Thank you Steve and thank you John.
I did import from a DVD or from similar files on my hard drive.
Bill Hunt's article was useful.
Meantime, I did some more experimentation, and also contacted PE "Chat" desk, which threw some more light on the subject.
I found that as soon as I imported a VOB file to PE, it (sometimes) immediately showed the synchronisation errors. (For some other files, it could be that there were NO sync. problems).
In all cases the VOB file ON THE DVD was fine to start with.
So, with a damaged file within PE, any editing I do thereafter, would also show those same sync errors ? So if I create MPG or AVI or whatever, they will show those same sync errors.
The "chat" desk felt that the issue was with my source DVD material, because it must be missing some "metadata" ?
But, other readers (rather than editors, eg. VLC, ) COULD accept the VOB files without any issues. (Don't forget that at this stage, I am only reading the files in PE. I haven't started any editing yet.)
So, the chat desk recommended another piece of software called Format Factory. With their help, I tried that, and it did fix the problem. But now, I am having to double my work (or worse), to first of all produce an mpg file without sync errors, THEN start to edit those files. If there were 4 VOB files to start with, I could have 4+1 = 5 file manipulations, before I even started editing (the new concatenated mpg file).
So, have I discovered some basic shortcoming of PE (with the handling of metadata) ? There must be a simpler way to avoid sync errors which were not in the original source files ?
First, Premiere (both Pro and Elements) do not handle MPEG Audio perfectly - they like some files, but not all files with MPEG Audio. That makes a VOB a less-than-perfect source file. Still, with a bit of work, one should be able to edit it just fine. One of the factors is that there is a very slight block-size difference between the Encoded Video Stream and the Encode Audio Stream in a muxed MPEG-2 file. That often does not play into things, but can cause slight OOS (Out of Sync) issues. Also, both Premieres need to create all I-Frame files for the Video Stream, which is in GOP (Group of Pictures) structure, so what one sees on the Timeline is really a proxy of the MPEG-2 file's Video Stream. The Audio Stream must also be Conformed to PCM/WAV @ 48KHz 32-bit floating point, to be edited. That Conforming is perfect when one has PCM/WAV @ 48KHz 16-bit for the Audio Stream, but requires more work, when the Audio Stream is MPEG (one reason that some MP3's do not work well in Premiere). Several factors involved here, and a fair amount of work for the program. That is why DV-AVI Type II w/ 48KHz 16-bit PCM/WAV Audio works so perfectly.
Now, fixing OOS might be easy, or might require a bit more work. This article goes into some workflows, that might be helpful: http://forums.adobe.com/thread/436751?tstart=0
I can feel your pain, as I almost went crazy trying to fix OOS in a client's Project. They ONLY had the finished DVD, from which to work. The disc met the DVD-standards, so everything ripped/Imported fine, and when the simple edits were done (IIRC, there were four scenes, that had to be shortened, and then several Titles added), everything played fine in the Timeline. However, when I Transcoded that Timeline to be authored in Adobe Encore, two scenes went OOS. I went back to Premiere, and checked - all perfect there. I tried to judge the number of Frames that the Audio was out, in those scenes, and nudged them, tested, nudged, tested, and no matter what I did, I could never get the output files perfect, when Imported into Encore for authoring to DVD-Video. I tried DV-AVI, and letting Encore set the Transcoding automatically (usually a great way to work), I tried manually setting the Transcoding in Encore. I tried outputting to MPEG-2 from Premiere, and Importing that. No matter what I did, those two scenes were just OOS, and I could not even seem to improve them - it was like they were just locked OOS. I finally did some more editing, to break things up a bit, added a cut-away shot here, and there, and minimized the perceived OOS, but could never get it perfect. It was like trying to pick up quicksilver with a pair of tweezers!