The Digital Video Recorder or CCTV DVR is an industry specific product, central to any CCTV system and essentially does two jobs. Firstly, it arranges the camera footage on screen for you. Secondly, it stores images from the cameras and in some cases the DVR has a third function whereby it allows you to remotely access your CCTV system via the internet or a local network. This CCTV DVR buyers guide explains what you should look at when comparing different recorders on the market and explains what some of the key functions do.
There's no point in producing top quality images if the DVR is only going to record them at a low quality. There are 3 industry standard recording resolutions:
D1 is best quality and comprises a frame size of 704 x 576 pixels
Half D1, also known as "Field" comprises a frame size of 704 x 288 pixels
CIF is the lowest quality used and comprises a frame size of 352 x 288 pixels
Make sure your DVR records at D1 resolution - all ours do.
If you purchase both a DVR and hard drive from us at the same time we will install and format the hard drive for you before we deliver. We will also configure the DVR so when it arrives your DVR will be ready to plug in and play. This saves a lot of time and you don`t have to worry about programming or setting up your CCTV DVR system. It is important to purchase hard drives designed specifically for CCTV purposes because they will be running 24 hours a day, 7 days a week. Normal computer hard drives are designed around 8 hours use per day and even then, they are not constantly reading and writing data. A CCTV hard drive is working 365 days, 24 hours a day and there is 100 % data churn. All the products for sale on this site have been carefully selected to ensure they are the right specification for CCTV equipment purposes.
Left un-compressed the raw footage coming into the DVR from the cameras would soon fill up home CCTV hard drive. To get round the problem, people far cleverer than you or I have devised methods of compressing the information down so it takes up less space. There are 2 formats in use. Motion JPEG (or MJPEG) and H.264. Compression codec
mpressor - dec
ompressor) such as MJPEG & H.264 has uses far beyond the DVR in a CCTV system
. Computers and the internet are a much larger market for the technology but the aim is the same. Squash information down so it takes up less space and can be sent across the internet quicker.
H.264 is the current buzz word in the DVR industry and all our DVRs use this at their heart. The big advantage H.264 has over MJPEG is that it compresses files down into a smaller size than MJPEG. Because the file sizes are smaller they take up less hard drive space resulting in more recording time for the same size hard drive.
DVR Recording speed - frames per second
A lot of people selling CCTV
equipment place great importance on how many frames per second a DVR can record. "Real life" movement on a cinema screen requires 25 frames a second to provide perfect live motion playback. Unless you want to be the next Steven Spielberg, in which case you're buying the wrong equipment, then realistic movement is actually not that critical when it comes to CCTV, certainly not if it comes at the expense of image quality or the length of time you can store footage on your DVR.
We recommend a target of between 3 and 6 frames per second for CCTV use. This takes up a quarter of the space on your hard drive compared to 25 frames per second without costing much in footage quality. To put 3 frames per second into perspective we`ve done a little experiment.
This is 3 frames per second - and she is running faster than a speeding gazelle!
Recording Modes - All our DVRs can be set to record in a number of ways
You hit record, it records. And keeps on recording until you tell it to stop. When the hard drive fills up it goes back to the start and records over the earliest footage on a rolling basis. Our machines allow you to decide what happens when the disc is full, you can opt to stop recording so it doesn`t just over write the earliest footage although we don`t recommend you choose this option.
A feature whereby the DVR looks at the picture coming in from the camera. If nothing has changed then it doesn`t record. If it sees movement then it says I`ll save the footage from just before the movement and also keep recording for the next few seconds (you determine how long). You can choose to block out certain parts of the picture such as a road outside the target area you wish to monitor.
A word of warning about motion sensing - It is easy to get false alarms when using motion sensing, particularly when filming outside. Insect movement, spider`s webs blowing in front of the camera, changing light conditions and rain are all things that can trigger the DVR. To avoid this use small trigger windows rather than the whole screen. Our DVR recorders allow you to do this. You can select several different trigger areas for each camera if necessary.
The DVR starts recording when triggered by an external sensor such as a PIR (passive infra-red) motion sensor or magnetic contact "reed switch". You can set how long the DVR records for after it`s been triggered. This method is extremely reliable in terms of not generating false triggers meaning you can have a quick look to see if the CCTV DVR has detected any incidents and look at them rather than scanning through hours of footage to see if anything untoward occurred.
Here you can decide which camera is recording by any of the available methods during the day. You might want your shop or bar area to be recorded constantly during working hours but then only by motion trigger outside working hours. You could even have a camera in say a store room motion triggered for the full 24 hours. This helps reduce the amount of space taken up on the hard drive.
How many days footage will my CCTV hard drive store?
There are a number of factors which will determine this, some of which we have already covered in this section. The main things to consider are:
The higher the quality the less time a given hard drive will record for. However we strongly recommend you use D1 (the best quality), wherever possible. Choosing a lesser resolution compromises the effectiveness of your home CCTV system.
The number of frames per second you record at.
This is something you can change without compromising your CCTV system. Rather than recording at 24 frames per second adjust the DVR to record each camera at 6 frames per second. This will give a 4 fold benefit in recording time for a given hard drive.
The number of cameras you have on your system.
Each camera requires space for its footage to be stored.
As a rough guide 250GB of hard drive space per camera will give around 14 days constant recording capacity on a system using H.264 compression and recording 24 hours a day at 6 frames per second at D1 quality. At CIF resolution this would increase to around 8 weeks.
Always fit the largest hard drive your budget allows and be aware that doubling the size of the drive doesn't double it's cost. Larger drives work out much better value per unit of memory. If there is any chance of adding additional cameras to your system once up and running try to account for the additional cameras in your choice of hard drive.
NTSC, PAL and SECAM - will it work in the UK?
For reasons best known to someone else there is no worldwide standard method of broadcasting television images. North America, half of South America and most of Asia use a format known as NTSC. We in the UK along with most of Europe, Australia, East Africa and parts of Asia use a system known as PAL. There is a third broadcasting system called SECAM used in France, Eastern Europe and Western Africa. Normally SECAM televisions will also accept PAL signals but don`t bet your life on it!
If purchasing CCTV equipment make absolutely sure it is compatible with your television system. NTSC and PAL do not work together. All our products are sold as PAL versions so you will have no problems in the UK.
Duplex, Triplex, Pentaplex, Hexaplex - How many jobs a DVR can do at once
Recording - Displaying images on a monitor - Playing back previously recorded footage - Accessing the DVR`s settings - Accessing the DVR via a network (on a computer or over the internet) - Backing up recorded footage to a storage device (such as a computer or memory stick). These are all separate tasks a DVR has to do.
The phrases duplex, triplex, hexaplex etc denote how many of these jobs a DVR can do at once. With a Duplex or Triplex DVR you can only do 2 or 3 different things at the same time. You might have to stop recording if you wanted to play back footage and store the images to use as evidence. Similarly you might only have limited functionality if you are accessing your DVR remotely via the internet. All our DVR units are all hexaplex, as good as you can get, which means you can do all 6 tasks at once.
Networking a CCTV system - seeing the cameras on a computer or my mobile phone
Imagine you`re sunning yourself on the back deck of your Sunseeker motor yacht just round the coast from Monte-Carlo and think, "I`ll just check on the weekend shag pad in Sandbanks". Out comes the iPhone, equally you could use the internet WiFi but couldn`t be bothered to ask the Jacuzzi boy to get your laptop. There, on screen are the cameras showing all is well. It could be that you don`t own a Sunseeker motor cruiser but networking still has its uses.
Plugging a network enabled DVR into the back of your broadband router allows you to remotely access to your CCTV system when away from home or the workplace. This has many uses including checking to see if a Burglar alarm activation is genuine or not, making sure everything is all right in an unoccupied property or just checking everything is going smoothly at work in your absence.
Now for the really clever part. If you fit our PTZ (pan - tilt - zoom) cameras it`s even possible to control them remotely allowing you to have a good look round.
You can also access recorded home CCTV footage remotely, change settings on your DVR and take still or video copies from current or recorded footage. You can even get our DVR`s to email you images if they detect motion or are alarm triggered via a PIR detector.
Our DVR recorders also have an update client facility built into them which means you don`t need a static IP address to access your CCTV system remotely. It gets round the problem of Dynamic IP addresses.
Setting up port forwarding on a CCTV system
Networking doesn`t come without it`s complications. Port forwarding, dynamic IP addresses and client updating are terms that mean nothing to 99% of us. Luckily we have people who eat sleep and breathe technology.
To get round this we have come up with a fantastic service whereby once you`ve set your CCTV system up and plugged it into your internet router we can correctly set all the settings for you remotely using your own computer. This is called our remote network set up and is available for £49.95 in the accessories shop section.
The control panel when accessing our DVRs remotely over the internet using a computer
As seen in our video tutorial - "Seeing your CCTV over the internet"
Access our CCTV systems using a PDA or mobile phone such as an iPhone
As seen in our video tutorial - "Viewing your CCTV system using an iPhone"
Why not save money and just use my computer for CCTV rather than buying a DVR?
A logical question, after all your computer uses a very similar hard drive. There are a number of reasons why we don`t recommend this.
Video data takes up a large amount of storage space. 500GB is becoming more common in terms of what to fit in a DVR. All this video data filling up your computer could prove problematic. Your normal computer hard drive is not man enough to be constantly reading and writing data all day every day. Our hard drives are designed to handle this heavy usage.
You could find performance issues caused by the extra processing strain caused by asking your computer to handle the CCTV footage.
If your CCTV caused problems with your computer the results could spell disaster as most of us keep vital information on our PCs.
What gets stolen in a burglary? The PC - so not much use storing images of the break in there then! A DVR can be hidden away or kept under lock and key.
The software and capture card that fits in your computer costs money. It`s not hard to spend £150-300 on a good quality package. Why not just spend the same amount (or less) on the right tool for the job - a DVR !
Backing up your captured images
If you have captured something on your CCTV which you want to keep for reference or to use as evidence then you will need to make a copy or back up. We like to keep things flexible so all our DVRs use a USB port for back up. This means you can use a memory stick or a stand alone hard drive for large capacity storage.
If you connect your DVR to a network (such as your internet wireless hub) you can then access it via a computer and create AVI files using the software we provide with each DVR. These can then be shared amongst other computers or easily burnt onto writable CD or DVD discs for distribution, archive, evidence etc.
Finally - a little tip when making comparisons of DVRs
Congratulations on making it all the way to the end of the CCTV DVR buyers guide, as a reward for your effort we'll let you into a little secret. If you have been scouring the internet looking at the various CCTV sites out there you will have seen specifications thrown around like confetti. In almost every case DVR specifications are quoted assuming recording at CIF quality. You will remember from the top of the page that is the lowest quality and we recommend recording at D1, the highest quality.
Because CIF quality recordings are 1/4 the size of D1 recordings it makes the various claims somewhat ambiguous. As an example a 4 channel DVR which supposedly records at 100 frames per second will only really record at 6 frames per camera per second at D1. Not necessarily a problem but just be aware. The same is usually true when it comes to quoting recording times for different sizes of hard drives - that may be more of an issue!
We also have a CCTV camera advice
section and a CCTV cables, power supply and general accessory