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

[Ivan Kalvachev]

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.
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:
                  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