I've taught yoga since 2009. First, don't start with videos. If you go to a class, introduce yourself to the instructor and inform them that you're a rookie and you'll need all the help you can get, you will become more comfortable practicing yoga within 4-5 sessions than you would have doing videos at home for 4-5 months. After you get the fundamentals, videos are fine.
Second, if you want to focus on breath work, go to a class and ask the instructor before hand. It's called pranayama, and it's exactly what you are looking for. This you might be fine using videos for.