[XviD-devel] Re: qpel smearing/noise problem

[James Hauxwell]

In qpel mode you can have 8x8 and 16x16 blocks

The process is
8tap filter horizontal
Bilinear filter horizontal
8tap filter vertical
Bilinear filter vertical

If you are only half pel then you only need to the 8tap
horizontal/vertical interpolation

Maybe under both H&V you are not doing the filtering in the correct
order.  This would explain the problems.

Jim

-----Original Message-----
From: xvid-devel-admin@xvid.org [mailto:xvid-devel-admin@xvid.org] On
Behalf Of radoslaw@syskin.cjb.net
Sent: 09 January 2003 12:20
To: xvid-devel@xvid.org
Subject: Re: [XviD-devel] Re: qpel smearing/noise problem

This problem is - obviously - not only related to idct.

However, the results are very strange:

When XviD idct was used, xvid could decode everything correctly, but
ffdshow with xvid idct - couldn't.

When 'simple' idct was used in xvid, ffdshow (with 'simple' or
'reference' idct) is able to decode H and V interpolation correctly -
but not HV. No other changes has been made to anything.
Does anyone has any explanation? There must be an explanation for
this...

HV interpolation wasn't decoded correctly in any case - using
reference idct, both in encoder and decoder, didn't help either.

Does anyone remember where can I find in the specs, what size of block
is used for halfpel interpolation in qpel mode? I've been doing all my
experiments both on 8x8 blocks and 16x16 blocks, simply because I don't
know which is correct. I'v been looking for it, but I havn't found the
answer.

Radek

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