Selective Visual Attention: Computational Models and Applications

8.3 Applications in Image/Video Coding

8.3.1 Image and Video Coding

Along with the rapid development of multimedia and internet techniques, digital media are widely applied, such as digital television, internet streaming video and DVD-video. Raw media signals hold enormous amounts of redundancy in the time domain or the spatial domain, which means unnecessarily high storage capacity. Therefore the original media signal is disadvantageous for storage and internet applications with limited bandwidth. That is, media content usually needs to be compressed/encoded into smaller memory capacity and lower bitrate on the premise of quality. Of course, the encoded signal should be decoded before viewing.

For the language with which an encoder and decoder communicate, many image and video coding standards are developed. The currently deployed image coding standards are JPEG and JPEG 2000, while the development of video coding standards has evolved through H.261, H.262/MPEG-2, H.263/MPEG-4 (part 2), and H.264/MPEG-4 (part 10). The main video encoding standards comply with the architecture of Figure 8.6.

Let us explain more on two of the standards: MPEG-2 and H.264. In the MPEG-2 system, compression is completed by motion prediction, two-dimensional discrete cosine transform (DCT) performed on blocks of pixels and entropy coding shown in Figure 8.6. The coding gain of H.264 over MPEG-2 is in the range of 30–50%. Rather than using floating point DCT in MPEG-2, H.264 adopts integer DCT which ...