hdr.n_alloc_len = (global_flags.width * global_flags.height * 3 / 2) * bytes_per_pixel;
hdr.n_filled_len = hdr.n_alloc_len;
hdr.n_tick_count = 0;
hdr.n_alloc_len = (global_flags.width * global_flags.height * 3 / 2) * bytes_per_pixel;
hdr.n_filled_len = hdr.n_alloc_len;
hdr.n_tick_count = 0;