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> Date: Fri, 26 Nov 1999 01:17:43 -0500 (EST)
> From: [EMAIL PROTECTED] (Ambrose Feinstein)
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> X-UIDL: pI;!!,2K!!?on!!R^ed9
>
> > and more exactly speaking, 16kHz cutoff is used when compression ration
> > is bigger than 9.
> >
> > converting 44.1kHz 16bit stereo PCM into 128kbps mp3, the ratio is about
> > (44100 * 16 * 2) / (128 * 1024) = 10.7
> > so 16kHz cutoff is used.
> >
> > converting 32kHz 16bit stereo PCM into 128kbps mp3, the ratio is about
> > (32000 * 16 * 2) / (128 * 1024) = 7.8
> > so 16kHz cutoff is not used.
>
> this makes me wonder... how exactly do you get energy at frequencies
> above 16khz from a 32khz input? is that meaningful, since it is above
> nyquist?
> --
The "16kHz cutoff" is just shorthand for the "scalefactor band 21 cutoff".
It is only 16kHz at a 44.1kHz sampling rate. At other sampling rates,
you'd have to look up the frequency range of scalefactor band 21 in
the mpeg tables - it cuts off around the top 25% of the frequencies.
--
MP3 ENCODER mailing list ( http://geek.rcc.se/mp3encoder/ )
