If you experience stuttering, jerky video playback on an Apple PowerBook or iBook, here are some ideas.

Check Energy Saver settings. Open your System Preferences and click Energy Saver. In Energy Saver, click the Options tab. Now check the setting for Processor Performance. If it’s set to Reduced, change it to Highest or Automatic. Video playback may be smooth now.

If you’re running on battery, be sure to change the Processor Performance setting back to Automatic or Reduced when you’re done watching video. The Highest setting drains the battery the fastest. Note that on a notebook, the Energy Saver preference lets you save different settings for Battery and Power Adapter.

You might see the effect of the Reduced setting any time you perform processor-intensive tasks such as audio or video rendering, or gameplay. In those situations, you’ll want to set Processor Performance to Automatic or Highest.

Note: The Energy Saver tip won’t work with MacBooks and MacBook Pros, because Intel CPUs automatically try to balance smooth playback against battery drain. The older PowerPC CPUs were not as smart.

Check for other processor hogs. If you set Processor Performance to Highest and you still see choppy performance, the cause may be another application that’s using processor cycles. Open your Activity Monitor utility, view the CPU tab, show all processes, and sort the list by %CPU to see if any applications are using an unusually high percentage of CPU cycles. While new computers can handle today’s streaming video easily, the same video demands almost all the CPU power available in older computers, so any unnecessary tasks can interrupt smooth video playback.

Watch out for HD video. If you have a PowerBook or iBook, you’ll probably have to avoid HD and choose the SD (standard definition) option when you watch Internet video. Smooth HD streaming works best with a recent Intel multi-core CPU. When PowerBooks and iBooks were made, Internet video was much lower quality and there was no high-definition streaming. As CPUs got faster, what made high-quality HD streaming possible were new codecs that made up for limited Internet bandwidth by leaning on the CPU in your computer to process the highly compressed stream. Newer Intel CPUs are optimized for those codecs, so they can decompress video files and Web streaming video very quickly without slowing down the whole computer.

But the G3 and G4 CPUs in PowerBooks and iBooks do not have those Intel optimizations (PowerPC G3 and G4 CPUs were not made by Intel), so they are are too old and slow to decode HD without stuttering. A PowerBook G4 might have a CPU running at 1GHz, while a MacBook Pro has multiple multimedia-optimized CPU cores running at over 2GHz each. Even an old, used MacBook Pro has many times the processing power of a PowerBook G3 or G4.

Also, check the speed of your connection to the Internet. You need a fast enough connection to stream HD smoothly. My old Internet connection was too slow for HD streaming, forcing me to watch SD streaming even on my newest Mac, or let HD video buffer longer before I play it back. My current Internet connection is capable of carrying HD video data fast enough for smooth playback on a computer that’s fast enough to decode it.