can x.264 be used instead of h.264 with edius

[eperkins153]

I would like to export to mp4 and maintain the same quality and a smaller file size, but when i do it as h.264 the video comes out darker. I have read some articles and they say that if you use the (x.264) codec you can fix the gamma issue

is it possible to use x.264 instead of h.264 with edius 5? or with procoder 3?