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Edge Storage of IP Cameras Print
November 2012

Edge Storage or Edge Recording refers to the storage of camera video footage including snapshots and video clips in the same camera that generates the footage.  It is called edge as against the standard arrangement of central storage.  The storage medium for edge is Micro SD card with physical dimensions of 15mm x 11mm and a thickness of 1mm.  See Slide 1.  A camera with its own storage would not need an external storage for footage such as a Network Video Recorder (NVR) if the latter is not economical or feasible.  This article examines how Edge Storage operates and its real life applications and desirable arrangements. 

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Standard NVR uses hard disk drives (HDD) for storage of video footage.  HDD with a form factor of 3.5” and a SATA interface has a large storage capacity such as 2 Terabytes (TB) or more as of November 2012 and is inexpensive.  Micro SD card is small in physical size and rigid storage capacity.  We have 32GB as the largest capacity at present.  Fortunately, we can allocate the whole lot of 32GB to one camera whereas the HDD storage of 2TB will be shared by 10 or whatever count of cameras supported by the NVR. 

Micro SD card is not designed for high volume or high speed recording.  It is used for camera edge storage mainly for its small size and low cost.   As such, we have to reduce our expectation of the quality of the recording from edge storage.  For a 4 mega-pixel camera equipped with H264 compression, we should be able to achieve 2 frames per second on edge whereas it would be 12 frames per second with central storage. 

Video footage is meant for review.  In order to review the footage recorded at the edge, we will need to connect the camera to a PC or server via a standard IP network cable unless the camera has been equipped with wireless transmission.  This is the requirement at least for setting up the camera initially before deployment.  The footage files will be in a standard format for snapshots and could be in a proprietary format for video clips.  We will supply a software program to play back the video clips in a PC running Windows.  Files would have been set up to have date and time as part of the filename for ease of reference.   See Slide 2.  It is not possible to obtain live views of the camera without connecting the camera to an IP network full time.

While edge camera is easy to install and low cost, it does not enjoy the benefits offered by a centralised NVR.   Even if edge is connected with IP full time, we can review the footage on a file basis only and not in synchronization with other cameras with a graphical user interface as offered by NVR.  There are indeed situations where centralised storage is too expensive to achieve and edge is an acceptable compromise.

We can also use edge as a back up of centralised storage.  If we store snapshots only in edge, we will have footage for a long period such as one or two months.  These snapshots could be valuable in case the NVR does not support such a long recording period or when the NVR breaks down when it is needed for police investigation.

As of November 2012, the Compucon stable has 4 models with edge storage.  They are K3911, K5211E, K7111 and K7311.   See Slide 3.