[Vorbis] several questions

[Monty]

On Mon, Sep 26, 2005 at 01:36:47PM +0200, Balatoni Denes wrote:
> Hi!
> 
> hétf?? 26 szeptember 2005 04.51-kor fangchao ezeket a bolcs gondolatokat 
> fogalmazta meg:
> > Second, from the previos letter,I know that floor is the least squared
> > error approximation of the maximum amount of noise allowable for each mdct
> > coefficient/frequency (determined by the psychoacustic model). Now I am
> > just confused whatever the floor really is .Is it a predition to the MDCT
> > coefficient or just an estimation to the maximum allowable noise? 
> 
> The email "Re: [Vorbis] Floor 1 Decode" from 16 september on this list might 
> help. 
> 
> > And how  the psychoaustic result is applied to the compution of the floor?
> 
> IMHO the psychoacustic result is the allowable noise for each mdct 
> coefficient/frequency.

No; vorbis does not track allowable noise (this strategy was used by
original mp3, but was a big red herring).  The floor is intended to
represent desired unit-scale in a band, in essence, the desired amount
of resolution.  During encode, the spectrum is quantized according to
the floor and then normalized in an effort to preserve tone and noise
energy over any given critical band.

Monty