(1 << (4 + ctx->frame->interlaced_frame)) - 1) >>
(4 + ctx->frame->interlaced_frame);
- remainder = ctx->num_x_mbs & ((1 << slice_width_factor) - 1);
+ remainder = av_mod_uintp2(ctx->num_x_mbs, slice_width_factor);
num_x_slices = (ctx->num_x_mbs >> slice_width_factor) + (remainder & 1) +
((remainder >> 1) & 1) + ((remainder >> 2) & 1);