first of all, thanks for the response.
This is the deal : it is heavily graphics created in 3d and animated in After and played via Flash player with interaction with a mobile device. from tests we did on avrage computers with a pretty simple (not 3d and little animation) video, the computer had a hard time playing it with flash. now we might move to a different platform HTML 5 but either way the idea is to creat the smallest videos in size with the best looking results. pixilazation in uncceptable.
Thanks a million for the help. Sorry for my unperfect English.
Have a great day.