Configuring video in the Pre-alarm record mode

The Pre-alarm record mode is the record mode for recording pre-alarm events for a specified period before recording an alarm. Pre-alarm record is performed at the hot record rate. If the hot record rate is not specified, then at standard record rate.

Attention!

For cameras without video compression that have been added to the corresponding list in the Video subsystem section in the tweaki.exe utility (see The Settings panel of the Video subsystem section), video is not recorded in Pre-alarm record mode.

By default the recording in this mode is disabled. To enable the pre-alarm recording, do the following:

Go to the Hardware tab in the System settings dialog box (1).
Select the Camera object corresponding to the required camera in the objects tree (2). The settings panel for the selected object is displayed on the right of the Hardware tab.
Go to the Basic settings tab on the settings panel of the Camera object (3).
In the Pre-alarm record field specify the required interval (sec) of pre-alarm events recording (4).
Click the Apply button (5).

Information on pre-alarm recording options is given in the table.

Camera state	Recording initiator	Recording
Armed	Macro	Without pre-alarm recording
Armed	Manually	Without pre-alarm recording
Armed	Alarm	With pre- alarm recording
Armed	Program	With pre-alarm recording
Disarmed	Macro	Without pre-alarm recording
Disarmed	Manually	Without pre-alarm recording
Disarmed	Alarm	-
Disarmed	Program	With pre-alarm recording

In INTELLECT™ one can make pre-alarm recording if camera is disarmed. One can do it with the help of DoReact("CAM","1","REC","rollback<1>") program; (see The Script object. Programming using the JScript language ).

Specifying the long pre-record time can result in increasing the waste of running memory. Recommended pre-record time is not more than 20s.

To count the memory consumption ascertain the average size of video signal frame. To perform this, record the video fragment of 500 frames length to the archive (maximal size on default) and use the following formula:

Frame size = Fragment size / 500

The frame size is also depends on percent of motion in the frame.

It is possible to count the size of pre-record buffer for one camera it the frame size is known:

Size of pre-record buffer for one camera, MB=Pre-record time, sec * Frame frequency in the pre-record mode, fps * Frame size, MB.

General memory consumption in the pre-record mode is defined by sum of values for each camera.

It is possible to use the following formula in case of cameras perform pre-record with equal frame frequency:

Size of pre-record buffer for all cameras in system, MB = Number of cameras * Pre-record time, sec * Frame frequency in the pre-record mode, fps * Frame size, MB

Note

Example.

Camera performs pre-record for 15 seconds with the hot record speed 25 fps. Size of 500-frames fragment is 20 Mb. It is required to define size of pre-record buffer for such camera.

First, you it is necessary to define the average frame size:

Frame size = Fragment size / 500 = 20 MB/500 frames = 0.04 MB.

So, the size of pre-record buffer is:

The memory consumption in the pre-record mode for one camera, MB = Pre-record time, sec * Frame frequency in the pre-record mode, fps * Frame size, MB = 15 sec * 25 fps * 0.04 MB = 15 MB.

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Documentation for Intellect 4.11.0-4.11.3. Documentation for other versions of Intellect is available too.