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The Pre-alarm record mode is the record mode for recording a pre-alarm event for a specified time period before recording an alarm event. 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.

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
3. adjusted camera in the object tree.
Go to
4. Select the Basic settings tab on the settings panel of the Camera object.
   Image Modified
5. In the Pre-alarm record field, specify the time interval
(sec) of
6. in seconds during which the pre-alarm event
recording
7. is recorded.
8. Click the Apply button.

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

In Axxon PSIM,one you can perform prerecording in the Pre-alarm recording record mode if the camera is disarmed. You can do it with using the help of the DoReact("CAM","1","REC","rollback<1>") program ; (see The Script object. Programming using the JScript language).

Specifying the If you specify a long pre-record time, it 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-alarm record time, sec *

...

• Frame frequency in the

...

• Pre-alarm record mode, fps * Frame size, MB.

General memory consumption in the pre Pre-alarm record mode is defined determined by the sum of values received 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-alarm record time, sec * Frame frequency in the

...

• Pre-alarm record mode, fps * Frame size, MB.

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