Browse Prior Art Database

Programmable Video Merging

IP.com Disclosure Number: IPCOM000121088D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 75K

Publishing Venue

IBM

Related People

House, DL: AUTHOR [+3]

Abstract

Disclosed is a method for overlaying two separate multi-colored display images, thus merging them into one distinct and accurate image. If the two images are both mono-color in nature, the video merging is easily accomplished using a simple OR gate. However, this article presents a solution for the more complex problem of merging two multi-colored images coming from two distinct Video Random-Access Memories (VRAMs).

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Programmable Video Merging

      Disclosed is a method for overlaying two separate
multi-colored display images, thus merging them into one distinct and
accurate image.  If the two images are both mono-color in nature, the
video merging is easily accomplished using a simple OR gate.
However, this article presents a solution for the more complex
problem of merging two multi-colored images coming from two distinct
Video Random-Access Memories (VRAMs).

      When merging multi-colored images the combinational integrity
of the colors must be maintained.  If the color RED is coming from
one VRAM and GREEN from the other, the resultant color should be
YELLOW or some other inconsistent color.  A more accurate picture is
presented when one of the two colors dominates and overrides the
other color.

      This article presents a solution for the determination on a
pixel by pixel basis of the proper selection of one consistent color,
when two images are merged from separate VRAMs.  The method described
uses no additional hardware and is completely flexible and
programmable.

      The hardware solution makes use of any off-the-shelf Color
Palette (for instance, Brooktree part number B1453/883 shown in the
figure), which uses a 8-bit binary input to look-up a 24-bit value in
a 256-word entry table.  The 8-bit input value is used to define the
desired color in terms of a 24-bit binary selection.  Normally, the
Color Palette receives a serial stream of data 8-bits...