Inventors:
Bo Ye - Cupertino CA, US
Jimmy Yang - Saratoga CA, US
Edmund Cheung - Palo Alto CA, US
Assignee:
NeoMagic Corp. - Santa Clara CA
International Classification:
G06F 13/00
G09G 5/00
US Classification:
345537, 345558, 345559, 345531, 345589, 345629
Abstract:
A graphics system reduces fetching from memory of color-key pixels when video pixels from a video-overlay window are displayed. A frame buffer is divided into multi-line, multi-pixel blocks that are arranged in block-rows and block-columns. Each block-row has primary and secondary row indicator bits and each block-column has two column indicator bits. When the primary row indicator bit is cleared, all pixels in the block-row are fetched from a frame-buffer memory. When the primary row indicator is set, a secondary row indicator bit selects either first or second column indicator bits for reading. When the selected column indicator bit for a block-column is set, fetching of pixels from the frame buffer memory is skipped. Instead, dummy color-key pixels are generated and inserted into the pixel stream. These dummy pixels match the color key and cause video pixels to be sent to the display.