> These have a fixed data rate of 64 kbit/s (bidirectional). You can see that, at that bitrate, even a sophisticated codec, like AAC, will be limited in quality.<p>It needs a little more explaining. It is 64kbps while keeping it extremely low latency that makes it difficult. AAC-ELD has a coding delay down to 7.5 ms at a sampling rate of 48 kHz.<p>Considering they have to paid for AAC-ELD and EVS, I wonder why they didn't choose EVS over AAC-ELD, or Opus.<p>I think audio codec is mostly a solved problem for music, the next frontier is how do we get sub 5ms latency to sound exceptionally good with 64kbps only.