Critical to any surveillance solution, recordings should be of the best possible quality and have sufficient capacity to record for the required minimum duration and at a suitable frame rate. For IP cameras this requires a Network Video Recorder (NVR) – and for analogue systems it’s a Digital Video Recorder (DVR).
Both devices rely on large hard drives for the storage medium, these should be “surveillance grade” that typically have better heat management capabilities and are rated for more read/write cycles. The daily storage calculation is basically the number of cameras x frame size (Mb) x frames per second x 24. For example a 16 channel NVR with 16 cameras recording at 25fps will require approximately 428GB per day, whereas if you lower the frame rate to 15fps you will only require 257GB of storage per day. If you need to work this out we have a simple online calculator to assist – find it at: http://www.lilin.tv/bandwidth-and-storage-calculator. This demonstrates why we supply recording devices with multiple Terabytes of storage as standard.
In order to achieve the required duration, any of the elements can be adjusted – frame rates reduced (do they actually need 25fps? As 6-12 fps produces good evidential recordings) or reduce the image quality by increasing the compression? Luckily our recorders will calculate the estimated recording time based on the settings and the actual camera views so you can make adjustments as required.
The NVR usually performs many other functions above recording and playback, usually handling audio recording, alarm event notification and streaming to remote devices. It also provides the HDMI and SVGA outputs for local monitors and can be controlled by IR remotes, web interfaces, touch screen monitors and the mouse.
Critically for the custom install sector, LILIN NVRs integrate deeply with all major control systems via IP based drivers, so the user can have full control along with 1080p quality over 16 cameras using their home automation remote or touchscreen controls.
Many home automation system touchscreens have some ability to decode IP camera streams, but there are limitations on frame rates and image quality as these units do not usually have sufficient processing power. Additionally there is currently no solution for viewing playback on these screens.
Not all hardware (standalone) NVRs are able to support all manufacturers’ IP cameras, there is an interoperability standard known as ONVIF but there are numerous releases of this protocol and a large number of uncertified products claiming compatibility. The result is that the ONVIF tag does not guarantee that an ONVIF camera will work flawlessly on an ONVIF compliant recorder, so it’s always best to test this prior to install or work with a single brand to ensure compatibility.
DVRs work in much the same way but take the analogue camera feed and encode it prior to recording – this is why the playback quality from many DVRs is lower than the live camera stream – whereas IP systems record exactly what you see from the camera – there is no secondary compression. Where the client already has an analogue CCTV system, replacing the DVR with one that is driver supported will bring many of the benefits of integration to their existing system.
Encoders take an analogue video feed and convert it to IP, this is sometimes done to bring legacy analogue equipment onto modern IP solutions, however this can be a false economy – once the user sees the HD image quality of IP cameras next to their old analogue ones they may not be very happy and often ask to then have them upgraded to IP, making the encoders and expensive experiment. Encoders are sometimes used to digitize other video sources for integration into the system but can only support PAL resolution.
These do the opposite to encoders but are much more useful; enabling IP video stream to be displayed on televisions. The LILIN standalone decoder can display up to 9 HD streams on a single HDMI monitor at 1080p resolution. It can also display the video output from NVRs or DVRs and enable full independent control – allowing camera selection, playback etc. remotely without affecting what is being displayed on any other monitor, it’s an excellent way of getting cameras to multiple monitors without the need of an HDMI matrix. The LILIN decoder uses the same driver as our NVR and DVR so is supported by the same platforms and works in exactly the same way.
Video Management Systems (or servers) are PC or servers that run software applications for recording, decoding and displaying camera streams. Most run on Windows platforms and have a license based model but many IP camera manufacturers have their own proprietary software that may be free if it only supports their own cameras. In large commercial projects where hundreds of cameras are being managed the VMS platform is the recommended way to manage and record, unfortunately there is currently no deep integration of these solutions for the automation platforms although this is likely to change in 2015.
Using a combination of these recording solutions can still achieve integration even though the VMS may not be supported, however at this level of system design bandwidth management becomes critical and we would recommend working with a manufacturer to do a complete system design.
Recorders work very hard, 24 hours a day 7 days a week and rely on mechanical hard drives and powerful processors, so they require cooling and thoughtful positioning. The fans in recorders are necessary to keep the drives cool as drive failure can increase dramatically with temperature, so they can be noisy and can draw through a lot of dust if it’s in the environment.
In the case of a drive failure (it will happen eventually!) alerts can be delivered, but if these are not enabled or responded to then the user may not realize that their system has stopped recording – until they then need to replay some critical footage…