The importance of the bi-directionally predicted pictures in video streaming

Video streaming over a hostile environment such as the Internet, where the available bandwidth varies in time, requires the source to adjust its transmission rate dynamically. Moreover, inevitable packet losses cannot be totally avoided and, hence, the video-streaming schemes should be complemented with appropriate error concealment techniques. In this paper, we highlight the vitality of the bi-directionally predicted pictures in the MPEG coded bitstreams to applications of video streaming and error concealment. In particular, we show how the properties and the motion parameters of such pictures can be exploited for efficient video transcoding into lower resolutions and different encoding formats for pre-encoded video streams. At the decoder side, however, we also emphasize on the important role of the bidirectional prediction on interframe error concealment.