[XviD-devel] gmc problem - who to blame? version 2.0

Christoph Lampert chl at math.uni-bonn.de
Sat Aug 9 15:11:36 CEST 2003


On Sat, 9 Aug 2003, Radek Czyz wrote:

> > If I'm right, it's in gmc.c. If I compile this module with
> > optimizations, it decodes my buggy clip flawlessly. If without them,
> > it decodes just like libavcodec.
> 
> It was easier than I thought to narrow it down. It's Predict_16x16_C()
> function - with optimizations works differently than without.
> 
> Unfortunately, I have problems unserstanding what this function does
> (or rather, how).
> 
> I'm doing my best to discover the difference. :)

Output of Predict_16x16_C only depends on data in NEW_GMC_DATA This.
You might want to check if this contains identical data in both cases
first.

If that is the case, you might want to try if the compiler treats 

if ((uint32_t)u<=(uint32_t)W)

and 

if ((uint32_t)v<=(uint32_t)H)

correctly.

The rest I find pretty straighforward, I can't see problems there. 

gruel



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