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International audienceThe use of multiple transforms in video coding can lead to substantial bit-rate savings. However, these savings come at the expense of increased coding complexity and storage requirements, which challenge the usability of this approach. In this paper, a systematic procedure is proposed to design low complexity systems making use of transform competition. Multiple trade-offs accommodating the complexity are unveiled and it is demonstrated that they can keep a certain level of performance. Compared to the HEVC standard, some of them provide bit-rate savings around 2% with a 50% increase in the encoding time, using less than 4 kB of extra ROM and no added decoding complexity. © 2016 IEEE

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The high efficiency video coding (HEVC) standard and the joint exploration model (JEM) codec incorporate 35 and 67 intra prediction modes (IPMs) respectively, which are essential for efficient compression of Intra coded blocks. These IPMs are transmitted to the decoder through a coding scheme. In our paper, we present an innovative approach to construct a dedicated coding scheme for IPM based on contextual information. This approach comprises three key steps: prediction, clustering, and coding, each of which has been enhanced by introducing new elements, namely, labels for prediction, tests for clustering, and codes for coding. In this context, we have proposed a method that utilizes a genetic algorithm to minimize the rate cost, aiming to derive the most efficient coding scheme while leveraging the available labels, tests, and codes. The resulting coding scheme, expressed as a binary tree, achieves the highest coding efficiency for a given level of complexity. In our experimental evaluation under the HEVC standard, we observed significant bitrate gains while maintaining coding efficiency under the JEM codec. These results demonstrate the potential of our approach to improve compression efficiency, particularly under the HEVC standard, while preserving the coding efficiency of the JEM codec.

International audienceThe High Efficiency Video Coding (HEVC) standard defines 35 Intra Prediction Modes (IPM) to provide an efficient compression of intra coded blocks. Those IPMs are signalled to the decoder through the use of three compression tools: prediction, clustering and coding. In this paper we provide improvements to these three tools through: new labels for the prediction, new tests for the clustering and new coding schemes for the coding. The most significant improvement consists in the provision of a cluster-dependent code: adapting the coding scheme to the available information enables the average symbol cost to get within close margin of the entropy of the data. The system providing the best compression efficiency based on these improvements is then computed, enabling significant reduction in the average cost required to code the IPMs. The proposed method builds a new coding system with the same complexity as HEVC with 0.41% bit-rates savings in All Intra coding configuration