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Next-Gen Low-Latency Open Codec Beats HE-AAC
Aldenissin writes "From the Xiph.org developers, Opus is a non-patent encumbered codec designed for interactive usages, such as VoIP, telepresence, and remote jamming, that require very low latency. When they started working on Opus (then known as CELT), they used the slogan 'Why can't your telephone sound as good as your stereo?', and they weren't kidding. Now, test results demonstrate that Opus's performance against HE-AAC, one of the strongest (but highest-latency) codecs at this bitrate, bests the quality of two of the most popular and respected encoders for the format, on the majority of individual audio samples receiving a higher average score overall. Hydrogenaudio conducted a 64kbit/sec multiformat listening test including Opus, aoTuV Vorbis, two HE-AAC encoders, and a 48kbit/sec AAC-LC low anchor. Comparing 30 diverse samples using the highly sensitive ABC/HR methodology, Opus is running with 22.5ms of total latency but the codec can go as low as 5ms."
and remote jamming
Took me a while to figure out they meant in a band. I was wondering how they were going to jam some sort of signal with this codec.
Sent from my PDP-11
As mentioned, it's needed for VoIP systems. With a full-duplex system, more than 150ms of lag is audible and noticeably uncomfortable, breaking the flow of conversation (As the apparent lag is doubled in a "conversation", with the delay at each end adding cumulatively). For simple half-duplex systems like gaming, more lag is not really noticeable.
Yes, 5 to 22.5 ms is the algorithmic delay of the codec. By comparison, codecs like AAC/MP3/Vorbis have more than 100 ms algorithmic delay (you need to give the encoder side more than 100 ms of audio before the decoder side gives you any audio back).
Opus: the Swiss army knife of audio codec
Lol what? You're crazy. I suppose it is never worth inventing a new codec ever, since everyone uses old codecs! /fail argument
To be exact, there *are* patents, but they will be available without fee in a way that is compatible with FOSS licences such as the GPL. The main idea behind these patents is that your license terminates if you sue someone by claiming Opus infringes your patents. Almost like a copyleft, but for patents (of course the details are different because copyright != patent).
Opus: the Swiss army knife of audio codec
While your rant appears informative if not insightful on its face, it is completely missing the point.
This is a test of audio codecs at low bitrates.
I don't know what this "LE-AAC" is you speak of (and rather suspect you don't either) but AAC-LC was actually in this test, as the low anchor.
At these bitrates (~64kbps) HE-AAC (despite its "low-accuracy" as you put it) is perceptually better sounding than AAC-LC. Lossy audio codecs (even the LE-AAC [sic] encoder in Apple's Core Audio framework you love) can only be judged by how they sound, not how they look. "Accuracy" is not a metric very worthy of discussion.
What makes you say that? If you find a real issue, please raise it -- either on the mailing list: codec@ietf.org, or to me privately (jmvalin@jmvalin.ca). Skype is on the good side on this one. The technology they have contributed is very useful and they're open about resolving any licensing issue.
Opus: the Swiss army knife of audio codec
If we were talking about a 96 kb/s test, I'd agree with you. But at 64 kb/s, HE-AAC sounds much better than AAC-LC. The guys who organized this test picked the best AAC implementation they could find at the rate the test was run at.
Opus: the Swiss army knife of audio codec
Perhaps they could switch to "has not yet been challenged in court for any possible patent infringement". But who would use a codec like that? Besides Google, of course.
Companies do this all the time. Anyone shipping H.264 has this risk, as the patent pool provides zero guarantee no outside patents will pop up.
Actually, anyone shipping anything at all has this risk.
Realistically, it's more like "does not infringe any known patents, or has licenses for them, and is not infringing any other patents that we could find in a patent search".