Live-streaming platform Justin.tv now supports high-resolution videos using H.264 encoding. The codec, which has made headway in consumer electronics, is also a great format for the Web since it can fit high resolutions in relatively small file sizes--making it ideal for something like streaming.
For now there are a few caveats that keep it from being accessible to the average user. For one, videos streamed in high resolution H.264 will not be saved into user archives, and there is no way to do it without using special software to process the stream before it hits Justin.tv's servers.
Users are encouraged to be running a rig with a fast processor and modern graphics card, as it takes some considerable horsepower to crunch down video in real time. Eventually the company hopes to offer such processing power on its own servers, so that you'll be able to get similar results with any commodity high-resolution Webcam and a good connection.