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7700 MultiFrame Manual
7735AVC-LB Video Composite Encoder and Audio DAC with SoftSwitch
7.7.6.1. Setting the Audio Phase Reversal Level
Fault definitions
Phase reversal level
0.5 to 1 in 0.01
increments
0.9
7.7.6.2. Setting the Audio Phase Reversal Duration
Fault definitions
Phase reversal duration
0.5 to 127 sec
10 sec
7.7.7. Detecting Audio Mono Faults
Mono audio material can take two forms: one channel with information and the other quiet or both
channels with the same information. The AVC cards will detect both types of mono material.
If there is only a small amount of phase difference between the two channels (perhaps caused by the
noise present on the audio) then the content may be mono. If there is no significant difference for a period
of time, then this is a sign that the audio signals are mono.
Mono is detected by comparing the difference of the two channels to the average of the two. If a signal
always has no out of phase information (or just a small amount) for a period of time, then the signal may
be mono.
The Mono threshold level and Mono duration controls are used to detect when two audio channels are
considered to be mono. The Mono threshold level control sets the threshold that determines whether the
signals are the same. The audio difference must be less than the Mono threshold level amount for the
duration set by the Mono duration control before the fault condition exists. When the fault condition exists,
the audio difference must be more than the Mono threshold level amount for the duration set by the Mono
duration control before the fault condition will be removed.
Material that is both mono and out of phase will be detected as being out of phase and not mono. Once
the phase polarity is fixed, then the card will detect mono material.
7735AVC-LB - 30
This control sets the amount of phase difference before the audio is
considered to be out of phase. This phase reversal is calculated by
comparing the difference of the two channels to the average of the two.
If a signal is always out of phase, then the difference between the two
will be high compared to the average of the two. This corresponds to 1
in this control.
If there is only content on one of the channels (i.e. left only or right
only), then the difference is equivalent to the average of the two
channels. This corresponds to 0.5 in this control.
This control sets the period over which to analyze the audio content
for phase reversal.
Note that conditions of silence are not included in this value. This
means that if the audio is 50% quiet then it will take twice the period
set with this control to detect a phase reversal condition.
Revision 1.6
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