No abstract

In 2018, the Alliance for Open Media (AOMedia) finalized its first video compression format AV1, which is jointly developed by the industry consortium of leading video technology companies. The main goal of AV1 is to provide an open source and royalty-free video coding format that substantially outperforms state-of-the-art codecs available on the market in compression efficiency while remaining practical decoding complexity as well as being optimized for hardware feasibility and scalability on modern devices. To give detailed insights into how the targeted performance and feasibility is realized, this paper provides a technical overview of key coding techniques in AV1. Besides, the coding performance gains are validated by video compression tests performed with the libaom AV1 encoder against the libvpx VP9 encoder. Preliminary comparison with two leading HEVC encoders, x265 and HM, and the reference software of VVC is also conducted on AOM's common test set and an open 4k set.

In this paper, we propose a new class of search ordering algorithms to reduce the computational cost of motion estimation in video coding. We show that conventional search orderings, such as spiral search, can weaken the filtering criterion of rate-constrained successive elimination algorithms. Based on this new insight, we derive a new search ordering that takes into account the impact of the rate constraint. Our simulation results demonstrate that, on average, the amount of SAD operations required to encode the tested sequences, is reduced by 2.86%, when compared to the H.264 JM reference software's implementation of spiral search. For sequences with unpredictable motion, this reduction is greater than 5% and can exceed 10% when smaller block partitions are evaluated.

In mobile video applications, where unreliable networks are commonplace, corrupted video packets can have a profound impact on the quality of the user experience. In this paper, we show that, in a wide range of operating conditions, selectively reusing data resulting from decodable errorneous packets leads to better results than frame copy. This selection is guided by a novel concept that combines motion estimation and a measure of blocking artifacts at block edges to predict visual degradation caused by the decoding of erroneous packets. Simulation results show that, by using the proposed solution, the H.264/AVC JM reference software decoder can select the best option between frame copy and the erroneous frame decoding in 82% of test cases. We also obtain an average gain of 1.95 dB for concealed frames (when they differ from those concealed by the JM decoder).