TABLE OF CONTENTS Certainly, MPEG video compression technologies are very important to video networking. However, a number of other video compression technologies are used for video transport over IP networks. Fortunately, many of them use the same underlying technologies as MPEG, so our discussion can be much simpler. In the following sections, we'll look at some of these other technologies and where they are used.
H.261 and H.263 are international standards that are used extensively in videoconferencing, published by the International Telecommunication Union's Telecommunications Standardization Sector (ITU-T) for video compression. One of the most popular standards for videoconferencing on IP networks, H.323 uses the H.261 and H.263 video compression standards. Other videoconferencing formats, such as H.320 (for ISDN networks) and H.324 (for standard dial-up telephone lines, including some wireless ones), also use H.261 and H.263. [3]
H.261 compression was designed for operation on digital telephone lines that operated in multiples of 64 kbps (one DS0 or one voice connection) up to a maximum of 2048 kbps, which corresponds to the rate of an E1 line in Europe (see Chapter 1). These interfaces are collectively known by the label "p 64" (read as "p times sixty-four") where "p" can range from 1 to 30. In North America, when "p" equals 24, the system bandwidth will be equivalent to a T1 signal. There is nothing in the compression algorithm that forces it to operate in multiples of 64 kbps, so this kind of compression is available for use...
