The aim in video compression is to remove those parts of the signal which we do not essentially need.
The reason why video compression works so well is that video data is described as being ‘very redundant’, due to the way the human psychovisual system operates. There are three types of redundancy in video:
• spectral (brightness and colour)
• spatial (similarities in parts of the picture)
• temporal (similarities between one TV frame and the next).
Bright pixels tend to be bright in all three colours, red, green and blue, and therefore there is said to be spectral redundancy – the similarity between colour values at any one point in the picture.
Earlier we mentioned the ability to fool the human brain ...