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

[Ulrich Windl]

>>> Jan Stary <hans at stare.cz> schrieb am 05.11.2018 um 20:01 in Nachricht
<20181105190138.GA78488 at www.stare.cz>:
> On Nov 05 18:00:06, hans at stare.cz wrote:
>> 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).
> 
> Attached I send the spectrogram (vic SoX) of the first 20 seconds
> for the wav file and the opus file. Indeed, there is extra noise
> for the low frequencies, but somewhere around ‑100 dB.

OK, that looks very much convincing; I'll investigate...

> 
> 	Jan