I don’t think it was intended by the makers for the audio to be played in very low volume and obviously very compressed sounding. The raw AC3 plays just fine when played by basically all media players. It’s only when you import it in audacity, it’s when the quality degrades a lot. I finished my project using audacity unbeknownst of the drc_scale issue and all my videos sound worse than the source videos/source DVDs.
I rip DVDs losslessly with makemkv and extract AC3 files losslessly from mkvs with mkvcleaver. As I said, now that I know of the drc_scale issue, I always convert AC3s with ffmpeg to proper waves with drc_scale disabled before importing them in audacity, but this step should be included in audacity’s ac3 import function imo.
An option for drc_scale is a possibility, but the default should never be as it is now because drc_scale literally has only disadvantages. There is nothing to lose if you disable drc_scale, only things to gain. Files that don’t have DRC ignore the drc flag and import as usual and files with drc will import in their full quality. Audacity prides itself in being the best audio editing software, so it only makes sense that it would import AC3s in their full quality and not in a compressed state. Please disable drc_scale in Audacity’s AC3 import function. The code is already there.