sr_set_blocklength
int sr_set_blocklength(Scsi_CD *, int blocklength);
if (0 != (rc = sr_set_blocklength(cd, blksize)))
rc |= sr_set_blocklength(cd, CD_FRAMESIZE);
sr_set_blocklength(cd, 2048);
sr_set_blocklength(cd, 2048);