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Another example tells us what you can get from a CCTV system.
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There are no two kinds of DVRs are exactly same. Even they mark out similar specifications. It is impossible for end users to try out all DVRs and learn their advantages and drawbacks. The only way is to ask several key questions about their DVRs.
Basically, a DVR system should become your eyes to do daily monitoring of business operation, anti-staff theft, anti-shoplifting, customer dispute and etc.
To achieve those purposes, you have to look into system specifications much deeper:
1) Display frame rate Vs Recording frame rate.
To obtain smooth images, minimum frame rate is 20 frames per second (fps) for each channel. Please ask those sales, can their systems do 16 channels all real time 30 fps recording (not only real time display)? What is their total recording frame rate? Our system will do 30fps recording and display for each channel (that is 480fps for 16 channels);
2) Display resolution Vs Recording resolution.
Live viewing is only part functions of a DVR system. Playback is another important function of a DVR system. If the resolution of a recording footage is not high enough, how can it be useful in investigations? Some sales may tell you that they can reach 684x480 resolution, but they intentionally forgot to tell you that it is display resolution; their recording resolution is only 342x240. Our system will reach resolution 704x480 for both recording and display.
OK, please ask those sales with following questions. If they say "NO" to anyone of them, they should be out of your view already:
Can your system be recording at 30fps(or 60ips) for each channel? For 16 channels, total recording frame rate should be 480fps.
Can your system be recording at 704x480 resolution not only display at that resolution?
Does your system feature "instant playback"?
It allows user to instantly review what happened in last minute. This feature will be very helpful in retail store. When something happened, users can instantly find out the recording and review it without interrupting viewing of other cameras. For other systems, users usually have to enter search mode, choose time and play. That will take more steps and time to find what is needed.
Does your system feature " smart search" or "intelligent search" or "object search"?
Can your system be expandable to 20-channel system or 24 cameras system?
Can your system do recording file backup on DVD disk or USB hard drive?
Can your system be integrated into one multi-store video system?
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The frame rate is number of images that are being displayed or recorded over a specific period of time. Typically frames per second or “fps” is the specification most often used. Remember frame rate record and frame rate display are two different items. 1 fps equals to 2 ips.
Industry standards typically speak of 60 images per second (or 30 fps) as real motion video. Think of frames per second in terms of how a cartoon is made with cells or even think of the projector in a movie theater where multiple frames pass in front of the lamp to give the appearance of “real motion.”
The vast majority of DVR manufacturers describe a system in terms of “shared frame rate” which is somewhat misleading. What that means is a 30fps system is 30 frames per second over the entire number of cameras being displayed. Therefore, a 16 camera system sharing 30 frames may yield less than 2 images per second
What the manufacturers often fail to tell you is that a 30fps video capture board is the “maximum” frame rate that the video will display. The maximum frame rate is what can be achieved prior to the introduction of other important criteria such as hardware and software processing and video compression and network connection speeds; either of which attributes to the degradation of the capture rate. A 30 fps capture board may lose as much as 20% of its capacity through software compression.
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Basicly , for most dvr systems with network feature, users have two ways to view cameras remotely, with a viewer software or with IE brouser(IE6.0 and above).
The difference is that, if viewing with the software, after you install it, you will have full control of your remote DVR system, you almost can do any thing as you are at local, execpt user setting. Just one click to connect, you dont need to remember the user name and password. If you can not install remote viewer software on remote PC or Laptop, then you have to use IE brouser to connect with remote DVR system. You only can view or search in this way, no any setting you can change on DVR system. Although you do not need install any viewer software(20-30MB), for some PCs, you have to adjust security level to allow a tiny ActiveX plug-in(100K-150K) to be installed before you can start to view.
If you have any questions for remote viewing, please visit our "how to" page to get the answer.
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This brief white paper demystifies analog video resolutions and their relationship to their digital counterparts. By understanding the relationship, we can optimize the use of our original camera video, without wasting effort compressing, transmitting, and storing parts of the image that can never be seen.
NTSC Analog Video
An NTSC analog video picture is composed of 480 active horizontal lines. When the picture is sent to a monitor or another receiving device, the first field of 240 even-numbered lines is sent, and then the second field of 240 odd-numbered lines is transmitted. This occurs at a rate of 60 fields per second.
The odd and even fields are offset one line apart, so when they are viewed in rapid succession (60 fields per second), they slot into one another to give the illusion of the complete picture — also called a frame, which is made up of 2 x 40 (or 480) lines. This is called interlaced video.
Resolution (TVL - or TV Lines) is a monochrome specification that states how many black and white lines can be seen in a given area. With 480 active scan lines, we can see how the theoretical maximum vertical TVL resolution is directly affected by the number of scan lines. (Note: TVL is not equal to scan lines, but vertical TVL is affected by the number of scan lines.)
Now that we understand the vertical resolution, we need to understand the horizontal TVL resolution (the number of vertical sampling points). This number varies by camera manufacturer, but they all follow the same definition.
As you can see in the drawing above, the picture is wider than it is high. This is called a 3x4 aspect ratio. (3 units high by 4 units wide). Horizontal resolution is defined as the amount of vertical black and white lines you can see in 3 of the 4 units. In other words, how much detail you can measure in 75 percent (3/4) of the picture's width.
This resolution number varies by camera type and camera manufacturer — many "standard" CCTV cameras have 380 TVL, but high-resolution cameras have more, typically 540 TVL.
Assuming all things are equal, if you were to connect an analog CCTV camera via coax to an analog monitor, you would see everything. However, when you digitize the analog video, compress it, transmit it across an IP network, and then decompress it again, the video changes. To understand how it changes, we need to understand CIF - resolution in the digital world.
Analog to Digital
In the analog world, 480 active scan lines and 75 percent of the horizontal area identify resolution. With digital, we still have a 3x4 aspect ratio, but pixels or sensing points now take the place of scan lines. Like cameras, these digital "picture grabbers" (digitizers) come in different levels of resolution (e.g., 176x144, 352x240, or 704x480). Like a steel chain, the picture quality of your system will only be as good as your weakest link.
What is CIF?
CIF and derivatives of this word are terms used to identify the level of resolution that the "picture grabber" can produce. CIF (pronounced "SIF") stands for "Common Interchange Format" or "Common Intermediate Format." It ranges from: CIF 352x240, 2CIF 704x240, or 4CIF 704x480.
The table above shows cameras and their CIF recommendations. Note that statements such as 'Good, Better, Best' are subjective and you are encouraged to try the settings for yourself:
- Acceptable: significant image quality loss, but still usable depending on application
- Good: respectable, yet efficient image
- Better: optimized image (default recommendation)
- Best: as perfect as possible
- Unnecessary: compressed image contains wasteful/redundant information since the camera's resolution is lower
CIF is Economical, But Does Not Bring Out the Best in Your Camera
Digitized NTSC video at CIF resolution is an image that is 352 x 240. It intentionally matches the NTSC 240 horizontal lines in a field so that there is a one-to-one conversion from analog to digital CIF. However, the 352 only produces a theoretical 264 TVL (remember 75 percent of 352), which does not match the 330, 380, 480 , or 540 TVL from the cameras — so what happens to the extra vertical lines of resolution? They are lost. At CIF, any camera capable of delivering over 264 TVL will not appear superior: 264 TVL and 1,000 TVL cameras will produce identical images.
When compression solutions use CIF resolution, they typically use every other field and simply discard the others — so a CIF system throws away half the video information from the camera. Because the eye is good at averaging things, it's not that noticeable, but this cuts the vertical resolution in half, and makes the resulting video "jerky" and less smooth.
2CIF is an Effective Solution for High-Resolution Cameras
To benefit from higher resolution cameras, 2CIF (704 x 40) can be used. Once again, the 240 matches the 240 horizontal scan lines in a single field and the 704 will give us 528 TVL. In the case of 330, 380, and 480 TVL cameras, we have an excess of vertical lines — if we have a 540 TVL camera, we can see almost all of the detail.
In other words, 2CIF is the lowest setting that maintains the horizontal resolution of the cameras. But note that the vertical resolution is reduced (because again, we discard alternate fields).
4CIF is the Ultimate Choice for High-Resolution Cameras
A 4CIF picture has 704 x 480 pixels. Like 2CIF, the 704 provides 528 TVL horizontally - but 4CIF provides 480 pixels in the vertical direction. This improvement supports the full 480 vertical resolution provided by the NTCS analog signal.
480 scan lines corresponds to 480 pixels. 4CIF systems use both fields. However, some 4CIF systems combine pairs of fields into frames (through a process called de-interlacing) and then code these frames as images. This leads to "zippering" artifacts on objects moving horizontally through the scene and can be very distracting to watch.
4CIF (similar to D1) contains substantially more horizontal and vertical data. Consequently, the data streams and data files are large.
2/3 D1 and 1/2 D1
There is a very effective compromise setting offered by some manufacturers called 2/3 D1 (pronounced "two-thirds D1").
2/3 D1 is 464 x 480. Its 464 horizontal resolution is a near-perfect fit for most cameras and the benefits in bandwidth and disk space savings can be very substantial.
1/2 D1 is another option: at 352 x 480, it has the width of CIF and the height of 2CIF. But as discussed earlier, the eye is less discerning in the vertical direction, which makes 1/2 D1 a less popular option.
Summary
Cameras have specific resolution capabilities that are measured in TVL, while digital and IP encoders measure in CIF. It's important to understand the relationship between camera TVL and horizontal resolution for digital systems so that you're getting the most out of your camera, but not storing extra and completely redundant data thinking that your final image will look better. In the vertical direction, the number of scan lines (240 or 480) is also a quality factor, but due to the nature of the human eye, it's less important than horizontal resolution.
Remember why this is so important: if you are about to spend $10,000 on storing video for a week at CIF resolution, you will need $20,000 at 2CIF or $40,000 at 4CIF.
We encourages you to get the best image possible out of your camera, and hopes that this white paper will help you understand the difference between what you think you're getting and what you're actually getting. You want to be sure you're selecting the right equipment and the right configuration.
Source: white paper of Bosch Security
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One of the most frequently asked questions about DVR's is: Which is better a PC-Based or Non PC-Based DVR solution?
There isn't much that a non-PC based DVR solution cannot do today, which a PC-Based DVR can. The difference has more to do with the “footprint”. PC interfaces tend to be more user-friendly and less “mechanical.”
PC-Based DVR's tend to be more flexible and easier to manage. PC-Based solutions also tend to allow for upgrades of compression technology, which can be vital to the end user. Remember, in the IT world, you blink and they are onto the next technology.
Non-PC-based solutions tend to use “ASIC” (Application Specific Integrated Circuits) technology, which does not allow for upgrading of a technology platform, similar to your microwave oven. ASIC, is a chip that is custom designed for a specific application rather than a general-purpose, such as a microprocessor. ASIC, unlike an FPGA, has fixed functionality and is not reprogrammable.
In the PC environment, the latest technology utilizes DSP’s (digital signal processors). A DSP is a specialized digital microprocessor used to efficiently and rapidly perform calculations on digitized signals that were originally analog in form, such as audio and video. The big advantage of DSP lies in the programmability of the processor, allowing parameters to be easily changed.
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Let's give you a quick lesson in translation and calculation of video “speed” or “frame rates.”
Some manufacturers use different expressions when identifying the speed capabilities of their product. It will become increasingly apparent why this is misleading.
Thirty (30) “frames-per-second”(abbreviated as “fps”) is “real-time,” ”real-motion” video in the NTSC (North America) video standard.
Twenty-five (25) “frames-per-second”(abbreviated as “fps”) is “real-time,” ”real-motion” video in the PAL (International) standard.
This is not to be confused with “fields-per-second” (also abbreviated as “fps”). Unfortunately, two (2) fields equal one (1) frame. So when a manufacturer states “30 fps” on their literature are they talking fields or frames? Are they talking about each channel of video or total capacity of the system? Are they talking about the system limitation or the operating capability?
When comparing a DVR's fields (FPS), images (IPS) or frames-per-second (FPS); display, recording or playback performance claims; be careful to take into consideration all the factors that will apply to your particular application. Once again, manufacturers' claims may be based on “optimal” conditions and have little to do with reality and what you are trying to achieve. So always check to see if the total number of FPS/FPS/IPS quoted is for the entire DVR capture card or is it on a per 
channel basis. Is it for display and record? You simply have to test it anyway, as claims are just that; claims. Besides if you don’t the regulators will.
It’s kind of like the MPG sticker on a new car. Do you know anyone that ever got that kind of mileage? Not unless they were going downhill, in neutral, with a strong tail-wind!
Remember also what you are viewing live has nothing to do with the recorded quality, they are separate and distinct. So watching a live picture has little value, although if the live video is poor you are already in trouble.
Source: ATI247
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If you can not directly connect via IE brouser with your CPC 4004 DVR system, please click here to download and install ActiveX control plug-in, and refresh the page. Then click on Setup tab to add your DVR IP and password/user ID before you log on to do remote viewing.
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