A) Scalability is the ability of a decoder to decode an ordered set of bit streams to produce a reconstructed sequence. Moreover, useful video is output when subsets are decoded. The minimum subset that can thus be decoded is the first bit stream in the set which is called the base layer. Each of the other bit streams in the set is called an enhancement layer. When addressing a specific enhancement layer, lower layers refer to the bit stream which precedes the enhancement layer.

b) A characteristic of MPEG-2 that provides for multiple quality levels by providing layers of video data. Multiple layers of data allow a complex decoder to produce a better picture by using more layers of data, while a more simple decoder can still produce a picture using only the first layer of data.

c) The degree video and image formats can be combined in systematic proportions for distribution over communications channels for varying capacities.

d) Scalability implies that it is possible to decode just a fraction of the information in a bit stream. In MPEG, we find SNR scalability, spatial scalability, and temporal scalability, and even in combination (hybrid scalability).

In connexion with scalability we find the terms “lower layer,” which represents the basic information, and the “enhancement layer,” which represents the additional information. In case of hybrid scalability, up to three layers are found. All types of scalability may be used for transmission systems with split data channels with different error rate. The lower layer is transmitted on a channel with high protection rate, whereas the enhancement layer is transmitted on a channel with higher bit error rate. e) A feature of the Indeo video codec with which quality can be optimised during playback depending on the system resources being used to play the video.