[vorbis-dev] Spectral band replication

[Aleksandar Dovnikovic]

"Stefan T. Böttner" <virtual.man at t-online.de> wrote:

> Harmonic frequencies are integer multiples of the fundamental frequency.
> That means if you take all frequencies in a particular block (say up to
> 11 KHz for a medium bitrate encoding), double them and add them to the
> original at a lower volume, then this results in frequencies up to 22 KHz.
>
> I suppose that taking anything else but harmonics will rather end up in
> more noise. And don't know if that's it what mp3pro does, because I
> didn't find any details, and they probably won't give them out.

No, there are no details as to how SBR really works. But there's probably
more to it then just adding the harmonics. After all, SBR is probably
patented and it would look silly if they would try to patent a simple thing
like adding harmonics. :-)

> I already tried this with music that I downsampled to 11 KHz, i.e.
> frequencies up to 5.5 KHz, and it did sound much better when adding the
> harmonics x2, x3, x4 or even more.

Hmmm... maybe Vorbis should implement something like this for
low bitrates?


---
Aleksandar @ Vorbis Xtreme | http://solair.eunet.yu/~aldov
Ogg Vorbis is the free, open source alternative to MP3

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