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Circuits and Systems for Video Technology, IEEE Transactions on

Issue 11 • Date Nov 2002

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Displaying Results 1 - 9 of 9
  • Drift compensation for reduced spatial resolution transcoding

    Page(s): 1009 - 1020
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (575 KB) |  | HTML iconHTML  

    This paper discusses the problem of reduced-resolution transcoding of compressed video bitstreams. An analysis of drift errors is provided to identify the sources of quality degradation when transcoding to a lower spatial resolution. Two types of drift error are considered: a reference picture error, which has been identified in previous works, and error due to the noncommutative property of motion compensation and down-sampling, which is unique to this work. To overcome these sources of error, four novel architectures are presented. One architecture attempts to compensate for the reference picture error in the reduced resolution, while another architecture attempts to do the same in the original resolution. We present a third architecture that attempts to eliminate the second type of drift error and a final architecture that relies on an intrablock refresh method to compensate for all types of errors. In all of these architectures, a variety of macroblock level conversions are required, such as motion vector mapping and texture down-sampling. These conversions are discussed in detail. Another important issue for the transcoder is rate control. This is especially important for the intra-refresh architecture since it must find a balance between number of intrablocks used to compensate for errors and the associated rate-distortion characteristics of the low-resolution signal. The complexity and quality of the architectures are compared. Based on the results, we find that the intra-refresh architecture offers the best tradeoff between quality and complexity and is also the most flexible. View full abstract»

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  • Variable complexity DCT approximations driven by an HVQ-based analyzer

    Page(s): 1021 - 1024
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    Transform approximations are explored for speeding up the software compression of images and video. Approximations are used to replace the regular discrete cosine transform (DCT) whenever only a few DCT coefficients are actually encoded. We employ a novel hierarchical vector quantization (HVQ)-based image analyzer to drive a bank of coders, thus switching to the fastest coder depending on the image contents: smoother areas would produce less bits than detailed ones but faster. The HVQ analyzer is fast and simple enough to not offset the complexity gains brought by the DCT approximations. The approximations in this paper are applicable to high compression environments, where lower complexity is also required. View full abstract»

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  • Rate-constrained multihypothesis prediction for motion-compensated video compression

    Page(s): 957 - 969
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (727 KB) |  | HTML iconHTML  

    This paper investigates linearly combined motion-compensated signals for video compression. In particular, we discuss multiple motion-compensated signals that are jointly estimated for efficient prediction and video coding. First, we extend the wide-sense stationary theory of motion-compensated prediction (MCP) for the case of jointly estimated prediction signals. Our theory suggests that the gain by multihypothesis MCP is limited and that two jointly estimated hypotheses provide a major portion of this achievable gain. In addition, the analysis reveals a property of the displacement error of jointly estimated hypotheses. Second, we present a complete multihypothesis codec which is based on the ITU-T Recommendation H.263 with multiframe capability. Multiframe motion compensation chooses one prediction signal from a set of reference frames, whereas multihypothesis prediction chooses more than one for the linear combination. With our scheme, the time delay associated with B-frames is avoided by choosing more than one prediction signal from previously decoded pictures. Experimental results show that, multihypothesis prediction improves significantly coding efficiency by utilizing variable block size and multiframe motion compensation. We show that variable block size and multihypothesis prediction provide gains for different scenarios and that multiframe motion compensation enhances the multihypothesis gain. For example, the presented multihypothesis codec with ten reference frames improves coding efficiency by up to 2.7 dB when compared to the reference codec with one reference frame for the set of investigated test sequences. View full abstract»

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  • Evaluating MPEG-4 video decoding complexity for an alternative video complexity verifier model

    Page(s): 1034 - 1044
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1071 KB) |  | HTML iconHTML  

    MPEG-4 is the first object-based audiovisual coding standard. To control the minimum decoding complexity resources required at the decoder, the MPEG-4 Visual standard defines the so-called video buffering verifier mechanism, which includes three virtual buffer models, among them the video complexity verifier (VCV). This paper proposes an alternative VCV model, based on a set of macroblock (MB) relative decoding complexity weights assigned to the various MB coding types used in MPEG-4 video coding. The new VCV model allows a more efficient use of the available decoding resources by preventing the overevaluation of the decoding complexity of certain MB types and thus making it possible to encode scenes (for the same profile@level decoding resources) which otherwise would be considered too demanding. View full abstract»

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  • An HDTV-to-SDTV spatial transcoder

    Page(s): 998 - 1008
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (834 KB) |  | HTML iconHTML  

    Both high-definition television (HDTV) and, standard-definition television (SDTV) use the MPEG-2 video coding standard, but they have different spatial resolutions. In order to support the interlaced video coding, MPEG-2 incorporates various macroblock prediction modes. Thus, the HDTV-to-SDTV transcoding needs to handle spatial resolution downscaling and various MEPG-2 macroblock prediction modes. We investigate schemes to exploit the correlations between the input and output video in the design of an HDTV-to-SDTV transcoder so that the computation can be greatly saved while the quality of video is preserved as much as possible. First, by utilizing the motion vectors and macroblock coding modes of the input video, efficient motion reestimation and macroblock mode decision algorithms are proposed. Then a novel picture target bit allocation algorithm taking advantage of the coding statistics of the input video is presented. Simulation results showing the effectiveness of the proposed approaches are also presented. View full abstract»

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  • A congestion control strategy for multipoint videoconferencing

    Page(s): 1025 - 1029
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (398 KB) |  | HTML iconHTML  

    We formulate a congestion control problem for multipoint videoconferencing by introducing the concept of generalized fairness. A numerical method is provided to solve such a congestion control problem. The proposed method is much simpler than an earlier proposed method. This is desirable because congestion control is executed in real time. View full abstract»

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  • On the security of the digest function in the SARI image authentication system

    Page(s): 1030 - 1033
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    We investigate the image authentication system SARI, proposed by Lin and Chang (see ibid., vol.11, p.153-68, Feb. 2001), that distinguishes JPEG compression from malicious manipulations. In particular, we took at the image digest component of this system. We show that if multiple images have been authenticated with the same secret key and the digests of these images are known to an attacker, Oscar, then he can cause arbitrary images to be authenticated with this same but unknown key. We show that the number of such images needed by Oscar to launch a successful attack is quite small, making the attack very practical. We then suggest possible solutions to enhance the security of this authentication system. View full abstract»

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  • A linear source model and a unified rate control algorithm for DCT video coding

    Page(s): 970 - 982
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1098 KB) |  | HTML iconHTML  

    We show that, in any typical transform coding system, there is always a linear relationship between the coding bit rate R and the percentage of zeros among the quantized transform coefficients, denoted by ρ. Based on Shannon's source coding theorem, a theoretical justification is provided for this linear source model. The physical meaning of the model parameter is also discussed. We show that it is directly related to the image content and is a measure of picture complexity. In video coding, we propose an adaptive estimation scheme to estimate this model parameter. Based on the linear source model and the adaptive estimation scheme, a unified rate control algorithm is proposed for various standard video coding systems, such as MPEG-2, H.263, and MPEG-4. Our extensive simulation results show that the proposed rate control outperforms other algorithms reported in the literature by providing much more accurate and robust rate control. View full abstract»

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  • Design, performance analysis, and implementation of a super-scalar video-on-demand system

    Page(s): 983 - 997
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (649 KB)  

    Despite the availability of video-on-demand (VoD) services in a number of cities around the world, large-scale deployment of VoD services in a metropolitan area is still economically impractical. This study presents a novel super-scalar architecture for building very large-scale and efficient VoD systems. The proposed architecture combines the use of static multicast, dynamic multicast, and intelligent client-side caching to vastly reduce server and network resource requirement. Moreover, in sharp contrast to conventional VoD systems where the system cost increases at least linearly with the system scale, the proposed architecture becomes more efficient as the system scales up and can ultimately be scaled up to serve any number of users while still keeping the startup latency short. This paper presents this new architecture, proposes methods to support interactive playback controls without the need for additional server or client resources, and derives an approximate performance model to relate the startup latency with other system parameters. The performance model is validated using simulation and the architecture is evaluated under various system settings. Lastly, a system implementation is presented and benchmarking results obtained to further verify the architecture, the performance model, and the simulation results. View full abstract»

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Aims & Scope

The emphasis is focused on, but not limited to:
1. Video A/D and D/ A
2. Video Compression Techniques and Signal Processing
3. Multi-Dimensional Filters and Transforms
4. High Speed Real-Tune Circuits
5. Multi-Processors Systems—Hardware and Software
6. VLSI Architecture and Implementation for Video Technology 

 

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Dan Schonfeld
Multimedia Communications Laboratory
ECE Dept. (M/C 154)
University of Illinois at Chicago (UIC)
Chicago, IL 60607-7053
tcsvt-eic@tcad.polito.it

Managing Editor
Jaqueline Zelkowitz
tcsvt@tcad.polito.it