Browse Prior Art Database

Transmission of Chroma-Keyling over HSync andor VSync Signals

IP.com Disclosure Number: IPCOM000105333D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Chen, I: AUTHOR [+2]

Abstract

Disclosed is a transmission system of chroma-keying over HSync and/or VSync signals. Such a system provides the remote accessibility of chroma keying, enabling the multiplexing/mixing of graphics and image/video implemented in another system or any slot of the same system. The chroma keying is generated by a comparison between palettized graphics color index and a so-called "transparent" color index. The keying is then sent over the Composite Video Sync signal as a bi-level video, positioned in time so as not to interfere (eg. superimposed) with the HSync or VSync signals.

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Transmission of Chroma-Keyling over HSync andor VSync Signals

      Disclosed is a transmission system of chroma-keying over HSync
and/or VSync signals.  Such a system provides the remote
accessibility of chroma keying, enabling the multiplexing/mixing of
graphics and image/video implemented in another system or any slot of
the same system.  The chroma keying is generated by a comparison
between palettized graphics color index and a so-called "transparent"
color index.  The keying is then sent over the Composite Video Sync
signal as a bi-level video, positioned in time so as not to interfere
(eg.  superimposed) with the HSync or VSync signals.

      A typical window environment is shown in Fig. 1 in which both
graphics window and graphics are overlaid on the top of a video
window.  Also shown is the signal of chroma keying of a scan-line,
masked by an arrow ( rarrow ).  The levels of chroma keying imply
sources of graphics (eg.  logic 0) or video (eg.  logic 1), while the
transitions of the levels of chroma keying indicate their positions.

      In the encoder part Fig. 2, the preliminary chroma keying is
generated by a comparison between palettized graphics color index and
a "transparent" color index.  If matched, it is a video pixel, which
is represented by "1"; otherwise, it is a graphics pixel and is
represented by "0".  Through a flip-flop, the chroma keying is
over-ridden by cursor/sprite information.  Basically, the preliminary
chroma keying...