[XviD-devel] Questions on Quantization

[Luca Piccarreta]

Hi Skal,
Are you sure about what you said about Intra DCT Mismatch Control?
I checked the MS ref sw (W4866) and it looks like mismatch control
for intra dct is there (see inverseQuantizeIntraDCTcoefMPEG).
Of course it's not there for H263 Quant Type
(see inverseQuantizeDCTcoefH263).
I'm also checking the latest 14496/2 I have available (N5546,March 2003)
and I can't see anything about different mismatch control for Intra DCT.
Now, for my personal opinion, I think that the whole float DCT stuff is
crazy, mismatch control is crazy, long live integer-defined transform and
bit exact conformance :)
And of course the impact of not having mismatch control for Intra frames
is almost null.
Regards,
Luca Piccarreta.



----- Original Message ----- 
From: "Skal" <skal at planet-d.net>
To: <xvid-devel at xvid.org>
Sent: Thursday, March 24, 2005 10:35 AM
Subject: Re: [XviD-devel] Questions on Quantization


>
> Hi Arthur,
>
> On Thu, 2005-03-24 at 03:53, Arthur.Jiang at dintop.com wrote:
>
> >
> > 2) According to the implementation of MPEG quantization method in
xvidcore,
> >
> > the mismatch control isn't performed for intra-block. Why?
>
> > The mismatch control should be performed for both inter-block and
intra-block according to the standard's description.
>
> two remarks:
>
> you should be precise about what 'standard' you are referring to.
> MPEG-2 (ISO 13818-2) do have mismatch control for Intra, but MPEG-4
> (ISO 14496-2) hasn't. Only inter dequantization needs it.
>
> Moreover: you are talking about *quantization*, not
> *dequantization*, right? In such case (quantization.
> that is: the encoder), one is free to do anything he
> wants during quantization (including feeding the matrix
> with random numbers;). And taking the mismatch-controlled
> coefficient #63 into account for RD-opt, e.g,  really isn't
> worth the hassle.
>
> hope it helps,
> Skal
>
>
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