OPUS

Hizzi
2013-03-24
2013-03-30
  • Hizzi

    Hizzi - 2013-03-24

    Hello developppers and users i have a question about mumble 1.2.4 i've seen
    we can use the OPUS codec so 1 found this link http://www.opus-codec.org/
    and i'am confused,
    it's say :

    • Bit-rates from 6 kb/s to 510 kb/s
    • Sampling rates from 8 kHz (narrowband) to 48 kHz (fullband)
    • Frame sizes from 2.5 ms to 60 ms
    • Support for both constant bit-rate (CBR) and variable bit-rate (VBR)
    • Audio bandwidth from narrowband to fullband
    • Support for speech and music
    • Support for mono and stereo
    • Support for up to 255 channels (multistream frames)
    • Dynamically adjustable bitrate, audio bandwidth, and frame size
    • Good loss robustness and packet loss concealment (PLC)
    • Floating point and fixed-point implementation

    But in mumble client 1.2.4-rc1-9-gdeeeb72
    bit-rates can only be from 8 to 97kb/s
    And frame sizes from 10ms to 60ms


    i know this is not the final version but i've search all the day for
    testing this codec with mumble but i just wondering if it is just a mistake
    or it is normal to always have this number.
    (sorry for my english)

     
  • Stefan H.

    Stefan H. - 2013-03-30

    Mumble doesn't use the full range of what Opus could theoretically provide. Frame sizes below 10ms produce inapropriate overhead in encoding and transmission and your run-of-the-mill audio device isn't able to deliver them either so we don't use them. The bitrates are limited by what we consider sensible and what our protocol can support without too much changes. 97kbit/s for a mono audio stream is quite a lot. Stereo Mumble doesn't support (yet). We also only use CBR because of security and jitter considerations.

    When adopting a codec for a specialized application you generally won't use all of its features and operating modes but select ranges/points that fit your application.

     

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