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Dolby Dolby Surround Surround Mixing Mixing Manual Manual Chapter Chapter 5 5 - - Mixing Mixing Techniques Techniques
5-3 5-3
in the Surround channel. This results in out of in the Surround channel. This results in out of phase or inverted information in the stereo pair, phase or inverted information in the stereo pair,
which XY stereo microphone techniques typically produce. While this may which XY stereo microphone techniques typically produce. While this may sound pleasing by sound pleasing by
itself and no encoding seems necessary, this is an unpredictable process that should not itself and no encoding seems necessary, this is an unpredictable process that should not be relied be relied
upon. Adding another element to the mix, such as upon. Adding another element to the mix, such as a voiceover, could easily change the a voiceover, could easily change the mix’s mix’s
phase characteristics of the mix and alter the phase characteristics of the mix and alter the decoding process. It is best to put at decoding process. It is best to put at least a little least a little
information from this signal source through the surround input of the encoder, ensuring the information from this signal source through the surround input of the encoder, ensuring the
decoding of the real surround signals, not some random out of
decoding of the real surround signals, not some random out of phase information. phase information.
In some cases, too much surround information is present, as with electronic keyboards, which In some cases, too much surround information is present, as with electronic keyboards, which
achieve a stereo signal from a
achieve a stereo signal from a mono source via electronic processing. If your favorite sound mono source via electronic processing. If your favorite sound
produces too much information in the Surround channel, simply pan the left produces too much information in the Surround channel, simply pan the left a little towards a little towards
center and the right an equal a center and the right an equal amount towards center. This cancels out some of the mount towards center. This cancels out some of the out of phase out of phase
information and corrects the decoder. The panning required varies with the sound, but information and corrects the decoder. The panning required varies with the sound, but usually usually
does not take much to produce a good does not take much to produce a good result. result.
5.7 5.7 Decoder Decoder Mistracking Mistracking and and Steering Steering Artifacts Artifacts
When mixing, the decoder can only steer in When mixing, the decoder can only steer in one direction at a one direction at a time, so you must plan the time, so you must plan the sound sound
field carefully. Movie mixers have been doing this field carefully. Movie mixers have been doing this successfully for over 20 years, so do not be successfully for over 20 years, so do not be
overwhelmed—it can be done quite easily. overwhelmed—it can be done quite easily.
Problems result when two very different and unrelated sounds are sent to Problems result when two very different and unrelated sounds are sent to two different channels two different channels
at once. For example, crickets in the at once. For example, crickets in the Surround channel and chickens in the front cause Surround channel and chickens in the front cause the sounds the sounds
to bleed into the other channels and to bleed into the other channels and produce a dynamic image shift. This effect produce a dynamic image shift. This effect is distracting and is distracting and
undesirable. undesirable.
It is also common for a music It is also common for a music track to contain a prominent lead track to contain a prominent lead instrument in the Left or Right instrument in the Left or Right
channel while an announcer comes from the Center channel. The channel while an announcer comes from the Center channel. The instrument appears to move instrument appears to move
from its intended speaker towards the center when the from its intended speaker towards the center when the announcer speaks and then return to the announcer speaks and then return to the
correct speaker when the announcer stops talking. The solution is to correct speaker when the announcer stops talking. The solution is to either pan the music element either pan the music element
towards center or temporarily reduce its level. towards center or temporarily reduce its level.
Often, when producing motion picture sound effects, the sound effects designer removes all Often, when producing motion picture sound effects, the sound effects designer removes all
ambient sounds briefly so that another may be heard
ambient sounds briefly so that another may be heard more prominently. For example, more prominently. For example,
background sounds might contain a little traffic. A door background sounds might contain a little traffic. A door slam may be next. At slam may be next. At this, the traffic and this, the traffic and
night sounds are either very low level or night sounds are either very low level or disappear entirely. After the door slams the other disappear entirely. After the door slams the other sounds sounds
are already back in the mix. are already back in the mix. Because the door slam covered them, they aren’t missed by Because the door slam covered them, they aren’t missed by the the
audience. audience.
5.8 5.8 Surround Surround Pumping Pumping
Bad transmission paths frequently cause pumping of the Surround channel that is rarely heard Bad transmission paths frequently cause pumping of the Surround channel that is rarely heard in in
the mixing environment. Often a limiter is the mixing environment. Often a limiter is active in one channel of active in one channel of the transmission path but not the transmission path but not
the other, or a stereo limiter the other, or a stereo limiter is not set up the same is not set up the same for both channels. The solution is to either for both channels. The solution is to either
remove the limiters or set them up remove the limiters or set them up identically and verify that they identically and verify that they are linked together. This are linked together. This
problem can be heard during the mix problem can be heard during the mix if a stereo limiter is being if a stereo limiter is being used excessively or if only part used excessively or if only part
of the element is limited. of the element is limited. It is impossible to discuss all possibilities, but always It is impossible to discuss all possibilities, but always look for look for