[polshaw]

They mention 256kbps in regards to that, at which point all of vorbis, aac and mp3 (lame) are 'perceptually lossless', so it wouldn't be much new. While it is hard to tell (because tests at higher bitrates don't really work out/ produce winners), it seems that any sonic advantage held is at the lower bitrate end.

[nullc]

Measuring the point where something becomes perceptually lossless is quite difficult because, by definition, you're measuring at the bounds of perceptibility.

In terms of simple objective measures (e.g. the masking weighed SNR, http://people.xiph.org/~greg/celt/NMR.v.c.l.png) Opus does better than Vorbis (and AAC) at high rates too. Between that and the overall better time domain performance, my _expectation_ is that Opus can become perceptually lossless at lower rates, but this is hard to validate.

Getting the lowest possible average perceptual lossless rate is also a product of the encoder having a good psymodel, and released opus encoders have pretty much no explicit psymodel at all (but still manage to be competitive). So this reduces the interest in doing a bunch of very difficulty listening tests to determine the exact perceptually-lossless points, since they'll likely go down with near term encoder improvements.