The advantage of network attached cameras is that you can store the video right on your computer hard drive. It replaces the need for special video tape recorders or even digital video recorders. But, how do you know how much hard drive space you will need? Will you need to add some Network Attached Video Storage? This article makes it all clear.
The amount of storage required for holding the video depends on the number of cameras, the resolution (image size), the frames/sec, the type of compression used, the percentage of time there is motion, and the length of time you want to store the video. Here’s how you estimate the storage – Number of Cameras
: The video from many different cameras can be stored on one hard drive and then retrieved according to the identity of the camera and the time marker. Obviously 4 cameras will require twice as much storage as 2 cameras. The Resolution
: Resolution determines how much information you will store for each frame of video. The higher the resolution the more storage it takes up. You should first determine the resolution you will need. For example you may need higher resolution if you want to identify someone’s face, but lower resolution if you only need to see that a person walked by. Very high resolution will also allow you to electronically pan/tilt and zoom around an image. For example the IQeye3
camera is capable of 1288 x 968 resolution. This is high enough to allow a user to pan/tilt/zoom even after the video has been stored. The Axis 2420
can be set for resolution of 352x240 or 704x480.
We use the following estimates of frame size based on the resolution.
Frame Size in Bytes
|352 x 240
|704 x 480
|1024 x 768
|1280 x 1024
|1600 x 1200
: The number of frames per second relates to how smooth the video appears. Video viewed at 30 frames per second looks like your TV, but uses up quite a lot of storage. For example, if you store 100 KB per frame and the frame rate was 30 frames per second, you would be storing a total of 3000 KB per second (using MJPEG compression). That’s 180 MB/minute or 10.8 GB/hour or over 259 GB/day. If you record at 1 frame/sec (instead of 30 frames/sec) you only use 8.64 GB/day. Make sure you understand what you are viewing before deciding the frame rate. If you are viewing people walking around, then 5 fps or less is adaquate; if you are viewing fast moving vehicles, then maybe 20fps or more is required. Motion Detection
: The Storage requirement can be reduced by using motion detection. Motion detection can be enabled by the camera or by software (like NetDVR
) running on your computer. In this case the video is recorded only when motion is detected. For example if motion is not detected 25% of the time, the storage requirement is reduced by 25%. Compression used
: The latest cameras usually provide a choice of MPEG4 or MJPEG compression. But, if you need a high resolution camera then MJPEG is only available. MPEG4 improves the compression by only transmitting the difference between one frame and another. For example if a person is walking in a field, then the camera only sends a picture of the person walking, and sends the complete picture only once in a while. This can dramatically reduce the data sent. Note that if the person is very close, and fills up the entire field of view, the compression is not very good. We usually estmate a 4 X benefit, so camera that uses 30KBytes when MJPEG is used requires only 7.5KBytes, when MPEG4 is used.Length of time
: The video can be stored for a period of time and then over written. For example if you stored video for two days, at the end of the second day new video would start replacing the video that was 48 hours old. The more time stored, the more storage required.
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: To make it easy to estimate your storage requirements, download
our free storage calculator.
Need some help calculating your storage or need some extra storage for your network, just contact us. We will be happy to help. 1-800-431-1658 (in the USA) or 914-944-3425 (outside the USA) or send us an Email