Posts Tagged ‘ D1’

Security DVR Recording Resolutions

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Friday, March 19th, 2010

You’re in the market for a security surveillance system for your home or your business. What is the one most important component of that system? The Digital Video Recorder, or DVR, is the single most important component. And the most important aspect of choosing a DVR is the recording resolution.

In manufacturing a DVR, the recording resolution is a balancing act between being able to actually see what’s being recorded and having the storage space to store the video. The better the resolution, the better the images look, but the more space it takes to store it, and the beefier the processor it takes to record it. Manufacturers try to offer that ideal balance between being able to actually have usable recorded footage for evidence of an event if needed, being able to process the enormous amounts of data involved while recording it at a usable resolution, and not running out of recording room to store events. How the manufacturers succeed at this is what you need to evaluate when shopping for DVRs. Budget will be a huge consideration here, since the units that juggle these factors in the most optimum way are, of course, the most expensive. Putting together the optimum system which takes into account all your needs, including your budget, and gives you recordings from all DVRs that can actually be used as evidence takes a bit of knowledge and the help of a qualified reputable professional.

When referring to recording resolution the industry usually uses either a variant of CIF, which is 360 x 240 pixel resolution, or D1, which is 720 x 480 pixel resolution. There is a distinction that needs to be addressed here. Each DVR has a recording resolution and a live video resolution. The live video is always going to be clearer, so when you are evaluating DVR units you really need to know how the recorded video will look, since that will be your actionable evidence in the event of a security problem. D1 is currently the highest resolution used for recording, but most standalone DVRs are not able to record in D1 in realtime, which is 30 frames per second (fps) on all the channels at the same time, though some of the new units coming out are starting to improve on that.

The strength and capacity of the processor that is running the DVR will determine how high a resolution can be set for recording. The memory in the unit is also a big factor. Most processors can’t yet record at a realtime resolution, though some of the newer units that are beginning to show up in the marketplace are hitting 4CIF recording in real time on all channels, which is a 704 x 480 pixel resolution. The current average for a DVR is a CIF recording resolution, which is 360 x 240 pixels in real time at 30 fps.

When looking at the specifications, the three things you need to consider together are the recording resolution, the frame rate, and the recording speed. Of the three, the recording resolution carries the most weight in a carefully considered purchasing decision. If there is a security event, you want to be able to clearly identify the face of the person involved, and if the resolution doesn’t allow this, it’s useless. A 640 x 480 recording resolution is the minimum recording resolution which will easily allow this. 720 x 480 has the same quality but in a wider screened aspect ratio to allow viewing on the typical widescreen computer or tv monitor. 1600 x 1200 is ideal for viewing from an actionable standpoint, but the speed, storage and processing needed to maintain this recording resolution make the cost prohibitive for all but the most deep pocket organizations.

When putting together a budget system, the best way to approach it is to choose a better resolution for key points of security, ie near the front door and the cash register, while choosing lesser resolutions for areas which would be more likely to be monitored in realtime but where recording resolution is a bit less critical, and would simply be support footage when combined with the higher resolution footage from the other areas, not an ideal approach, but one which would allow security on a smaller budget.

Whatever your security needs, the help of a qualified and reputable security monitoring specialist will shortcut your efforts enormously. Juggling all the factors involved in the purchase, including the recording resolution needed for actionable evidence, is key to the overall success of your security efforts.


Basics of Facial Capture and Facial Recognition

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Sunday, January 31st, 2010

It is likely that if you get a security camera system, that you will want to be able to identify an intruder that has been captured on security camera footage. This process is called facial capture. Some people also call it facial recognition although they are really two different processes. Facial capture means to get enough usable details to be able to identify the person of interest by comparing facial features. It doesn’t mean the security cameras will identify the person, only that enough detail has been captured that he can be identified. Facial recognition actually refers to analytic software that can compare and match captured images of a persons face against another in a database. There are many interesting applications for such a process, but that is an entirely separate article.

Getting proper facial capture is an important process to understand because what good are your security cameras if you cannot identify the person of interest in the video? Proper identification requires at least 25% of the video image to be occupied by the face. This means that you really need to use a dedicated camera for this process. Begin the installation by finding an ideal spot to capture the face. Usually an entrance or exit would be ideal, but maybe there is a room entrance to something valuable. Once you have found the perfect spot to capture the face details, decide on the type of camera you will use for this process. It is best to use a good quality day/night security camera with a vari-focal lens rather than an infrared camera. Infrared cameras will be taking video in black and white in low light and this could make identifying the intruder more difficult. Since you will be using a good low light camera, make sure there is at least a little bit of ambient lighting. A night light, motion light or something of the like will be fine. Mount the camera close enough to the capture point so that at least 25% of the video (preferably much more) is the subjects face. Make sure to accommodate for people of different heights. Next, mount a second camera in a corner, or somewhere else in the room to provide you with a good overview. Now you have one cameras that is used to only capture facial details and a second camera that is providing the general overview of what is going on in the room. Make sure that the channel that the facial capture camera is on is set to record at the highest resolution possible. A D1 resolution image will be 4 times larger than a CIF resolution image and therefore will provide you with 4 times more detail. Use the higher resolution setting even if the frame rate has to be reduced. The overview camera can be set at CIF resolution rather than D1.


The Relationship Between The Camera TVL And The Resolution Of The DVR

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Saturday, August 8th, 2009

Here is a very common question. How many TVL should the camera have to best use the resolution of my DVR? This is one of the most misunderstood relationships in CCTV. The resolution that the DVR records in refers to the SIZE of the image being recorded. So CIF resolution (360×240) and 4CIF resolution (704×480) refer to how large the image actually is. 4CIF is an image that is 4 times larger than CIF.

TVL refers to the Horizontal lines of resolution the camera can display in. This will determine the amount of detail you may see within a certain size image (CIF, 2CIF, 4CIF). When selecting the right camera, keep in mind that the resolution being recorded and the resolution being displayed are usually different. In most cases a DVR will display live video at 4CIF (704×480) or D1 (720×480) resolution, but be recording in a lower resolution like CIF (360×240). Though a live 4CIF display of video will benefit from a 520TVL camera, the recorded image in CIF will not see the difference between a 520TVL camera and a 420TVL camera. So in essence you will only benefit from the live view, not the recorded image.

You will notice that the maximum benefit for a cameras horizontal resolution when recording in 4CIF is actually around 520TVL. Also, notice when recording in CIF resolution a 420TVL camera and a 520TVL camera will look exactly the same in the recorded image if recorded in CIF, but the 520TVL camera will display an enhanced image when recording at 4CIF. This also applies to the live video since it is usually displayed at 4 CIF.