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

Ulrich Windl Ulrich.Windl at rz.uni-regensburg.de
Tue Nov 6 06:48:07 UTC 2018

>>> Jan Stary <hans at stare.cz> schrieb am 05.11.2018 um 18:00 in Nachricht
<20181105170002.GA72174 at www.stare.cz>:
> 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).


I actually doubt it: I have a sound system with a sub-woover, and I can see the subwoover move before I can hear anything; looks kind of funny... Similar for my headphones: It's not the cheap dirt they sell you everywhere (but also it is not high-end). Still, I'm trying to investigate.


> 	Jan
>> > 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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