Apple’s iTunes Podcasting Team (nameless, faceless people) sent me the following tips for getting along with Apple TV:
If you’re encoding your video podcast at 320×240, please increase the resolution to either 640×480 or 640×360 (depending on the aspect ratio of your source files). Why? Because video podcasts at this resolution look great on Apple TV and still port to video iPods. Lower resolution podcasts might also work on both platforms, but they don’t look nearly as good on a widescreen TV. As always, make sure to test any encoding changes you make to ensure device compatibility. QuickTime 7.1’s “Export to iPod” function will ensure that a video file is encoded at a width of 640 and is iPod-compatible.
It’s best not to create two different podcast feeds for different resolutions. By doing so, you dilute the popularity of your podcast and reduce exposure in our charts. It’s better to have one feed high in the charts than two that are lower.
If your source files are 16:9, stick with that aspect ratio. Don’t add letterboxing to make them 4:3. By doing so, you prevent the video from expanding to fill a 16:9 widescreen TV and instead end up with black space on all four sides. Also, your original source files should be at least 640 pixels wide.
Of course these are just recommendations. We understand that there are good reasons for 320×240 (bandwidth bills) and 720p (looks fantastic). Do whatever makes the most sense for your show. For more information on formatting video, see the recently updated spec.