Request to Implement Proper DVD-Audio Support
DVD-Audio is a separate format that is very similar to DVD-Video defined in the DVD Specifications. There are a couple thousand releases on the format, most of them being high-profile releases, largely released from 2001 to 2006. There are still titles that use this format coming out today. It's purpose is really to deliver high-resolution and multichannel music, similar to SACD or Blu-ray Audio.
The reason I bring this up is because this is the only prominent "niche" format (the others being SACD and BD-A) that you cannot playback easily on a modern device, even though it's part of the DVD Books! Your only option for proper, full-menu playback is to find a really old copy of PowerDVD or WinDVD (Foobar2000 can play these discs, but without menus).
Now, as a non-developer, I have no clue what it would take to implement playback functionality. From what I understand based on the internet and reverse-engineered specifications, the actual format is coded very similarly to DVD-Video. In fact, it has more restrictions/less complicated code allowed, which may help with testing? Here are some resources I think will give enough info to implement basic playback functionality.
Reverse Engineered Specifications
Incomplete listing of DVD-Audio releases, in case anybody needs to buy discs to test out
Now, VLC doesn't actually appear to be able to play these discs properly, contrary to what the internet suggests. This is why issues 27313, 27314, and 27315 exist. VLC seems to recognize only the audio from the AOB files, sure, but doesn't actually read the chapter/grouping data from the IFO files, which cannot be considered proper basic playback. Furthermore, menus and still images are non-functional, as VLC recognizes the image data (which is stored in the same way as a DVD-Video) but not the instructions from the DVD-Audio IFO files. This poses problematic, because there are many DVD-Audio titles with significant visual content that cannot be accessed as intended.
To whichever developer (or developers) read this, thank you for your time.