High Efficiency Video Coding (HEVC) significantly reduces bit-rates over the proceeding H.264 standard but at the expense of extremely high encoding complexity. In HEVC, the quad-tree partition of coding unit (CU) consumes a large proportion of the HEVC encoding complexity, due to the bruteforce search for rate-distortion optimization (RDO). Therefore, this paper proposes a deep learning approach to predict the CU partition for reducing the HEVC complexity at both intraand inter-modes, which is based on convolutional neural network (CNN) and long-and short-term memory (LSTM) network. First, we establish a large-scale database including substantial CU partition data for HEVC intra-and inter-modes. This enables deep learning on the CU partition. Second, we represent the CU partition of an entire coding tree unit (CTU) in the form of a hierarchical CU partition map (HCPM). Then, we propose an early-terminated hierarchical CNN (ETH-CNN) for learning to predict the HCPM. Consequently, the encoding complexity of intra-mode HEVC can be drastically reduced by replacing the brute-force search with ETH-CNN to decide the CU partition. Third, an early-terminated hierarchical LSTM (ETH-LSTM) is proposed to learn the temporal correlation of the CU partition. Then, we combine ETH-LSTM and ETH-CNN to predict the CU partition for reducing the HEVC complexity for intermode. Finally, experimental results show that our approach outperforms other state-of-the-art approaches in reducing the HEVC complexity at both intra-and inter-modes. Index Terms-High efficiency video coding, complexity reduction, deep learning, convolutional neural network, long-and short-term memory network.
This approach was extended in REF to reduce the encoding time of both intra and inter modes using a combination of a CNN with a long short-term memory (LSTM) architecture.
Reducing Complexity of HEVC: A Deep Learning Approach
Published in IEEE Transactions on Image Processing, Oct. 2018
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