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Suche nach „[F: Angewandte Informatik]“ hat 352 Publikationen gefunden
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    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.

    DigitalNachhaltigF: Angewandte InformatikS: TC Plattling MoMo

    Vortrag

    Nicki Bodenschatz

    Optimierte Ladeplanung von E-Fahrzeugflotten

    2. TRIOKON 2020 – Die ostbayerische Transferkonferenz für Wirtschaft, Wissenschaft und Gesellschaft, Landshut

    DigitalNachhaltigF: Angewandte InformatikS: TC Plattling MoMo

    Vortrag

    Markus Eider

    Projekt CITRAM - Citizen Science for Traffic Management

    2. TRIOKON 2020 – Die ostbayerische Transferkonferenz für Wirtschaft, Wissenschaft und Gesellschaft, Landshut

    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.

    DigitalF: Angewandte Informatik

    Hochschulschrift

    Gökçe Aydos

    Parity-based Error Detection with Recomputation for Fault-tolerant Spaceborne Computing

    Abstract anzeigen

    In radiation environment (e.g., space, nuclear reactor), electronics can fail due to bitflips in the flipflops of integrated circuits. A common solution is to triplicate the flipflops and connect their outputs to a voter. If one of the three bits is flipped, then the voter outputs the majority value and tolerates the error. This method is called triple modular redundancya (TMR). TMR can cause about 300% area redundancy. An alternative way is error detection with on-demand recomputation, where the recomputation is done by repeating the failed processing request to the processing circuit. The computation is done in consecutive transactions, which we call transaction-based processing. We implemented and evaluated the aforementioned alternative approach using parity checking on the Microsemi ProASIC3 FPGA, which is often used in space applications. The results show that parity-based error detection with our system recovery approach can save up to 54% of the area overhead that would be caused by the TMR, and achieve in most circuits slightly better timing results than TMR on ProASIC3. This area saving can be the key for fitting the application to a space-constrained chip.