John, in the article “NPR Labs Eyes Streaming Technology” [radioworld.com, keyword Kean], I wish that you had also looked at Opus (http://opus-codec.org/).
I would love to see how it stacks up against the others at 24 through 48 kbps. The low latency of Opus and its widespread implementation (e.g. Firefox, softphones, patched BUTT and VLC) make this a natural but bleeding-edge codec. Some proponents of Opus are calling it the Swiss Army Knife audio codec because it does everything at least pretty well.
Its open-source implementation (li-cense free), IETF standard approval, low latency and high performance at low data rates make it very interesting for stream distribution (Icecast), high-fidelity VoIP and remote broadcast transport.
I know that Opus is head and shoulders better than MP3 at 24 to 48 kbps, and even sounds nice on voice at 16 kbps; but how does it measure up against the high-performance older codecs?
Edward (Ted) Schober, PE
Consulting Engineer
Radiotechniques Engineering
Haddon Heights, N.J.
John Kean of NPR Labs replies: I am sure the Opus codec would beat AAC+/HE-AAC at 32 kbps and below, but one of the qualifications was that it be natively available in most consumer devices, such as tablets, phones, etc. As good as Opus may be, it didn’t meet that requirement, and we were constrained by the number of codecs we could test (xHE-AAC, which beat HE-AAC at low bit rates, was included for its potential as a future codec, and it appears to be increasing in new consumer devices since our test). Some stations continue to stream MP3 with HE-AAC, to minimize the chance of disenfranchising some listeners, so availability across all platforms seems to remain an important factor. I’m with you — I’d love to do a test with Opus!
