[vorbis-dev] Spectral band replication

[Stefan T. Böttner]

Hello!
I have the following idea about this "spectral band replication":

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.

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.

Stefan T. Boettner

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