Chroma Block Research Articles

Integer Modified Sine-Cosine Transforms Type VII. A construction Method and Separable Directional Adaptive Transforms for Intra Prediction with 8 × 8 Chroma Blocks in Image/Video Coding

A matrix method for constructing a modified order-8 integer sine-cosine transform type VII is proposed. Based on the method, two order-8 integer modified sine-cosine transforms type VII are constructed and algorithms for fast computing of these transforms are developed, which require only integer operations. These algorithms are of low multiplicative complexity, which is 7 and 10.5 times less, and they require 23.3 and 44.2% less additional operations than the well-known algorithm of the discrete sine transform type VII. These transforms have higher coding gain performance for quality and compression ratio compared to the well-known sine transforms. Algorithms for fast computing of 2D separate directional integer cosine and modified sine-cosine type VII adaptive transforms for intra prediction with 8 × 8 chroma blocks are developed. These algorithms have low multiplicative complexity, which is 6.6 and 16.5 times less than that of the well-known algorithms.

A Semi-fragile Video Watermarking Algorithm Based On Chromatic Residual DCT

In this paper, a semi fragile video watermarking scheme based on chromatic DCT is proposed, which can protect copyright and tamper detection simultaneously. Firstly, through the experiment, it is found that the chroma block has a more stable prediction mode relative to the luminance block, which can effectively reduce the asynchronous probability brought by the change of the prediction mode. At the same time, blocks contains more the number of nonzero (NNZ) coefficients, the less the prediction mode changes. Therefore, for each macroblock, the algorithm sort its 4 × 4 sub macroblock according to the NNZ of chroma DCT coefficients, then select the sub block which has most NNZ residual coefficients. According to the secret key K and medium frequency stability of Intra 4 × 4 coefficients, modulate the relationship of three DCT coefficients near medium frequency. Secondly, the sensitivity of the prediction mode to malicious attacks and recompression operations is different. Therefore, the algorithm classifies the prediction mode of the macroblock and generates the authentication code using the prediction mode. The experimental results show that the video quality is negligible affected after watermark embedding, and the change of video bit rate is basically constant. At the same time, the chromatic DCT algorithm can also use the authentication code of the prediction mode to detect and locate the tampering at the 4 × 4 sub block level with good robustness.

High-Throughput Deblocking Filter Architecture Using Quad Parallel Edge Filter for H.264 Video Coding Systems

With the increasing demand in electronic gadgets expecting better video quality for multimedia applications, various coding standards evolved for the past two decades and optimization on the architectures of the various modules used in the video codec is most popular. In this paper, an efficient architecture for deblocking filter used to smoothen the pixels of the decompressed video data is proposed, which utilizes both pipelining and parallelism. The filtering process follows a sequential order as filtering vertical edges of luma block and chroma block followed by the horizontal edges of the luma block and chroma block. Three pipeline stages are used and four edges, either vertical or horizontal are filtered in parallel. Internal buffers which hold the sub-blocks read from the external frame buffers are accessed in a ping pong fashion to filter the adjacent sub-edges and thus reducing the external memory access cycles. Due to parallelism with novel edge filtering order, self-transposing mechanism, and ping pong buffer access, the throughput is increased. The proposed quad parallel edge deblocking filter architecture is implemented using Synopsys 90 nm library. It achieves a target area of 19.8 K and can process a Macro Block in 58 clock cycles.

Reduction of intra-coding time for HEVC based on temporary direction map

The high-efficiency video coding (HEVC) standard uses 35 intra-prediction modes for 2N × 2N (N is an integer number ranging from six to two) luma blocks and five modes for chroma blocks. To find the luma block with the minimum rate–distortion, it must perform 11935 different rate–distortion cost calculations. Although this approach improves coding efficiency compared to the previous standards such as H.264/AVC, computational complexity is increased significantly. In this paper, an intra-prediction technique has been described to improve the performance of the HEVC standard by minimizing its computational complexity. The proposed algorithm consists of two stages. The first stage, called prediction unit size decision (PUSD) was introduced to decrease evaluation of prediction unit sizes by ~ 38%. The second stage called prediction mode fast decision (PMFD) was developed to minimize the number of modes in the rough mode decision (RMD) stage. The simulation results show that the time complexity is decreased by ~ 47%, while the BD rate is increased by 1.08%, and PSNR is decreased by 0.04 db. Accordingly, the proposed algorithms have a negligible effect on the video quality with great saving in the time complexity.

Gravity direction-based ultra-fast intraprediction algorithm for H.264/AVC video coding

The H.264/AVC video coding standard uses in intraprediction, 9 directional modes for 4 × 4 and 8 × 8 luma blocks, and 4 directional modes for 16 × 16 luma macroblocks, and 8 × 8 chroma blocks. The use of the variable block size and multiple modes in intraprediction makes the intracoding of H.264/AVC very efficient compared with other compression standards; however, computational complexity is increased significantly. In this paper, we propose a fast mode selection algorithm for intracoding. This algorithm is based on the vector of the block’s gravity center whose direction is used to select the best candidate prediction mode for intracoding. On this basis, only a small number of intraprediction modes are chosen for rate distortion optimization (RDO) calculation. Different video sequences are used to test the performance of proposed method. The simulation results show that the proposed algorithm increases significantly the speed of intracoding with negligible loss of peak signal-to-noise ratio quality.