Dolby Surround Mixing Manual
Dolby Surround Mixing Manual
6-1
6-1
Chapter 6
Chapter 6
Live Broadcast Applications
Live Broadcast Applications
6.1
6.1
Transmission
Transmission Path
Path Consideration
Considerations
s
Because fiber optic and satellite transmission lines are standard services at sports arenas
Because fiber optic and satellite transmission lines are standard services at sports arenas and
and
stadiums, this part of the signal chain is
stadiums, this part of the signal chain is usually repeatable and predictable. Frequency response
usually repeatable and predictable. Frequency response
and headroom are consistent from event to event. Most of
and headroom are consistent from event to event. Most of the early problems encountered in
the early problems encountered in
Dolby Surround broadcasts were related to signal processing added by the station. The
Dolby Surround broadcasts were related to signal processing added by the station. The two most
two most
common causes were
common causes were
phase chasers
phase chasers
and stereo synthesizers.
and stereo synthesizers.
6.2
6.2
Phase
Phase Chasers
Chasers
Dolby
Dolby
®
®
Surround uses phase encoding of the Surround channel, so it is entirely
Surround uses phase encoding of the Surround channel, so it is entirely possible to have
possible to have
situations where significant out of phase information in the program cannot and
situations where significant out of phase information in the program cannot and should not be
should not be
corrected, even by well-meaning devices. Phase chasing devices perform two basic
corrected, even by well-meaning devices. Phase chasing devices perform two basic functions.
functions.
One is to correct the
One is to correct the small phase errors between two audio channels, such as from
small phase errors between two audio channels, such as from azimuth
azimuth
misalignment or drift in analog video tape recorders and cart
misalignment or drift in analog video tape recorders and cart machines; the other is to correct
machines; the other is to correct
polarity inversions in one channel relative to the other.
polarity inversions in one channel relative to the other. When either function occurs in response
When either function occurs in response
to Dolby Surround signals, the results can be both
to Dolby Surround signals, the results can be both unnecessary and unfortunate.
unnecessary and unfortunate.
With it becoming the norm to
With it becoming the norm to source live feeds or audio from a
source live feeds or audio from a digital recorder, phase correction
digital recorder, phase correction
is essentially unnecessary, as no azimuth error is introduced. Relative polarity can be
is essentially unnecessary, as no azimuth error is introduced. Relative polarity can be easily
easily
checked before air time, and this
checked before air time, and this is especially easy when monitoring at the
is especially easy when monitoring at the station through an
station through an
SDU4. If the announcer or dialogue co
SDU4. If the announcer or dialogue comes out the Surround channel, or becomes virtually
mes out the Surround channel, or becomes virtually
inaudible in mono, the polarity is inverted! As
inaudible in mono, the polarity is inverted! As many people still listen in mono, loss of
many people still listen in mono, loss of the
the
announcer either during the game or during a
announcer either during the game or during a commercial is bound to raise complaints.
commercial is bound to raise complaints.
6.3
6.3
Station
Station Limiters
Limiters
No matter how good your mix is,
No matter how good your mix is, stations will always try
stations will always try to extract that last quarter dB from the
to extract that last quarter dB from the
transmitter. This is usually done with a
transmitter. This is usually done with a program limiter. In general, avoid using these. But reality
program limiter. In general, avoid using these. But reality
dictates that stations need to set
dictates that stations need to set these up for minimal effect. Mixers need
these up for minimal effect. Mixers need to mix so that these
to mix so that these
devices are not required to limit t
devices are not required to limit the program material in order to keep t
he program material in order to keep the mix in the useful
he mix in the useful range
range
of the transmitter.
of the transmitter.
6.4
6.4
Station
Station Processing
Processing
Along with station program limiters, other signal processors may be used, including the
Along with station program limiters, other signal processors may be used, including the Dolby
Dolby
Model 740 Spectral Processor. While there is little that a mixer can do while on location to defeat
Model 740 Spectral Processor. While there is little that a mixer can do while on location to defeat
the use of these units, if they
the use of these units, if they have been properly set up, without too
have been properly set up, without too much radical signal
much radical signal
processing, they should not pose a
processing, they should not pose a problem.
problem.