Operating instructions

E-2
recorded on both the left and the right tracks. And the surround information
is also split between the two channels, but is recorded with a distinct phase shift
to distinguish it from the left, center, and right information.
In the theatre, when the signals from the two tracks on a Dolby Stereo print
reach the CP45 processor, its 2:4 decoder constantly compares the two signals.
Those signal elements which differ primarily in amplitude are assigned to the
left and right speakers. Those which are essentially identical in both phase and
amplitude are assigned to the center speaker. And those parts of the signal
which were recorded with the distinct phase shift are assigned to the surround
speakers. To accomplish the decoding process effectively requires very
sophisticated circuitry. That is why the 2:4 decoder within your CP45 is one of
the most complex circuit cards. Feature films are produced using the Dolby
phase-matrix technique as a reference. Only Dolby cinema processors can
correctly decode these soundtracks the way they were intended.
4-CHANNEL
MIX
L
C
R
S
DOLBY
4:2
ENCODER
ENCODED 2-TRACK
MAGNETIC RUNNING
MASTER
STEREO
OPTICAL
RECORDER
LAB
PRINTER
ENCODED 2-TRACK
35mm DOLBY STEREO
OPTICAL RELEASE PRINT
a. Encoding
PROJECTOR
SOUND HEAD
WITH DUAL
SOLAR CELL
35mm DOLBY STEREO
RELEASE PRINT
PREAMP
DOLBY
NOISE
REDUCTION
DOLBY
NOISE
REDUCTION
PREAMP
2:4 CHANNEL
DECODER
SPEAKER EQ
(L)
SPEAKER EQ
(R)
SPEAKER EQ
(C)
SURROUND
RIGHT
CENTER
LEFT
TO FADER
b. Decoding
Block Diagram, Dolby Cinema Stereo Encoding/Decoding