iTunes – Control Playback Speed of iTunes U Lectures on macOS

This might come a little bit as an obvious question but… have you restarted your box since you installed that? A zombie process could be causing delays in other areas.

Check with /Applications/Utilities/Activity Monitor.app and sort by CPU usage to see if there’s anything “red” (zombie) or any process not behaving.

In any case, a sane box restart (if you haven’t already) is usually a good advice. Turn the box off for a few secs and then turn it on again, the VRAM might be corrupted and a simple “restart” won’t always do the right thing. (It happens to me in the Mac Pro).

The reason for mentioning this is that your computer is more than capable to play videos.

Do you have Perian or any other third party codecs laying around that might interfere?

I had the same problem and setting iTunes to run in 32-bit mode fixed it for me. There might be an issue with the video encoding on some of the older WWDC videos like the "Working with Core Data" video that can be found at the Apple developer video site under iOS.

To set iTunes to run in 32-bit mode:

• Quit iTunes.
• Open your applications folder and control-click or right-click on the iTunes icon.
• Select "Get Info".
• Click the checkbox next to "Open in 32-bit mode".
• Open iTunes again and you should be able to download the videos to your collection.

When you are done with your videos, you can always reverse these steps to set iTunes back to 64-bit mode.