Bandwidth vs Quality

Factors Impacting Quality

Even with the same resolution, two common settings impact quality:

  • Bit Rate: Most cameras can have their bit rate adjusted to specific levels (e.g., 512 Kb/s, 2 Mb/s, 8Mb/s, etc.)
  • Quantization Level: Most cameras can have the level of compression adjusted (often called a quality or compression setting with options from 1-10 or 0-100)

Typically, these are mutually exclusive. If you lock in bit rate, the camera will automatically adjust the quantization level to not exceed the bandwidth set. Vice versa, if you set the quantization level, the camera will automatically change the bandwidth consumed to make sure the quality / compression always stays at the same level.

Our Test Process

For the bandwidth tests, we tested each camera at the following levels:

  • 512 Kb/s
  • 1 Mb/s
  • 2 Mb/s
  • 4 Mb/s
  • 8 Mb/s

We did this across a series of scenes to see how quality would vary in different conditions:

  • Daytime Indoors (300 lux)
  • Nighttime Indoors (.5 lux)
  • Daytime Intersection
Source
Advertisements

What is Frames Per Second

What is frames per second?

The frames per second (fps) relates to how many pictures the DVR will record in a second. Real time recording is about 30 fps on each camera. To calculate the fps per camera take the total fps in the system and divide it by the number of video inputs. For example, a 60 fps digital video recorder with 4 video inputs would result in about 15 fps per camera. The technology has finally gotten to the point now where real time recording is affordable. If you are recording cash registers or something similar then you should definitely invest in real time recording.

How big a hard drive do I need?

The amount of hard drive space is very important because it will limit how many days of recording you can store before the system has to start recording over the oldest video. Each DVR will have its storage capacity listed in the specifications. But this calculation is just a rough estimate as there are many factors that affect hard drive use. The most critical factor being the compression format used by the DVR (for more info on compression formats click here). But also the type of cameras that are connected to the DVR make a difference (specifically the chip size and resolution) and also the features that are selected on the DVR. If you use the scheduling or motion detection features or tune down the frame rate that will extend the storage capacity of the unit. Even the field of view (what you are recording) will affect the storage capacity – the more complex the image, the more hard drive space it will take to capture the complexity.

What is the difference between a PC-based DVR and an Embedded DVR?

A PC-based digital video recorder is basically a personal computer that has been modified with hardware and software to work as a DVR. An embedded digital video recorder is a machine that has been manufactured specifically to work as a DVR. In embedded DVRs there is typically one circuit board with software burned into the chip.

There used to be significant differences in features between the PC-based and the embedded machines. But with recent advancements in the embedded DVR technologies the differences are becoming less. The advantages of an embedded digital video recorder is that they are extremely stable and reliable since they contain fewer parts. The software is often written in basic machine code or Linux code which tends to be more stable than Windows software. The advantages of the PC-based digital video recorders is that they are easier to interact with because you use the on-screen menus and a mouse (as opposed to embedded which you interact with more like a VCR – via buttons). And you tend to have more features and options on the PC-based machines.

How does a CCTV digital video recorder work?

CCTV digital video recorder (or “DVR” for short) is essentially a computer that saves security video images to a hard drive. Most security cameras in use today capture an analog picture. The DVR converts the analog signal to digital and then compresses it.

Many cameras can be connected to one DVR. DVRs generally come with 4, 8, 16, or 32 camera inputs. The DVR will allow you to view all of these images at once or one at a time, and all of the video is saved to the hard drive. Additional switches, quads, or multiplexors are not required.

Are security digital video recorders hard to install?

Not at all. You simply plug the cameras into the back of the unit. For the PC-based: Plug in the power, monitor, keyboard and mouse – just like a regular computer. You will receive instructions on how to set up the machine with your shipment.

What comes with the DVR?

Most of our DVRs come standard with an 120 gig hard drive (unless otherwise noted). They also include the software (for setup, local, and remote viewing), power cord, and documentation. PC-based machines also come with the mouse and keyboard. You just need to add the cameras, whatever cable you need, and a monitor. For embedded machines you can use a TV set or security monitor. For PC-based machines you need a standard computer monitor. Also, we have on-site technical support available at no additional cost.

Why doesn’t the computer monitor come with the PC-based Digital Video Recorders?

We don’t supply the computer monitor with the DVR because frankly you can get one cheaper and easier locally. Large computer stores such as Best Buy or Comp USA sell these monitors practically at cost. And due to their heavy weight, they are very expensive to ship (and subject to damage). Also, we found that many of our customers have spare computer monitors available.

How do I see pictures from a remote site?

You can view the camera video over the internet using a modem which is slow but can display 1 or 2 frames every 5 seconds. Better is a DSL or cable modem connection which can generally display 1 frame per second. When viewing remotely, the refresh rate is restricted by the communications medium (your internet connection speed). When viewing or playing back locally, the display is dependent of the unit’s frame rate (fps). You will need a static ip address available to assign to the DVR (more about this in your documentation).

What is ‘Smart Search’?

Our PC-based DVRs come standard with smart search capability. This allows you to highlight one area of a captured image and look for changes just to that area. For example, if an item is stolen off of a counter… you can go to a moment in the video where the item is still on the counter, then highlight the area around the item and search automatically through the video for the moment in time when that particular area changes, that is precisely when the item is removed and then view that part of the video. Pretty slick!

Should I purchase the card and software and build my own digital video recorder or buy one pre-built?

It is much better to purchase a DVR system pre-built than to build one yourself. There are many compatibility issues with DVR cards and related software. They are very sensitive to the type of motherboard in the computer, the cpu, the memory, even the video card makes a difference! We had to test many different configurations to find one that worked reliably. You also don’t want to be running any other software on the computer that your DVR is running on so you need a dedicated computer anyway. We have had so many customers call us that have had problems installing cards in their own systems that we won’t even sell the cards separately anymore.

Source:  www.discount-security-cameras.net

DVR and Hard Drive Calculator

We found a good website that actually computes your hard disk requirements.

Please check out:  http://www.dvrsystems.net/calc.html

They have provided the tips below:

  1 frame per second is the lowest frame rate recordable and 30 frames per second is the maximum which is real time

There is no real need to record in real time unless there are regulatory reasons as in case of government facilities or casinos

Recording at 1 frame per second is what traditional analog systems record

You can always rewind in high speed so the lower the frame rate the faster it is to playback an entire day

At 3 – 5 frames per second recording you will not miss any activity (remember this is per second)

Camera Specifications – 380 TVL, 420 TVL up to 700 TVL

Analog camera resolution or picture quality is measured by the number of horizontal lines the chip in the camera provides. It is called “TV lines of resolution” or TVL. The higher the TVL, the better the quality of the image.

  • Standard image quality is 380TVL to 420TVL.
  • High image quality is 480TVL.
  • Very high image quality is 540TVL to 700TVL.

Super Wide Coverage

One of the factors that has contributed to the explosive popularity of megapixel IP cameras is their ability to provide wider coverage and more detail. A 2-megapixel IP camera can cover an area 6 times greater than an analog camera. With a 2-megapixel camera potentially taking the place of 6 Analog cameras, the installation costs can be significantly reduced (see the diagram below)

AnalogvsMP.jpg

Source:  www.apexcctv.com

Wired versus Wireless CCTV

Wired security cameras are the optimal choice, as they provide the best video quality, zero interference, and are cost effective. They can be installed hundreds of feet away from the security DVR system.

With wired security cameras you do not have to power the camera locally. Siamese cable provides video and power in the same cable, so you can connect your cameras to the DVR and power them remotely. We have a comprehensive inventory of wired security cameras. We also offer Siamese cable pre-cut to commonly used lengths and on a spool. For runs longer than 700 Ft., we recommend using CAT5e cable and Balun connectors. Using this method, the video signal can be transmitted up to about 1,300 Ft.

We can refer you to professional installers in your area; however, using our step-by-step installation guide, the layperson can easily and quickly install our video surveillance products.

Wireless cameras are relatively expensive and are not as reliable as wired systems. Most wireless systems are Line of Sight (LOS). Remember that wireless security cameras require power to operate. So even though by going with a wireless solution you can eliminate the need for coaxial cable for video transmission, you still have to wire the camera to a power source.

Power Source

Each camera requires a power source. There are two types of power supplies: 12V DC and 24V AC. Most cameras operate on 12V DC.

Individual power supplies are a good choice for 1-2 camera projects. If you have 3 or more cameras, a multi-port power supply is advisable. You can connect 4, 8 or 16 cameras to a multi-port power supply.

Previous Older Entries

%d bloggers like this: