Specifications

244 Appendix C Display Issues
you’ve plugged in another display and change its behavior (for example,
its refresh rate), thereby causing the problem you’re troubleshooting to
change or disappear.
The most common reason for such artefacts is lack of synchronization between
the video signal fed to the display and its internal operation. This is sometimes
a problem with digital display technologies, such as LCD and DLP. It is not a
problem with CRT-based computer displays, since they’re generally driven
directly by the incoming analog video signal.
Even if your display device supports multiple frequencies, it may work best at
one particular frequency. You may want to try setting both the display card
and WATCHOUT to 60 Hz/fps even if you’re using video optimized for other
frame rates, since this is the optimal display frequency of many projectors and
other display devices.
It is sometimes difficult to determine the optimal frequency of digital display
devices, or whether the display device is at all capable of synchronizing its
internal operation to the frame rate of the incoming video signal. Often,
changing the programming to use other rates for moves and other effects can
make artefacts less obvious. If possible, you may also try connecting the
display computer to the display device using other means, for example using a
digital DVI cable instead of the analog VGA.
Dropped Video Frames Just as lack of synchronization in the display device can affect the smoothness
of positioning and other effects created in WATCHOUT, it may have a similar
impact on the video material used in your presentation. This is often particu-
larly noticeable in slow zooms and pans, or in objects moving across.