Digital Video Recorders (DVR) and Network Video Recorders (NVR) are the heart of every security camera system. It critiques the final outcome of your captured footage, which is the entire complexity of its existence. Naturally a consumer wants to know how clear the video resolution will be from a system before making a purchase decision. Our whole site is filled with relevant material in pursuit of a well educational experience for our guests. This segment focuses on resolution qualities and what they consist of.
A CCTV cameras resolution is measured in vertical and horizontal TVL (television lines) dimensions and often limited by the capabilities of both the camera and the recorder. CCTV systems use an analog video signal which derives from television specifications. NTSC (National Television System Committee) and PAL (Phase Alternating Line) resolutions are two respected analog video standards. They are the relevant formats to network video since video encoders provide like-wise resolutions when they digitize signals from the transmissions received from analog cameras. In the NTSC world, a true classification of "D1" entails 720x480 pixels. In the digital video recorder (DVR) world you get a type of, if you will, a cropped D1; which is a pixel ratio 704x480, also referred to as 4CIF. For me to accurately describe the concept of resolution of an analog video in a simplistic manner is difficult. Let’s begin with first understanding the difference between a TVL line and a pixel. Resolution in an analog or digital picture is similar, but there are some vital differences in how it is defined. As I stated before, an analog video is an image consisting of TV-lines since analog video technology is derived from the television industry. In a digital system, an image is made up of square pixels. This picture is composed over a 480 active horizontal lines. When the picture is sent to the DVR the first field of 240 even-numbered lines is sent followed by the second field of 240 odd-numbered lines. This occurs at a rate of 60 fields (or “i’ frames) per second. The odd and even fields are offset one line apart, so when viewed in rapid succession (60 fields per second) they interfix into one another to contrive a complete picture, commonly referred to as a frame, which is made up of 2 x 240 (480) lines. This is called interlaced video.
In the picture above, you’ll notice it has more width than height. This is called a 3x4 aspect ratio, 3 units high by 4 units wide. Horizontal resolution size is defined as the amount of vertical black and white lines you can see in 3 of the 4 units. E.G., how much detail you can measure in 75 percent (3/4) of the picture’s width. Horizontal Resolution is contributed as the number of alternating black and white vertical lines that can be resolved per a pictures height, referred to as Television Lines (TVL). When analog video is digitized, the maximum amount of pixels that can be created is based on the number of TV lines available to be digitized. The maximum size of a digitized image is typically 704x480 (D1/ 4CIF).
In the analog DVR world, the only adequate resolution is the "horizontal lines of resolution size". Be careful when you explain about the vertical pixel resolution of a picture. When you speak of horizontal lines of resolution means that you can display up to 480 alternating black and white horizontal lines and see them all distinctly. Similarly, the horizontal resolution is defined in terms of vertical lines. Horizontal resolution is tricky to prove and test. In an analog system, there is no other way to tell how many vertical lines of resolution the system can show without measuring/testing it, either with physics or by running a test signal (or chart) through a system and viewing the result.
For the most part, nowadays analog cameras provide a line resolution range between a 420TVL to 700TVL. For close-up & short distances, a lower TVL resolution camera can save you some money and provide an adequate image for your criteria but a 700TVL and above have superior images. The pictures are sharper and the contrast is great. If you want great clarity the 630-700TVL range of resolution is the way to go. There are other factors for a good clear picture like lenses, chipsets, lux, WDR etc.
Once the camera captures the images that you want, it sends them through coaxial cable, or Cat 5 with the use Baluns, to the DVR. At the DVR, the images are converted from an analog signal into a digital format to be stored on a hard drive. This is the most important part of the chain. The greatest most powerful camera will not be effective if the image is compressed down to nothing by the DVR. The two most popular DVR resolution types are CIF and D1. CIF is defined as 320×240 pixels and D1 is 704×480. As you can tell, D1 is 4 times larger than CIF. This entails that the raw analog signal of the camera will be compressed less, giving you better detail.
I have seen a lot of misconceptions of the newly introduced 960H. Amongst the confusion, I have seen a statement along the lines of 960H provides you a 960x480 and/or 720x480 picture; as well that it improves the picture of any camera fitted with a 960H sensor via your current DVR. This is a BIG misconstrued myth. Submitted for your approval are the facts of 960H:
960H actually refers to a new class of advanced imaging sensors that capture more pixels per target in an object to provide a maximized resolution in vertical TVL. This new technology serves as a bridge between standard analog and Mega Pixel solutions, making 960H the best option for ultra-high resolution video within the realm of analog. It’s imperative you also note that your current DVR must have the capability of being able to capture and store the 960H digital format into a resolution size of 928x480. The benefit of 960H is having a larger and more refined picture resolution.
A camera containing a 960H sensor maintains high image contrast to clearly distinguish closely-spaced vertical lines. Other sensors are incapable of providing the same level clarity. As well, the 960H image is smoother providing more vibrancy and detail.
There is hope for our dying CCTV super hero. For those of you interested in mega pixel resolutions but feel at a loss with the thought of scrapping your investments in your analog systems. For those of you who are hesitant of exploring into a whole new technology. Let me introduce you to analogs side-kick: TheHybrid and Hybrid Federal!!! Feel comfortable in your transition into an IP based mega pixel system without the loss of your current analogs. Simply by replacing the current DVR with our Hybrid you can attach your current cameras and add additional Hi-Def mega pixel cameras where they are most beneficial.
HD-SDI: Analogs Savoir
I’ll begin with what HD-SDI stands for: High Definition Serial Digital Interface. This recent analog interface introduced by the SMPTE (Society of Motion Picture and Television Engineers) and is an upgrade to the current SD-SDI (Standard Definition Serial Digital Interface). What an HD-SDI camera does is it allows you the ability to have megapixel resolutions in a non-network fashion. Utilizing an HD-SDI DVR, it also gives you the ability to upgrade your system without rerunning cables. For those of you thinking about going IP based mega pixel cameras, compare the upgrading cost of your system along with the time and material to run new data lines. Without the necessity of an intricate high speed network or a large capacity of storage space, HD-SDI avoids this venture. Bottom line is, HD-SDI makes for an easy transition to higher-end megapixel solutions, with half of the cost of a network based Mega Pixel system and the time cost of reconfiguring your site. It’s as simple as replacing your current DVR and cameras with HD-SDI products utilizing the same existing coaxial wiring.
Analogs Successor: The Mega Pixel Camera
Pixels, Pixels, Pixels! High-Def resolution is the number of pixels that make up the picture on your HD Television or monitor screen. A Mega Pixel camera has the quality of capturing footage consisting of high amounts of pixels. IP cameras nowadays are becoming more relevant with higher end HD or High Definition video resolutions. You might have heard of phrases like “megapixel” associated along with IP cameras but please be weary, not all IP cameras are megapixel resolutions. An IP based mega pixel camera uses data lines (Cat5e/Cat6) to transmit the video signal through the network in digital form, which means the NVR (Network Video Recorder) or software will not need to decode the video footage back to digital.
For example, a full 1080P (1920x1080 or 2MP) means that there are 1,920 individual colored points of light across your screen's width and 1,080 across its height for a total of 2,073,600 pixels. Each pixel is capable of changing color as needed to display images on your screen. The higher a screen's resolution, the clearer the images it can display. When you hear the terminology of 2MP this is defined by how many individual pixels make up a mega pixel. With this technology you are not limited to just 1.3- 3MP qualities. You can, depending on your demand and of course budget, obtain higher resolutions. Just imagine 5MP, 12MP, 22MP resolutions!!!
For all footage across every system, after video is recorded it can be magnified (zoomed in) but only digitally either through a computer or the DVR (if capable). That means, the individual pixels that create the picture can be made bigger. However, for analog footage, there will be no real advantage at detail due to the low-res of pixels.
Essentially, I hoped you walked away with the following understanding: