[opus] Why does opus scale down frequency from 22k to 20k ?
Timothy B. Terriberry
tterribe at xiph.org
Sat Aug 25 07:12:20 PDT 2012
Orange Ubuntero wrote:
> this action will affect the quality of audio.
Any affect will be inaudible to human ears. For a more detailed
explanation, see http://people.xiph.org/~xiphmont/demo/neil-young.html
> *Can this feature be disable in future ?*
No. It is not possible to encode information for frequencies above 20
kHz in the bitstream, even if an encoder wanted to.
> *Can opus add no noise and echo in audio at high kbps *(192kbps +) *?*
Opus is a lossy codec, so it will always change the numerical values in
the actual signal. But if you can find a sample that you can distinguish
from the original in an ABX _listening_ test (as opposed to by looking
at a spectrogram) at 192 kbps, then we'd certainly be interested in
knowing about it.
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