The iPhone 4 is capable of recording movies in 1280 x720p. When using the default .mov format they can get quite big.
When exporting with a default mencoder command the movies are upside down and 5 times to wide and up/side down.
After a lot of fiddling around with different mencoder paremeters i found a nice way to convert to xvid, while forcing the aspect and rotating the moviles also in a single pass; with good quality and low filesize:
mencoder IPHONE4.MOV -ovc xvid -aspect 16:9 -vf mirror,flip -oac mp3lame -xvidencopts bitrate=687 -o test.avi
I used mencoder on Ubuntu 10.04 for it; Debian has a crappy mecoder with no lame support by default..
It depends on how you recorder your movie if you have to flip or rotate….