[MPlayer-dev-eng] vf.c & PEREFER_ALIGNED_STRIDE

[Arpi]

Hi,

> I was browsing the source of mplayer to understand what and how the vo
> system works.
> Well this peace of code amaze me. I cannot understand what it does. In
> fact i cannot understand why it does that it does. Well sounds confusing.

Why?
It's quite easy:

if the codec/filter wants aligned stride, then we ask the next filter/vo if
it supports stride!=width (ACCEPT_STRIDE) and if yes, then adjust stride to
be macroblock aligned.

> Take a look
> vf.c:325  (vf_get_image)
> 
>  // check if codec prefer aligned stride:
>           if(mp_imgflag&MP_IMGFLAG_PREFER_ALIGNED_STRIDE){
>               int align=(mpi->flags&MP_IMGFLAG_PLANAR &&
>                          mpi->flags&MP_IMGFLAG_YUV) ?
>                          (8<<mpi->chroma_x_shift)-1 : 15; // -- maybe FIXME
>               w2=((w+align)&(~align));
>               if(mpi->width!=w2){
>                   // we have to change width... check if we CAN co it:
                                       typo, should be 'do' ------^^

>                   int flags=vf->query_format(vf,outfmt); // should not fail
>                   if(!(flags&3)) mp_msg(MSGT_DECVIDEO,MSGL_WARN,"???
> vf_get_imag
> e{vf->query_format(outfmt)} failed!\n");
> //                printf("query -> 0x%X    \n",flags);
>                   if(flags&VFCAP_ACCEPT_STRIDE){
>                       mpi->width=w2;
>                       mpi->chroma_width=w2>>mpi->chroma_x_shift;
>                   }
>               }
>           }
> 
> //--------------------------------------------
> My question is: Why when PREFER_ALIGNED_STRIDE is set and
> decoder confirms ACCEPT_STRIDE, then the "width" is changed!
> Why the stride is not changed, as requested?
> I may have missed some other part of code.
> Place explain.
> 
> Best Regards
>   Ivan Kalvachev
> 
> 
> 
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> 
> 


A'rpi / Astral & ESP-team

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