Two newbie question about TMPGEnc (XPress)

[Birdie1]

As a newbie with conversion I would like to ask 2 questions about the use of TMPGEnc XPress for converting divx files to dvd.
1) With some divx files I have the strange (?) phenomen that under clip info I find the correct length of the video but the length of the audio source is almost 4x longer. Subsequently when I add the file the source info of the clip gives the audio length as length of the clip (e.g. 4.22h for a clip that is really 1.19h). What could be causing this ?
2) Anyway I found a way to solve this by extracting the audiofile with VirtualDub to a wav. file. But what I would like to know is what is the best way to process the audiofile. Should I do it by adding it in TMGEnc XPress as audiosource, or is it better to save it and add it during authoring (in my case with TMPGEnc DVD Authoring) ? Or doesn't that matter ?
I would appreciate any help, because I would like to learn as much as possible and as soon as possible.
Thanks
Ton

[johns0]

Best way is to add it during authoring,i use ffmpeg to make the wav into ac3 and just use tmpgenc for encoding the video only.Tmpgenc has problems with vbr mp3 audio,thats why you will get strange file sizes.

[Birdie1]

Thanks johnsO. I checked the files that gave incorrect lengths in TMPGEnc with GSpot and they had indeed VBR audio. The ones with correct length were all CBR.
Btw I realise that I have bought TMPGEnXpress complete with the AC3 plugin (looking at it afterwards, maybe unnecessary ?) . I assume that then the only way to use this plugin is to add the extracted audio in TMPGEnc itself ?
Thanks again for your explanation.