low-delay hierarchical coding structure (LD-HCS), as one of the most crucial components in the High Efficiency Video coding (HEVC) standard, substantially complicates the temporal reference relationship and achieves b...
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low-delay hierarchical coding structure (LD-HCS), as one of the most crucial components in the High Efficiency Video coding (HEVC) standard, substantially complicates the temporal reference relationship and achieves better compression ratios. There have been lots of research work on increasing the error resilience of HEVC coding. However, most of them neglect the characteristics of LD-HCS and cannot achieve the optimum trade-off between coding efficiency and error robustness. To this end, in this paper, a non-feedback reference picture selection algorithm is proposed to improve the error robustness of HEVC streaming under LD-HCS, by reducing temporal error propagation in case of packet loss. Specifically, the temporal relationship among different frames under LD-HCS is firstly analyzed, and then frames with the lowest temporal layer are considered as the potential key-frame which is capable of preventing error propagation. Secondly, the end-to-end distortions of using two different reference schemes for the potential key-frame are compared based on an overall distortion estimation model, and the reference scheme that has less total distortion is chosen ultimately. Moreover, the potential key-frame will be encoded entirely in intra-mode if the error propagation is severe. Extensive experiment results demonstrate that the proposed reference picture selection method significantly reduces the effect of temporal error propagation. Compared to the state-of-the-art approaches, the proposed method is able to improve the video quality over error-prone networks.
low-delay hierarchical coding structure (LD-HCS), as one of the most important components in the latest High Efficiency Video coding (HEVC) standard, greatly improves coding performance. It groups consecutive P/B fram...
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low-delay hierarchical coding structure (LD-HCS), as one of the most important components in the latest High Efficiency Video coding (HEVC) standard, greatly improves coding performance. It groups consecutive P/B frames into different layers and encodes them with different quantization parameters (QPs) and reference mechanisms in such a way that temporal dependency among frames can be exploited. However, due to varying characteristics of video contents, temporal dependency among coding units differs significantly from each other in the same or different layers, while a fixed LD-HCS scheme cannot take full advantage of the dependency, leading to a substantial loss in coding performance. This paper addresses the temporally dependent rate distortion optimization (RDO) problem by attempting to exploit varying temporal dependency of different units. First, the temporal relationship of different frames under the LD-HCS is examined, and hierarchical temporal propagation chains are constructed to represent the temporal dependency among coding units in different frames. Then, a hierarchical temporally dependent RDO scheme is developed specifically for the LD-HCS based on a source distortion propagation model. Experimental results show that our proposed scheme can achieve 2.5% and 2.3% BD-rate gain in average compared with the HEVC codec under the same configuration of P and B frames, respectively, with a negligible increase in encoding time. Furthermore, coupled with QP adaption, our proposed method can achieve higher coding gains, e.g., with multi-QP optimization, about 5.4% and 5.0% BD-rate saving in average over the HEVC codec under the same setting of P and B frames, respectively.
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