Complexity and compression efficiency analysis of libaom AV1 video codec

The recent research effort aiming to provide a royalty-free video format resulted in AOMedia Video 1 (AV1), which was launched in 2018. AV1 was developed by the Alliance for Open Media (AOMedia), which groups several major technology companies such as Google, Netflix, Apple, Samsung, Intel, and many others. AV1 is currently one of the most prominent video formats and has introduced several complex coding tools and partitioning structures in comparison to its predecessors. A study of the computational effort required by the different AV1 coding steps and partition structures is essential for understanding its complexity distribution when implementing fast and efficient codecs compatible with this format. Thus, this paper presents two main contributions: first, a profiling analysis aiming at understanding the computational effort required by each individual coding step of AV1; and second, a computational cost and coding efficiency analysis related to the AV1 superblock partitioning process. Experimental results show that the two most complex coding steps of the libaom reference software implementation are the inter-frame prediction and transform, which represent 76.98% and 20.57% of the total encoding time, respectively. Also, the experiments show that disabling ternary and asymmetric quaternary partitions provide the best relationship between coding efficiency and computational cost, increasing the bitrate by only 0.25% and 0.22%, respectively. Disabling all rectangular partitions provides an average time reduction of about 35%. The analyses presented in this paper provide insightful recommendations for the development of fast and efficient AV1-compatible codecs with a methodology that can be easily replicated.