Surround sound for movie theaters
Table of Contents
- Encodes 4 audio channel: left, right, center and surroud to 2 optical channels in 35 mm film.
- The film soundtracks are decoded back to 4 channels in the theater:
- left, right, center channels for front
- array of surroud loudspeakers for rear
- Center channel:
- remover listener disorientation
- most of the main dialogues is at the center of the screen
=> sound images position relating to visual presentation for wide range of seating positions
- Rear channel:
- atmosphere information (rain, distant sounds, thunder, ambience)
- bandlimited to 7 kHz, since ambience information mostly nondirectional
- Dolby B noise reduction
- delayed 15-30 ms in decodind to remove HAAS effect
- DOLBY SURROUND
- home version of the Dolby stereo
- center channel is optional
- passive networks
- DOLBY PRO LOGIC
- Dolby surround using active networks with steering logic
- direction of the loudest sound on the soundtrack is determined
=> control signals are generated to increase gain in the appropriate (left, center, surround) combination of channels
=> sharply focused sound images and directionality
- channel separation between any channel pair 30 dB
normally slow (one dominant sound)
fast mode (two distinct sound) time-division multiplexing
- Digital 35 mm sound format
- Both 6-channel and 4-channel analog soundtracks
- discrete channels
- playback can be switched between analog and digital if there are some severe errors
- Channel configuration: left, right, center, left surround, right surround, and subwoofer
- Both digital and analog soudtracks are printed optically between the sprocket holes
- Psychoacoustical audio coding (AC-3)
- Threatre requirements
- digital decoder DA10 from Dolby, which interfaces with theatre`s existing Dolby Stereo Cinema processor
- digital reader for each projector
- speakers, amplifiers, HVAC noise, break-through from adjacent theatres, and theatre acoustics should meet standards recommended for Dolby Stereo SR releases
- Production and laboratory requirements similar than for Dolby Stereo
- First release Batman returns
- Trademark owned by Lucasfilm
- Originally developed for monitoring purposes, but since 1983 it has been marketed to the exhibition industry.
- De facto standard in Hollywood
- THX is a standards and certification program allowing considerable latitude in equipment choice, and theater size and layout
- only unvarying component is the THX electronic crossover sold by Lucasfilm
- THX program specifies detailed standards for equipment selection and installation and room acoustics
- partition wall reinforcement and sound deadening treatment
- one-third-octave room equalization
- front speaker location
- use of constantdirectivity horns for upper mids and highs
- subwoofer for the deep bass
- Digital Theater System, USA
- 6 digital soundtracks for 35 mm film
- Digital audio data is recorded on two CD-ROM discs.
- Timecode is printed on the motion picture print along with conventional stereo optical sound track.
- synchronize the sound and picture
- DTS-6 system provides left, center, right, 2 surrounds, and a subwoofer channels
- DTS-6 system will operata in either the discrete 6 track mode or the digital stereo mode depending on the CD-ROM disc or discs loaded
- Compatible with equipment found in the most theaters
- Compression is used, about 1:4
- First release Jurassic Park
- 8 channels
- Left, Right, Center, Left Center, Right Center, Left Surround, Right Surround, Subwoofer
- SDDS is aimed to prove complete compatibility with any setup,
- 8 tracks can have 4, 5.1, or 6 discrete track mixes placed on the system and the system decoder will interpolate and spread the sound to other channels if available without user intervention.
- The reverse is also true - the system can be used in a 4, 5.1, or 6 track auditorium and the system will convert the data correctly without user intervention.
- Digital information is placed on film.
- The digital tracks are placed outside the sprocket holes on both sides of the film.
- The optical tracks are retained.
=> the system is backward compatible with existing Dolby optical surround systems.
- Compression is used, about 5:1
- Sound field
- DSP for sound field processing