Different styles for different media types.

Alrighty, I’ve got an issue.
I’m integrating my client’s wordpress blog with a custom site I’m building, and I need some help with the styling on posts.
Here’s the problem:
On this site is a mixture of video and text posts. I need the videos to be centered, while the text remains left-aligned. I’m no good at php, so I’m not sure where to even begin on this. Any help much appreciated!

Here’s the php I use to pull posts.

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