round_power_of_two
round_power_of_two(gaussian_sequence
round_power_of_two(wsum, ar_coeff_shift),
round_power_of_two(gaussian_sequence
round_power_of_two(gaussian_sequence
av_luma = round_power_of_two(av_luma, 2);
round_power_of_two(wsum_cb, ar_coeff_shift),
round_power_of_two(wsum_cr, ar_coeff_shift),
new_prob = round_power_of_two(pre_prob * (256 - factor) +
round_power_of_two(pre_prob * (256 - factor) +
round_power_of_two(pre_prob *