You could also try Davis Pan's (Motorola...or Freescale now I guess)
tutorial on MP3. It deals with filterbank aliasing and cancellation.
On 9/26/05, Ruckert Martin <[EMAIL PROTECTED]> wrote:
>
> Tamij wrote:
> > Dear All,
> >
> > I am DSP engineer working on MP3 decoder implementation. I got
> > doubts while analyzing subband synthesis and IMDCT. In between these two
> > modules, frequency inversion is done for IMDCT output samples. Why is it
> > done here??. What will happen if it is not done? I have searched many
> > forums but couldn't able to get. Eagerly expecting your response.
> >
>
> The point here is that the alias reduction step, that combines two
> freuencies of adjacent subbands (the original and the suspected alias),
> will work only, if the phase difference is correct. To achive the correct
> phase, the frequency inversion step is applied (and its effect must be
> reversed in
> the decoder). For a somewhat more detailed explanation I could recomend
> the book "Undestanding MP3" (sorry, I usually do not like self
> advertisement, but if
> you work on an MP3 decoder, it is probably a good investment anyway) or
> you can
> consult the PhD thesis of Bernd Edler for a very detailed treatment (in
> German) or
> the article in the Electonic Letters, both cited below.
>
>
> Yours
> Martin Ruckert
>
>
> @PhdThesis{Edler95,
> author = {Bernd Edler},
> title = {\"Aquivalenz von {Transformation} und {Teilbandzerlegung} in d
> er {Quellencodierung}},
> school = {University of Hannover},
> year = {1995}
> }
>
>
> @Article{Edler92,
> author = {Edler, Bernd},
> title = {Aliasing Reduction in Sub-Bands of Cascaded Filter Banks with
> Decimation},
> journal = {Electronic Letters},
> year = {1992},
> volume = {28},
> number = {12},
> pages = {1104--1105},
> month = {June}
> }
>
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