Hiya,
> I dont think it was ever in doubt that xr is an amplitude? xr(i)
> is the i'th the MDCT coefficient in the expansion of the original wave
> form in terms of cosine functions with wave number i.
>
Not exactly... Term i in the mdct corresponds to sine/cosine waves number
i _and_ i+1, added together. And of course we have two overlapping mdct
blocks, _both_ of which give some i and i+1 waves... sigh.
>
> > I think we should use energy difference in db, so the noise formula
> > should be
> > sum (10 log (xr^2 - ix^(8/3)))
> > or
> > 10 log (sum(xr^2 - ix^(8/3)))
> >
For the psy model we should use whatever the model was made for; I think
energy difference is better, but a model that relies on amplitude diff.
should be implemented that way.
> > and I think the latest quantization method will do the best aproximation
> > even when we use this noise formula.
However, quantization comes _after_ the psy model, and energy difference
quantization gives the best result (theoretical & in listening tests).
Hope I hurt no-ones feelings,
Ciao,
**Segher
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