Xuan Jing

An efficient three-step search algorithm for block motion estimation

The three-step search algorithm has been widely used in block matching motion estimation due to its simplicity and effectiveness. The sparsely distributed checking points pattern in the first step is very suitable for searching large motion. However, for stationary or quasistationary blocks it will easily lead the search to be trapped into a local minimum. In this paper we propose a modification on the three-step search algorithm which employs a small diamond pattern in the first step, and the unrestricted search step is used to search the center area. Experimental results show that the new efficient three-step search performs better than new three-step search in terms of MSE and requires less computation by up to 15% on average.

Frame Complexity-Based Rate-Quantization Model for H.264/AVC Intraframe Rate Control

In this letter, we present an adaptive intraframe rate-quantization (R-Q) model for H.264/AVC video coding. The proposed method aims at selecting accurate quantization parameters (QP) for intra-coded frames according to the target bit rate. By taking gradient-based frame complexity measure into consideration, the model parameters can be adaptively updated. Experimental results show that when employing our proposed R-Q model, the intraframe target bits mismatch ratio can be reduced by up to 75% as compared to the traditional Cauchy-density-based model. Hence, this is extremely useful for H.264/AVC rate control applications.

A novel intra-rate estimation method for H.264 rate control

In this paper, we present a novel intra-rate estimation method for H.264 rate control. The proposed method establishes the intra-frame rate-quantization (R-Q) estimation model by using gradient-based picture complexity measure. The proposed model aims at selecting accurate quantization parameters for intra-coded frames which can fully comply with buffer constraints. By adaptively updating this R-Q model, the performance of the model can be guaranteed regardless of the changing of video frame characteristics. Simulation results show that by using our proposed scheme, better rate control for intra-frames and frames at scene changes can be achieved. As a result, the number of skipped frames is significantly reduced thus it provides improved visual quality of the reconstructed pictures

An efficient inter mode decision approach for H.264 video coding

Variable size block motion estimation is a very important technique for video coding. The new H.264 standard employs 7 different size block types which can significantly improve the coding performance compared with the previous video coding standards. On the other hand, the computational complexity of H.264 encoder increases dramatically due to the various coding modes used. In this paper, an efficient inter mode decision approach is presented. The objective is to reduce the number of candidate block types in the motion estimation while maintaining the coding efficiency. Experimental results show that the proposed method can save the computation cost by up to 42% at the same PSNR and bitrate

Efficient three-step search algorithm for block motion estimation in video coding

The three-step search algorithm has been widely used in block matching motion estimation due to its simplicity and effectiveness. The sparsely distributed checking points pattern in the first step is very suitable for searching large motion. However, for quasi-stationary blocks it will easily lead the search to be trapped into a local minimum. In this paper we propose a modification on the three-step search algorithm which employs a small diamond pattern in the first step, and the unrestricted search step is used to search the center area. Experimental results show that the proposed algorithm performs better than new three-step search in terms of MSE and requires less computation by up to 15% on average.

Smooth constrained motion estimation for video coding

In this paper, a novel and efficient criterion for block matching motion estimation is presented. The proposed criterion is to enhance the conventional mean absolute difference (MAD) scheme with a new smoothness constraint on the residue block. The objective is to reduce the bit rate for encoding the residue image without any degradation of the reconstructed image quality. Simulation results show that by applying the new criterion in motion estimation, both the improvement in peak signal-to-noise ratio (PSNR) and the reduction in bit rate up to 4.3% can be achieved compared to MAD.

Partial Distortion Search Algorithm Using Predictive Search Area for Fast Full-Search Motion Estimation

In this letter, a fast partial distortion search algorithm for motion estimation is presented. The proposed method is based on the observation that when normalized partial distortion is utilized, the false rejection of impossible candidates most likely occurs within a small area adjacently located near the true motion vector. Our objective is to enhance the prediction accuracy in this small predictive search area and further save computations outside this area. Experimental results show that the proposed algorithm achieves an average 42 times speedup ratio as compared to full-search algorithm with only 0.05 dB degradation in PSNR performance.

Improved Frame Level MAD Prediction and Bit Allocation Scheme for H.264/AVC Rate Control

In this paper, we present an improved frame level mean absolute difference (MAD) prediction model for H.264/AVC rate control. Based on the histogram information of successive frames, the MAD of current frame can be accurately estimated. Instead of only using buffer status in the frame target bits allocation process, we also take into consideration the frame complexity which depends on the improved predicted frame MAD value. The objective of this frame complexity based bit allocation is to follow the non-stationary characteristics of video source and to provide smoother visual quality. Simulation results show that by using our proposed scheme, smaller frame target bits mismatch can be achieved. In addition, the average peak signal-to-noise ratio (PSNR) for the reconstructed video is improved by up to 0.5 dB with up to 62% reduction in picture quality variation.

Efficient inter mode decision for H.263 to H.264 video transcoding using support vector machines

This paper presents an efficient mode decision algorithm for H.263 to H.264 interframe transcoding. The proposed scheme uses a support vector machines (SVMs) approach to investigate the relationship between data extracted from H.263 decoding stage and the optimal coding mode in H.264 re-encoding process. Based on the SVM classifier, the transcoder only enables a subset of candidate modes for each macroblock in the rate-distortion-optimized mode decision in H.264. The objective is to eliminate unlikely modes in earlier stages in order to achieve computation saving. Simulation results show that the proposed method can reduce the computational complexity of interframe transcoding by up to 77% while maintaining similar rate-distortion performance.

Fast intra mode decision algorithm for H.263 to H.264/AVC transcoding

In this paper, we present a fast mode decision method for H.263 to H.264/AVC intraframe transcoding. The proposed algorithm is based on the observation that features of DCT coefficients extracted from H.263 coded intraframe strongly relates to the optimal mode in H.264/AVC intra mode decision. Specifically, the total number of non-zero AC coefficients of four 8times8 DCT blocks in H.263 is taken as a measurement in the intra block size decision. The objective is to reject improbable block types in earlier stages in order to achieve computation saving. In addition, a transform domain edge direction estimation is also adopted into our scheme to further speed up the intra mode prediction. Simulation results show that the proposed approach can reduce the computational complexity of intraframe transcoding by up to 65% while maintaining the rate-distortion (R-D) performance.