[Mp4-tech] HE-AAC downsampled synthesis filterbank

[Andreas Schneider]

As far as MPEG (and the national bodies that are represnted there) is 
concerned, this corrigendum is finished. The only step that is missing is 
publication by ISO. Once this has happened it will be available at no cost 
for download from the ISO-store. But I have no way to tell when this will 
happen.
BR,
Andreas
mp4-tech-bounces lists.mpegif.org wrote on 26.09.2023 03:16:35:
> Thank you! Is this corrigendum currently under drafting? It is nice if
> I can read the details. But do you mean that the documentation you
> mentioned is not available from ISO, no matter being free or not?
> 
> On 9/25/07, Andreas Schneider <Andreas.Schneider codingtechnologies.
> com> wrote:
> > Hi Andy,
> >
> > this is no trick. It was a typo in the specification that has been
> > corrected by ISO/IEC 14496-3:2005/Cor.4:200X. As the 200X suggests, 
this
> > corrigendum is not yet published.
> >
> > Kind regards,
> >
> > Andreas
> >
> >
> > mp4-tech-bounces lists.mpegif.org wrote on 25.09.2023 14:25:14:
> >
> > > Hi folks,
> > >
> > > I read the ISO spec 14496-3 Amd 1 on downsampled complex synthesis 
QMF
> > > filter. On page 67, it is said the filterbank coefficients are 
defined
> > > as (1/64)*exp(i*pi*(k+.5)*(2*n-127)/64).
> > > However, when I turn to the ISO reference, in ct_polyphase.c, the 
code
> > > defines the coefficients like:cos( PI / 64.0 * (k+0.5) * (2*l-127.5)
> > > ).
> > >
> > > My question is why the spec uses 127 while its reference code
> > > implementation uses 127.5. I don't understand this 0.5 trick. Can 
any
> > > one explain this for me? Thanks in advance.
> > >
> > >
> > > --
> > > Regards,
> > > Andy Quan
> > > _______________________________________________
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> >
> > --
> > Andreas Schneider
> > Senior Research Engineer
> > mailto:snd CodingTechnologies.com
> >
> > +49 911 92891 -26 (phone)
> > +49 911 92891 -99 (fax)
> >
> > Coding Technologies GmbH
> > Deutschherrnstr. 15-19
> > D-90429 Nuernberg, Germany
> > http://www.codingtechnologies.com
> > HRB 17557, Amtsgericht N?rnberg, GF: Dipl.Ing. Martin Dietz (Managing
> > Director)
> >
> >
> 
> 
> -- 
> Regards,
> Quan Zhengyuan （全正元）
> 
> _______________________________________________
> NOTE: Please use clear subject lines for your posts. Include [audio,
> [video], [systems], [general] or another apppropriate identifier to 
> indicate the type of question you have.
> 
> Note: Conduct on the mailing list is subject to the Antitrust 
> guidelines found at http://www.mpegif.org/public/documents/vault/mp-
> out-30042-Antitrust.php

--
Andreas Schneider
Senior Research Engineer
mailto:snd CodingTechnologies.com
+49 911 92891 -26 (phone)
+49 911 92891 -99 (fax)
Coding Technologies GmbH
Deutschherrnstr. 15-19
D-90429 Nuernberg, Germany
http://www.codingtechnologies.com
HRB 17557, Amtsgericht N?rnberg, GF: Dipl.Ing. Martin Dietz (Managing 
Director)