Introduction

Whereas in the past the quality of digitally transmitted video was considered inferior to that of analog, with modern compression techniques this is definitely no longer the case. It is now possible to encode the complete video image at full resolution, and transmit images around a network at full frame rate (25 fps for PAL, 30 fps for NTSC). It can even be argued that, since IP-based transmission is lossless, digitally-transmitted video is superior to analog as no degradation occurs during transmission, recording or playback.

Currently three digital compression standards are commonly used for CCTV over IP:

• MPEG-2 is the standard compression algorithm for broadcast quality video and is the compression technique often used for transmitting live video over IP. It was specially developed for digital TV and takes account of the line interlacing used for standard TV signals. It allows data transfer rates of up to 15 Mbit/s.
  
  
• MPEG-4 Part 2 offers higher compression rates than MPEG-2 and can easily handle data rates of 512 Kbps to 1 Mbps without compromising image quality. Being less space hungry than MPEG-2, it is the most popular standard used for archiving video.
  
  
• H.264, MPEG-4 (Part 10), Advanced Video Coding (AVC) is designed to be up to 50% more efficient than MPEG-2 and MPEG-4 Part 2 while offering the same video quality. It is designed to fit many applications – high and low resolutions, high and low bandwidths and many kinds of media ranging from IP networks to DVDs to telephony systems.