This paper proposes a novel fast intra prediction method to optimize H.264/MPEG-4 AVC video coding. In H.264, coding performance is enhanced through spatial prediction besides temporal prediction. In its luminance intra prediction, 4 modes for 16×16 block-size and 9 directional modes for 4×4 block-size are utilized, and the optimal intra mode is selected by R-D optimization, so the intra mode selection results in high coding complexity. To reduce the complexity of intra prediction, the fast hierarchical mode selection method is proposed with fewer modes to be examined, and intermediate computing results are reused. Therefore the intra prediction mode decision process is accelerated greatly. With the proposed fast intra prediction mode selection method, the intra prediction time can be reduced above 30% with less than 2% increase of bitrate, and up to 0.04dB loss in performance compared to the brute intra prediction mode selection method in H.264 reference software. The results are obtained by encoding with all I-frames, and even less performance loss can be achieved with the same time saving if encoding in I, P and B frames. So the complexity of computation can reduce constantly.
This paper proposes a robust video transmission system over lossy packet-switched networks with block-based fine granularity scalable (B-FGS) coding including source coding, efficient rate allocation and packetization, which works effectively when packet loss occurs. The compressed B-FGS bit-stream can be truncated in fine grain for its block-based bit-plane coding at enhancement layer. Therefore channel adaptive rate allocation can be implemented and the time-varying bandwidth can be exploited efficiently. Distortion associated rate allocation method is proposed to substitute Rate-Distortion optimal rate allocation in order to reduce the streaming server’s complexity. In addition, packetizing with independent data provides robust video transmission, which restrains the error propagation across packets. Furthermore, in order to mitigate quality flicking of decoded video induced by packets loss, spatial interleaving is applied in packetizing. Thus, in proposed video transmission system, available bandwidth variation and packet loss, two key problems in video streaming applications, are well dealt with. In order to validate the effectiveness of proposed transmission system, MPEG-4 FGS transmission system and that with conditional retransmission are compared in simulations. Proposed transmission system is more robust to packet-loss errors than the other two, especially when packet-loss rate is high.
KEYWORDS: Video, Multimedia, Analytical research, Semantic video, Video coding, Internet, Personal digital assistants, Visualization, Motion estimation, Mobile devices
Along with growing up of wireless network and mobile devices, more and more users expect to access multimedia content not only by PC terminal, but also through those pervasive devices. In this paper, we proposed a content-based video-streaming framework for universal multimedia access (UMA). The framework that mainly combines the video analysis with the video streaming technology can make the pervasive device access the multimedia information at anywhere, anytime and anyhow. Our contribution of this paper is to streaming video data according to the video analysis result, the video data during transmission is no more “meaningless information” bits. We have implemented a UMA server, which customizes the video stream according to the video analysis result and the capabilities of client, and a UMA client that receives the adapted video stream.
This paper proposes the extraction scheme of global motion and object trajectory in a video shot for content-based video retrieval. Motion is the key feature representing temporal information of videos. And it is more objective and consistent compared to other features such as color, texture, etc. Efficient motion feature extraction is an important step for content-based video retrieval. Some approaches have been taken to extract camera motion and motion activity in video sequences. When dealing with the problem of object tracking, algorithms are always proposed on the basis of known object region in the frames. In this paper, a whole picture of the motion information in the video shot has been achieved through analyzing motion of background and foreground respectively and automatically. 6-parameter affine model is utilized as the motion model of background motion, and a fast and robust global motion estimation algorithm is developed to estimate the parameters of the motion model. The object region is obtained by means of global motion compensation between two consecutive frames. Then the center of object region is calculated and tracked to get the object motion trajectory in the video sequence. Global motion and object trajectory are described with MPEG-7 parametric motion and motion trajectory descriptors and valid similar measures are defined for the two descriptors. Experimental results indicate that our proposed scheme is reliable and efficient.
Sprite coding for video content is a novel coding technique for low bit-rate compression applications. It has been used in MPEG-4 standard, which is a new generation coding standard of MPEG. But the bottleneck of usage of sprite coding in the real-time coding is the speed of global motion estimation because the speed of calculation of global motion estimation is too slow at present. The fast method of sprite coding is studied in the paper. A new fast and robust approach of global motion estimation is proposed. Compared to the traditional algorithm of global motion estimation, the new algorithm is much faster, and the estimated results are comparable. The global motion estimation is the most time-consuming process in the sprite coding for video, so to accelerate the calculation of global motion estimation will increase the speed of sprite coding. Thus the approach of sprite coding using the proposed global motion estimation is challenging in real-time video coding application. The technique of robust statistics and noise filter is introduced in the algorithm of improved global motion estimation. Some comparative experimental results about sprite coding are shown at the end of paper.
Classifying different sorts of programs is very important and necessary in order to realize fast retrieval in large multimedia retrieval systems. This paper focuses on classification of sports program with motion information in MPEG domain. It is fast and efficient to analysis motion information in compressed data without the preprocessing of total decoding and many programs are compressed in MPEG- 1/MPEG-2 format. The paper proposes an approach to classify the sports programs by dominant motion information. There is motion information in forward prediction coded frames (P- frame) in MPEG compression data. The motion information can be extracted form MPEG domain. Principal component analysis method is utilized in order to get the dominant motion information from the macroblock's motion vectors, which can simplify the motion information. Principal components of motion information are used to recognize which kind of sport it belongs to with hidden Markov model after those patterns are trained with different kind of sports programs. Some testing sets are used to do some experiment in order to evaluate the performance of the method proposed in paper. Classifying sports programs with motion is available from the experimental results.
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