header_start[0] = extradata;
header_start[1] = header_start[0] + header_len[0];
header_start[2] = header_start[1] + header_len[1];
header_start[0] = extradata;
header_start[1] = header_start[0] + header_len[0];
header_start[2] = header_start[1] + header_len[1];