Browse Prior Art Database

Use of Masking Register for VLT Animation Speedup

IP.com Disclosure Number: IPCOM000042977D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Bantz, DF: AUTHOR [+2]

Abstract

The present disclosure concerns a mask register, whose contents are bitwise ANDed with pixel data from a frame buffer before that data is applied to a VLT (Video Look-up Table) as an address. This facility increases the speed with which the display can be switched from one prestored picture to another, at minimal cost. It is especially suitable to frame-buffered systems with large numbers of bits per pixel. In frame-buffered raster computer display systems it is often the case that pixel values read from the frame buffer undergo translation before video is generated. The pixel values are used as the addresses to a read/write memory (called the Video Lookup Table or VLT) and the values read from this table are used as input to digital-to-analog converters for the purposes of video generation.

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Use of Masking Register for VLT Animation Speedup

The present disclosure concerns a mask register, whose contents are bitwise ANDed with pixel data from a frame buffer before that data is applied to a VLT (Video Look-up Table) as an address. This facility increases the speed with which the display can be switched from one prestored picture to another, at minimal cost. It is especially suitable to frame-buffered systems with large numbers of bits per pixel. In frame-buffered raster computer display systems it is often the case that pixel values read from the frame buffer undergo translation before video is generated. The pixel values are used as the addresses to a read/write memory (called the Video Lookup Table or VLT) and the values read from this table are used as input to digital-to-analog converters for the purposes of video generation. The table can be used for a number of purposes: 1. Nonlinearities in the display system can be compensated for by storing a tabular function in the VLT. 2. In color systems, since the VLT entries are usually longer than the pixel values, finer control of color can be obtained. 3. Several images can be stored in the pixel values, and the screen can be rapidly switched by changing the VLT entries. The latter capability, sometimes called VLT animation, is the concern of this disclosure. A reference Fundamentals of Interactive Computer Graphics by Foley and Van Dam (Addison-Welsey, 1982), pages 489- 492) illustrates the technique. As an example of VLT animation, suppose that each pixel in the frame buffer contains 8 bits, and that the high-order 4 bits of each pixel contain data from one picture while the low-order 4 bits contain data from another picture. In order to show the picture that is sorted in the high-order portion of each pixel, the VLT should contain the same data in each block of 16 entries. For example, the data in VLT addresses 0...