[Mp4-tech] AAC: PR property of the SBR QMF

[mark_wezelenburg zonnet.nl]

Dear all,
With respect to 4.B.18.2 and 4.6.18.4.2 of 14496-3
Amd 1 (SBR)
The pair of analysis and synthesis (complex) QMF
filterbanks is not quite PR. This may be part of the
design, but inspecting the filter structure and PR
conditions, one can observe that by either applying
in the analysis or synthesis filter, the reverse template,
the reconstruction noise is substantially lower.
The question is then: Is the non-PR property the
intended one, or should one indeed reverse the template
at either encoder or decoder ?
Regards,
Mark
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