Increased compression efficiency of AVC and HEVC CABAC by precise statistics estimation

The paper presents Improved Adaptive Arithmetic Coding algorithm for application in future video compression technology. The proposed solution is based on the Context-based Adaptive Binary Arithmetic Coding (CABAC) technique and uses the authors’ mechanism of symbols probability estimation that exploits Context-Tree Weighting (CTW) technique. This paper proposes the version of the algorithm, that allows an arbitrary selection of depth of context trees, when activating the algorithm in the framework of the AVC or HEVC video encoders. The algorithm has been tested in terms of coding efficiency of data and its computational complexity. Results showed, that depending of depth of context trees from 0.1% to 0.86% reduction of bitrate is achieved, when using the algorithm in the HEVC video encoder and 0.4% to 2.3% compression gain in the case of the AVC. The new solution increases complexity of entropy encoder itself, however, this does not translate into increase the complexity of the whole video encoder

HEVC encoding assisted with noise reduction

Optimization of encoding process in video compression is an important research problem, especially in the case of modern, sophisticated compression technologies. In this paper, we consider HEVC, for which a novel method for selecting of the encoding modes is proposed. By the encoding modes we mean e.g. coding block structure, prediction types and motion vectors. The proposed selection is done basing on noise-reduced version of the input sequence, while the information about the video itself, e.g. transform coefficients, is coded basing on the unaltered input. The proposed method involves encoding of two versions of the input sequence, further, we show realization proving that the complexity is only negligibly higher than complexity of a single encoding. The proposal has been implemented in HEVC reference software from MPEG and tested experimentally. The results show that the proposal provides up to 1.5% bitrate reduction while preserving the same quality of a decoded video

Analysis of Compressed Data Stream Content in HEVC Video Encoder

In this paper, a detailed analysis of the content of the bitstream, produced by the HEVC video encoder is presented. With the use of the HM 10.0 reference software the following statistics were investigated: 1) the amount of data in the encoded stream related to individual frame types, 2) the relationship between the value of the QP and the size of the bitstream at the output of the encoder, 3) contribution of individual types of data to I and B frames. The above mentioned aspects have been thoroughly explored for a wide range of target bitrates. The obtained results became the basis for highlighting guidelines that allow for efficient bitrate control in the HEVC encoder

A browser based system for remote evaluation of subjective quality of videos

The evaluation of the quality of videos is posing a significant problem in research on video processing, including compression. Different algorithms and their modifications aim to improve the quality of the video, while keeping the necessary bitrate as low as possible, and every time, the performance of the method must be evaluated. The bitrate can be measured readily, while for quality there are different metrics and, therefore – different results. The ultimate verdict always has to be the subjective opinion about the quality that is expressed by the viewers. For now, the only reliable way to measure the quality of the video is to perform a subjective test with a group of viewers. Subjective tests are difficult to perform – not only one has to gather all viewers in one place, but also the evaluation schemes may be difficult to follow. In the paper we present an implementation of a system that greatly simplifies the process of performing the subjective quality assessment of videos. We discuss strengths and weaknesses of the system when compared to the commonly used procedures. Finally, we also provide the results of a quality assessment for the HEVC video encoder. Presented data proves that the idea of remote quality evaluation together with the usage of the two-level grade is a valid one and provides reliable results

Analysis of the Limitations of Further Improvement of the Efficiency of VVC-CABAC

Hybrid video compression plays an invaluable role in digital video transmission and storage services and systems. It performs several-hundred-fold reduction in the amount of video data, which makes these systems much more efficient. An important element of hybrid video compression is entropy coding of the data. The state-of-the-art in this field is the newest variant of the Context-based Adaptive Binary Arithmetic Coding entropy compression algorithm which recently became part of the new Versatile Video Coding technology. This work is a part of research that is currently underway to further improve the Context-based Adaptive Binary Arithmetic Coding technique. This paper provides analysis of the potential for further improvement of the Context-based Adaptive Binary Arithmetic Coding technique by more accurate calculation of probabilities of data symbols. The mentioned technique calculates those probabilities by the use of idea of the two-parameters hypothesis. For the needs of analysis presented in this paper, an extension of the aforementioned idea was proposed which consists of three- and four-parameters hypothesis. In addition, the paper shows the importance of proper calibration of parameter values of the method on efficiency of data compression. Results of experiments show that for the considered in the paper variants of the algorithm improvement the possible efficiency gain is at levels 0.11% and 0.167%, for the three- and four-parameter hypothesis, respectively