Linear Acoustic UPMAX2251, Руководство пользователя, Страница: 10 / 34

Linear Acoustic upMAX 2251 User Guide Introduction
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• Main Outputs (Lf/Rf, C/LFE, Ls/Rs) - Main audio outputs in SMPTE 320M format
• LtRt Main Output - A utility two-channel downmix of the 5.1 channel program (this
output is also available as an analog signal on the LtRt/Aux connector)
1.3 Downmix Compatibility
Downmixing is the process where the individual channels of a Dolby Digital signal
are combined in order to be reproduced from a given number of channels. For exam-
ple, a 5.1 channel program must be downmixed to be reproduced from a stereo speak-
er system and so the left and right channels are combined with the left and right
surround signals and an attenuated version of the center channel before being output
as a stereo signal. This type of signal is called LoRo (for Left only/Right only).
Downmixing may also produce an LtRt compatible signal by performing a pseudo-
surround encode. A 90-degree phase shift is applied to the surround signals in the
Dolby Digital encoder prior to the actual encoding stage so that after downmixing
from 5.1 to 2-channels in the consumer decoder the signal can be heard in surround
by the many consumers that only have a matrix surround decoder.
An extremely important design goal of the Linear Acoustic
UP
MAX 2251 was that
the output be downmix compatible. Not only stereo and surround, but also mono-
and it had to sound good in 5.1! A tall order that has been satisfied.
One important thing to remember is that to ensure widest compatibility, the Dolby
Digital encoder must be set to apply a 90-degree phase shift. Luckily, this is the de-
fault position for most of the presets, however please consult the encoders user man-
ual to find the menu location where this setting can be checked.