The linked-list command structure aids in intensive video operations including bit block transfers, video capture, and video display.

Abstract: A system for preprocessing computer programs before downloading them into terminals includes a packager which processes certain information contained in compiled but unlinked programs. The packager partially resolves undefined symbols and relocations based on knowledge of a dispatch table in the destination terminal and other information known prior to the downloading process. Additionally, the packager determines the sizes of separate code, data, dispatch table and temporary symbol areas, incorporates this size information into a header, and transmits a data stream including the header and the aforementioned areas, including partially resolved symbols, to one or more terminals such as home communication terminals (HCTs) in a cable television network. Each receiving terminal extracts the size information and allocates only as much memory as is needed to store each of the separate areas, thus avoiding the need for a temporary holding buffer.