[XviD-devel] Quarterpel problem.

Tue, 8 Oct 2002 16:12:30 +0800

Hi,

In standard 7.6.9.5.3, it did say that. But it's describing the DIRECT
mode, isn't it?
Anyone has MomuSys reference you may look at function B_MotionCompensateMB.
It does InterpolateBlock with 16x16 blocks... As the standard section
7.6.9.2 ~ 7.6.9.4,
the luminance MC are all in 16x16 blocks.

Is that my misunderstanding?? :p
--
Jeanson Hung
BU2, ADMtek Inc.
Phone: +886-3-5788879-521

                    Christoph                                                                                       
                    Lampert               收件人：     xvid-devel@xvid.org                                          
                    <chl@math.uni-b       副本抄送：                                                                
                    onn.de>               主旨：  Re: [XviD-devel] Quarterpel problem.                              
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                    xvid-devel-admi                                                                                 
                    n@xvid.org                                                                                      

                    2002/10/08                                                                                      
                    03:26 PM                                                                                        
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                    xvid-devel                                                                                      

Hi,

On Tue, 8 Oct 2002 jeansonh@admtek.com.tw wrote:
> [...]
> I also modified the code to decode B-VOP with quarterpel. If combined the
> core
> with xvid_decraw frontend, the decoding process 'SEEMS' okay, but failed
> if compiled as directshow filter... :( The source sequences are generated
> from
> DivX 5 CODEC...
>
> And... in standard, B-VOP with quarterpel in forward, backward, and
> bi-directional
> mode should be interpolated within the 16x16 pixels. But in DivX
> implementation
> it looks like using 4 8x8 pixel blocks to do the interpolation. Anyone
> knows
> whether it's correct or that's my misunderstanding?

Where does it say 16x16? I just found

7.6.9.5.3 Generation of prediction blocks
Motion compensation for luminance is performed individually on 8x8 blocks
to generate a macroblock. [...] Note that in the case of quarter sample
mode, the motion compensation of four 8x8 blocks, using the same motion
vector for each block, does not lead to the same result as the motion
compensation of a single 16x16 block using the same vector. This is due to
the block boundary mirroring described in subclause 7.6.2.2.

> How could I provide my codes? :)

Easiest method at the moment is to send a patch to xvid-devel.

gruel

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