I have been using the following process to extract audio from DVDs. The process works OK, but I'm not sure whether any of the steps is compromising the quality of the final audio unnecessarily.

Step 1 - rip DVD to separate vob files per chapter using Smartripper
Step 2 - demux vob files to AC3 using DVDLAB (I already had DVDLAB and it can demux vobs - that is only reason for this choice of tool)
Step 3 - convert AC3 to WAV using Nero Wave Editor. (I just open the AC3 and "save as" WAV - no actual editing is done).
Step 4 - downsample from 48kHz to 44.1kHz and Normalise with Adobe Audition.

Could one of you good people advise if any of these steps is degrading audio more than would be the case with alternative methods. If you can recommend a way that gives noticeably better result, I'll make the change.
Thanks

AC3 to 16 bit /channel WAV at 48k, then going to 44.1k, is probably a little weaker than making that transition in one step - isn't there any AC3 input capability in Audition ?

http://ac3filter.sourceforge.net/ this can output higher resolution, if your software can handle it
'Sample format' combo box sets output sample format. There are PCM 16 bit, 24 and 32 bit and PCM Float formats are now supported.

Cutting the resolution to 16 bits before rate conversion and normalizing could be losing you a bit or 2 from the final result, more if you need a lot of normalizing or compression...

I haven't found any way to get Audition to open AC3 files - that is the only reason I use Nero for that step. If anyone knows how to get Audition to read AC3 files, please let me know.

For 1 or 2 channel only, for 5.1 etc. this gets more complex.

Audition/Cool Edit Pro will not read AC3 compressed format, you need to uncompress them into WAVs which you are doing. You can skip all that and just use "DVD Audio Extractor" and rip them directly on the fly into WAVs = http://www.tucows.com/preview/343833.html

There is no reason to downsample to 44.1kHz unless you want to make a CD Audio disc from them, Audition/Cool Edit Pro will easily support 48kHz WAVs and you can edit them ect.

I can't comment directly on quality of the following steps, but I do know your procedure can be simplified to only two steps rather than 4.

DVD decrypter (freeware) will rip a DVD and demux the audio to an AC3 file in one step.

HeadAc3he (freeware) will convert to WAV and downmix to 44.1 khz in one step.

The main time is in the ripping stage of dvd decrypter (typically 15 mins for a DVD of 1 hour of recording). Headac3he is very fast (typically 4 mins for 1 hour of recording).