Low-complexity quantization for H.264/AVC

In this paper, an improved quantization technology with low-complexity is presented for H.264/AVC video codec. Multiplication factors of H.264/AVC quantizer are modified. Therefore, it is possible to reduce the bit width of the quantization and substitute large bit-width multiplier by some small bit-width adders without noticeable rate-distortion degradation in integrated circuits (ICs) design. Quantization error introduced by the modified multiplication factors is not only theoretically but also experimentally analyzed. Quantizer is optimized on register transfer level of IC design, and under the same cell CMOS technology, about 75.2% area and 76.3% dynamic power consumption are saved in each quantization unit on average compared with original H.264/AVC quantization. Experimental video coding results show that the Bjontegaard delta peak signal-to-noise ratio (PSNR) and Bjontegaard delta bit rate between the improved and original H.264/AVC quantization are very slight, which means that the improved quantization scheme is approximately the same as the original quantization scheme of H.264/AVC in rate-distortion performance.

Simple intra prediction algorithms for heterogeneous MPEG-2/H.264 video transcoders

Recent developments have given birth to H.264/AVC: a video coding standard offering better bandwidth to video quality ratios than MPEG-2. It is expected that the H.264/AVC will take over the digital video market, replacing the use of MPEG-2 in most digital video applications. The complete migration to the new video-coding algorithm will take several years given the wide scale use of MPEG-2 in the market place today. This creates an important need for MPEG-2/H264 transcoding technologies. However, given the significant differences between both encoding algorithms, the transcoding process of such systems is much more complex to other heterogeneous video transcoding processes. In this work, we start by analyzing the methods defined in the H.264 video coding standard for the intra prediction: a central element of every H.264 encoder. We then introduce and evaluate six fast intra mode decision algorithms which should enable the development of MPEG-2 to H.264 transcoders. Having evaluated all the proposed methods, we have come out with a high-efficient method, namely DC-ABS pixel. Our results show that our algorithm considerable reduces the complexity involved in the intra prediction with respect the mode decision algorithms used in H.264 JM reference software, while exhibiting a slight degradation on the RD function.. Finally, we analyze a comparative study with two of the most prominent fast intra prediction methods presented in the literature. The results show that the proposed DC-ABS pixel method achieves the best results for video transcoding applications.

Effective algorithms for fast transcoding of AVS to H.264/AVC in the spatial domain

This paper proposes a transcoding scheme from AVS to H.264/AVC. As high-compression video coding standards, H.264/AVC jointly developed by MPEG and ITU and AVS developed by the Audio Video Coding Standard Working Group of China will co-exist in the future market. Therefore, it is worthy to transcode the AVS format to the H.264/AVC format or vice versa. After an insight into the inter transcoding from AVS to H.264/AVC, a simple and effective method is proposed by reusing the mode and motion vectors to achieve high-efficient and fast transcoding. The problem in reusing the skip mode is studied and an effective method to eliminate the artifacts is proposed. Furthermore, a fast intra transcoding algorithm based on the distribution of the DCT coefficients is proposed to speed up the transcoding process. Detailed experiment results demonstrate that the proposed algorithm can effectively reduce the transcoding complexity.

Distributed Video Coding using Turbo Trellis Coded Modulation

Distributed Video Coding (DVC) has been proposed for increasingly new application domains. This rise is apparently motivated by the very attractive features of its flexibility for building very low cost video encoders and the very high built-in error resilience when applied over noisy communication channels. Yet, the compression efficiency of DVC is notably lagging behind the state-of-the-art in video coding and compression, H.264/AVC in particular. In this context, a novel coding solution for DVC is presented in this paper, which promises to improve its rate-distortion (RD) performance towards the state-of-the-art. Here, Turbo Trellis Coded Modulation (TTCM), with its attractive coding gain in channel coding, is utilized and its resultant impact in both pixel domain and transform domain DVC framework is discussed herein. Simulations have shown a significant gain in the RD performance when compared with the state-of-the-art Turbo coding based DVC implementations.

Motion mapping and mode decision for MPEG-2 to H.264/AVC transcoding

This paper describes novel transcoding techniques aimed for low-complexity MPEG-2 to H.264/AVC transcoding. An important application for this type of conversion is efficient storage of broadcast video in consumer devices. The architecture for such a system is presented, which includes novel motion mapping and mode decision algorithms. For the motion mapping, two algorithms are presented. Both efficiently map incoming MPEG-2 motion vectors to outgoing H.264/AVC motion vectors regardless of the block sizes that the motion vectors correspond to. In addition, the algorithm maps motion vectors to different reference pictures, which is useful for picture type conversion and prediction from multiple reference pictures. We also propose an efficient rate-distortion optimised macroblock coding mode decision algorithm, which first evaluates candidate modes based on a simple cost function so that a reduced set of candidate modes is formed, then based on this reduced set, we evaluate the more complex Lagrangian cost calculation to determine the coding mode. Extensive simulation results show that our proposed transcoder incorporating the proposed algorithms achieves very good rate-distortion performance with low complexity. Compared with the cascaded decoder-encoder solution, the coding efficiency is maintained while the complexity is significantly reduced.

Video collage: presenting a video sequence using a single image

The explosive growth of video data demands the video presentation technique which supports fast browsing of video content. In this paper, we present an automatic procedure for constructing a compact synthesized collage from a video sequence. The synthesized image, called “Video Collage”, is a kind of static video summary—to select the most representative images from video, to extract salient regions of interest (ROIs) from these images, and to seamlessly arrange ROIs on a given canvas with the temporal structure of video content preserved. We formulate the generation of Video Collage as a unified energy minimization problem in which each of above desirability is represented by an energy term. We start from the basic setting of Video Collage in which both the shape of ROIs and collage are fixed as rectangular, and then show how it can support arbitrary shapes of ROIs, as well as a variety of collage templates and region of interest (ROI) arrangement layouts (i.e., book, diagonal, and spiral). The experiments show its effectiveness to present a video in a very compact and visually appealing form while preserving the necessary information to understand the video.

Accelerating the multiple reference frames compensation in the H.264 video coder

Using the multiple reference frames compensation in the H264 coder improves the coding efficiency for sequences which contain uncovered backgrounds, repetitive motions and highly textured areas. Unfortunately this technique requires excessive memory and computation resources. In this article, we proposed and implemented a technique based on Markov Random Fields Algorithm relying on robust moving pixel segmentation. By the introduction of this technique, we were able to decrease the number of reference frames from five to three while keeping similar video coding performances. The coding time decreased by 35% and the sequence quality was preserved. After the validation of our idea, we evaluated the processing time of the Markov algorithm on architectures intended for embedded multimedia applications. Both DSP and FPGA implementations were explored. We were able to process 50 frames(128 × 128)/s on the EP1S10 FPGA paltform and 35 frames(128 × 128)/s on the ADSP BF533.

Fast video transcoding from H.263 to H.264/MPEG-4 AVC

In the past 10 years detailed works on different video transcoders have been published. However, the new ITU-T Recommendation H.264—also adapted as ISO/IEC MPEG-4 Part 10 (AVC)—provides many new encoding options for the prediction processes that lead to difficulties for low complexity transcoding. In this work we present very fast transcoding techniques to convert H.263 bitstreams into H.264/AVC bitstreams. We will give reasoning, why the proposed pixel domain approach is advantageous in this scenario instead of using a DCT domain transcoder. Our approach results in less than 9% higher data rate at equivalent PSNR quality compared to a full-search approach. But this rate loss allows the reduction of the search complexity by a factor of over 200 for inter frames and still a reduction of over 70% for intra frames. A comparison to a fast search algorithm is given. We also provide simulation results that our algorithm works for transcoding MPEG-2 to H.264/AVC in the aimed scenario.

Efficient video encryption scheme based on advanced video coding

A video encryption scheme combining with advanced video coding (AVC) is presented and analyzed in this paper, which is different from the ones used in MPEG1/2 video encryption. In the proposed scheme, the intra-prediction mode and motion vector difference are encrypted with the length-kept encryption algorithm (LKE) in order to keep the format compliance, and the residue data of the macroblocks are encrypted with the residue data encryption algorithm (RDE) in order to keep low cost. Additionally, a key distribution scheme is proposed to keep the robustness to transmission errors, which assigns sub-keys to different frames or slices independently. The encryption scheme’s security, time efficiency and error robustness are analyzed in detail. Experimental results show that the encryption scheme keeps file format unchanged, is secure against replacement attacks, is efficient in computing, and is robust to some transmission errors. These properties make it a suitable choice for real-time applications, such as secure IPTV, secure videoconference or mobile/wireless multimedia, etc.

Streaming of scalable h.264 videos over the Internet

To investigate the benefits of scalable codecs in the case of rate adaptation problem, a streaming system for scalable H.264 videos has been implemented. The system considers congestion level in the network and buffer status at the client during adaptation process. The rate adaptation algorithm is content adaptive. It selects an appropriate substream from the video file by taking into account the motion dynamics of video. The performance of the system has been tested under congestion-free and congestion scenarios. The performance results indicate that the system reacts to congestion properly and can be used for Internet video streaming where losses occur unpredictably.

Mixed architectures for H.264/AVC digital video transrating

In this paper, we investigate transrating architectures for H.264/AVC video streams. Basic architectures are presented with their strengths and weaknesses. None of the existing architectures provide an appropriate solution for H.264/AVC transrating with an optimal balance between visual quality and complexity. In order to find such an appropriate solution, we propose the use of mixed transrating architectures. These architectures combine different transrating techniques which are applied depending on the picture/macroblock type. The intra-predicted pictures are decoded and re-encoded, while open-loop transrating or transrating with compensation is applied to motion-compensated pictures. Performance results show that the mixed architecture which applies spatial compensation to motion-compensated pictures gives rate-distortion results which approach the cascade of decoder and re-encoder with a complexity only slightly higher than the open-loop transrater. Adding temporal compensation for motion-compensated pictures further improves the visual quality, albeit to a lower extent, at the expense of increased complexity.

Architecture of an application-specific processor for real-time implementation of H.264/AVC sub-pixel interpolation

This paper presents an efficient VLSI architecture for fast implementation of sub-pixel interpolation of H.264/AVC. Several optimization techniques at different design levels, such as parallel processing, vector register, pipeline architecture, and in-place computation, are utilized to reduce the number of memory access and accelerate the interpolation computations. The proposed application-specific processor can meet the real-time constraint of the sub-pixel interpolation algorithm for the 16:9 video format (4,690 × 2,304) at 30 frames per second (fps) at 100 MHz clock rate.

Distributed video coding based on part intracoding and soft side information estimation

Recently, distributed source coding (DSC) has been proposed to implement source compression by exploiting source statistics at the decoder only, which enables low-complexity video coding. However, to date, the video codecs based on DSC have been unable to compress as efficiently as traditional predictive video codecs, such as H.264. So, new techniques have to be investigated to improve the performance of the distributed video coding scheme for practical applications. In this paper, I propose a novel distributed video coding scheme based on part intracoding and soft side information estimation. Firstly, at the encoder side, to improve the compression performance of distributed video coding system, we divide the video data into strongly correlative data encoded by Slepian–Wolf codec and weakly correlative data encoded by Intracoding codec. Secondly, at the decoder side, to improve the accuracy of side information estimation, a soft side information estimation method is proposed, which is more suitable for video coding due to the non-stationary feature of video data. Our experimental results show that the performance of our coding system is better than that of the traditional distributed video coding system while keeping the simple encoding property. Also the concept of soft side information is a new idea in distributed video coding and will significantly influence the side information estimation method.

A first approach to speeding-up the inter mode selection in MPEG-2/H.264 transcoders using machine learning

The H.264 standard achieves much higher coding efficiency than the MPEG-2 standard, due to its improved inter and intra prediction modes which come with a cost of higher computation complexity. Transcoding MPEG-2 video to H.264 is important to enable gradual migration to H.264. However, given the significant differences between the MPEG-2 and the H.264 coding algorithms, transcoding is much more complex and new approaches to transcoding are necessary. In this paper, we introduce and evaluate a low complexity macroblock partition mode decision algorithm, to be used as part of a high-efficient inter-frame prediction in MPEG-2 to H.264 transcoder. The proposed tools are used to compute an optimal MB coding mode decision with significantly reduced computational complexity. Specifically, we achieve the computational savings by using the following MB information coming from MPEG-2: the MB coding modes, the coded block pattern (CBPC) in MPEG-2, and the mean and variance of the 16 4 × 4 sub blocks of the MPEG-2 residual MBs. We use data mining algorithms to develop a decision tree for H.264 coding mode decisions. The decision trees are built using RD optimized mode decisions and result in highly efficient mode decisions, with significantly reduced computational complexity. The proposed transcoder is 35% faster than the RD optimized H.264 reference transcoder without a significant PSNR degradation (0.05 dB on average). The proposed transcoder performs over 0.4 dB better on average than the SAE cost based H.264 transcoding.

Real time data hiding by exploiting the IPCM macroblocks in H.264/AVC streams

A new method for data hiding in H.264/AVC streams is presented. The proposed method exploits the IPCM encoded macroblocks during the intra prediction stage in order to hide the desired data. It is a blind data hiding scheme, i.e. the message can be extracted directly from the encoded stream without the need of the original host video. Moreover, the method exhibits the useful property of reusing the compressed stream for hiding different data numerous times without considerably affecting either the bit-rate or the perceptual quality. This property allows data hiding directly in the compressed stream in real time. The method perfectly suits to covert communication and content authentication applications.

Transform coding on programmable stream processors

Stream processors can achieve high performance in stream applications that share stream characteristics of large parallelism, intensive computation and little data reuse. Transform coding, as a core component in video compression, is widely used in video storage and video transmission. This paper summarizes stream execution mechanism and explores design approaches of programmable stream processors including the Imagine stream processor and graphics processing unit (GPU). Based on the stream processing model, stream algorithms for block-based and frame-based (nonblock-based) transform coding are presented and mapped onto stream processors. Especially, an Interleaved Streaming Transform (IST) algorithm on Imagine and a Row-wise Zonal Transform (RZT) algorithm on GPU for 4×4 integer transform in H.264 are proposed to exploit great potential of stream processing for block-based transform. Our experiments of transform coding suite on Imagine and GPU show that the coding efficiency of stream processors is far beyond the real-time requirements of current video applications, dealing with a variety of different video resolutions ranging from QCIF to high definition (HD). The performance evaluation of stream implementations discusses the architectural supports for transform coding, and presents the significant improvements over other programmable platforms. Transform coding may take advantage of the flexibility of programmable stream processors with high performance to play an important role in the future.

Security and privacy for multimedia database management systems

This paper describes security and privacy issues for multimedia database management systems. Multimedia data includes text, images, audio and video. It describes access control for multimedia database management systems and describes security policies and security architectures for such systems. Privacy problems that result from multimedia data mining are also discussed.