Browse Prior Art Database

Low-Cost Addressing of Frame Buffer for a Multi-Media Rasterizer

IP.com Disclosure Number: IPCOM000112296D
Original Publication Date: 1994-Apr-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Roberson, J: AUTHOR [+2]

Abstract

Disclosed is a system that permits the graphics programmer to make Direct Frame buffer Access (DFA) calls using the same data format regardless of pixel size. This is accomplished by emulating frame buffer formats. The emulation process shown in the Figure involves three modules which are BLT Format Converter, Data Format Converter, and Memory Controller.

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Low-Cost Addressing of Frame Buffer for a Multi-Media Rasterizer

      Disclosed is a system that permits the graphics programmer to
make Direct Frame buffer Access (DFA) calls using the same data
format regardless of pixel size.  This is accomplished by emulating
frame buffer formats.  The emulation process shown in the Figure
involves three modules which are BLT Format Converter, Data Format
Converter, and Memory Controller.

      The rasterizer may support several Frame Buffer pixel sizes.
When a Bit Block Transfer (Blt) operation is performed the pixel data
from the system will be in a packed format.  For example, an 8 bits
per pixel format Blt may pack 4 pixels in a 32 bit data word.  The
Blt hardware will unpack the pixel data into the real Frame Buffer
pixel data format.  The real Frame Buffer pixel data may be quite
different.  Twelve bits per pixel may be the actual Frame Buffer size
and 8 bits per pixel data will be shifted to align correctly within
the larger field.  It is also possible that a larger bit per pixel
format is reduced to fit into a smaller bit per pixel real Frame
Buffer.  Techniques such as dither and color processing are used to
accomplish this reduction.  A Direct Frame buffer Access mode of
operation will typically expose the real Frame Buffer format for read
or write access.  In this case the software is responsible for
converting the pixel format to the real Frame Buffer format.  This
invention allows the format conversion...