Avi to Mpeg2 bitrate query

[Gavin1910]

I have lost count of how many avi files I have converted to DVD, yet I never really bothered with one aspect of the encoding process - the bitrate.
I always just used 2-pass VBR (TMPGEnc) at the maximum bitrate possible, ie so that the output would be around 4200MB. I have always been satisfied with the quality of the output.
The question I wanted to ask which I cannot seem to find 'definitively' answered anywhere is, if the video bitrate of my avi is say 1000kbps, is there any advantage, when encoding, to using a bitrate higher than 1000kbps? I know that source avi quality will not improve no matter how high the bitrate, but if I can get away with encoding at 1000kbps instead of the usual 4000-ish, it would save a lot of CPU time. I vaguely remember being told a few years back that output bitrate should be set at 3-4 times that of the source bitrate in order to maintain the same quality?

Any input appreciated, thanks.

[paglamon]

A 1000kbps avi and a 1000kbps mpeg will have the same size.So, why, do you think the file was in avi format(XviD/DivX) in the first place ? Because ,at a given bitrate(usually lower),an XviD/DivX has better quality than the mpeg. So,to convert to mpeg from avi,you must increase the bitrate to maintain the quality.But yes,raising the bitrate too high is useless. Roughly,an usual 2hr. DVD-Video should fit a SL disc.

[Gavin1910]

Thank you.

[NFS]

It seems to me that the best way to know what bitrate is the most appropriate in any particular case is to handle a few experiments with say a 1-min file. Just play with bitrate a little and decide