Specifications

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Video compression
Video compression technologies are about reducing and removing redundant video
data so that a digital video le can be eectively sent over a network and stored on
computer disks. With ecient compression techniques, a signicant reduction in le
size can be achieved with little or no adverse eect on the visual quality. The video
quality, however, can be aected if the le size is further lowered by raising the com-
pression level for a given compression technique.
Dierent compression technologies, both proprietary and industry standards, are
available. Most network video vendors today use standard compression techniques.
Standards are important in ensuring compatibility and interoperability. They are par-
ticularly relevant to video compression since video may be used for dierent purposes
and, in some video surveillance applications, needs to be viewable many years from
the recording date. By deploying standards, end users are able to pick and choose from
dierent vendors, rather than be tied to one supplier when designing a video surveil-
lance system.
Axis uses three dierent video compression standards. They are Motion JPEG, MPEG-4
Part 2 (or simply referred to as MPEG-4) and H.264. H.264 is the latest and most ecient
video compression standard. This chapter covers the basics of compression and provides
a description of each of the three standards mentioned earlier.
7.1 Compression basics
7.1.1 Video codec
The process of compression involves applying an algorithm to the source video to create a
compressed le that is ready for transmission or storage. To play the compressed le, an inverse
algorithm is applied to produce a video that shows virtually the same content as the original
source video. The time it takes to compress, send, decompress and display a le is called latency.
The more advanced the compression algorithm, the higher the latency.
VIDEO COMPRESSION - CHAPTER 7