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7.10.11.2.
Setting the Picture Freeze Duration
Fault definitions
Picture freeze duration
6 to 902 frames
302 frames
When increasing Picture noise level, it is recommended that you increase Picture freeze duration as well.
This is because higher Picture noise level settings also lowers the motion sensitivity, thus long periods
without significant on-screen movement are more likely to trigger a "false" freeze alarm.
7.10.11.3.
Optimizing the Picture Noise Level and Picture Freeze Duration Parameters
Setting up the optimum Picture noise level and Picture freeze duration parameters will depend on the
amount of noise in the video path from the first equipment with freeze-frame capability to the monitoring
point. The system designer should determine the maximum amount of time permissible between the
moment of freeze and the alarm.
Setting this time as high as tolerable has two benefits:
•
It lowers the frequency of "false" freeze alarms generated when a perfectly valid content contains long
motionless periods.
•
It allows raising the Picture noise level parameter, without increasing frequency of "false" freeze
alarms.
It is suggested that Picture noise level should be set after setting the Picture freeze duration.
If the user can place the equipment farthest upstream in the video path to go to a 'freeze frame' mode,
then the Picture noise level should be optimized by initiating the 'freeze frame' mode in the upstream
equipment and adjusting Picture noise level as low as possible, without losing the freeze alarm generated
by the card. The user should note that because of the random nature of noise, the freeze alarm may be
intermittent at some Picture noise level settings. The optimal Picture noise level setting is obtained when
the loss of freeze alarm in the card occurs no more then once every 5 minutes.
If the equipment farthest upstream in the video path cannot go to a 'freeze frame' mode, then Picture
noise level should be optimized by adjusting it as high as possible. If you trigger false freeze alarms more
often than acceptable; lower the Picture noise level setting. Since the acceptable rate could be on the
order of a day perhaps (depending on the facility), this adjustment procedure may consume a couple of
days.
Failing to accomplish optimal adjustment of the Picture noise level will result in either:
•
A large number of false alarms, or
•
Lack of alarm condition when the video is frozen.
The Picture noise level and Picture freeze duration controls have been designed to be able to detect short-
term "digital" freezes such as MPEG or motion JPEG server artifacts. When these devices have a
significant problem with the content that they are de-compressing, they will typically start to produce a
"blocky" effect. If the problem is severe enough, they will freeze a frame of video and play it out for a
number of frames. With the Picture noise level set to 1 (i.e. only detect exact, or nearly exact pictures) and
the Picture freeze duration set to minimum, the card can detect these quick "digital freezes". You cannot
however detect both this type of freeze and a freeze from a link that has added noise to the picture.
Gray background indicate un-implemented or un-tested features
7735CEM Composite Encoder with Monitoring
This control sets duration of video activity under the Picture noise level
that is considered a fault.
Revision 1.1.1
7700 MultiFrame Manual
7735CEM-51
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