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What is a DVR? A DVR or Digital Video Recorder, records images to a hard disk. There are many advantages of a DVR over a traditional VCR, these include no degradation of image quality, rapid access to stored footage, no tapes to worry about, and due to motion technology you only need to scan through relevant footage to find what you are looking for.

What should I look for when purchasing a DVR? Frame Rate vs Image quality, both handled below individually. Firstly determine what it is that you need to record? ie door traffic - lower resolution because of the general view required but high frame rate due to speed of traffic. Till coverage - high frame rate and high resolution because detail over the till is required and activity at the till happens at a relatively high speed.

What is Video Compression? The method of compression will directly affect both the image quality and the amount of storage required. Popular methods of compression are MPEG4 and Wavelet, Wavelet requires approximately 4 times as much storage capacity of MPEG4. The downside of using MPEG4 compression is reduced image quality during playback; MPEG4 images appear blocky when reviewed.

Will the use of Motion Detection mean I need less Disk Storage? Well Yes and No, if the environment is very busy the cameras will be recording continuously and will therefore not reduce the amount of storage required. We do not advocate reducing disk storage based on the use of motion detection, after all how do you know how busy the environment will be in the future?

Should I use Motion Detection? Yes, the main benefit of Motion Detection is that it will reduce the time to find the video footage you are looking for during playback. If you know that an item was stolen between 5:30pm and 9am the next day then you can start your search from 5:30pm, if there was no activity between 5:30pm and 1:00am the next day the first images displayed will be from 1:00am. Motion Detection has saved you searching through 7.5 hours of footage!

How many Frames Per Second do I need? This depends on the circumstances, if you are interested in vehicles entering your premises at 40 mph then you will need to use higher frame rates. In general if the objects you are interested in are moving relatively slowly i.e. people the 1 FPS (Frame Per Second) is likely to be OK. If however you are using high magnification to view details of objects moving slowly you need to consider the fact that even slow moving objects will not be in the frame for very long and therefore a higher frame rate maybe required.

What video resolution should I use? This depends on your requirement, if you require very high quality images then you will need to opt for a higher resolution. You should be aware that increasing the resolution will increase your storage requirements dramatically. In general we recommend that you should consider 320 x 240 as a good starting point, when used with Wavelet compression this provides good image quality and does not use excessive disk storage.

So how much disk space do I really need? Taking into consideration the above points we now know that increasing the frame rate and increasing the resolution will directly affect the storage requirements. We have included a disk space calculator in the download area, where you can put in your exact specs and determine the right amount of hard drive space you require.

What is RAID and do I need it? RAID disk systems offer improved data security and reliability, so if this is important to you the answer must be yes. We recommend the use of RAID 5 configurations which require a minimum of 3 hard drives, in this configuration a single disk can fail but the video data will not be lost. When the faulty disk is replaced the data on it can be rebuilt from the remaining disks.

What other features should I look for in a DVR? Good quality DVRs provide many additional features, the following have good merit and are useful in many instances. Remote access, scheduled recording, pre-recording, multiple motion detection zones, video loss alarms and notifications.

To view our recommended DVRs click here

There are basically two types of DVR systems, PC Based DVR systems and Embedded DVR systems. Both systems essentially do the same thing, by taking the analogue video signal from the camera, digitising and compressing it and then storing it to hardrive.
This tutorial will handle only the basics of the PC based system, the pro's and cons of both systems will be handled elsewhere on this site.

A typical video capture card is a system of hardware and software which together allow a user to convert video into a computer-readable format by digitising video sequences to uncompressed or, more normally, compressed data files. Uncompressed PAL video is an unwieldy beast, so some kind of compression has to be employed to make it more manageable. It's down to a codec to compress video during capture and decompress it again for playback, and this can be done in software or hardware. Even in the age of GHz-speed CPUs, a hardware codec is necessary to achieve anything near broadcast quality video.
Most video capture devices employ a hardware Motion-JPEG codec, which uses JPEG compression on each frame to achieve smaller file sizes, while retaining editing capabilities. Some video capture cards keep their price down by omitting their own recording hardware. The recording and compression is then left up to the computer's CPU to do, this can results in all kinds of hardware clashes as well as dropped frames. Basic rule of thumb when evaluating a DVR card is to look at the amount of chips on board, the more the better. Less than 7 and you are buying a whole lot of trouble. Dont buy cheap, you will pay later.

Video capture cards are equipped with a number of input connectors depending on the amount of camera's required. The more camera's required, the higher the processing power of the PC has to be.

Performance requirements
Digital video relies primarily on hard disk power and size, and the important characteristic is sustained data throughput in a real-world environment. Video files can be huge and therefore require a hard disk drive to sustain high rates of data transfer over an extended period of time. If the rate dips, the video stream stutters as the playback program skips frames to maintain the playback speed. Speed plays a major role in PC based systems, ensure that your CPU, Memory and Harddrive are up to at least the recommended spec prior to purchasing a DVR card. An item not always required on the specs is a 3D graphics card, this will assist greatly on playback, especially while recording is happening simultaneously. Again more is better!

Accessibility

Once the DVR card is installed in a PC, this unit essentially becomes the video server. Allowing the user to view live and recorded footage locally. One of the main advantages of the DVR system is to view only relevent footage at the click of a mouse i.e. If an incident occurred between 10:00am and 11:00, you could just scroll to the specified time and select the footage for viewing rather than spending hours rewinding and fast forwarding tape based systems. Record on motion detection is another feature of DVR systems, this not only saves disk space but also assist in bring the amount of information down to incident based activities.

Remote Viewing
With the required software loaded, any PC can now gain access to the either the Live or Recorded video footage by means of Network Lan/Wan or via a telephone line. This opens up a whole new world of opportunities for the PC based DVR. Now you could monitor your home, business, or just about anything from anywhere in the world. All that would be required essentially is a modem on the Video Server and access to PC and a telephone line at the remote site. However the speed of the Video would be dependent on the speed of the line you were using. i.e. Over a standard phone line you would only be able to view 3 to 5 frames per second, ISDN or ADSL could triple or quadruple that speed.

Other Considerations
Alarm alerts can assist by calling or emailing you if a camera picked up motion in an area that was not meant to have any.

If you should require any further help putting together your DVR system, Please contact us for a free quotation.