4G Wireless Video Communications

12

Wireless Video Streaming

12.1 Introduction

This chapter discusses the basic elements of wireless video streaming. Unlike download-and-play schemes, which require the entire video bitstream to be received by the client before playback can begin, video streaming allows a client to begin video playback without having to download the entire bitstream. Once video playback starts, it can continue without interruption until the end of the presentation. In order to enable playback without interruption even when the network bandwidth fluctuates, a client initially buffers the data it receives and begins playback after a delay of up to several seconds. This delay is fixed and does not depend on the length of presentation [1]. In order to achieve continuous playback, the interval between the time a video frame is transmitted by the server and the time it is displayed by the client should be the same for all frames. This means that there is a deadline for each frame when all packets that correspond to the frame must be available to the client for display. If some packets are missing at the deadline, they will be considered lost and error concealment will be employed in the decoding of the video frame. If packets that missed the deadline happen to arrive at the client later, they will simply be discarded. This concept of deadlines for the video packets is central to video streaming and will be discussed in detail later in this chapter.

With respect to the number of clients, video streaming ...