Dolby Digital
Dolby Digital is the name of the highly sophisticated and versatile audio encoding and decoding compression technology developed by the Dolby Laboratories. This technology can transmit mono, stereo—two channel—, 5:1 channel surround sound or even discrete multi-channel audio effects by employing superior coding devices to create and transmit high quality discrete multi-channel audio sound without any adverse effects on the video quality.
Dolby Digital has become the supreme benchmark for cinematic surround sound effects in general and 5:1 channel surround sound in particular in thousands of cinemas and millions of homes across the world. You can enjoy Dolby Digital on DVDs, DVD recordable and playback discs, for computers, laser discs, digital cable systems, direct broadcast satellite (DBS) and direct-to-home (DTH) systems and digital television (DTV/DVB).
The popularity and versatility of Dolby Digital has made it a multi-channel audio standard for direct satellite broadcast to the millions of homes through the satellite and digital cable systems and equal number of satellite set-top boxes being used all over the world supported by audio and video receivers equipped with 5:1 channel Dolby Digital decoding. Practically every DVD-Video player that is sold nowadays offers two channel mix down of Dolby Digital 5:1 movie sound track and digital output for a 5:1 channel audio/video receiver.
Dolby Digital technology is used to create special effects sound track on 35mm film rolls by optically encoding it in the space between the perforated holes. When the soundtrack is placed directly on the film, it can work with the analog track. The process makes it cost effective and simple both for the film distributors and cinema hall owners. The area around the hole where the sound track is encoded is highly resistant to wear and tear allowing the sound track to remain free from pops and hissing sounds till the film strip lasts.
The sound transmitted by the Dolby Digital or AC-3 goes through each of the six discrete channels, called 5:1 system, and remains distinct and independent. Out of the six channels, five channels are meant for normal range speakers of 20 Hz - 20,000 Hz. They are identified position wise as Right front, Center, Left Front, Right Rear and Left Rear, while the sixth channel of 20Hz-120 Hz is for the subwoofer driven low frequency effects.
Dolby Logo is displayed on the DVDs before the feature film starts.
