Network video > An IP videosurveillance system
| Several factors have to be taken into consideration when designing a high-quality IP surveillance system, especially image quality and broadband management. |
| Image quality |
| Image quality is clearly one of the most important feature of any camera, if not the most important. This is especially true of security surveillance and remote monitoring applications,where lives and property may be at stake. |
| The building blocks |
| Unlike traditional analog cameras, network cameras are equipped with the processing power not only to capture and present images, but also manage and compress them digitally for network transport. A compromise must be found between the compression levels and images quality....... |
- Image sensor type
- Camera capacity in scantly lit places
- Possibility of replacing the lens
- Resolution
- Compatible compression formats
- Image-capture techniques used (see below)
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| Digital image quality has three main supports: |
- Processing of advanced signals, image improvement algorithms and video compression technologies.
- Personalized processing of both the image and the electronic components of IP video
- The rigorous choice of the most recent types of lens and high-technology sensors.
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| Bandwidth considerations |
| Network video products utilize network bandwidth and storage space based on their configuration. As mentioned earlier, this depends on the following: |
- Image resolution
- Video compression type: Motion JPEG, MPEG-4, H.264.
- Framerate per second
- Scenery: Image complexity (e.g. gray wall or a forest), lighting conditions and amount of motion (office environment or crowded train stations)
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| The following techniques facilitate an optimal management of the broadband: |
- Commuted networks:
Thanks to the VLAN, the same physical network (computers and IP surveillance systems) can be separated into two autonomous networks. Whilst remaining physically connected, this method makes a logical split into two virtual and independent networks.
- Faster networks: most of today’s networks used 100 Mbit/s or more, providing sufficient broadband capacity for IP video applications. As Gigabit networks become cheaper every day, hundreds of network cameras can use the same physical infrastructure, without reducing network performance.
- Evolving frequency: most applications do not require the quality level given by a camera configuration constantly recording 25 images per second. In normal conditions this frequency can be reduced (to 5 images/sec) thanks to the configuration capacity and integrated intelligence of IP video products, thereby considerably reducing broadband use. When, for instance an alarm is set off by a motion detector, the recording frequency can automatically adjust to a higher level. In most cases, after a motion is detected, the camera will only send a recording of the video images which present any interest. Otherwise no data are transferred on to the network.
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| Image capture techniques: |
| Many network cameras use the guard mode or progressive scanning techniques because it has a greater capacity to capture a moving image and view the detail of moving objects. This technique, which is more advanced than the interlaced scan, captures the image once, thereby producing crisp-clear results, even if there is a lot of movement. |
VIDEOIP_CONCEPT5_BAL_PROG | 
Interlaced scanning |
