Pauline Senkowsky - As my connection isn't SUPER high speed, I always broadcast in 4:3 and use Freemake Video Converter for all of my video stream rendering. In my experience, despite it's dubious reputation as a video codec, I've found that WMV works best for streams.

My specs:

• Frame size - 640x360 for 16:9 and any wider ratios. 480x360 for 4:3 stuff.
• Video codec - VC1
• Frame rate - Depends. "Original" usually works, but it's stubborn sometimes, so just input the original frame rate if you want to be precise.
• Bitrate - 550 to 720 kbps.
  
• Audio - WMA. Switch to mono if the film doesn't have any major directional sound or sounds flat to begin with. It'll save you a couple megabytes. Other wise, use stereo if the audio is high bitrate.
  

If you experience connection trouble, switch to medium bandwidth. The low bandwidth isn't worth it.