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While Buying an IP Camera

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While Buying an IP Camera

Bài gửi  duyminh on Tue Jan 26, 2010 10:39 am


















While Buying an IP Camera
1. How large an area do you want to view with each camera?
The distance to and the width of the area you want to view will determine the type of lens you need. The higher the “mm” (focal length) the smaller the field of view and the more magnification you get.

2. How much light is available?
Do you want to monitor and record at night? The amount of light determines how sensitive the camera needs to be. You may want to select a low-light camera. The "Lux" rating tells you how well a camera sees in dim light.

3. Do you want to use the camera outside?
If the camera needs to be used in a wide variety of lighting conditions, you need an auto-iris lens that adjusts to the light.

4. Do you have a large area that requires a Pan, Tilt, Zoom (PTZ) camera?
You can select a camera with either digital PTZ or mechanical PTZ.

5. What frame rate is required?
A high frame rate is required if you want to record a fast moving object. But if you are using the camera for general surveillance; you may only require 1 or 2 frames/sec. The higher the frame rate the more storage space you will require.

6. How much image clarity and detail do you require?
If you want to view a larger area then you need a higher resolution camera. Higher resolutions provide more clarity and better image quality. But if you want to monitor a smaller area and do not want to see a detailed view, a camera with lesser resolution might do. Higher-resolution images also mean larger recorded video and snap files, thus taking up more storage space.

7. Do you want to monitor manually or need automatic alerts?
if you simply want to view your IP camera from any location, you need either a PC or a mobile device like a PDA (Personal Digital Assistants) or cell phone with an Internet connection. Surveillance software can automatically start video recording when motion is detected. Special video software like WebCam Monitor is used to control the video from IP cameras. It stores the video, sounds alarms when motion is detected, controls PTZ movement, and much more. Once motion is detected you can be notified by email, sound alarm, or even receive a page.
It's important to consider the compression method used by an IP camera. Compression reduces the size of the video files generated while monitoring. Since video files contain a huge amount of data, compression is required to reduce the storage and bandwidth requirements. The commonly used compression techniques are MPEG-4 and MJPEG. Let us try to quickly understand how these work.

MJPEG (Motion JPEG)
IP cameras using this type of compression can capture images at rates of up to a maximum of 30 frames per second. In MJPEG recording, each frame consists of a complete JPEG image. This is referred to as Motion JPEG. By compressing each frame as an individual image, this produces high picture quality, but when compared with MPEG4, the bandwidth required for transmission and the disk space required for storage are both higher.

MPEG-4
The Moving Picture Experts Group (MPEG) is the organization that defined the standards for this format. With MPEG4, only a small fraction of the video frames are sent as a complete image. For other frames, only information about the difference between this frame and the previous one are actually transmitted, not the complete image. Frame to frame coding techniques are based on the knowledge that most frames are similar to the ones preceding and succeeding them. This means that most of these frames can be transmitted as differences between their neighbors, which in turn means that a lot less information has to be transferred. The result of sending only image changes is both reduced bandwidth usage and storage space. However MPEG4 has a lower image quality when directly compared to MJPEG.
If you want your family and friends to watch the live feed, inform them of your IP address and the port (if you have specified one) to which they can connect to. You may have to Configure Your Camera and PC For Internet Streaming.

Choosing MJPEG for Video Surveillance
Most IP cameras currently available in the marketplace are based on MJPEG. MPEG4 provides better compression so less storage is required but image quality is lower. MJPEG offers higher image quality.
In video surveillance applications that require storage of the video, MPEG4 is not as easy to deal with as MJPEG. To find a particular frame in MPEG requires first finding the reference frame with regard to which the changes in subsequent frames have been transmitted and then moving to the exact time period you would like. MJPEG is a less complicated compression. When you retrieve MJPEG video you can go to the exact frame you want very quickly and easily.
MJPEG (Motion JPEG) is the compression of choice for video surveillance because it has better image quality and shows graceful degradation at bandwidth constraint. MJPEG guarantees a defined level of picture quality, which is vital in most security applications.
View your camera remotely
You want to be able to see what's happening on your property, even when you're not there. You can maintain video surveillance from your office or any other location. You only need four things: a camera, your PC, Webcam Monitor and an Internet connection. The remote monitoring features in CMS software offer several solutions. You can keep an eye on things from anywhere in the world. All you need to do is to connect your camera to your PC and start remote monitoring in WebCam Monitor, and you can always be aware of what is happening as it happens.

Using WebCam Monitor, you can remotely view your camera in three different ways.
1.You can watch a live broadcast from your webcam
2.View uploaded video recordings and photos on your web site
3.Receive email with embedded photo
Let us look at each of the three different ways to turn your PC and camera into a remote video surveillance system.

1. Live Broadcast:
In live broadcasting, WebCam Monitor sends a live stream of the video and/or audio from your camera over the Internet. If you have the Internet bandwidth, this is the best way to monitor the action live.

Preparing for broadcasting
First, you need a static IP address for the PC where the camera is connected. An Internet Protocol (IP) address is a unique number assigned to each computer in a network. A static IP address does not change. In contrast, a dynamic IP address can change frequently. A dynamic IP address may work temporarily for broadcasting, but when it changes the broadcast will no longer be available.As an alternative to a static IP address, you can assign a domain name to your PC. Services like no-ip.com and dyndns.org will assign a name to your PC, which can then be used to view the broadcast video. For instance, a computer might be assigned the domain name joeblowshome.no-ip.com. Broadcasting will not work from non routable IP addresses. Non-routable addresses cannot be used over the Internet. These addresses can only be connected to over a local network (LAN). All addresses starting with 192.168 are non-routable, as are some others. If you are not sure what type of IP address you have, you need to find out from your ISP or a network professional. If your PC has a non-routable address, you can still broadcast video by reconfiguring your network router to use "Port Forwarding", as explained in the article Configuring Your Camera and PC for Internet Broadcasting.

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