In the cinema Dolby Digital

batman returns first film use dolby digital technology when premiered in theaters in summer of 1992. dolby digital cinema soundtracks optically recorded on 35 mm release print using sequential data blocks placed between every perforation hole on sound track side of film. constant bit rate of 320 kbit/s used. charge-coupled device (ccd) scanner in image projector picks scanned video image of area, , processor correlates image area , extracts digital data ac-3 bitstream. data decoded 5.1 channel audio source. film prints dolby digital data have dolby stereo analogue soundtracks using dolby sr noise reduction , such prints known dolby sr-d prints. analogue soundtrack provides fall-back option in case of damage data area or failure of digital decoding; provides compatibility projectors not equipped digital soundheads. current release cinema prints of type , may include sdds data , timecode track synchronize cd-roms carrying dts soundtracks.

a dolby digital penthouse soundhead mounted on mid-1950s vintage kalee model 20 projector



a photo of 35 mm film print featuring 4 audio formats (or quad track)- left right: sony dynamic digital sound (sdds) (blue area left of sprocket holes), dolby digital (grey area between sprocket holes labelled dolby double-d logo in middle), analog optical sound (the 2 white lines right of sprocket holes), , dts time code (the dashed line far right.)

the simplest way of converting existing projectors add so-called penthouse digital soundhead above projector head. however, new projectors made sense use dual analogue/digital soundheads in normal optical soundhead position under projector head. allow dual-soundhead arrangement data recorded 26 frames ahead of picture. if penthouse soundhead used, data must delayed in processor required amount of time, around 2 seconds. delay can adjusted in steps of time between perforations, (approximately 10.4 ms).

as of 2017, dolby digital in cinema being gradually replaced dolby surround 7.1, more advanced dolby atmos technology gaining in popularity.