"Canon isn’t the only game in town when it comes to hacking camera firmware. The famous CHDK firmware hacks now have a rival, at least if you are shooting with a Panasonic GH1, and especially if you are using the Micro Four Thirds camera to shoot video. The hack, called PTool, doesn’t add nearly as many features as the Canon hacks, but what it does is startling. With PTool, you can up the video bitrate of the GH1 from a pedestrian 20Mbit to 32MBit in AVCHD. If you opt for Motion JPEG (MJPEG), you can shoot at an astonishing 50 Mbit/sec at a full 1080p. This, according to testers, offers better quality footage than you get from the EOS 5D MkII. Above you can see an example. To view it in its full HD glory, click through to the Vimeo page."
So I'm just a wee bit late on finding this out, partly because I haven't been visiting the excellent DVXuser.com forums for some time. Amazingly, Tester13 (the guy who started all this) was only asking for volunteers not too long back. I'm amazed at the amount of work he's managed to do in such a short time. Short recap: The GH1 encodes its AVCHD files in 17 Mbps with no B frames, so any fast movement in the scene generally won't look good. Upping the bitrate helps, and if you follow the link, 32 Mbps in AVCHD is possible, and using MJPEG, 50 Mbps has been achieved. Check the link for more; Wired's article has a nice list of links appended at the bottom. I'm going to be messing around with this on my own GH1, and see what I get.