What encode rate for Xvid to DVD-R

[RimmeR]

I want to Re-encode my xvids to DVD-R with my hardware MPEG encoder. The thing is I don't want to go overkill on the encode rate. How can I find out whats the maximum bit-rate that the Xvids been encoded at. I don't think that I'd need to encode at 7mbs VBR like my usual DV to M2V's.
How can I achieve this? What bitrate do I use to reencode Xvids?
Thanks

[RimmeR]

Sorry to bump this but I've looked places but no help

[mats.hogberg]

As always with MPEG, you can't use a too high bitrate, since how high you go (up to the point where you actually hit a bitrate that makes compression of the frames unnecessary) you'll end up with an end result slightly worse than the original. The higher the bitrate, the closer to the original. Bitrate has more to do with target resolution, and how well the source is suited for compression (=amount of change between frames).
If the XviD is encoded at a low bit rate, resulting in macro blocks and artefacts galore, it doesn't imply that you can use a low bitrate when encoding to MPEG. That would only make it look even worse. By using a high bit rate, you'll get as good result as you can from your source.
Now, if a low bitrate XviD is at all suited as source for a DVD is entirely another matter!

/Mats