IOS 8.1.3 Video Playback

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?

What I do to stop alarm sound is to call Siri twice. First time to stop the alarm itself, second time to stop Siri from listening. This can be done with a very short interval. For reassurance, you can tap thrice each time (in case you tend to miss one of 2 taps required for the command to be registered by AirPods).

P.S. I know the question is about EarPods, but it's quite similar to what some people experience with AirPods. And for EarPods the same could be performed by double-clicking the central button.