//Copy paste this function in libmpcodecs/vo_scale.c after put_image()

mp_image_t * mplayerMex_get_mpi(struct vf_instance_s* vf, mp_image_t *mpi){
    mp_image_t *dmpi=mpi->priv;

//    printf("vf_scale::put_image(): processing whole frame! dmpi=%p flag=%d\n",
//	dmpi, (mpi->flags&MP_IMGFLAG_DRAW_CALLBACK));
    
  if(!(mpi->flags&MP_IMGFLAG_DRAW_CALLBACK && dmpi)){
  
    // hope we'll get DR buffer:
    dmpi=vf_get_image(vf->next,vf->priv->fmt,
	MP_IMGTYPE_TEMP, MP_IMGFLAG_ACCEPT_STRIDE | MP_IMGFLAG_PREFER_ALIGNED_STRIDE,
	vf->priv->w, vf->priv->h);
    
      scale(vf->priv->ctx, vf->priv->ctx, mpi->planes,mpi->stride,0,mpi->h,dmpi->planes,dmpi->stride, vf->priv->interlaced);
  }

    if(vf->priv->w==mpi->w && vf->priv->h==mpi->h){
	// just conversion, no scaling -> keep postprocessing data
	// this way we can apply pp filter to non-yv12 source using scaler
        vf_clone_mpi_attributes(dmpi, mpi);
    }

    if(vf->priv->palette) dmpi->planes[1]=vf->priv->palette; // export palette!
    
    return dmpi;
}