Plugins to embed audio/video or use HTML, please read

If you have a pluginPlugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the Plugin Directory or can be cost-based plugin from a third-party with the sole purpose of embedding video into WP posts, or one that makes HTML5 work in WP, you need to know that there is HTML5 support for Audio and Video coming in WordPress 3.6, so please test ASAP.

Read Audio/Video Support in Core