This book is about interactive multimedia in the Internet. We are used to conventional multimedia in every day life through the telephone and television, through Hi-Fi/CDs and through video cameras and VCRs. A great deal of effort in the telecommunications research world has been aimed at trying to mimic these technologies in the digital telephony world. However, the work in Internet based multimedia has gone a great deal further in flexibility and usability of services, due to its emphasis on computer based solutions. Applications can be more intelligent, and can be integrated with each other making them more useable, and more efficient. A simple example of this is the use of shared whiteboards during voice conferences, with visual indications of who is speaking and who is drawing. Another example is the idea of customisable call handling in Internet Telephony (``if I am talking to the boss, and the caller is my employee, forward their call to my assistant, otherwise hand them to my answerphone avatar''). The only limit here is the imagination of the application creator.
The Internet was originally developed to support data communications between computers, but the definition of data has a habit of broadening, just as computers have a habit of becoming more flexible. The processing and storage capacity of computers have increased exponentially. So has the size and capacity of the Internet. All three have now reached the point where we can capture, compress, store, decompress, replay, send and receive digital audio and video almost as easily as files of text.
From early research experiments in the late 70s and early 80s, through to the deployment of the late 80s and early 90s, multimedia has grown as a presence in the network. Interactive multimedia, whether for media-on-demand from World Wide Web servers, or between users in multimedia conferencing systems is becoming quite pervasive.
The Internet has undergone a number of enhancements to make this possible, as have its protocols. There is also a huge investment in middleware, software systems to enable more complex applications to be built quickly and effectively for distributed computing. Then there is a surprising variety of applications, not just conferencing or video-on-demand, but also image dissemination, games, multi-player multimedia VR, and so on.
In this book, we describe the technologies and systems that make this possible. Unlike previous books about multimedia and networking, which are descriptive, we attempt to prescribe the approach that has emerged in the the Internet Engineering Task Force, or IETF. This is the group that carries out standards development for Internet protocols, services and applications. There are working groups on Audio/Video Transport, Multimedia Conference Control, Integrated and Differentiated Services and Resource Reservation (to name but a few).
We believe that the model that has evolved in this environment is more scalable and flexible and caters for more heterogeneity than alternative models, and is thus more suited to deployment for the public at large. It is also a very good model for how to develop multimedia distributed systems in general for many purposes, and it is also fun.