. ▁To ▁maintain ▁quality ▁the ▁main ▁title ▁and ▁the ▁ex tras ▁may ▁be ▁released ▁on ▁several ▁disc s , ▁or ▁the ▁ex tras ▁may ▁be ▁omitted ▁completely ▁like ▁in ▁the ▁" Super bit " ▁line ▁of ▁DVD s . ▁ ▁Rest rict ions ▁ ▁DVD - Video ▁has ▁four ▁complement ary ▁systems ▁designed ▁to ▁restrict ▁the ▁DVD ▁user ▁in ▁various ▁ways : ▁Mac ro vision , ▁Content ▁Sc ram ble ▁System ▁( CSS ), ▁region ▁codes , ▁and ▁disabled ▁user ▁operations ▁( U OP s ). ▁There ▁are ▁also ▁anti - ri pping ▁techniques ▁intended ▁to ▁fo il ▁ri pping ▁software . ▁ ▁Content ▁Sc ram ble ▁System ▁▁ ▁Many ▁DVD - Video ▁titles ▁use ▁Content ▁Sc ram ble ▁System ▁( CSS ) ▁encryption , ▁which ▁is ▁intended ▁to ▁disc ou rage ▁people ▁from ▁copying ▁the ▁disc . ▁Usually , ▁users ▁need ▁to ▁install ▁software ▁provided ▁on ▁the ▁DVD ▁or ▁downloaded ▁from ▁the ▁Internet ▁such ▁as ▁M Player , ▁Total Media ▁Theatre , ▁Power D VD , ▁V LC ▁or ▁Win D VD ▁to ▁be ▁able ▁to ▁view ▁the ▁disc ▁in ▁a ▁computer ▁system . ▁ ▁CSS ▁does ▁not ▁make ▁it ▁difficult ▁( any ▁more ) ▁to ▁copy ▁the ▁digital ▁content ▁now ▁that ▁a ▁dec oder ▁( De CSS ) ▁has ▁been ▁released , ▁nor ▁is ▁it ▁possible ▁to ▁distinguish ▁between ▁legal ▁and ▁illegal ▁copies ▁of ▁a ▁work , ▁but ▁CSS ▁does ▁restrict ▁the ▁play back ▁software ▁that ▁may ▁be ▁used . ▁ ▁CSS ▁has ▁caused ▁major ▁problems ▁for ▁the ▁inclusion ▁of ▁DVD