[opus] opusenc constant quality setting

[Larry Fenske]

I'm a bit confused about VBR with Opus.  I see that the default is VBR,
but I don't see any way to specify a quality setting.  I can set a
target bitrate, but that's definitely not what I want; I want a constant
quality level, like "-q" in oggenc, and for the encoder to select
bitrates based on the desired quality.

For example, for playback through earbuds or laptop speakers, I wouldn't
need anything better than low quality; through good headphones or decent
stereo speakers, medium quality; and for playback through $5000
speakers, high quality.  Bitrate is not relevant in these cases, except
I don't want the file to be larger than necessary for the desired quality.

Is this possible with opusenc?

Thanks,
- Larry