The next challenge is to install Mythtv on Ubuntu for PS3 either from source or pre-compiled binaries (which I don't know if they exist). Since the support for the HDHomerun is built into Mythtv that would be all that was needed to have a Mythtv Box. Given that the 80 GB drive is small under Linux you could just plug in a number of USB harddrives to store the HD content
The biggest problem in this setup is that Sony has not granted access to the video card in the PS3 for fears of open source developers making games for the PS3 that would edge Sony out of the game development. I find this funny given all the games that are out there for Linux are pretty basic. So what if I play Tron on the PS3; I don't think that will stop me from buying Madden. This means that the video card works but does not help with rendering. Without a good driver for the video card I have read that HD playback is choppy. This is a problem now but it may be resolved in the future by reverse engineering or Sony relenting. There is a petition to Sony to open up the Video Card Petition. This still does not leave out the PS3 from becoming a Mythtv backend that would be great for turning the HD into Divx or Xvid given the processing power of the Cell. Look at what the Cell processor is doing for research Folding at Home


