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Next-Gen Low-Latency Open Codec Beats HE-AAC

Posted by timothy on from the ogg-still-rocks-anyhow dept.

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."

2 of 166 comments (clear)

  1. Re:Total Latency by jmv · · Score: 5, Informative

    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
  2. Re:HE-AAC is worse than LE-AAC in terms of quality by woolpert · · Score: 5, Insightful

    HE-AAC uses SBR to reduce its data footprint. This results in worse reproduction of the source audio than LE-AAC at same bitrate (and often even lower bitrate). The whole deal with HE is that it can maintain good quality at very low bitrate, by giving up accuracy. So far, Apple's LE-AAC encoder in their Core Audio framework is the best choice for digitally non-lossless compression.

    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.