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

[Ivan Kalvachev]

Arpi said:
> 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.
But we DO NOT change the stride! We change the width.
That is what i cannot understand!
>
>> 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