> are there codecs that have much better (perceptible) quality than Apple AAC 256kbps (or achieving similar quality at, say, 160kbps?)
Opus achieves ABX transparency at around 128kbps (as in, the threshold where the vast majority of users taking a fidelity test are unable to tell the difference between the opus-encoded and lossless version).
> NOTE:Opus doesn't support 44.1kHz sample rates, so encodes to 48kHz sample rate. As this causes browser playback issues, it has been resampled back to 44.1kHz. This may affect the sound quality, so this test should be taken with caution.
Is very surprising to me, in two ways.
Firstly I knew 44100 is a relic due to historical reasons, but it's still a quite widely used sample rate in audio world. I have no idea Opus does not support it.
Secondly, it seems to imply browser can't playback 48kHz audio properly. I didn't dig the details, but this sounds weird. Just like 44100, 48k is a very common sample rate, I can't imagine browser would have trouble with it (or any arbitrary sample rate, to be honest).
Like jasomill mentions, the browser playback issues statement has not been true on desktops for a long time. The most recent (or only) example I know of is iPhones, which finally added passable support for non-44.1kHz audio somewhere between iOS 15.7 (late 2022) and last august. Until then they'd sound like a broken vinyl deck when playing 48 kHz audio, oscillating in playback rate and crackling like crazy -- especially when passing through an AudioContext.
The browser audio limitation is presumably a workaround to some bug or performance limitation that was relevant at some point in history (the site was created in 2014).
Opus achieves ABX transparency at around 128kbps (as in, the threshold where the vast majority of users taking a fidelity test are unable to tell the difference between the opus-encoded and lossless version).
https://abx.digitalfeed.net/opus.html