[mgdlbp]

Yeah, opus is incredible for speech, but at those bitrates it gives music a kind of sibilant buzzing that I find really hard to listen to, whereas the muffled/underwater effect of mp3 and aac isn't much worse than just a lowpass filter.

What I found a few years ago was that explicitly lowpassing beforehand to match the other encoders (around 4-8kHz) gets rid of the buzzing. Apparently opus' threshold for automatically doing this is a lot lower than the other encoders; it keeps higher frequencies at the cost of more artifacts. I concluded that decimating or setting the encoder to 8kHz/"wideband" or lower was an improvement, with a similar resulting quality to AAC, but I still slightly preferred Fraunhofer at 12-28kbps.

By default, 12 and 24kbps are particularly bad; at 16k the quality goes up from going mono-only, and by 8k bandpassing is automatic.