You sure Dolby Digital is that low of quality? From what I understood it was lossy compression but mainly limited by the bandwith of things like optical cables and could approach some pretty decent levels. Just because it might be at a similar sounding bitrate does not mean the quality is the same.
edit: This explains the differences pretty well - Dolby Digital (original version) can go higher than 320kbs
edit: This explains the differences pretty well - Dolby Digital (original version) can go higher than 320kbs
https://ottverse.com/mp3-aac-ac3-wav-wma-opus-audio-codecs-d...