Appendix B: Using Shaped And Unshaped Keying; About Shaped And Unshaped Keying; Shaped Vs. Unshaped Compositing; Shaped - Pinnacle Systems Deko1000 Technical Reference And Service Manual

Appendix B: Using Shaped And Unshaped Keying

About Shaped And Unshaped Keying

Working with multiple sources in a video production environment requires a mixing operation to
properly combine independent Video + Key elements. This operation is normally found in
graphics systems, character generators, DVE's (Digital Video Effects) and switchers that are used
for On-Air broadcasts. Traditionally, two different methods of keying have been used in this
environment: "Shaped" and "Unshaped" Keying. These two methods cannot be used
interchangeably and can sometimes lead to confusion and improper operation.

Shaped vs. Unshaped Compositing

In the broadcast environment, video and key signals are normally transported on two separate
signals. The terms "Shaped" and "Unshaped" refer to how a separate key signal is used in
conjunction with an associated video (or fill) signal to represent a non-opaque source.

Shaped

"Shaped" refers to a video and key pair that has the key "pre-applied" (or pre-multiplied) to the
video signal. This is most apparent on objects with a soft, semi-transparent border as shown in
Figures B-1 and B-2.
Figure B-1: Shaped Video Signal Figure B-2: Key Signal
In this example, the letter "O" has a soft border that is apparent on both the video and key signals.
Once this graphic is keyed, the background image shows through the semi-transparent border as
shown in Figure B-3.
Figure B-3: Keyed Result
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