CNN Accelerated Intra Video Coding, Where Is the Upper Bound? The very high complexity of the High Efficiency Video Coding standard (HEVC) is the main hurdle for its wide deployment and use. To tackle this problem, a number of recent research outcomes exploit Convolutional Neural Network (CNN) in each HEVC module for reducing the coding complexity. In this paper an effective method to analyse the potential of CNN techniques to reduce the computational cost of HEVC is proposed. A theoretical upper bound for the effectiveness of this approach in common HEVC modules is investigated. The theoretical maximum of learningbased complexity reduction in HEVC and possible reasons for RateDistortion (RD) loss are investigated. On the basis of this analysis, an Intra Video Coding Acceleration (IVCA) scheme is proposed, where Border Considered CNN (BCCNN) based Coding Unit (CU) partition and heuristic Prediction Unit (PU) partition are seamlessly integrated. According to the experimental results, 66.7% of intra coding time can be saved with negligible 1.71% Bjontegaard delta bitrate (BDBR) loss. These results partially demonstrate the superiority of the proposed technique against other stateoftheart approaches aiming at reducing HEVC complexity in intra mode.

An IBPCNN Based Fast Block Partition For Intra Prediction The increase of block size to 64xc3x9764 in HEVC leads to the increase of computational complexity of intra prediction. The convolution neural network (CNN) shows advantages in the extraction and application of image features than the traditional intra prediction optimization algorithm which is developed manually. For reducing the computational complexity of intra prediction, a CNNbased algorithm, intra block partition CNN (IBPCNN) is proposed in this paper to get the block partition. First, a database which is consisted of coding tree unit (CTU) images and label images is established. The position of pixels in the label images are consistent with those in CTU images. Second, the texture features are analyzed by IBPCNN to get the block partition. Then the output of the network is adjusted according to the quadtree structure of HEVC to facilitate the calculation of rate distortion (RD) cost. The method proposed in this paper reduces the average coding time of about 59.07% and the average BDrate is about 1.55%.