After a lot of testing I decided to use 2 main codecs for my in-car circuit movies:

Real player 8 for low bandwidth users as its blocky but no other compression method can match its quality (at least for high speed footage) at such small filesizes. Its also very faithful to original colours and most people have Realplayer installed.

Do NOT discount this format; people just think Real is bad because its always associated with tiny 600K porn loops that are some of the worst quality ever seen on the net ! In my mind, Real is the very best compression/size compromise and certainly whips anything you can play on quicktime. Its only true competitors at teh moment are DivX and wmv. The only downside to it is that the software does have a habit of trying to take over your whole computer.

Windows Media WMV for high bandwidth users. The quality of WMV from windows media encoder version 8, I found infinitely preferable to equivalent filesize offerings using Sorensen 3, better than DivX or anything else for that matter.

For filming I use a Sony PC9 Mini DV cam rigged up to a Cullman universal clamp. I use a pair of cheap and nasty in-ear walkman type headphones as an external mic.. These are located deep in the passenger footwell to cut down on eth windnoise.

Unless its steamed up with moisture I use a x0.42 superwide lens converter. This gets a lot more into the frame and makes the action seem fast (instead of slowing it down as most regular focal lengths will do). It also stretches distance to a very unatural extent. Cars that are close will actually look far away, the tightest of bends are warped back to gentle arcs and long straight sections of track turn into 10 mile runways ! Still, the sensation of speed is good and its nice to have the scenery, the wheel & dash of my car in the picture as well as the oncoming circuit.