Documentation for Axxon PSIM 2.0. Documentation for other versions of Axxon PSIM is available too.

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The Pre-alarm record mode is the record mode for recording a pre-alarm event for a specified period before recording an alarm. Pre-alarm recording is performed at the hot record rate. If you don't specify the hot record rate, then the recording is performed at the standard record rate.

Attention!

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

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

  1. Go to the Hardware tab in the System settings window.
  2. Select the Camera object corresponding to the required camera in the object tree.
  3. Go to the Basic settings tab on the settings panel of the Camera object.
  4. In the Pre-alarm record field, specify the time interval (sec) of pre-alarm event recording.
  5. Click the Apply button.

The table provides the information on pre-alarm recording options.

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

NA

Disarmed

Program

With pre-alarm recording

In Axxon PSIM, you can perform pre-alarm recording if the camera is disarmed. You can do it with the help of the 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. The recommended pre-record time is no more than 20 seconds.

To count the memory consumption, figure out the average size of the video signal frame. To do this, you must record the video fragment of 500 frames in length to the archive (maximum size, by default) and use the following formula:

Frame size = Fragment size / 500

Note that the frame size also depends on the percent of motion in the frame.

You can count the size of the pre-record buffer for one camera if 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 the sum of values for each camera.

If cameras perform pre-recording with equal frame frequency, you can use the following formula:

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

Note

Example.

The camera performs pre-recording for 15 seconds with a hot record speed of 25 FPS. The size of the 500-frame fragment is 20 MB. It is required to define the size of the pre-record buffer for such a camera.

First, 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 the 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.

Configuring video in the pre-alarm record mode is complete.

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