With digital video, there are many storage options from single drives to multiple terabyte arrays. Estimating storage requirements depends on a number of factors including the number of cameras, video compression method used, desired retention time and the method of recording.
Recording methods are one of the most effective ways of maximizing storage by simply reducing the amount of video recorded. This is accomplished by using standard features that can be found on nearly any modern DVR or IP camera: scheduled recording, motion detection and adjusting the number of frames per second that are recorded. Scheduled recordings are obvious – you set the start and end time for the security cameras to be recorded. Advanced features include the ability to have schedules for different days of the week and holiday support. For example: some businesses may wish to record during off-business hours only to respect the privacy of staff.
Motion detection is another feature found on most modern video security recording devices. It allows you to highlight one or more areas in the camera’s field of view which will trigger the recording of video. This can be especially useful to mask out areas that you do not wish to record such as moving cars or swaying trees.
Frames Per Second (fps) is a very clearly defined specification on all recording devices. 30 fps is considered to be full motion video, that is, it is smooth, fluid video. Quite often, 10 fps is perfectly acceptable and can reduce your storage requirements by one third.
Storage for DVRs are limited only by the capabilities of the unit itself. Some allow for one hard drive only, some allow for multiple hard drives to be installed and configured with forms of RAID for redundancy. Some allow for external storage to be added via USB, SCSI or through a proprietary device.
Mobotix IP cameras take a decentralized approach to storage and take advantage of inexpensive flash storage – several models allow for SD cards up to 16GB in size for surveillance storage. This can be used in addition to remote storage and is useful in bridging planned or unplanned network outages. Mobotix cameras can be deployed without the need for centralized storage systems.
IP cameras allow for much more flexibility with respect to storage. Network Video Recorders (NVRs) are typically used to record streams of digital video from IP security cameras. Mobotix IP cameras are more open in that they can write video streams to an existing Windows file share, NFS share or FTP server. Using a remote FTP server is an excellent method of implementing off site surveillance storage.
How long CCTV recordings should be kept is entirely dependent on the needs of the organization and the industry in which they are in. Factors that may influence it include how often video is reviewed or how long it may take for an event, such as burglary or vandalism to be noticed.