Ring Buffer Concept

This chapter describes the configuration required for implementing a custom ring buffer with combined video and alarm stream.

This concept does not require separate streams for the alarming and regular video.

Please note, that this is only a concept and must be adjusted to the actual project requirements.

Required Configuration:

Following configuration steps must be taken for implementing a ring buffer with alarm recording while using only one stream:

Figure 1. Description
For the time range in which the alarm is active the recording of the corresponding camera must be set to protected to prevent it from being deleted.
In addition to the actual alarm time range, an additional lead and follow-up time must be protected.
Figure 2. Description
The recording of the camera is configured as ring buffer.
Recording time ranges that are older than
```
(Current Time) - (Ring
                        Buffer Time)
```
and not protected are automatically deleted by the system.
Time ranges that are protected should only be deleted when they are set to unprotected.
Figure 3. Description
In case a CAME error is detected, following time range must be set to protected:
- From: (Current Time) - (Lead Time)
- To:
```
(Current Time) + (Maximum Alarm Time
                            Range)
```
If the GONE message is not detected due to a system failure, this configuration prevents the defined time range of the recording from being deleted.

This Maximum Alarm Time Range should not be defined higher than the ring buffer storage time.
Figure 4. Description
In case a GONE alarm is detected the end of the alarm recording should be updated.

The protected state for following ranges must be removed:
- From: (Current Time) + (Follow-Up Time)
- To: (Current Time) + (Ring Buffer Time)
This behavior can only be used if only one alarm is defined for each camera and the maximum alarm time range is equal to or less than the ring buffer time!
Figure 5. Description
In cyclic intervals (Deletion Interval) the alarm videos must be released for deletion.

This can be done for all cameras by removing the protected state in cyclically manner for following ranges:
- From:
```
(Current Time) - (Maximum Storage Time For An
                                Alarm)
```
- To:
```
(Current Time) - (Maximum Storage Time For an Alarm) -
                                (2* Deletion Interval)
```