Here's a line I found for AVI > h.264 mp4
ffmpeg -i test.avi -acodec libfaac -ab 128k -ar 44100 -s 704x400 -r 20 -vcodec libx264 -b 256000 -cmp +chroma -partitions +parti4x4+partp8x8+partb8x8 -me_method umh -subq 5 -trellis 1 -refs 2 -bf 1 -coder 1 -me_range 16 -g 300 -keyint_min 25 -sc_threshold 40 -i_qfactor 0.71 -bt 256000 -maxrate 4M -bufsize 4M -rc_eq 'blurCplx^(1-qComp)' -qcomp 0.6 -qmin 10 -qmax 51 -qdiff 4 -level 21 test.mp4
"Then move the MOOV atoms to the beginning of the file for fast loading:"
MP4box -isma test.mp4