void(* scale_block)(const uint8_t src[64], uint8_t *dst, int linesize)
void(* idct_put)(uint8_t *dest, int line_size, int32_t *block)
void(* idct_add)(uint8_t *dest, int line_size, int32_t *block)
void(* add_pixels8)(uint8_t *av_restrict pixels, int16_t *block, int line_size)