const int cx = x >> f->chroma_h_shift;
const int cy = y >> f->chroma_v_shift;
decode_plane(fs, p->data[0] + ps*x + y*p->linesize[0], width, height, p->linesize[0], 0, 1);
const int cx = x >> f->chroma_h_shift;
const int cy = y >> f->chroma_v_shift;
decode_plane(fs, p->data[0] + ps*x + y*p->linesize[0], width, height, p->linesize[0], 0, 1);