bs_write
bs_write(s, 8, 0x42); /* profile_idc, baseline */
bs_write(s, 1, 1); /* constraint_set0_flag */
bs_write(s, 1, 1); /* constraint_set1_flag */
bs_write(s, 1, 0); /* constraint_set2_flag */
bs_write(s, 5, 0); /* reserved_zero_5bits */
bs_write(s, 8, 0x1e); /* level_idc */
bs_write(s, 1, 0); /* gaps_in_frame_num_value_allowed_flag */
bs_write(s, 1, 1); /* frame_mbs_only_flag */
bs_write(s, 1, 0); /* direct_8x8_inference_flag */
bs_write(s, 1, 0); /* frame_cropping_flag */
bs_write(s, 1, 0); /* vui_parameters_present_flag */
bs_write(s, 1, 0); /* entropy_coding_mode_flag */
bs_write(s, 1, 0); /* pic_order_present_flag */
bs_write(s, 1, 0); /* weighted_pred_flag */
bs_write(s, 2, 0); /* weighted_bipred_idc */
bs_write(s, 1, 0); /* deblocking_filter_control_present_flag */
bs_write(s, 1, 0); /* constrained_intra_pred_flag */
bs_write(s, 1, 0); /* redundant_pic_cnt_present_flag */
bs_write(s, ilog2(MAX_GOP_SIZE), frame_gop_seqno); /* frame_num */
bs_write(s, ilog2(MAX_GOP_SIZE), frame_gop_seqno);
bs_write(s, 2 * fls(val) - 1, val);
bs_write(s, s->bits_left, 0x00);