A Two-Stage Approach for Robust HEVC Coding and Streaming

The increased compression ratios achieved by the High Efficiency Video Coding (HEVC) standard lead to reduced robustness of coded streams, with increased susceptibility to network errors and consequent video quality degradation. This paper proposes a method based on a two-stage approach to improve the error robustness of HEVC streaming, by reducing temporal error propagation in the case of frame loss. The prediction mismatch that occurs at the decoder after frame loss is reduced through the following two stages. First, at the encoding stage, the reference pictures are dynamically selected based on constraining conditions and Lagrangian optimization, which distributes the use of reference pictures, by reducing the number of prediction units that depend on a single reference. Second, at the streaming stage, a motion vector (MV) prioritization algorithm, based on spatial dependencies, selects an optimal subset of MVs to be transmitted, redundantly, as side information to reduce mismatched MV predictions at the decoder. The simulation results show that the proposed method significantly reduces the effect of temporal error propagation. Compared with the reference HEVC, the proposed reference picture selection method is able to improve the video quality at low-packet-loss rates (e.g., 1%) using the same bitrate, achieving quality gains up to 2.3 dB for 10% of packet loss ratio. It is shown, for instance, that the redundant MVs are able to boost the performance achieving quality gains of 3 dB when compared with the reference HEVC, at the cost using 4% increase in total bitrate.

I. Introduction

The current diversity of multimedia applications and services, and the emergence of Ultra-HD formats (e.g., 4k or 8k resolution) are continuously reinforcing the need for efficient video coding. Moreover, the increasing amount of mobile multimedia traffic demands for more bandwidth, and the use of higher resolutions impose more challenging bounds on quality and error tolerance. The High Efficiency Video Coding (HEVC) [1] is the most recent standard developed by the Joint Collaborative Team on Video Coding (JCT-VC), essentially aiming to extend previous standards towards increased video resolutions and use of parallel processing architectures. The higher coding flexibility and efficiency of HEVC results from the use of new block partition structures, enabling flexible block partitions [2], improved prediction modes [3], [4] and new high-level features [5], such as explicit reference picture management and new parameter sets.