The wavelet-based video coders are excellent in providing the fine granular scalability (FGS), i.e. progressive bitstream, which can be used to multicast the video transmission to different users requiring different b...
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ISBN:
(纸本)9781479912025
The wavelet-based video coders are excellent in providing the fine granular scalability (FGS), i.e. progressive bitstream, which can be used to multicast the video transmission to different users requiring different bit-rate, resolution and frame rate, from single coded bitstream. However, transmission of these bitstreams over erroneous channel is a challenging task. In this paper, application layer unequal error protection (UEP) using RS codes to embedded video bitstream transmitted over Additive White Gaussian Noise (AWGN) channel is investigated. The UEP of embedded bitstream exploits the non-uniform importance of the bits, in the reconstruction of the video. The bitstream is partitioned into two substreams namely, high priority (HP) and low priority (LP), depending upon their importance and sensitivity to channel errors. Then FEC based error protection is provided to them according to their priority. The results show that, under poor channel conditions, the UEP scheme improves the quality of the reconstructed video over EEP scheme for AWGN channel.
High Efficiency video coder (HEVC) will become a new MPEG International Standard by the end of 2012. HEVC is targeted to provide the same quality as H.264 at about a half of the bit-rate and will replace soon to its p...
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ISBN:
(纸本)9781467313636
High Efficiency video coder (HEVC) will become a new MPEG International Standard by the end of 2012. HEVC is targeted to provide the same quality as H.264 at about a half of the bit-rate and will replace soon to its predecessor in multimedia consumer applications. In this paper, a preliminary implementation of an HEVC video decoder based on a DSP is presented and compared with a formerly developed H.264 DSP-based decoder.
All standard video coders are based on the prediction plus transform representation of an image block, which predicts the current block using various intra-and inter-prediction modes and then represents the prediction...
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ISBN:
(纸本)9781479947614
All standard video coders are based on the prediction plus transform representation of an image block, which predicts the current block using various intra-and inter-prediction modes and then represents the prediction error using a fixed orthonormal transform. We propose to directly represent a mean-removed block using a redundant dictionary consisting of all possible inter-prediction candidates with integer motion vectors (mean-removed). In general the dictionary may also contain some intra-prediction candidates and some pre-designed fixed dictionary atoms. However, simulation results reported in this papers are obtained by using the inter-prediction candidates only. We determine the coefficients by minimizing the L0 norm of the coefficients subject to a constraint on the sparse approximation error. We show that using such a self-adaptive dictionary can lead to a very sparse representation, with significantly fewer non-zero coefficients than using the DCT transform on the prediction error. We further propose a modified orthogonal matching pursuit (OMP) algorithm which othonormalizes each new chosen atom with respect to all previously chosen and orthonormalized atoms. Each image block is represented by the quantized coefficients corresponding to the othonormalized atoms, to overcome the inefficiency associated with using non-orthonormal atoms. Each image block is represented by its mean, which is predictively coded, the indices of the chosen atoms, and the quantized coefficients. Each variable is coded based on its unconditional distribution. Simulation results show that the proposed coder can achieve significant gain over the H.264 coder (implemented using x264) and achieve similar performance comparing to the HEVC reference encoder (HM).
This paper proposes a multiple description (MD) video coder, which uses motion-compensated predictions. We suggested a new algorithm of MD named Polyphase DownSampling that describes Intra and Inter frames. Results sh...
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ISBN:
(纸本)0780377133
This paper proposes a multiple description (MD) video coder, which uses motion-compensated predictions. We suggested a new algorithm of MD named Polyphase DownSampling that describes Intra and Inter frames. Results show that by using the coder scheme and the error environment like those suggested by 161 our MD algorithm improves the performance of the system both in coding efficiency and error-resilience. Moreover our MD coding approach allows the introduction of a multi level scalability. This last topic is the direction follows in the further research.
Compressed video bitstream is sensitive to errors that may degrade the reconstructed images severely even the bit error rate is small. One approach to combat the impact of error is error concealment at the decoder wit...
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Compressed video bitstream is sensitive to errors that may degrade the reconstructed images severely even the bit error rate is small. One approach to combat the impact of error is error concealment at the decoder without increasing the bit rate and changing the encoder. We propose motion vector based error concealment algorithms to recover the motion vector per pixel instead of that per block according to the relation of neighboring motion vectors. The displacement per pixel can be estimated more accurately by using the tendency of neighboring motion vectors. Besides, we use not only the relation among motion vectors, but also the pixels. The pixels of the error block are divided into different parts according to their consistency with neighboring blocks and the displacement at each pixel of these parts is interpolated by relative motion vectors. From simulation results, the proposed motion vector based methods provide better reconstruction quality for damaged images than other methods.
All standard video coders are based on the prediction plus transform representation of an image block, which predicts the current block using various intra- and inter-prediction modes and then represents the predictio...
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ISBN:
(纸本)9781479947607
All standard video coders are based on the prediction plus transform representation of an image block, which predicts the current block using various intra- and inter-prediction modes and then represents the prediction error using a fixed orthonormal transform. We propose to directly represent a mean-removed block using a redundant dictionary consisting of all possible inter-prediction candidates with integer motion vectors (mean-removed). In general the dictionary may also contain some intra-prediction candidates and some pre-designed fixed dictionary atoms. However, simulation results reported in this papers are obtained by using the inter-prediction candidates only. We determine the coefficients by minimizing the L0 norm of the coefficients subject to a constraint on the sparse approximation error. We show that using such a self-adaptive dictionary can lead to a very sparse representation, with significantly fewer non-zero coefficients than using the DCT transform on the prediction error. We further propose a modified orthogonal matching pursuit (OMP) algorithm which othonormalizes each new chosen atom with respect to all previously chosen and orthonormalized atoms. Each image block is represented by the quantized coefficients corresponding to the othonormalized atoms, to overcome the inefficiency associated with using non-orthonormal atoms. Each image block is represented by its mean, which is predictively coded, the indices of the chosen atoms, and the quantized coefficients. Each variable is coded based on its unconditional distribution. Simulation results show that the proposed coder can achieve significant gain over the H.264 coder (implemented using ×264) and achieve similar performance comparing to the HEVC reference encoder (HM).
We consider the motion-compensated temporal prediction loop at the heart of modern video coders. Rather than using motion-compensated reference frame blocks directly as predictors, we incorporate their spatially-filte...
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ISBN:
(纸本)9781467369985
We consider the motion-compensated temporal prediction loop at the heart of modern video coders. Rather than using motion-compensated reference frame blocks directly as predictors, we incorporate their spatially-filtered versions into the prediction loop. We design adaptive filters that are geared toward successful prediction over sophisticated temporal evolutions involving lighting changes, focus changes, structured noise, and so on. The spatially and temporally varying nature of such video evolutions requires the learning and transmission of many filters, necessitating parameter reduction for compression and related applications. Unlike earlier work that tries to limit parameters by using a small set of general filters, or by restricting to symmetric filters, etc., we propose a novel parametrization of filters in terms of a set of base-filter kernels and modulation weights. Given a filter dictionary of K-tap filters, our work can be seen as providing a reduced-rank, prediction-optimal approximation of this dictionary that represents its filters with K' << K parameters.
Current video coders exploit temporal dependencies via prediction that consists of motion-compensated pixel copying operations. Such per-pixel temporal prediction ignores important underlying spatial correlations, as ...
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ISBN:
(纸本)9781479983407
Current video coders exploit temporal dependencies via prediction that consists of motion-compensated pixel copying operations. Such per-pixel temporal prediction ignores important underlying spatial correlations, as well as considerable variations in temporal correlation across frequency components. In the transform domain, however, spatial decorrelation is first achieved, allowing for the true temporal correlation at each frequency to emerge and be properly accounted for, with particular impact at high frequencies, whose lower correlation is otherwise masked by the dominant low frequencies. This paper focuses on effective design of transform domain temporal prediction that: i) fully accounts for the effects of sub-pixel interpolation filters, and ii) circumvents the challenge of catastrophic design instability due to quantization error propagation through the prediction loop. We design predictors conditioned on frequency and sub-pixel position, employing an iterative open-loop (hence stable) design procedure that, on convergence, approximates closed-loop operation. Experimental results validate the effectiveness of both the asymptotic closed-loop design procedure and the transform-domain temporal prediction paradigm, with significant and consistent performance gains over the standard.
Medical applications like Computed Tomography (CT) or Magnetic Resonance Tomography (MRT) often require an efficient scalable representation of their huge output volumes in the further processing chain of medical rout...
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ISBN:
(纸本)9781509041183
Medical applications like Computed Tomography (CT) or Magnetic Resonance Tomography (MRT) often require an efficient scalable representation of their huge output volumes in the further processing chain of medical routine. A downscaled version of such a signal can be obtained by using image and video coders based on wavelet transforms. The visual quality of the resulting lowpass band, which shall be used as a representative, can be improved by applying motion compensation methods during the transform. This paper presents a new approach of using the distorted edge lengths of a mesh-based compensated grid instead of the approximated intensity values of the underlying frame to perform a motion compensation. We will show that an edge adaptive graph-based compensation and its usage for compensated wavelet lifting improves the visual quality of the lowpass band by approximately 2.5 dB compared to the traditional mesh-based compensation, while the additional filesize required for coding the motion information doesn't change.
To progress the compression performance of standard video coding algorithms, emerging motion compensation techniques will need to be integrated with the current standard techniques such as those used in the H.264. Hig...
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ISBN:
(纸本)9781424456536;9781424456543
To progress the compression performance of standard video coding algorithms, emerging motion compensation techniques will need to be integrated with the current standard techniques such as those used in the H.264. Higher order motion models, geometry-adaptive partitioning and motion-assisted merging are such techniques that can be considered for the next generation of video coders. In this paper, we examine how geometry information can benefit the use of elastic motion models to accomplish better prediction. Relative complexity issues are also discussed which is important in the standardization process. Experimental results suggest that geometry-adaptive block partitioning can add to the performance of elastic motion models to a certain extent, although the increased complexity is of some concern for real-time coding applications.
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