" ▁and ▁lack ▁the ▁file ▁and ▁header ▁structure ▁that ▁defines ▁DVD - Video . ▁Standard ▁DVD - Video ▁files ▁contain ▁extra ▁information ▁( such ▁as ▁the ▁number ▁of ▁video ▁tracks , ▁chap ters ▁and ▁links ▁to ▁extra ▁features ) ▁that ▁DVD ▁players ▁use ▁to ▁navigate ▁the ▁disc . ▁ ▁The ▁maximum ▁chap ters ▁allowed ▁per ▁title ▁is ▁ 9 9 ▁and ▁the ▁maximum ▁titles ▁allowed ▁per ▁DVD ▁is ▁ 9 9 . ▁ ▁File ▁system ▁ ▁Al most ▁all ▁DVD - Video ▁disc s ▁use ▁the ▁U DF ▁bridge ▁format , ▁which ▁is ▁a ▁combination ▁of ▁the ▁DVD ▁Micro U DF ▁( a ▁subset ▁of ▁U DF ▁ 1 . 0 2 ) ▁and ▁ISO ▁ 9 6 6 0 ▁file ▁systems . ▁The ▁U DF ▁bridge ▁format ▁provides ▁backwards ▁compatibility ▁for ▁operating ▁systems ▁that ▁support ▁only ▁ISO ▁ 9 6 6 0 . ▁Most ▁DVD ▁players ▁read ▁the ▁U DF ▁filesystem ▁from ▁a ▁DVD - Video ▁disc ▁and ▁ignore ▁the ▁ISO 9 6 6 0 ▁filesystem . ▁ ▁Directory ▁and ▁file ▁structure ▁ ▁A ▁DVD ▁volume ▁for ▁the ▁DVD - Video ▁format ▁has ▁the ▁following ▁structure ▁of ▁directories ▁and ▁files : ▁▁ ▁A U DI O _ TS ▁directory : ▁empty ▁or ▁not ▁present ▁on ▁DVD - Video ▁disc s ; ▁contains ▁files ▁only ▁on ▁DVD - Audio ▁disc s ; ▁it ▁is ▁also ▁known ▁as ▁an ▁Audio ▁Title ▁S ets ▁directory ; ▁included ▁on ▁DVD - Video ▁disc s ▁for ▁compatibility ▁reasons ▁ ▁V IDE O _ TS ▁directory : ▁stores