TABLE OF CONTENTS The MPEG-4 standard absorbs many features of the MPEG-1, MPEG-2 and other related standards and was introduced primarily to compress audio and visual (AV) digital data, under the formal standard ISO/IEC 14496 [10]. The MPEG-4 project started as a standard for video compression at very low bitrates. After working on this project for two years, the committee members, realizing that the rapid development of multimedia applications and services will require ever more compression standards, revised their approach. Instead of a compression standard, they decided to develop a set of tools (a toolbox ) to deal with AV objects. All the video coding techniques (e.g., H.263, MPEG-1/2, etc.) discussed so far have been based on pixels. Each video frame is a rectangular set of pixels and the algorithm looks for correlations between the pixels in a frame and between frames. The compression paradigm adopted for MPEG-4, however, is based on objects; that is why MPEG-4 was also named the coding of audio-visual objects. Thus MPEG-4 relies on an object-based representation of the video data. It was standardized with the following features for handling audio and visual media objects (see Figure 5.28) [30] [31].
Media objects coding allows the data compression of media objects which include audio, visual, or audio-visual content. These two-dimensional or three-dimensional media objects can be natural or synthetic signals, meaning they could have been recorded with a camera or microphone or could be graphics or animation generated by a computer.
Media object...
