Streaming video from shared Mac folder to AppleTV?
You are right about streaming to the iPhone (or iPad) and then to the ATV. Check out the VLC streamer. The application is installed on iOS, and a companion app goes on the computer. VLC Streamer will transcode non-native video (e.g., AVI) from the computer, pipe it to the iOS device, and then pipe that to the ATV via AirPlay. I have tested this and it works exactly as described. The quality of your results will be dependent, of course, on your LAN bandwidth and processing speed of the machines. You can set some of these parameters in VLC Streamer, though, which maximizes output. Enjoy!