Motion Vectors Merging: Low Complexity Prediction Unit Decision Heuristic for the Inter-prediction of HEVC Encoders

Abstract

This paper presents the Motion Vectors Merging (MVM) heuristic, which is a method to reduce the HEVC inter-prediction complexity targeting the PU partition size decision. In the HM test model of the emerging HEVC standard, computational complexity is mostly concentrated in the inter-frame prediction step (up to 96% of the total encoder execution time, considering common test conditions). The goal of this work is to avoid several Motion Estimation (ME) calls during the PU inter-prediction decision in order to reduce the execution time in the overall encoding process. The MVM algorithm is based on merging NxN PU partitions in order to compose larger ones. After the best PU partition is decided, ME is called to produce the best possible rate-distortion results for the selected partitions. The proposed method was implemented in the HM test model version 3.4 and provides an execution time reduction of up to 34% with insignificant ratedistortion losses (0.08 dB drop and 1.9% bitrate increase in the worst case). Besides, there is no related work in the literature that proposes PU-level decision optimizations. When compared with works that target CU-level fast decision methods, the MVM shows itself competitive, achieving results as good as those works.

Effective coding unit size decision based on motion homogeneity classification for HEVC inter prediction

“…Fig.7 and Fig. 8 demonstrate rate-distortion performances and encoding time performances with respect to HM12.0 reference software [10] and MVM based approach discussed in Sampaio et al [5] for two CIF sequences and Fig. 9 shows the same performance graphs for a HD sequence.…”

“…Considering the partitioning behavior of CUs with respect to inter prediction, it can be observed that blocks with similar motion tend to utilize large CUs while blocks with complex motion utilize smaller CUs [5][6][8] [9]. Fig.…”

“…A Motion Vector Merging (MVM) approach is proposed in [5] to determine the best PU size. A 34% time reduction has been achieved with respect to the HM3.4 reference software, but this approach doesn't consider the CU size decision.…”

A highly parallel SAD architecture for motion estimation in HEVC encoder

“…However, this comes at the expense of computational complexity and poses a challenge to hardware design and implementation. Profiling shows that ME unit reaches up to 96% of the encoding time [9], and SAD unit takes the majority of this complexity, especially in the case of CTB size 64x64, which can be divided into more than 600 PBs with different sizes. Sseveral hardware architectures were proposed to speed up the SAD unit for ME in HEVC [10][11][12].…”

Inter Prediction Complexity Reduction for HEVC based on Residuals Characteristics

“…Inter frame prediction alone consumes from 60% to 96% of the total encoding time [26]. In [13], inter prediction is shown to consume 84% of the encoding time while only 3% is taken by intra prediction for High Definition (HD) sequences.…”