Activity Detection (AD)
Activity Detection (AD) is the identification of movement in defined areas of a picture. Movements that are detected trigger pre-defined reactions.
AD control means that significantly less database storage capacity is required in contrast to permanent recording, since images are only saved when movements have triggered the start of recording.
Saving database capacity is one thing, high image quality when required is another: An empty corridor requires neither high frame rates nor high resolutions – 1 or 2 fps are sufficient in this case.
However, within 40 ms of detecting movement, the AD switches to the full frame rate and to a higher resolution, maintaining this performance for the duration of the alarm.
AD is of particular value for indoor applications. For outdoor applications see Video Motion Extended (VMX).
Description of the User Interface
The AD's user interface screen is divided into four areas:
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The media channels of the connected servers whose images can be displayed on the viewer are listed in the left area. In addition, the available media channel templates are shown. |
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In the area to the right of that you will find the setting for the Sensitivity and the Directional Filter. |
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The largest part of the interface is taken up by the viewer with its controls.
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Below the viewer you will find the setting for the alarm duration and the display for the AD status and the AD measurements. |
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:
If AD is used on a media channel with DVSP8 hardware, Sensor Video Alarm (with the sensor type AD) is no longer used, instead the action G-Tect/AD Alarm is used! Accordingly, for the stopping action, Sensor Alarm finished (with the sensor type AD) is longer used, but rather G-Tect/AD Alarm finished is used. In addition, it is not necessary to activate AD in the VCA Editor for this channel, or even to use the G-Tect service! The analysis of the image changes is performed within the DVSP8 card.
The action Sensor Video Alarm with the sensor type AD and IP-AD, are now only required by IP camera plugins for triggering events by the camera-internal sensors.
All configured media channels of the connected server are found in the Media Channel List. Click on a media channel to activate it on the viewer and to set up zones for the AD.
Different images can be used for the AD settings in the Viewer: live streaming, images from the database, and captured sequences of images. Any of these images can be used for drawing zones.
AD Status and Measurement Display
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The alarm status display shows the current status for the image analysis and the alarm. |
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When the image is analyzed, i.e. evaluated for movement, this is indicated, as can be seen in the above figure, with the icon shown on the left. |
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If no analysis takes place or streaming is interrupted, the icon for standby is displayed. |
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When motion is detected in one of the zones, if the alarm is active, the icon changes to indicate an alarm. |
The AD Measured Data display visualizes the detected motion in the zones, color coded, with each zone having its own color. The figure shows the measured values for two zones. From the shape of the curves you can also read out which zone was triggered first and the seamless transition indicates that the zones are close together or even overlap. Compare this with the first figure in this section: There the measurement values in the analysis phase can be seen and it is clear that the zones actually do lie close together. Apparently, someone has come through the door and then walked to the control panel.
Alarm Settings for Images
The Alarm duration (s) is the length of time that an alarm runs if no additional movement occurs. If there are further movements in the image during the alarm duration, the alarm is thus continued until no more movement occurs. For movements lasting 120 seconds, an alarm duration time of 1 seconds results in a total alarm duration of 121 seconds.
Sensitivity
The sensitivity is set using a slider. It can be individually adjusted for each area. The default setting is in the middle.
Move the slider to the left to reduce the sensitivity and to the right to increase it.
In most cases, the default setting is suitable.
Direction
Filtering the direction is set using the Direction Filter. The direction filter can be set only when an area was clicked on and activated (here as an example only, an area with the ID 3).
If you double click in the circle, a red triangle with a direction arrow is created. It represents the direction in which the movement must occur. The angle indicates the range, i.e. the area within which the direction is to be detected.
By clicking and dragging the outer edge of the angle, you can increase or decrease it.
If you grab the arrow, you can change its direction.
You can delete a direction filter by right clicking in the area.
Several directions can also be defined simultaneously. To do so, click as described above in different areas in the circle.
Controlling the User Interface
Selecting the Image Display
Three different types of display can be shown on the Viewer:
- Live streaming of the active media channel (simply drag the desired media channel onto the Viewer) or
- Display of an image from the database (double click the desired media channel, then use the toolbar to set the desired image display).
- Sequences of images can also be captured (in capture mode).
Before You Start
It is essential that you understand the method by which movement is detected in the zones if you are to adjust movement detection in the image properly.
In order to be able to detect movements in a picture, it is necessary to define the part of the picture in which movements are to be detected appropriately. For this purpose, zones can be arranged in the image. The position and shape of the zones can be freely configured so that the monitored area can be outlined precisely. This also makes it possible to match the measured areas to the sizes of the object or persons on the image. More on creating zones can be found here: Drawing Zones.
In each zone, the gray values of the pixels are determined and evaluated using a mathematical method. The values determined are compared with the previous values. When movements occur, differences are always generated.
Movements are identified by the fact that a limited area of the picture (one or a more zones) are affected. Movements primarily involve local changes.It is typical of brightness fluctuations that a larger area of the picture (many or all zones) is affected. Brightness fluctuations usually involve global changes.
In order to distinguish between movements and brightness fluctuations, the largest of all the measured values is determined, and is then processed as the maximum. In parallel with this, the sum is formed (from all the measured values). An alarm is created if the difference is large enough.
Procedure
- First, specify which type of images of the media channel will be displayed.
- Draw zones in the areas in the image that you want to analyze for movement.
- Adjust the sensitivity and (if necessary) the direction filter. Consider the situation and set a suitable alarm duration.
- Save the settings by transferring them to the server.
- Test the settings. Check the AD status and the measured values.
- If necessary, modify the settings and save them again.
- Now configure the events and alarms.
Saving the settings for later use.
The AD settings can be exported as a parameter set and reused later for another media channel. The export and a later import of the parameter sets is performed using a pop-up menu that appears when you right click on the configured media channel.
Export: For the export, click Export Settings. The Windows Explorer opens. Give the file a name and save it in a directory of your choice. The settings are saved as an xml file.
Import: For the import, right click on the desired media channel and then on Import Settings. The Windows Explorer opens. Go to the directory in which you saved the export file. Select the file.
Example Export/import of parameter sets:
An office building has four corridors, one above another. On their right hand sides are office doors with alarm zones. Proceed as follows:
Draw the alarm cells for just one corridor
Export these parameters as just described
Right click on the media channel whose connected camera shows the corridor above and and import the saved parameters as just described
You can also export the AD parameters and import them for use elsewhere, for instance, on another G-Core.
Template: With the Add Template command you can add a template to the active media channel. Select the template and also create zones. Enter a name (double-click on Templatexx) and save the configuration.
You can activate this template using the action ChangeADParameterSet. An example: In the corridor of an office building under watch in the above example, it is likely that someone goes down the corridor now and then. Most recently the cleaning services. After that, no one else should be in the corridor until the next morning. If you have created a time range for the evening and night time, with this change you could also modify the parameter set for the AD. The associated template would now not record the doors, but rather the entire corridor area.