Which bitrate is needed for dvd quality? As far as I know, cd quality for mp3s is at least 128 kbps.
What should the video bitrate be to obtain dvd quality? 

Note I'm using mp4 container with mp3 audio and mpeg4 video.
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.