void ff_ssim_4x4_line_xop (const uint8_t *buf, ptrdiff_t buf_stride,
const uint8_t *ref, ptrdiff_t ref_stride,
int (*sums)[4], int w);
void ff_ssim_4x4_line_xop (const uint8_t *buf, ptrdiff_t buf_stride,
const uint8_t *ref, ptrdiff_t ref_stride,
int (*sums)[4], int w);