Biblio
Context-based adaptive binary arithmetic coding (CABAC) is the only entropy coding method in HEVC. According to statistics, CABAC encoders account for more than 25% of the high efficiency video coding (HEVC) coding time. Therefore, the improved CABAC algorithm can effectively improve the coding speed of HEVC. On this basis, a selective encryption scheme based on the improved CABAC algorithm is proposed. Firstly, the improved CABAC algorithm is used to optimize the regular mode encoding, and then the cryptographic algorithm is used to selectively encrypt the syntax elements in bypass mode encoding. The experimental results show that the encoding time is reduced by nearly 10% when there is great interference to the video information. The scheme is both safe and effective.
Advances in virtual reality have generated substantial interest in accurately reproducing and storing spatial audio in the higher order ambisonics (HOA) representation, given its rendering flexibility. Recent standardization for HOA compression adopted a framework wherein HOA data are decomposed into principal components that are then encoded by standard audio coding, i.e., frequency domain quantization and entropy coding to exploit psychoacoustic redundancy. A noted shortcoming of this approach is the occasional mismatch in principal components across blocks, and the resulting suboptimal transitions in the data fed to the audio coder. Instead, we propose a framework where singular value decomposition (SVD) is performed after transformation to the frequency domain via the modified discrete cosine transform (MDCT). This framework not only ensures smooth transition across blocks, but also enables frequency dependent SVD for better energy compaction. Moreover, we introduce a novel noise substitution technique to compensate for suppressed ambient energy in discarded higher order ambisonics channels, which significantly enhances the perceptual quality of the reconstructed HOA signal. Objective and subjective evaluation results provide evidence for the effectiveness of the proposed framework in terms of both higher compression gains and better perceptual quality, compared to existing methods.
The enormous size of video data of natural scene and objects is a practical threat to storage, transmission. The efficient handling of video data essentially requires compression for economic utilization of storage space, access time and the available network bandwidth of the public channel. In addition, the protection of important video is of utmost importance so as to save it from malicious intervention, attack or alteration by unauthorized users. Therefore, security and privacy has become an important issue. Since from past few years, number of researchers concentrate on how to develop efficient video encryption for secure video transmission, a large number of multimedia encryption schemes have been proposed in the literature like selective encryption, complete encryption and entropy coding based encryption. Among above three kinds of algorithms, they all remain some kind of shortcomings. In this paper, we have proposed a lightweight selective encryption algorithm for video conference which is based on efficient XOR operation and symmetric hierarchical encryption, successfully overcoming the weakness of complete encryption while offering a better security. The proposed algorithm guarantees security, fastness and error tolerance without increasing the video size.