I'm trying to explore new ways of embedding videos on to my site as a few of my contributors are having trouble viewing flash embeds when they use the preview function.

Ideally it would be easiest to use oEmbed via the [embed] shortcode but i'm running into a problem that I don't seem to be able to find a solution for.

I know that you can specify the maximum dimensions of the embed via the Media tab, but that is not what I want to do. Every single photo or video displayed on our site is 560px x 340px for continuity purposes and those are the dimensions I want to force onto the oEmbeds, but I cannot find a way to do it!

Looking for help here as Google has been useless!