[Mp4-tech] SA-DCT Approach

[Herbert Thoma]

Forward and inverse SA DCTs are defined in Annex A of ISO/IEC 14496-2.
This annex is normative.
Andrew Kinane schrieb:
> 
> Hello,
> 
> I was wondering if it is a normative part of the MPEG-4 standard to take the
> SA-DCT of the columns of an 8x8 block followed by taking the SA-DCT of the
> resulting rows (coupled with taking and SA-IDCT of rows followed by the
> SA-IDCT of the resulting columns) i.e an encoding decoding sequence of
> COLUMN -> ROW -> ROW -> COLUMN
> What I am asking really is: is it permitted to do the sequence
> ROW -> COLUMN -> COLUMN -> ROW

No, its not permitted.
Regards,
 Herbert.
> I am asking this since for the shape adaptive transforms
> COLUMN -> ROW -> COLUMN -> ROW and
> ROW -> COLUMN -> ROW -> COLUMN
> may give erroneous results depending on the alpha mask for a boundary 8x8
> block so it is important that the SA-DCT and SA-IDCT be compatible in this
> sense.
> 
> Thanks,
> 
> Andy
> 
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-- 
Herbert Thoma
FhG-IIS A, Studio Department
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