Apple has updated its podcasting specs and is sending out emails to video podcasters with tips on how to make them look great on Apple TV.The tips include:

• Encode at 640×480 or 640×360. This will look much better than 320×240 on HDTV, and will still port to the iPod. While 720p looks great, they say, it won’t work on an iPod.
• Don’t make two formats for different resolutions - it dilutes the popularity of the podcast and reduces exposure in charts.
• Don’t add letterboxing to make videos to a 4:3 aspect ratio. Leave them at 16:9.

If you’re creating video podcasts, recognize that Apple’s recommendations are a compromise that sacrifice Apple TV quality for compatibility with video iPods. While they recommend using just one format to get the highest ranking within iTunes, there may be enough interest in HDTV that there could be benefits to moving to 720p widescreen and treating lower resolutions as legacy formats.

via Podcasting News