[MPlayer-dev-eng] another libavcodec bug ...

[Arpi]

Hi,

> > i just found a file which shows some artefacts on the left edge of the
> > image mostly on the bottom 50% (occures several times in the first 2min)
> > divx4 & divx3 are ok
> >
> > iam uploading it to incoming/left_edge_artifacts_in_ffmpeg.avi
> [...]
> fixed :) but the fix doesnt make much sense to me :(
> the fix simply deactivates the ac prediction for the leftmost middle blocks 1 
> lumi 2 chromi

uhh. it looks more like hotfix workaround than fix :)
doe sit work with all files, or only fix this one?

btw, ac prediction seems to by buggy for other files too, for example that
weird_al asf. mayeb some undiscovered tricks of divx fornat...

> perhaps someone knows whats broken...
> 
> ----hand written diff from libavcodec/h263.c----
>     }
>     ac_val += ((y) * wrap + (x)) * 16;
>     ac_val1 = ac_val;
> -    if (s->ac_pred) {
> +    if (s->ac_pred 
> +    	&& !(x==1 && y==s->mb_height  +1 && n==0) 
> +	&& !(x==1 && y==s->mb_height/2+1 && n>=4)) {
>         if (dir == 0 ) {
>             /* left prediction */
>             ac_val -= 16;
> ----end----
> 
> Michael
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> 
> 


A'rpi / Astral & ESP-team

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