I am writing about an export problem. I export a Quick time reference from Avid then I am using sorenson squeeze 4 to create the file. No problem to make .mov or mpeg but when I want to do a MP4 it transforms my original 16:9 into a 4:3. I have been searching on the internet for hours to get an answer but I can't find anything. I have tried with different footages and MP4 always has the same issue. so the problem does not seem to come from Avid but sorenson. What is really strange is that when I play the video with the actual windows media reader there is no problem (good 16:9) but when I play it with VLC or Quicktime player or upload on vimeo then comes the 4:3.