Which bitrate is needed for dvd quality?
Of course it depends on the used codec as well, it is not all about bitrate. But it is possible to have a reasonable quality @3,5 Mbit/s. But using the maximum range of ~9Mbit/s. usually looks much better, but the space of a DVD is limited, so that it is not enough for a 90 minute movie. The best thing is to try different settings for your mpeg4. Remember that this video must obey DVD restriction in order to be played in a DVD player.