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Suche nach „[Barkowsky] [Marcus]“ hat 114 Publikationen gefunden
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    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    U. Fecker, Marcus Barkowsky, A. Kaup

    Time-Constant Histogram Matching for Luminance and Chrominance Compensation of Multi-View Video Sequences

    Picture Coding Symposium (PCS), Lisbon, Portugal

    2007

    Abstract anzeigen

    Significant advances have recently been made in the coding ofvideo data recorded with multiple cameras. However, lumi-nance and chrominance variations between the camera viewsmay deteriorate the performance of multi-view video codecsand renderers. In this paper, the usage of time-constant his-togram matching is proposed to compensate these differencesin a pre-filtering step. It is shown that the usage of histogrammatching prior to multi-view video coding leads to significantgains for the coding efficiency of both the luminance and thechrominance components. Histogram matching can also beuseful for image-based rendering to avoid incorrect illumina-tion and colour reproduction resulting from miscalibrations inthe recording setup. It can be shown that the algorithm is fur-ther improved by additionally using RGB colour conversion.

    DigitalF: Angewandte Informatik

    Zeitschriftenartikel

    J. Bialkowski, Marcus Barkowsky, A. Kaup

    Fast Video Transcoding from H.263 To H. 264/AVC

    Multimedia Tools and Applications, vol. 35, pp. 127-146

    2007

    DOI: 10.1007/s11042-007-0126-7

    Abstract anzeigen

    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.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Marcus Barkowsky, B. Eskofier, R. Bitto, J. Bialkowski, A. Kaup

    Perceptually motivated spatial and temporal integration of pixel based video quality measures

    Mobile Content Quality of Experience 2007 (MobConQoE '07): Fourth International Conference on Heterogeneous Networking for Quality, Reliability, Security and Robustness

    2007

    Abstract anzeigen

    In the evaluation of video quality often a full reference approach is used, thus calculating some measure of difference between the reference frames and the distorted frames. Often this measure returns one value per pixel, in the simplest case the squared difference. Conventionally, this pixel based measure is averaged over space and time. This paper introduces a psychophysically derived algorithm for this step. It uses the distribution of the cells in the fovea and the assumption that in a subjective test the part with the highest distortion is most important. Additionally, a temporal integration step is proposed which models the recency and forgiveness effect. Different video quality measures are enhanced with these two steps and their performance is evaluated using the results of a subjective test.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Marcus Barkowsky, J. Bialkowski, R. Bitto, A. Kaup

    Temporal Registration using 3D Phase Correlation and a Maximum Likelihood Approach in the Perceptual Evaluation of Video Quality

    Proceedings of the IEEE International Workshop on Multimedia Signal Processing

    2007

    Abstract anzeigen

    The estimation of the video quality is often performed using a full reference approach. One of the most important steps in a video quality measurement algorithm is to find the corresponding frames between the reference and the distorted video sequence. In this paper an algorithm with three steps is proposed. First, an extended version of the phase correlation is used to find candidate images with an arbitrary temporal offset, spatial scaling or spatial shift. Based on the assumption that the spatial scaling and spatial shift does not change during the sequence a set of probable parameters is selected. Finally, a maximum likelihood estimation is applied to select those temporal offsets which support the smoothest playback. A set of video sequences degraded with several distortions which are typical for multimedia scenarios are used to compare the performance to other algorithms.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    J. Bialkowski, Marcus Barkowsky, A. Kaup

    A new algorithm for reducing the requantization loss in video transcoding

    2006 14th European Signal Processing Conference

    2006

    Abstract anzeigen

    Video transcoders are devices that convert one video bitstream into another type of bitstream, either with or without standard format conversion. One step to be applied in video transcoders is the requantization of the transform coefficients, if an adaptation to a lower data rate is necessary. During this step, the quality is in most cases degraded compared to a single quantization. This is a consequence of nonoverlapping quantization characteristics of the input and the output quantizer. In this work we propose a new choice of the reconstruction level for the requantization step depending on the effective quantization curve of both quantization parameters involved. The reconstruction level is calculated such that it is centered in each effective quantization interval after requantization. Compared to the standard midpoint requantization this leads to quality gains of 3 dB PSNR for most pairs of input and output quantization parameters (QP). The algorithm is useful for intra- and inter-frame coding.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    J. Bialkowski, Marcus Barkowsky, A. Kaup

    Overview of Low-Complexity Video Transcoding from H.263 to H.264

    2006 IEEE International Conference on Multimedia and Expo

    2006

    Abstract anzeigen

    With the standardization of H.264/AVC by ITU-T and ISO/IEC and the adaptatation into new hardware, the necessity of transcoding between existing standards and H.264 will arise to achieve interoperability between hardware devices. Because of the many new prediction parameters as well as the pixel-based deblocking filter and the new transform of H.264 this is a difficult task to perform. In our work we propose a fast cascaded pixel-domain transcoder from H.263 to H.264 for both intra- and inter-frame coding. The rate-distortion (RD) performance of the encoded bitstreams is compared to an exhaustive full-search approach. Our approach leads to 9% higher data rate in average, but the computational complexity for the prediction can be reduced by 90% and more. It will be shown that the algorithms proposed for H.263 are applicable for transcoding MPEG-2 to H.264, too

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    J. Bialkowski, Marcus Barkowsky, F. Leschka, A. Kaup

    Low-Complexity Transcoding of Inter Coded Video Frames from H.264 to H.263

    2006 IEEE International Conference on Image Processing

    2006

    Abstract anzeigen

    The presented work addresses the reduction of computational complexity for transcoding of interframes from H.264 to H.263 baseline profiles maintaining the quality of a full search approach. This scenario aims to achieve fast backward compatible interoperability inbetween new and existing video coding platforms, e.g. between DVB-H and UMTS. By exploiting side information of the H.264 input bitstream the encoding complexity of the motion estimation is strongly reduced. Due to the possibility to divide a macroblock (MB) into partitions with different motion vectors (MV), one single MV has to be selected for H.263. It will be shown, that this vector is suboptimal for all sequences, even if all existing MVs of a MB of H.264 are compared as candidate. Also motion vector refinement with a fixed ½-pel refinement window as used by transcoders throughout the literature is not sufficient for scenes with fast movement. We propose an algorithm for selecting a suitable vector candidate from the input bitstream and this MV is then refined using an adaptive window. Using this technique, the complexity is still low at nearly optimum rate-distortion results compared to an exhaustive full-search approach.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Marcus Barkowsky, B. Eskofier, J. Bialkowski, A. Kaup

    Influence of the Presentation Time on Subjective Votings of Coded Still Images

    Proceedings of the International Conference on Image Processing

    2006

    Abstract anzeigen

    The quality of coded images is often assessed by a subjective test. Usually the viewers get as much time as they need to find a stable result. In video sequences however, the viewer has to judge the quality in a shorter time that is defined by the changing content or a following scene cut. Therefore it is desirable to know the influence of a shorter presentation time on the perceptibility of distortions. In this paper we present the results of a suitable subjective test on coded still images. The images were presented for six different durations, ranging from 200 ms to 3 s. Special care was taken to avoid the memorization effect usually present after short presentations. The results show that the viewers tend to avoid extreme votings at short durations. The variance of the votings is also discussed in detail. Based on the result of the voting for the longest presentation time, we propose a prediction model for the voting of the shorter durations using a logistic curve fit. This presentation time model (PTM) is presented and analysed in detail.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    U. Fecker, Marcus Barkowsky, A. Kaup

    Improving the Prediction Efficiency for Multi-View Video Coding Using Histogram Matching

    Proceedings of the Picture Coding Symposium 2006, [Isernhagen]

    2006

    ISBN: 9783000187261

    Abstract anzeigen

    Applications for video data recorded witha setup of several cameras are currently attracting increasinginterest. For such multi-view sequences, efficientcoding is crucial to handle the enormous amountof data. However, significant luminance and chrominancevariations between the different views, which oftenoriginate from imperfect camera calibration, areable to reduce the coding efficiency and the renderingquality. In this paper, we suggest the usage of histogrammatching to compensate these differences in apre-filtering step. After a description of the proposedalgorithm, it is explained how histogram matching canbe applied to multi-view video data. The effect of histogrammatching on the coding performance is evaluatedby statistically analysing prediction from temporalas well as from spatial references. For several testsequences, results are shown which indicate that theamount of spatial prediction across different cameraviews can be increased by applying histogram matching.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Marcus Barkowsky, R. Bitto, J. Bialkowski, A. Kaup, B. Li

    Comparison of matching strategies for temporal frame registration in the perceptual evaluation of video quality

    Proceedings of the 2nd International Workshop on Video Processing and Quality Metrics for Consumer Electronics

    2006

    ISBN: 09774739

    Abstract anzeigen

    In this paper we compare the performance of different full-frameand block-based algorithms for the temporal alignment of twovideo sequences. The setup is typical for full reference videoquality estimation in a low-bitrate scenario. Lossless and lossydigital transmission scenarios are combined with different distortionsusually found in playback devices. The results show thatthe choice of the algorithm for temporal registration depends verymuch on the type of additional distortion expected.

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    J. Bialkowski, Marcus Barkowsky, A. Kaup

    On Requantization in Intra-Frame Video Transcoding with Different Transform Block Sizes

    2005 IEEE 7th Workshop on Multimedia Signal Processing

    2005

    DOI: 10.1109/MMSP.2005.248669

    Abstract anzeigen

    Transcoding is a technique to convert one video bit-stream into another. While homogeneous transcoding is done at the same coding standard, inhomogeneous transcoding converts from one standard format to another standard. Inhomogeneous transcoding between MPEG-2, MPEG-4 or H.263 was performed using the same transform. With the standardisation of H.264 also a new transform basis and different block size was defined. For requantization from block size 8times8 to 4times4 this leads to the effect that the quantization error of one coefficient in a block of size 8times8 is distributed over multiple coefficients in blocks of size 4times4. In our work, we analyze the requantization process for inhomogeneous transcoding with different transforms. The deduced equations result in an expression for the correlation of the error contributions from the coefficients of block size 8times8 at each coefficient of block size 4times4. We then compare the mathematical analysis to simulations on real sequences. The reference to the requantization process is the direct quantization of the undistorted signal. It will be shown that the loss is as high as 3 dB PSNR at equivalent step size for input and output bitstream. Also an equation for the choice of the second quantization step size in dependency of the requantization loss is deduced. The model is then extended from the DCT to the integer-based transform as defined in H.264

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    Marcus Barkowsky, J. Bialkowski, A. Kaup

    Subjektiver Videobetrachtungstest für niederratige Multimedia-Szenarien

    ITG Fachbericht 188: Elektronische Medien 2005

    2005

    ISBN: 978-3-8007-2898-5

    DigitalF: Angewandte Informatik

    Beitrag (Sammelband oder Tagungsband)

    J. Bialkowski, M. Menden, Marcus Barkowsky, A. Kaup

    A Fast H.263 to H.264 Inter-Frame Transcoder with Motion Vector Refinement

    Picture Coding Symposium (PCS) 2004, San Francisco

    2004

    Abstract anzeigen

    Video transcoding techniques supply interoperability of a great variety of devices that can be connected by various communication networks with different data rate requirements. Particularly inhomogeneous video transcoding is the conversion of an existing video bitstream from one standard into a bitstream of another standard, for example the conversion from H.263 data into H.264 data. It may also include parameter adaptations such as bitrate or frame rate reduction. In this work, we present a low-complexity transcoder design for transcoding Interframe macroblocks from H.263 to H.264. The large complexity reduction comes from reusing motion vectors of the input bitstream and from the fact that only a subset of all possible H.264 coding parameters is used. The selection of these parameters is based on statistical investigations of encoded H.264 parameters from a full parameter search on decoded H.263 sequences. Our approach leads to small rate-distortion losses compared to the full parameter encoder below 0.5 dB at comparable data rates, but the computational complexity reduction is over 98% for finding a suitable macroblock decision. Compared to simply copying the motion vectors without post-processing, the rate-distortion gain of our approach is up to 2 dB at equivalent rate.

    DigitalF: Angewandte Informatik

    Hochschulschrift

    Marcus Barkowsky

    Subjective and Objective Video Quality Measurement in Low-Bitrate Multimedia Scenarios

    ISBN: 978-3-86853-142-8

    Abstract anzeigen

    In recent years, many distribution channels for low-bitrate video transmissions were setup. The parameter settings for the encoder, the transmission channel, the decoder and the playback device are manifold. In order to maintain customer satisfaction, it is necessary to carefully select and continuously tune those parameters and to monitor the resulting video quality at the receiver. This thesis considers the quality measurement by a human observer and by an automated algorithm. In the first part of the thesis, several subjective tests are performed in order to draw conclusions about the choice of transmission parameters. The experience gained from those experiments led to three psychophysical experiments that focus on isolated aspects of the video quality in lossless or lossy low-bitrate transmissions. Three distinct algorithms are deduced from the subjective experiments which deal with the temporal aspects. First, the visibility of artifacts is modeled when the viewer only has a short period of time for the examination. Second, the influence of transmission outages is modeled: The video playback may pause and content may be skipped if retransmission is not possible. Third, the visual degradation introduced by a reduction of the frame rate is modeled. The second part of the thesis is dedicated to the objective measurement. It is assumed that the reference video sequence is available for comparison with the degraded sequence. Because the performance of the automated measurement depends strongly on the correct alignment of the degraded signal to the reference signal, various algorithms are reviewed, enhanced, and compared that locate the corresponding reference frame for a given degraded frame. So far, many algorithms have been published that reliably predict the visual quality of still images or temporally undistorted video sequences. In this thesis, a new framework is presented that allows to evaluate the performance of these algorithms for temporally distorted video transmissions. The processing steps and the signal representations follow the reasoning of a human observer in a subjective experiment as observed in the first part of the thesis. The improvements that can be achieved with the newly proposed framework are demonstrated by comparing the objective scores with the subjective results of the comprehensive Multimedia Phase I database of the Video Quality Experts Group.