If you happen to reencode video to iPhone with ffmpeg this will be useful to you:

ffmpeg -strict experimental -y -i <input> -s 960x396 -vcodec libx264 -acodec aac -ab 160k -ac 6 -b 4260k -threads 3 -flags +loop -cmp +chroma -partitions 0 -subq 1 -trellis 0 -refs 1 -coder 0 -me_range 16 -g 300 -keyint_min 25 - sc_threshold 40 -i_qfactor 0.71 -maxrate 10M -bufsize 10M -rc_eq \'blurCplx^(1-qComp)\' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 30 <output>

-ab audio bitrate
-ac audio channels
-b video bitrate
-s video size in WIDTHxHEIGHT (iPhone4 active matrix is 960x640 Original/3G/3GS: 480x320)