Adaptive bitstream switching of pre-encoded PFGS video

Abstract

With Progressive Fine Granularity Scalability (PFGS) video coding, one given encoding (with a prescribed bit rate) can flexibly be transmitted at any lower bit rate. However, the transmitted video is only efficiently encoded when the transmission bit rate is in the vicinity of the encoding bit rate; for transmission bit rates far from the encoding bit rate up on the order of 4 dB in video quality are lost. In this paper we develop and evaluate a suite of policies for accounting for this coding efficiency issue, which has been largely overlooked in previous PFGS streaming studies, in uni-and multicast streaming. Our adaptive policies select the PFGS encoding rate from a small number of pre-encoded versions and drop packets so as to maximize the reconstructed video qualities. Our policies consider both the visual video content, expressed using the motion activity level of MPEG-7 descriptor, as well as the channel variability. We find that an optimal non-adaptive streaming policy overcomes the 4 dB inefficiency and on top of this efficiency gain, our adaptive unicast streaming policy achieves 0.8 dB improvement over the optimal non-adaptive streaming. We also find that our contentdependent packet drop policies enforce fairness among multiple streams in terms of reconstructed video qualities and that our multicasting policy improves the average reconstructed video qualities at a group of receivers by up to 2 dB.

Adaptive bitstream switching of scalable video

“…The study [17] presents and evaluates adaptive streaming mechanisms, which are based on the visual content features, for non-scalable (single-layer) encoded video, whereby the adaptation is achieved by selectively dropping B-frames. The present study is complementary to [1,17] in that we consider scalable (layered) encoded video and develop content-based network-aware streaming mechanisms for layered encoded video.…”

“…We also verify in Section 3.2, that for AR-FGS the quality gain can reach up to 1.8 dB for the same content. In summary, PFGS encoding-and, in general, any SNR scalable coding concept known today-is only optimized for the rate that is used during the encoding process [1,13]. Essentially all existing studies on PFGS video streaming have ignored the important aspect of the encoding bit rate selection and focus primarily on modeling the rate-distortion (R-D) characteristics of a given encoding or the optimal selection of the transmission bit rate based on the R-D model of one encoding [14,15].…”