Abstract
High-Efficiency Video Coding (HEVC) is the latest video coding standard, in which the compression performance is double that of its predecessor, the H.264/AVC standard, while the video quality remains unchanged. In HEVC, the test zone (TZ) search algorithm is widely used for integer motion estimation because it effectively searches the good-quality motion vector with a relatively small amount of computation. However, the complex computation structure of the TZ search algorithm makes it difficult to implement it in the hardware. This paper proposes a new integer motion estimation algorithm which is designed for hardware execution by modifying the conventional TZ search to allow parallel motion estimations of all prediction unit (PU) partitions. The algorithm consists of the three phases of zonal, raster, and refinement searches. At the beginning of each phase, the algorithm obtains the search points required by the original TZ search for all PU partitions in a coding unit (CU). Then, all redundant search points are removed prior to the estimation of the motion costs, and the best search points are then selected for all PUs. Compared to the conventional TZ search algorithm, experimental results show that the proposed algorithm significantly decreases the Bjøntegaard Delta bitrate (BD-BR) by 0.84%, and it also reduces the computational complexity by 54.54%.
Highlights
The High-Efficiency Video Coding (HEVC) [1–5] standard, the latest video coding standard, is designed to replace the previous H.264/AVC standard owing to the fact that HEVC preserves the video compression quality of H.264/AVC and reduces the bitrate by as much as 50%
The conventional test zone (TZ) search algorithm can result in an improvement of more than 60% of the encoding time versus the full search algorithm, many optimization issues still exist. Attempting to solve these problems can decrease the encoding time significantly. Another problem associated with the traditional TZ search algorithm is that all search patterns used in the integer ME (IME) are fixed and limited in terms of the search range; the best match position can be trapped into a local minimum, which downgrades the video compression efficiency
Several works have addressed the issue of sum of the absolute difference (SAD) calculation [19–21], and many new SAD architectures and implementations are introduced to utilize the amount of data reuse for SAD costs
Summary
The High-Efficiency Video Coding (HEVC) [1–5] standard, the latest video coding standard, is designed to replace the previous H.264/AVC standard owing to the fact that HEVC preserves the video compression quality of H.264/AVC and reduces the bitrate by as much as 50%. Attempting to solve these problems can decrease the encoding time significantly Another problem associated with the traditional TZ search algorithm is that all search patterns used in the IME are fixed and limited in terms of the search range; the best match position can be trapped into a local minimum, which downgrades the video compression efficiency. The second approach determines the early termination conditions to reduce the computing time [9–15] In one of these studies [9], due to the smaller number of search points, a hexagonal search pattern is used instead of the basic diamond pattern. In a continuation of their work [10], rotating hexagonal patterns are shown to increase the peak signal-to-noise ratio (PSNR) slightly Another skipping method is presented based on the average motion cost among all previously examined search positions. The experimental results of all related TZ search algorithms show that they all involve a trade-off between the complexity and the compression quality and that none of them can reduce the computation time or the complexity with a significant decrease in the bitrate
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