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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
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
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
This is the license for the "old" SILK codec. The patent licenses for Opus has nothing to do with that. Please read them:
Xiph.Org IPR statement: https://datatracker.ietf.org/ipr/1524/
Broadcom IPR statement: https://datatracker.ietf.org/ipr/1526/
Skype IPR statement: https://datatracker.ietf.org/ipr/1525/
Opus: the Swiss army knife of audio codec
Skype will release their patents under a free software compatible license if the codec is standardized by the IETF: https://datatracker.ietf.org/ipr/1525/
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
He was discussing accuracy as being irrelevant because perception is more important in a medium designed to be perceived by a human. You've now apparently converted it to "because fewer people care about accuracy", which was in no way his point. Or: Straw man.