Optimal Global Threshold based on Two Dimension Otsu for Block Size Decision in Intra Prediction of H.264/AVC Coding

Abstract

The Advanced Video Coding (H.264/AVC) has proved its ability in finding the tradeoff between the compressed bit rate value and the visual quality of video comparing to the others of traditional coding. One of the most encoder stages consuming time is the intra prediction in which different sizes of a block are exhaustively examined for selecting the suitable block size to the best block mode decision. In this paper, an efficient approach is suggested to select the best block size for the intra prediction adaptively to achieve high compression efficiency. The proposed approach exploits the idea of quad tree decomposition for blocks partitioning based on a predefined threshold value. An optimal global threshold value based on two dimension Otsu technique is suggested for the decision of block division in this work. The proposed technique is carried out on different set of videos resolutions with different quantization parameters using Matlab software. The comparison of the proposed approach with the reference JM18.6 video coding is done in terms of bit rate (BR), time saving and peak signal to noise ratio (PSNR). A tangible acceleration on the running time can be accomplished besides improvement in both of visual quality and bit rate with some of QCIF and CIF videos resolution by the proposed technique. The simulation results demonstrate saving in time by average 42% to 68% with CIF and QCIF videos. Concerning the visual quality in terms of Bjontegaard Delta parameters, the PSNR improved in which its value increased from 0.2 to 1.6, while the value of BR reduced from 0.79 to 15.3 respectively with some videos of resolutions QCIF, CIF and 720p. In addition, the performance of the suggested approach with the high resolution videos achieves minor improvement with some of them while has a slightly degradation with others of them.

Image Segmentation Methods for Subpicture Partitioning in the VVC Video Encoder

“…In [20], the Otsu method was utilized in order to determine the complexity of each largest coding unit (LCU) and reduce the number of depth levels checked during the coding unit (CU) mode decision. In [21], an optimal threshold value was determined, using the 2-D Otsu method [22], [23], to accelerate the block size decision in intra-prediction for H.264. The proposed method calculates an appropriate threshold value that is then used in order to divide an image into blocks of size 4x4 or 16x16 pixels.…”