John G. Apostolopoulos, Wai-tian Tan, Susie J. Wee
Streaming Media Systems Group
Palo Alto, CA, USA
Video has been an important media for communications and entertainment for many decades. Initially video was captured and transmitted in analog form. The advent of digital integrated circuits and computers led to the digitization of video, and digital video enabled a revolution in the compression and communication of video. Video compression became an important area of research in the late 1980's and 1990's and enabled a variety of applications including video storage on DVD's and Video-CD's, video broadcast over digital cable, satellite and terrestrial (over-the-air) digital television (DTV), and video conferencing and videophone over circuit-switched networks. The growth and popularity of the Internet in the mid-1990's motivated video communication over best-effort packet networks. Video over best-effort packet networks is complicated by a number of factors including unknown and time-varying bandwidth, delay, and losses, as well as many additional issues such as how to fairly share the network resources amongst many flows and how to efficiently perform one-to-many communication for popular content. This article examines the challenges that make simultaneous delivery and playback, or streaming, of video difficult, and explores algorithms and systems that enable streaming of pre-encoded or live video over packet networks such as the Internet.
We continue by providing a brief overview of the diverse range of video streaming and communication applications. Understanding the different classes of video applications is important, as they provide different sets of constraints and degrees of freedom in system design. Section 3 reviews video compression and video compression standards. Section 4 identifies the three fundamental challenges in video streaming: unknown and time-varying bandwidth, delay jitter, and loss. These fundamental problems and approaches for overcoming them are examined in depth in Sections 5, 6, and 7. Standardized media streaming protocols are described in Section 8, and additional issues in video streaming are highlighted in Section 9. We conclude by describing the design of emerging streaming media content delivery networks in Section 10. Further overview articles include [1,2,3,4,5].