What is the NTSC and PAL Setting On DVR?

Many DVRs are compatible with both NTSC and PAL standards. NTSC standard is predominately in North America and PAL in Europe. The PAL and NTSC standard actually refer to the method used to transmit color. The PAL standard actually requires 2 NTSC decoders to display video (one for each line alternatively) while the NTSC standard only requires one. The NTSC standard is supposedly less accurate in color display, but more efficient in the use of resources. In general, the DVR can be set to either decode NTSC cameras or PAL cameras, but not a combination of both at the same time. If you order a DVR in a package with the security cameras, then you shouldn’t have to worry about the setting or compatibility. If, on the other hand you purchase your cameras from one country, and the DVR from another, then you definitely should make sure that the DVR is compatible with the cameras. Check the standard of the cameras (NTSC or PAL) and the standard of the DVR. Remember that you cannot mix and match the cameras.

Also, keep in mind that just because you are in the USA does not mean you cannot have a PAL DVR or PAL cameras, or because you are in Europe does not mean you cannot have NTSC cameras or DVR. In actuality, you only need to be sure that the cameras and DVR are both compatible.

Splitting / Amplifying the Video Signal

 Keep in mind the video signal used in CCTV equipment is nominally a one volt peak-to-peak signal and is impedance sensitive to 75 ohms for ideal video reproduction at the monitor. If these parameters are not kept, then the video will degrade.

Distribution Amplification

If the installation of a system requires viewing the video at multiple locations from a single camera, there are a few different ways of accomplishing this. One way is through using a distribution amplifier. This device basically takes the single video signal and reproduces the exact signal into multiple outputs; and in the case of the Pelco DA104DT you would get four identical outputs.

So, if the input signal is a one volt peak-to-peak signal you will get four output signals of the same amplitude. Providing the run distance for the type of coax used is kept within the specified length, no other equipment will be needed to reproduce a nice clear video display on each monitor. Another timesaving feature of the Pelco DA104DT is that there are not adjustments required. Just connect the unit, turn it on, and the installation is complete. If the need arises where more than four signals are required, multiple units can be linked together by simply using one of the output signals as an input signal to the next unit, and so on.

Equalizing Amplification

Due to the many factors that can effect the video signal, it is sometimes necessary to enhance the video signal (as in transmitting a nominal video signal level) directly out of the camera, through RG59 coax to a monitor, while still producing a clear video display across the entire length of the coax. In this case the coax should not exceed 750 feet (228 m).

However, let's say you need to use RG59 because it's more flexible and much easier to work with but the cable length must be 1,500 feet (457 m). The signal at this point is going to be weak and will display a very degraded picture on the monitor. As mentioned, there are many things that can effect signal strength before the signal reaches the monitor. If you find a weak signal, simply pass the weak signal through an equalizing amplifier, make the required adjustments, and once again there will be a good, strong signal that will produce a nice picture.

The Pelco model EA2010 is a post-equalizing amplifier which simply means that this device will be located close to the monitor. There's an advantage to this design in that AC power is usually more readily available at the monitoring location than it is somewhere back up the coax line, and with this type of design it only requires one person to view the monitor display while at the same time making the required adjustments to obtain the nominal signal level.

As mentioned in the example on RG59,the signal strength is good up to nominally 750 feet (228 m). With the Pelco EA2010 amplifying the signal, the same grade of coax can be used in runs of up to 3,000 feet (914 m).

In regard to any equalizing amplification system, there is another type of post-equalizing amplifier that Pelco offers. It is the half-duplex post-equalizing amplifier. This device (as far as the amplification of the video signal is concerned) is exactly like the EA2010.The difference is that the EA2000 was designed specifically for use with any of the Pelco Coaxitron (up-the-coax) control/transmitter systems. This device enables the video signal requiring amplification to be transmitted over the same coaxial cable over which the control signal is transmitted, whereas if you used the EA2010 it would block the Coaxitron control signal from being transmitted.

Video compression for DVR in CCTV systems

Advantage of using a DVR technology over analog recording is that the Digital Data recorded by DVR can be compressed and saved in special hard disk and can be reviewed later. Video compression plays an important role in overall operation, properly compressed video can also save disk space.

All DVRs use some kind of compression algorithm called a codec to keep the digital video files at a manageable size. The average size of an uncompressed still image frame at 320x240 resolution in 24-bit true color is about 230400 Byte or 2.3 Mega Byte. Same image frame in 32 bit color is about 307200 Byte or 3.07 Mega Byte.

An hour’s worth of one channel of uncompressed video at 25 frames per second would take up 21,600 megabytes (21.6 GB)

Uncompressed video of one hour will take hard disk space

Frame size 320*240 Pixel at 25 frames per second would take up

25*3600* 230400 Byte = 20736 Mega bytes

= 20.736 GB (24 bit color)

25*3600* 307200 Byte = 27648 Mega bytes

= 27.648 GB (32 bit color)

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Installing Compression Style Connectors to RG59/RG6 cabling

Installing Compression Style Connectors to RG59/RG6 cabling

1. Connectors are color coded for cable type. See chart below or manufacturer’s recommendation

2. Strip cable to dimensions shown on chart. Remove cable jacket and dielectric
3. Fold exposed braid back over cable jacket leaving smooth foil attached to dielectric
4. For Quad Shield Cable: Fold outer braid back over jacket, remove outer foil and fold inner braid back over jacket.

 5. Trim center conductor to proper length, see (A) dimension
6. Insert cable into rear of connector. Insertion depth is shown, on chart. For F-connectors, dielectric should be flush with support mandrel face.

Tips & Tricks:

• The key to a good crimp is proper cable & connector preparation
• When crimping other mfg’s connectors, minor adjustments to the crimp height may needed. Simply adjust adapter up or down
• Keep adapters secured in tool to prevent loss

 Tools required: Side cutters, needle nose pliers, X-acto knife, a cable stripper and a BNC crimper.

The stripper is required because the different bands in the coax cable have to be cut precisely to different lengths and depths, and this is difficult to do without the proper tool.

The BNC Crimper is used twice in the process - first to crimp the BNC pin to the main conductor, and then to crimp the collar over the outer insulation at the end of the operation. A quality crimper can make the difference between a connection that works and one that has to be discarded.

It is also a good idea to make a length of test cable and try it out between a couple of computers on the system before actually going through the trouble of pulling cable through wall and ceiling spaces. You don't want to do all that hard work only to find you've got the wrong cabling! The connector itself consists of three parts: the connector itself, the center pin, and the crimp barrel.
STEP 1: PREPARE CABLE
Prepare the end of the cable with the cable stripper tool. Leave yourself a few extra feet of cable length for mistakes. If you get a bad connector, you'll be able to cut it off and try again.
Setting up the cable stripper may require some trial and error adjustment.
Leave about 1/4 inch of cable sticking out the front of the stripper. You then rotate the stripper about the cable until the two layers of insulation and the shielding are cut through to their proper depths.
The center conductor is about 1/2 inch long (it will be cut to fit). The exposed portion of the inner insulation band is about 1/8 inch and the braided shielding between the two insulation bands has been cut back cleanly to the same length as the outer insulation band.
If the cable stripper does not completely do its job, you may have to clean up the cable end with an X-acto knife or needle file. Care counts here. The center conductor should not be nicked, nor should any of the braided shielding be exposed - the most difficult part of this operation is to strip the shielding without damaging the inner insulation band.

STEP 2: CRIMP PIN
Fit the center pin from the connector package over the center conductor as far as it will go. The resulting length of exposed center conductor is the amount of conductor that will have to be cut off for a proper fit. Take the pin back off and cut the center conductor to the correct length with side cutter pliers. It should be 3/16 inch plus or minus. Now when the pin is placed back on the conductor, its base should just reach the inner insulation band (the center conductor should no longer be exposed.)
Place the pin on the center conductor, snug up the crimping tool over the pin (in the special die portion of the crimper provided for the pin) . . . and when you're absolutely sure everything is properly aligned, crimp the pin to the center conductor. Be careful. If this is messed up, you have to start over prepping the cable again with a new connector. Have a few more connectors on hand, even though you'll get good at this, mistakes are made, and if you don't have enough you'll put a real time strain on your project. You will use them!
The base of the pin is seated on the top of the inner insulation band. The crimping process flattens out the pin a bit where the crimping tool applies pressure to it. Clean up any sharp edges left by the crimper with a jeweller’s file, if necessary.

STEP 3: INSTALL BNC CONNECTOR
Slide the Crimp Barrel (or collar) over the cable before installing the connector itself - we will come back to the crimp barrel in the next step, but you have to slide it onto the cable now (you can't force it over the much larger connector later).
You must insert the connector unto the cable. The knurled cylinder portion fits over the pin and inner insulation band and is press-fitted-twisted into place. It has to fit snugly between the outer and inner insulation bands, and during the process, it fights with the braided shielding for this tight space.
When you think you've got the connector inserted under the insulation as far as it will go, push it a little farther. You'll know you're finished when most of the knurled surface has disappeared under the insulation and the center pin is rigid in its seated location inside the connector. If the pin is loose and the connector is on as far as it will go, the length of exposed inner insulation band when the cable was stripped is too short. If the pin is tight but a lot of the knurled portion of the connector is still showing, the length of exposed inner insulation band and/or center conductor when the cable was prepared is too long.

STEP 4: CRIMP BARREL

You're almost done. Now slide the crimp barrel (placed on the cable at the beginning of the last step) up as close to the connector as you can get it.
It will take some effort to get as much of it as possible over the bulge in the cable caused by the last step.
If you have a general-purpose wire stripper/crimper, it has an "ignition terminals" opening that is a little bigger than the cable and a little smaller than the crimp barrel. This is a great tool for putting some leverage behind the crimp barrel when easing it over the bulge in the cable.
Now you can crimp the barrel using the other, larger opening in the BNC crimp tool die. This will tighten and deform the crimp barrel down over the connector and cable for a secure connection.
Crimping the barrel should force the bulge in the cable up over what remains of the exposed knurled portion of the connector to the connector's base. Now you can install another connector on the other end, and then test the completed length of cable. It is good practice to test each length of cable as you go rather than install all the connectors and cabling, and then try to track down a bad connection. With a little practice you will be installing the BNC connectors like a pro.

Installing a Twist-on type BNC Connector

STEP1:

Use a stripping tool to strip the shielding from the coax part of the cable. In order for the connector to go on smoothly you will want about 3/4" of the center conductor showing and about the same amount of the copper wire braid showing (see figure 2 below).

STEP2:

 

Make sure that none of the strands of copper wire braid touches the middle conductor wire when you twist on the BNC connector. If they accidentally touch, this will not damage the camera but can result in a black (shorted out) image from the camera.

Twist on the BNC Connector onto the wire until it is snug. You will repeat Steps 1 - 3 for the DVR end of the COAX cable.

Installation of the 2 Piece BNC Crimp type connector

A crimp type connection allows for quick and simple installation while still maintaining a mechanical and electrical connection fairly close to a solder type termination. Some of the key points to remember are as follows: Make sure to use the proper size connector for the type of cable you are using. Make sure all cuts and stripping is clean. Avoid nicks as much as possible. Use the proper crimp tool; don't try to improvise with pliers, etc. Follow these steps.

 BNC connectors are not hard to install, but they must be installed correctly or they can cause problems down the road. Reproduced below are the instructions from Amphenol (the biggest connector maker). Here is a technique which requires no special tools other than a cable stripper and a crimping tool and which you may find easier than trying to measure the dimensions given in the Amphenol instructions below. You should have a look at the instructions from Amphenol , since some important warnings are contained in them, you may find an easier technique than what is described here.

 

1. Place the Plug Body assembly on the work surface
2. Place the male contact pin on the table with the tip of the pin aligned with the front of the plug assembly
3. Place the cable next to the pin with the end of the cable just beyond the little hole in the side of the pin
4. Carefully cut the cable outer sheath right where it lines up with the cable-entry edge of the Plug Body.
   Do this with a razor blade or knife being very careful not to nick or cut any of the shield braid wires.
   It's better to remove too little sheath than too much. You can remove more later if necessary.
5. Slide the Outer Ferrule onto the cable
6. Push back the braid to expose the inner conductor
7. Using a razor blade or knife, cut off about 4mm (.156 in) of insulation from the end of the inner conductor.
   Again, be very careful not to nick any of the conductor wires.
• If using RG62 cable (93 ohm) put the little bushing onto the center conductor as shown in the picture below. Bushing not needed for RG58
8. Place the Male Contact Pin onto the inner conductor, making sure all wires are inside the pin. If the pin doesn't fit snugly against the insulation, remove it and trim the conductors until it does. NO INNER CONDUCTOR WIRES SHOULD BE EXPOSED
9. Using the appropriate crimp tool (the gold-colored one for RG58, found in the "miscellaneous wrenches" drawer in RM 107) crimp the pin onto the inner conductor
10. Push the Plug Body Assembly onto the cable until you feel it 'snap' into place. The end of the pin should be flush with the edge of the Plug Body. If you can't push it in far enough because not enough outer sheath was removed in step 4, trim a little more of the outer sheath off until the Plug Body goes all the way on and the pin snaps in. BE VERY CAREFUL AT THIS STEP THAT NO BRAID WIRES ENTER THE PLUG BODY. THIS CAN CAUSE A SHORT.
11. Push the braid up over the Plug Body and trim it with a cutter or scissors so that it comes just up to the larger diameter part of the Plug Body. It should come all the way up over the knurled or ridged crimp barrel. Having braid wires stick out because they're too long is unsightly, but a greater problem is having them too short and becoming disconnected from the Plug Body.
12. Slide the Outer Ferrule up over the braid and the plug body as far as it will go, then crimp it in place with the crimp tool.

That's it You're Done!!

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Little about CCTV Guidelines for Identification

This article is now slightly out of date as the standard height of a person has now changed to 1.7m and the percentage for Identification of an Unknown Person is now 100% and not be 120% shown. Nonetheless, we believe this is one of the best articles available with regards to the technical background of this The Home Office Requirement.

Some time ago the Home Office issued guidelines for the identification of persons and vehicles. This is fine, but many system engineers stumble when trying to find what camera and lens combination will satisfy these guidelines. And what about end users who know even less about camera and lens formats, how can they assess the merits of competing specifications? This month all will be revealed for both groups.

Charts showing the horizontal and vertical fields of view for many lenses and four formats are given in ‘The Principles and Practice of CCTV’ and were published in the first issue of CCTV Today (Jan ‘94). They also show the % of the screen height of a 1.7M person. The Home Office guidelines had not been published for general use when I produced the first draft of the book and so the 1.7M was my guess at the average height. The current guidelines use 1.6M as the height.

The values for various degrees of identification are given as the percentage the 1.6M figure would occupy of the monitor screen. I call this the ‘screen height ratio’. The complete guidelines are provided in several Home Office publications and so only the basic ratios are given in this article. The publications are available free from the Home Office and provide a lot more information as well. 

These criteria are now becoming increasingly used as part of the specification for many CCTV systems, particularly in Town Centre schemes. Sometimes the specification will state the distance from the camera for each criterion, sometimes the specification will ask the question, ‘at what distances from the camera will the criteria apply’? In either case it involves calculations that are not too difficult but can be tedious to keep repeating for each lens and camera location.

Another problem that many people find difficulty in resolving are the different fields of view obtained from various camera and lenses formats, i.e. what is the result of fitting a 2/3" lens onto a 1/2" camera, and how does this affect the screen height ratio at certain distances? 

A word of caution, just about all lens manufacturers brochures give the HORIZONTAL angle of view, whereas these calculations require the VERTICAL angles of view. The vertical angle of view is the horizontal angle times 3/4. 

Field of view

Diagram 1 Field Of View

The field of view is the ratio of the sensor size to the focal length and the distance to the subject. This is shown in diagram1. The 'width to height' ratio of the sensor is 4:3. The horizontal and vertical angles and therefore fields of view are different and must be considered separately. 

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Note when using these ratios all the units must be the same, i.e. millimetres or Metres. 

Sensor Sizes

Diagram 2 shows the sensor sizes to be used when calculating fields of view and angles of view. 

Diagram 2 Sensor Dimensions

Example

Supposing it required to recognise a known person at 50M, using a 2/3" lens, the following is the calculation.

The scene height at 50M needs to be twice the standard height, 2 x 1.6=3.2M. Therefore:

The nearest standard would be a 10.5:105mm zoom lens to satisfy this requirement.

The formula can be worked backwards to find the scene height for a given lens. It is a simple matter to put all these criteria into a spreadsheet program and find the result for any combination. However, this may not be very convenient for the many salespersons on the road.

NVR Software

First NVR software to feature instant video playback option. Search video by calendar, timeline, date, time, alarm event, or by file with simultaneous live view.. Add smart tags to video in real time for easy retrieval. Features step by frame, image export and playback speed functions. View recorded video from any remote site. Multi-Screen playback with pop out spot screen. Includes batch export for easy video archive & backup.

The new release introduces innovative features not found on other cctv software as well as several performance & usability enhancements.

- Support offloading of Video Analytics processing from CPU to GPU via Nvidia Cuda
- Digital Zoom on Live & Playback video
- Preview Sequence
- Preset Sequence
- Support Pelco-D Keyboard via RS232 / RS485
- Add Support for Pelco, Impath, IP Cameras
- Updated support for H.264 camera
- Support Secondary Port in Video Server
- Added On-Screen Keyboard Feature
- Added Smoke & Fire Detection Module
- Video Analytics & Fire Dectection are now purchased separately in per-channel license
- Pos function removed to seperate package

The addition of support for analogue PTZ keyboards means is the most compatible ip surveillance software on the market allowing users to support complete legacy analogue systems or build Hybrid systems without upgrading existing hardware infrastructure.

Why People Choose Wireless Security Cameras (WCCTV)

With the increase in need for security, the demand for security cameras is also on the rise. There are a variety of cameras available in the market, each made for specific purposes and have their own advantages and disadvantages. One of the never-ending debates is the choice between wired and wireless security cameras. While both have their own pros and cons, wireless cameras have become increasingly popular. Few reasons are:

1.) Wireless cameras can be placed at any location. You do not need to worry about installing wires or electric sockets at difficult to reach locations. All you need is a camera that can function within the signal range of your security system.

2.) You do not need to spend money on installing the new wiring system. In case of wireless security cameras, the expenditure on creating a network of insulated wires to connect the entire system can be saved. This is especially true for building that did not install extra wires at the time of construction.

3.) Wires can also make the presence of a camera obvious. If you looking at installing cameras that should not be noticed by every trespasser, wireless security cameras are the right option for you.

4.) Flexibility and mobility comes with wireless cameras. If you are investing in a security system for a building which you might leave in the future, it is best to invest in wireless security devices. Home owners who have taken their house on rent or lease prefer wireless cameras as they can take the cameras along as and when they move to the nest house.

5.) Save you decor with wireless cameras. You might have spent a lot of time and money in selecting the right decor for your home or office. Installing wires might interfere with the overall theme of your decor. Hence, you can opt for wireless cameras that can be installed with minimal disturbance to the entire property.

6.) If you are an owner of an ancestral property, you would not like to damage the masonry by drilling extra holes and wires into the invaluable structure. Hence, wireless cameras are the best option for you.

7.) Hidden cameras are best in wireless versions. While you can use wired cameras and hide them behind furniture, you need to be very careful in covering them. A wireless camera saves you from this effort. You can hide them anywhere without worrying about their getting discovered. Small toys, cutlery, pens and many other things can be equipped with wireless cameras easily.

8.) If you want to use internet to transfer images to you computer, you can go for wireless cameras. The data transmitted through internet can be accessed from any internet enabled system outside your home or office as well.

9.) If are installing the security system yourself, if is always better to choose wireless cameras as they are the easiest to install.

IP cameras with Audio Detection

What is the best IP cameras with audio you used?
What security audio and video applications have you had experience with and what is the best IP cameras with audio you used?
What is IP Camera Audio and Advanced Audio Detection?
-- Many More Question comeout in my mail/phones ...

If you’ve never considered having an audio component with your surveillance system that may be because analog CCTV systms require separate audio and video cables to be installed from end to end which becomes difficult and costly over long distances. IP cameras make the implementation of audio a lot simpler because the audio and video information are sent over the same network cable eliminating the need for extra cabling.

More and more IP camera audio is becoming a common feature not only because it’s easier to process over a network cable but also because the importance of this additional surveillance medium is now being recognized.

Importance of IP Camera Audio:

Detect emergency situations and make sense of other events.
Audio covers a 360° area - surveillance systems coverage is extended beyond the field of view.
Audio detection can trigger email or, other alerts and automatically direct where a camera should record.
Having audio integrated into your surveillance simply gives you more information about a situation. Many times something is brought to our attention first by what we hear, not what we see. Car alarms, gunshots, breaking glass, and screams will not be recognized by a surveillance camera without audio. With 360° coverage, an event happening behind a camera can still be detected.

Three Audio Modes
If you’re considering audio for your appliction your intended use should be clear because it can affect which IP cameras you can select as there are three audio modes available:
Simplex: Audio can be sent in one direction only. Either from the camera only (most likely) or, from the user only.
Half-Duplex: Audio can be sent and received in both directions (to/from camera and user), BUT only in one direction at a time.
Full-Duplex: Audio is sent and received at the same time - similar to a telephone conversation.
For example, Axis offers a camera, the Axis 207MW that offers one-way audio with a built in mic while the Axis M1054 offers two-way audio support with a built-in mic and speaker.
Features such as noise cancellation and echo cancellation are also available that reduce background noise or eliminate feedback.

Audio Detection Alarm
In the same way that an IP camera can analyze video, they can intelligently analyze audio as well. As noted above, audio can hear what the video cannot see. Audio detection complements video motion detection very well because it reacts to events in areas that are too dark for the video motion detector to pick up on.
Audio detection alarms can be programmed so that when any sound (glass breaking, voices in a room, etc.) is detected, they can trigger an IP camera to:
Send & record video and audio
Send email or other alerts
Active external devices - Alarms, floodlights
Trigger a PTZ IP camera to automatically pan to a preset location to begin recording.
Audio detection can be enabled all time, at specific times, or disabled. It can also be configured to trigger an event if a sound level rises above, falls below, or passes a certain level of sound intensity. Sony IP Cameras has a great video demonstration of this function here:
Some of the applicable Sony IP cameras and video servers that have this feature can be found here:
Sony SNC-CH140
Sony SNC-RS46N
Sony SNT-EX101

Audio Compression & Audio Bit Rates:
Audio compression and audio bit rates, just like video compression and video bit rates, are an important consideration when calculating total bandwidth and storage requirements.
Just like video, audio compression uses a codec to reduce the size for efficient transmission and storage. Some audio codecs support CBR (constant bit rate) mode only or both CBR and VBR (variable bit rate) - these factors affect quality and file size.
Bit rate is an important audio setting because it determines the level of compression or, quality of the audio. Generally speaking, the higher the compression level = the lower the bit rate = the lower the audio quality.

Audio/Video Synchronization
Audio and video are two separate packet (data) streams that are sent over a network. For audio and video to play back perfectly syncronized, the two packets must be time-stamped so that they match up.

Best Practices For Audio Implementation
Audio Equipment & Placement: Select a location that will minimize interferring noise and one that’s as close to the source of the sound as possible.
Amplify Audio Signal Early: This minimizes noise in the signal chain.
Acoustical Adjustments: Adjust input gain and use features such as echo cancellation to improve audio quality.
Codec & Bit Rate Selection: Codec and Bit Rate choice affect audio quality. High compression = low quality (but available bandwidth may be a deciding factor).
Shielded Cable: Shielded cable reduces disturbance and noise. Avoid running cable near power cables or high-frequency switching signals.
Legal Implications: What are you allowed to record? Some countries restrict the use of audio and video surveillance - be sure to check with your local authorities.

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RAW Formats

RAW Format implies that there is no compression done on the image. The major types of RAW format are RGB, YUV, YIQ. Our eye is more sensitive towards light intensity variation than color variation. So loss on color information will not affect the over all quality of the image. RGB is an end stream format. Information from the image sensor is in RGB format and we need the same format for displaying the image on an end

device. YUV & YIQ formats are developed for Analog TV transmission (NTSC & PAL respectively) and the digital version of YUV, YCbCr is the most common format used for image and video compressions.

Conversion from one format to another is described below:

RGB to YCbCr Conversion

Y = 0.299 R + 0.587 G + 0.11B

Cb = 0.564 (B - Y)

Cr = 0.713 (R - Y)

YCbCr to RGB

R = Y + 1.402 Cr

G = Y – 0.344 Cb – 0.714 C r

B = Y + 1.722 Cb

Y – Luminance Signal

Cb, Cr – Chrominance Signal, Color difference signal

R – Red

G – Green

B – Blue

Need for Compression

Consider an image of resolution 640 × 480. Let us calculate the size of the picture in RAW format. Each of the 10 Color is represented by 8 bits. Then for each pixel it needs 24 bits. Total no of pixels in the image is 640 × 480 = 307200 pixels. Therefore the size of the image turns to 307200 × 3 bytes = 921600 bytes. But an image in compressed format with the same resolution takes only 100 KB.

In the case of RAW video stream of length 1 sec its needs 640 × 480 × 3 × 25 = 23040000 bytes (23 MB) of storage if the frame rate is 25 frames/sec. But it’s known that the VCD format video having a size 700 MB plays for around 80 minutes. In the former case we need 110400 MBs (23 MB × 60 × 80) as storage space for 80 minutes video. Therefore we can achieve a high compression 150: 1 at the cost of computational complexities.

NAS, DAS, or SAN? - Choosing the Right Storage Technology ?

Data is unquestionably the lifeblood of today's digital organization. Storage solutions remain a top priority in IT budgets precisely because the integrity, availability and protection of data are vital to business productivity and success. But the role of information storage far exceeds day to day functions. Enterprises are also operating in an era of increased uncertainty. IT personnel find themselves assessing and planning for more potential risks than ever before, ranging from acts of terrorism to network security threats. A backup and disaster recovery plan is essential, and information storage solutions provide the basis for its execution.

Businesses are also subject to a new wave of regulatory compliance legislation that directly affects the process of storing, managing and archiving data. This is especially true for the financial services and healthcare industries, which handle highly sensitive information and bear extra responsibility for maintaining data integrity and privacy.

Although the need for storage is evident, it is not always clear which solution is right for your organization. There are a variety of options available, the most prevalent being direct-attached storage (DAS), network-attached storage (NAS) and storage area networks (SAN). Choosing the right storage solution can be as personal and individual a decision as buying a home. There is no one right answer for everyone. Instead, it is important to focus on the specific needs and long-term business goals of your organization. Several key criteria to consider include:
• Capacity - the amount and type of data (file level or block level) that needs to be stored and shared
• Performance - I/O and throughput requirements
• Scalability - Long-term data growth
• Availability and Reliability - how mission-critical are your applications?
• Data protection - Backup and recovery requirements
• IT staff and resources available
• Budget concerns
While one type of storage media is usually sufficient for smaller companies, large enterprises will often have a mixed storage environment, implementing different mediums for specific departments, workgroups and remote offices. In this paper, we will provide an overview of DAS, NAS and SAN to help you determine which solution, or combination of solutions, will best help you achieve your business goals.


DAS: Ideal for Local Data Sharing Requirements

Direct-attached storage, or DAS, is the most basic level of storage, in which storage devices are part of the host computer, as with drives, or directly connected to a single server, as with RAID arrays or tape libraries. Network workstations must therefore access the server in order to connect to the storage device. This is in contrast to networked storage such as NAS and SAN, which are connected to workstations and servers over a network. As the first widely popular storage model, DAS products still comprise a large majority of the installed base of storage systems in today's IT infrastructures. Although the implementation of networked storage is growing at a faster rate than that of direct-attached storage, it is still a viable option by virtue of being simple to deploy and having a lower initial cost when compared to networked storage. When considering DAS, it is important to know what your data availability requirements are. In order for clients on the network to access the storage device in the DAS model, they must be able to access the server it is connected to. If the server is down or experiencing problems, it will have a direct impact on users' ability to store and access data. In addition to storing and retrieving files, the server also bears the load of processing applications such as e-mail and databases. Network bottlenecks and slowdowns in data availability may occur as server bandwidth is consumed by applications, especially if there is a lot of data being shared from workstation to workstation.

DAS is ideal for localized file sharing in environments with a single server or a few servers - for example, small businesses or departments and workgroups that do not need to share information over long distances or across an enterprise. Small companies traditionally utilize DAS for file serving and e-mail, while larger enterprises may leverage DAS in a mixed storage environment that likely includes NAS and SAN. DAS also offers ease of management and administration in this scenario, since it can be managed using the network operating system of the attached server. However, management complexity can escalate quickly with the addition of new servers, since storage for each server must be administered separately.

From an economical perspective, the initial investment in direct-attached storage is cheaper. This is a great benefit for IT managers faced with shrinking budgets, who can quickly add storage capacity without the planning, expense, and greater complexity involved with networked storage. DAS can also serve as an interim solution for those planning to migrate to networked storage in the future. For organizations that anticipate rapid data growth, it is important to keep in mind that DAS is limited in its scalability. From both a cost efficiency and administration perspective, networked storage models are much more suited to high scalability requirements.

Organizations that do eventually transition to networked storage can protect their investment in legacy DAS. One option is to place it on the network via bridge devices, which allows current storage resources to be used in a networked infrastructure without incurring the immediate costs of networked storage. Once the transition is made, DAS can still be used locally to store less critical data.
NAS: File-Level Data Sharing Across the Enterprise

Networked storage was developed to address the challenges inherent in a server- based infrastructure such as direct-attached storage. Network-attached storage, or NAS, is a special purpose device, comprised of both hard disks and management software, which is 100% dedicated to serving files over a network. As discussed earlier, a server has the dual functions of file sharing and application serving in the DAS model, potentially causing network slowdowns. NAS relieves the server of storage and file serving responsibilities, and provides a lot more flexibility in data access by virtue of being independent.

NAS is an ideal choice for organizations looking for a simple and cost-effective way to achieve fast data access for multiple clients at the file level. Implementers of NAS benefit from performance and productivity gains. First popularized as an entry-level or midrange solution, NAS still has its largest install base in the small to medium sized business sector. Yet the hallmarks of NAS - simplicity and value - are equally applicable for the enterprise market. Smaller companies find NAS to be a plug and play solution that is easy to install, deploy and manage, with or without IT staff at hand. Thanks to advances in disk drive technology, they also benefit from a lower cost of entry.

In recent years, NAS has developed more sophisticated functionality, leading to its growing adoption in enterprise departments and workgroups. It is not uncommon for NAS to go head to head with storage area networks in the purchasing decision, or become part of a NAS/SAN convergence scheme. High reliability features such as RAID and hot swappable drives and components are standard even in lower end NAS systems, while midrange offerings provide enterprise data protection features such as replication and mirroring for business continuance. NAS also makes sense for enterprises looking to consolidate their direct-attached storage resources for better utilization. Since resources cannot be shared beyond a single server in DAS, systems may be using as little as half of their full capacity. With NAS, the utilization rate is high since storage is shared across multiple servers.

The perception of value in enterprise IT infrastructures has also shifted over the years. A business and ROI case must be made to justify technology investments. Considering the downsizing of IT budgets in recent years, this is no easy task. NAS is an attractive investment that provides tremendous value, considering that the main alternatives are adding new servers, which is an expensive proposition, or expanding the capacity of existing servers, a long and arduous process that is usually more trouble than it's worth. NAS systems can provide many terabytes of storage in high density form factors, making efficient use of data center space. As the volume of digital information continues to grow, organizations with high scalability requirements will find it much more cost-effective to expand upon NAS than DAS. Multiple NAS systems can also be centrally managed, conserving time and resources.

Another important consideration for a medium sized business or large enterprise is heterogeneous data sharing. With DAS, each server is running its own operating platform, so there is no common storage in an environment that may include a mix of Windows, Mac and Linux workstations. NAS systems can integrate into any environment and serve files across all operating platforms. On the network, a NAS system appears like a native file server to each of its different clients. That means that files are saved on the NAS system, as well as retrieved from the NAS system, in their native file formats. NAS is also based on industry standard network protocols such as TCP/IP, FC and CIFS.

SANs: High Availability for Block-Level Data Transfer

A storage area network, or SAN, is a dedicated, high performance storage network that transfers data between servers and storage devices, separate from the local area network. With their high degree of sophistication, management complexity and cost, SANs are traditionally implemented for mission-critical applications in the enterprise space. In a SAN infrastructure, storage devices such as NAS, DAS, RAID arrays or tape libraries are connected to servers using Fibre Channel. Fibre Channel is a highly reliable, gigabit interconnect technology that enables simultaneous communication among workstations, mainframes, servers, data storage systems and other peripherals. Without the distance and bandwidth limitations of SCSI, Fibre Channel is ideal for moving large volumes of data across long distances quickly and reliably.

In contrast to DAS or NAS, which is optimized for data sharing at the file level, the strength of SANs lies in its ability to move large blocks of data. This is especially important for bandwidth-intensive applications such as database, imaging and transaction processing. The distributed architecture of a SAN also enables it to offer higher levels of performance and availability than any other storage medium today. By dynamically balancing loads across the network, SANs provide fast data transfer while reducing I/O latency and server workload. The benefit is that large numbers of users can simultaneously access data without creating bottlenecks on the local area network and servers.

SANs are the best way to ensure predictable performance and 24x7 data availability and reliability. The importance of this is obvious for companies that conduct business on the web and require high volume transaction processing. Another example would be contractors that are bound to service-level agreements (SLAs) and must maintain certain performance levels when delivering IT services. SANs have built in a wide variety of failover and fault tolerance features to ensure maximum uptime. They also offer excellent scalability for large enterprises that anticipate significant growth in information storage requirements. And unlike direct-attached storage, excess capacity in SANs can be pooled, resulting in a very high utilization of resources. There has been much debate in recent times about choosing SAN or NAS in the purchasing decision, but the truth is that the two technologies can prove quite complementary. Today, SANs are increasingly implemented in conjunction with NAS. With SAN/NAS convergence, companies can consolidate block-level and file-level data on common arrays.

Even with all the benefits of SANs, several factors have slowed their adoption, including cost, management complexity and a lack of standardization. The backbone of a SAN is management software. A large investment is required to design, develop and deploy a SAN, which has limited its market to the enterprise space. A majority of the costs can be attributed to software, considering the complexity that is required to manage such a wide scope of devices. Additionally, a lack of standardization has resulted in interoperability concerns, where products from different hardware and software vendors may not work together as needed. Potential SAN customers are rightfully concerned about investment protection and many may choose to wait until standards become defined.

Conclusion

With such a variety of information storage technologies available, what is the best way to determine which one is right for your organization? DAS, NAS and SAN all offer tremendous benefits, but each is best suited for a particular environment. Consider the nature of your data and applications. How critical and processing-intensive are they? What are your minimum acceptable levels of performance and availability? Is your information sharing environment localized, or must data be distributed across the enterprise? IT professionals must make a comprehensive assessment of current requirements while also keeping long-term business goals in mind.

Like all industries, storage networking is in a constant state of change. It's easy to fall into the trap of choosing the emerging or disruptive storage technology at the time. But the best chance for success comes with choosing a solution that is cost-correct and provides long term investment protection for your organization. Digital assets will only continue to grow in the future. Make sure your storage infrastructure is conducive to cost-effective expansion and scalability. It is also important to implement technologies that are based on open industry standards, which will minimize interoperability concerns as you expand your network.