Dual Display Timing

“How do you keep multi-monitor systems precisely in sync?”

When we’ve created Art Gallery Image Presentations for clients, where the gallery desires to use their own Mac system sporting dual monitors (or more), we have to design our presentation around some common technical details. Please note this is for Mac OS X only, Windows only supports single monitors using Designer 4.

When using iScreensaver, multiple monitors are not designed to stay in sync. The ‘easy’ technical reason for this is that given the variety of video cards, video drivers, and media (images, flash, and various movie files) and the fact that the two monitors may be both different size and shape (which affects playback speed), there’s really no way to keep them in sync. Any sync seen is just luck. Even sequential monitors right off the assembly line can exhibit differences from one another.

Our recommendation is to design with this in mind, and not attempt to have fully synchronized presentations on multi-monitor setups. If you truly need perfect sync, then you’ll need to turn on Monitor Mirroring in the OS so that both monitors are showing the same thing. We also recommend a high-quality Solid State Drive.

How do we design around it?

We use shuffle, and purposely push the monitor displays further out of sync with having different durations for the images. Half are set to 6 seconds, the other half set to 8 seconds. Or during the opening, we use the HUD and tap the keyboard’s arrow keys to push to the next item early.

“Why can’t they stay in sync again?”

Short answer - computers aren’t magic, they only seem that way.

If this is a screensaver meant to be used as an addon to a computer used for professional / business purposes, then the end-user needs to understand that a screensaver runs at the whim of the Operating System (OS) and has to share resources (RAM, CPU, Disk) with other processes that are running in the background. As an example, if the user is on Mac OS X, and has a Time Machine backup proceeding, the screensaver will necessarily slow down as the OS divides time between the foreground and background operations.

This is not a flaw but rather a feature.
Imagine a screensaver that caused the user’s entire computer to come to a grinding halt!
Expectations need to be set reasonably based on these limitations.