7700 MultiFrame Manual
7736CEM Composite Encoder with Monitoring
Page - 12
Revision 1.5
*Grey background indicates un-implemented or un-tested features
6.
AUDIO ALARM CALIBRATION PROCEDURE
This section contains detailed description on setting the various audio warning/error detection parameters.
Some of the audio alarm detection algorithms are dependent on the state of other audio alarm detectors.
For instance, the mono detection algorithm will not use periods of silence as determined by the silence
detection. For this reason, the following sequence should be used to calibrate the audio alarms. The items
in
italics
refer to menu items in the CEM. See section 7.11 for a complete description of the fault
definition menu items.
6.1.
CALIBRATE AUDIO SILENCE DETECTION
1. Supply the card with your plant's noisiest audio feed without any audio program material present.
This will be a baseline noise level to calibrate the silence detector.
2. Turn off all sources of errors in a
Fault Condition
and assign
Audio Silence
as the only error. Also,
make sure that you set the
Fault Duration
to a small number of frames so that you will see when
the error condition disappears.
3. Set the
Silence Duration
to 0.5 sec so that you can see the results of adjusting the
Silence Level
parameter without getting confused with the detection time.
4. Adjust the audio
Silence Level
until the
Fault Condition
begins to go active. This will be the noise
floor level. Raise the
Silence Level
a few dB to make the detector insensitive to this noise level.
5. Set the
Silence Duration
to a time appropriate to your application. This should be set to a value
longer than your worst case acceptable quiet period.
6.2.
CALIBRATE AUDIO PHASE REVERSAL DETECTION
1. Supply the card with a stereo signal that has the phases reversed. Make sure that the material is
typical of normal content for this channel.
2. Turn off all sources of errors in a
Fault Condition
and assign
Phase Reversal
as the only error.
Also, make sure that you set the
Fault Duration
to a small number of frames so that you will see
when the error condition disappears.
3. Set the
Phase Reversal Duration
to 0.5 sec so that you can see the results of adjusting the
Phase
Reversal Level
without getting confused with the detection time.
4. Adjust the
Phase Reversal Level
so that the
Fault Condition
detects the phase reversal.
5. Set the
Phase Reversal Duration
to a time period appropriate to your application.
Warning:
Periods of silence (below the
Silence Level
) will extend this duration. In other words,
periods without audio content are not included in the phase reversal detection.
Warning:
Stereo material with long periods of dissimilar left/right content (i.e. music with plenty of
panning) may cause the phase reversal detector to fire. It is best to set the
Phase Reversal
Duration
to a value larger than what you would expect.
6.3.
CALIBRATE AUDIO MONO DETECTION
1. Supply the card with a stereo signal that originated from mono material and that has a large
amount of un-correlated noise added to each channel. This will allow you to set the
Mono
Threshold
to a value that will detect the mono condition in the presence of noise.
Warning:
Make sure that the material is in-phase. Mono material will not be detected if it is out of
phase.
2. Turn off all sources of errors in a
Fault Condition
and assign
Mono
as the only error. Also, make
sure that you set the
Fault Duration
to a small number of frames so that you will see when the
error condition disappears.
