[opus] recommended opus bitrate / opusenc setting for general?

Mark Harris mark.hsj at gmail.com
Sun Oct 25 21:21:29 PDT 2015

Christoph Anton Mitterer <calestyo at scientia.net> wrote:
> So basically, with 100 kB/s or say 128 kB/s one should be more or less
> safe and very close to transparency, right?!

Yes, assuming you mean kb/s (kilobits, not kilobytes, per second), and
no more than 2 channels (stereo).

> Are there any bitrates recommended (e.g. for quality or performance
> reasons)? E.g. that one should use 128 kB/s rather than 127 kB/s or is
> this anyway moot, since with VBR it's just a target value?

For VBR it is just a target value and the actual value will vary.
There is no need to choose any specific value; the target does not
even have to be an integer number of kb/s.

> When I increase the encoding complexity to 10, this won't have any
> noticeable effect on the decoding complexity, right?

10 (the maximum) is the default encoding complexity in opusenc, and
assuming you are encoding on a laptop or desktop from the past decade
there is little reason to use another value.  The complexity setting
is intended to impact the complexity of encoding only, not the
complexity of decoding.

> Last but not least, since my purpose would be listening to music, is it
> best to set the framesize to its maximum (60ms)?
> And will this have any bad side effects, like on gapless playback or
> so?

Sizes larger than 20ms reduce encoder flexibility and are generally
beneficial only at low bit rates, or when there is a large per-packet
overhead (e.g. when transmitting via RTP).  For your use case 20ms
(the default) is the most efficient.  Gapless playback works with any
frame size.

 - Mark

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