int w = plane ? c->chrSrcW : c->srcW;
int x_subsample = plane ? desc->log2_chroma_w: 0;
int y_subsample = plane ? desc->log2_chroma_h: 0;
int w = plane ? c->chrSrcW : c->srcW;
int x_subsample = plane ? desc->log2_chroma_w: 0;
int y_subsample = plane ? desc->log2_chroma_h: 0;