I was pleasantly surprised when I found someone concocted a clever way of using jPSXdec to decode CD-i audio.
As explained in Jonathan Atkins's CDXA documentation, the Sony Playstation 1 and the Phillips CD-i both used the same audio format on their CDs. It never occurred to me that the CD-i likely has a retro community still following it, much like the Playstation 1 does.
This video describes a working solution to extracting CD-i audio with jPSXdec that will work with any game. However, after the extraction, you have to manually break up the audio clips and possibly adjust the speed of some.
Alternatively, you could do the job that jPSXdec can't yet do so the extracted audio clips don't need any extra editing.
If you let jPSXdec do its best to index the CD (or raw music file), it will find all the audio sectors, but fails to concatenate most of the contiguous streams. You're left with several thousand audio clips with a duration of 1 sector. It wouldn't be too difficult to write a script that checks the audio properties (channel, frequency, etc) and finds what sectors should be combined into a single audio clip. It even sounds like someone has already managed to make some headway with this.
Adding better CD-i audio handling to jPSXdec is quite easy, and will be included in the next release (whenever I can get this redesign finished). As for CD-i video, I can't say I have much motivation (or time) to figure it out. But if anyone wants to get their hands dirty and write some decoding code of their own, I'd be happy to support them however I can.