Many types of data contain statistical redundancy and can be effectively compressed using lossless compression, so that the reconstructed data at the output of the decoder is a perfect copy of the original data. components that are not necessary for faithful reproduction of the data. The encoder/decoder pair is often described as a CODEC (en COder/ DECoder) (Figure 3.1).ĭata compression is achieved by removing redundancy, i.e. The encoder converts the source data into a compressed form (occupying a reduced number of bits) prior to transmission or storage and the decoder converts the compressed form back into a representation of the original video data. ‘Raw’ or uncompressed digital video typically requires a large bitrate (approximately 216 Mbits for 1 second of uncompressed TV-quality video, see Chapter 2) and compression is necessary for practical storage and transmission of digital video.Ĭompression involves a complementary pair of systems, a compressor (encoder) and a decompressor (decoder). Video compression (video coding) is the process of compacting or condensing a digital video sequence into a smaller number of bits. 6.4.11 The Complete Transform, Quantisation, Rescaling and Inverse Transform ProcessĬompress vb.: to squeeze together or compact into less space condenseĬompress noun: the act of compression or the condition of being compressedĬompression is the process of compacting data into a smaller number of bits.4.2.5 Deciding the Content of the Standards.3.3.4 Motion Compensated Prediction of a Macroblock.3.3.1 Prediction from the Previous Video Frame.