Uncompressed images and video are much too large to deal with and compression is needed for storage and transmission. Table 2 shows some important video encoding and compression techniques related to desktop videoconferencing. A video compression standard designed for communication bandwidths between 64 kbps and 2 Mbps, measured in 64 kbps intervals. Each type of channel has advantages and disadvantages when evaluating its suitability for the transport of data characteristic for desktop videoconferencing. Different types of data have different service requirements.
Some data types are sensitive to delay, while other types are sensitive to reliability.
Table 3 outlines different data types and their sensitivity to delay and reliability. An example is a data file that is sent over a network. It does not matter how long the file takes to get to its destination, but the information in the file is expected to be correct. Voice data is sensitive to delay but is not sensitive to reliability. Voice data must arrive at a constant rate with little variance for it to be intelligible, but some loss of information is acceptable.