[opus] Antw: Re: Antw: Re: Possible bug in Opus 1.3

Jan Stary hans at stare.cz
Mon Nov 5 17:00:06 UTC 2018

On Nov 05 11:32:49, hans at stare.cz wrote:
> On Nov 05 11:05:34, hans at stare.cz wrote:
> > > Did you also try to listen at the beginning, shortly before the real tone appears in the audible spectrum? While significantly larger, Opus had produced significant ghost noise (much less than Vorbis did)...

I experience the "same" low level noise even in a wav file,
even on frequencies a bit higher, when playing on shitty enough speakers.
I don't think it is a relict of the compression (it cannot be, here).

Every speaker (or headphones) is designed for a certain frequency range.
Outside of that range, all bets are off. I wouldn't bother with what you
"hear" outside of the audible spectrum.

My current bet is that the very low frequencies are correctly
represented in the Opus file, but your speaker/headphones
are not capable to play them properly (which is no wonder).


> > Yes. But given that these are not audible sounds,
> > the various codecs might use various strategies of throwing them away.
> > I have no solid knowledge of what e.g. Ogg vs Opus does, but I would
> > just throw away any frequency below, say, 15 Hz. Maybe they do/don't,
> > and this might be the result.
> Have you also tried creating a swepp only up to those frequencies?
> Say, 1 to 20 Hz? Is the low-freq noise still there?
> 	Jan

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