If you’re using S3MV, and your videos play fine, but take between 30 seconds to a minute to actually start playing, then there is an issue with the encoding of the actual video file itself.
It’s not a problem with Amazon S3 or with the S3MediaVault plugin. It’s an issue with the file encoding that’s causing it to load slowly (but then plays correctly once loaded).
You need to use a program called HandBrake, a desktop tool that will allow you to optimize your file encoding for playing on the web.
And once you’ve done that, all of your videos will play just fine.