# Load Balancing Strategies for Slice-Based Parallel Versions of JEM Video Encoder
###### Abstract  
The proportion of video traffic on the internet is expected to reach 82% by 2022, mainly due to the increasing number of consumers and the emergence of new video formats with more demanding features (depth, resolution, multiview, 360, etc.). Efforts are therefore being made to constantly improve video compression standards to minimize the necessary bandwidth while retaining high video quality levels. In this context, the Joint Collaborative Team on Video Coding has been analyzing new video coding technologies to improve the compression efficiency with respect to the HEVC video coding standard. A software package known as the Joint Exploration Test Model has been proposed to implement and evaluate new video coding tools. In this work, we present parallel versions of the JEM encoder that are particularly suited for shared memory platforms, and can significantly reduce its huge computational complexity. The proposed parallel algorithms are shown to achieve high levels of parallel efficiency. In particular, in the All Intra coding mode, the best of our proposed parallel versions achieves an average efficiency value of 93.4%. They also had high levels of scalability, as shown by the inclusion of an automatic load balancing mechanism. JEM; video coding standards; JEM slices; JEM parallel; OpenMP +
Footnote †: journal: _Algorithms_  
0000-0001-4000-0000-0000-0000-0000-0000-0000-00000-0000-0000-00000-0000-  
In order to deal with this increase in IP video traffic, new video coding techniques are required to obtain higher compression rates. Since the release of HEVC, both the ITU-T Video Coding Expert Group (VCEG) and the ISO/IEC Moving Picture Expert Group (MPEG) have been studying and analyzing new video coding technologies in order to improve the compression capability compared to that obtained by HEVC. To achieve this, a framework of collaboration has been created called the Joint Video Exploration Team (JVET). The compression enhancements studied by the JVET have been implemented in a software package known as the Joint Exploration test Model (JEM) [5]. Its main purpose is to explore new coding tools that can provide significant improvements at the video coding layer. Following an analysis of the new coding tools that have been proposed within the last few years, JVET has begun developing a future video coding standard called Versatile Video Coding (VVC) [6]. The main goal of this coding standard is to achieve bit rate savings of between 25% and 30% compared to HEVC [7; 8]. Preliminary results obtained with the new model (JEM 3.0) show an 18% reduction in bit rate using the All Intra (AI) coding mode configuration [9]. However, this is achieved at the expense of an extremely large increase in computational complexity (60x) with respect to HEVC. This increase requires the introduction of acceleration techniques that leverage hardware architectures to reduce encoding time. Since JEM is an exploration model, only a few articles have been published on the subject, and most of them are focused on rate distortion (R/D) comparisons between JEM, HEVC and AV1 codecs [10]. Recently, the authors of [11] proposed a pre-analysis algorithm that was designed to extract motion information from a frame in order to accelerate the motion estimation (ME) stage. Their proposal showed that around 27% of the reference frames could be skipped, and that a time saving of more than 62% was achieved on the integer ME operation, with a negligible impact of 0.11% on the Bjontegaard delta rate (BD rate) [12]. The authors in [13] proposed parallel algorithms based on the group of pictures (GOP) structure, increasing the BD rate when temporal redundancy is exploited. In this paper, we present two JEM parallel encoder versions that are specifically designed for shared memory platforms, in order to speed up the encoding process for the All Intra (AI) coding mode, as this coding mode is especially useful for video editing.