Scene Validation (SV)
G-Tect/SV stands for SceneValidation. G-Tect/SV recognizes changes in camera position or acts of sabotage to the camera, and triggers an action on recognition.
G-Tect/SV compares a reference picture with the current picture from the same camera. Both pictures are edge-filtered.
If on analysis significant differences are detected (low correlation between filtered reference picture and filtered live picture), the G-Tect/SV triggers a video sensor action that can be used via an event/alarm configuration.
User Interface
The interface itself has three components:
- A list of media channels
- A field with visualization of pictures, and in the lower third
- The settings and the display of measurement data.
Aside from the setting for the alarm duration and choosing between automatic setting, manual generation of the reference image in the Reference tab and the advanced timing, there are no additional settings.
Click on the symbol to switch the viewer image to black and white.
Click on the symbol to open the dialogue for event configuration. Events can be quickly configured using this dialogue:
Configuration
First select a media channel and then set the alarm duration.
Then go to the Reference tab. There you specify whether the G-Tect/SV will create the background model for the comparison itself (this is the recommended default setting, Adaptive) or whether you want to manually generate a reference image (Static). To generate a static background model, click Create.
Image sections that are constantly moving/changing (such as fade-ins) would also trigger alarms on a regular basis. A polygon can be plotted in order to hide these image sections, so that the moving/changing image sections are left blank.
Use the left mouse button to plot polygons in the viewer and the right mouse button to delete them. Here you can find more about plotting the zones.
IMPORTANT: It is only possible to create one polygon per channel!
The Advance Timing tab shows two settings:
|
Parameter |
Description |
|---|---|
|
Measure cycle [s]
|
This parameter passes on the intervals (in seconds) at which an picture should be retrieved from the server to the SV service in order to compare it to the reference picture. |
|
Pre-alarm threshold
|
This parameter defines the number of (internal) pre-alarms, after which a real alarm is issued. |
Example If the pre-alarm threshold is set to 3, then 3 internal alarms must occur before an SV alarm is triggered. For a measure cycle [s] of 30 seconds, for instance, this could be the case after a minimum 90 seconds.
The G-Tect/SV Measurement Data
You will see two lines in the G-Tect/SV Measured Data window: The red line represents the calculated threshold value below which the blue line may not fall. The blue line represents the actual measured values of the analysis. In the following figure you can see three different situations for the same media channel:
- A = The image of the media channel is analyzed and there are no changes compared to the stored background model
- B = The image of the media channel is analyzed and there are changes compared to the stored background model (e.g. persons in the image)
- C = The image of the media channel is analyzed. There are significant changes compared to the stored background model (camera rotated or covered, sync failure, ...). The G-Tect/SV sends a video sensor alarm action.
Contrast
The contrast monitor displays different colored lines: Green = current contrast, Red = threshold (adjustable via slider). Use the slider to determine the threshold. If the threshold is higher than the current setting, then a contrast error action is sent. The threshold should be set so that camera sabotage (concealing or covering the camera) can be detected quickly and not only once the camera fails. Therefore, you should check the contrast at different times of day and night and set the threshold just below the average contrast.
