The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Fernando Pereira - One of the best experts on this subject based on the ideXlab platform.
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exploiting spatial redundancy in Pixel Domain wyner ziv video coding
International Conference on Image Processing, 2006Co-Authors: Marco Tagliasacchi, A Trapanese, Stefano Tubaro, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed video coding is a recent paradigm that enables a flexible distribution of the computational complexity between the encoder and the decoder building on top of distributed source coding principles. In this paper we focus on the scenario where most of the complexity is shifted to the decoder, thus achieving light encoding. We elaborate on a well known Pixel based Wyner-Ziv architecture and we improve its coding efficiency by exploiting both spatial and temporal correlation at the decoder side, without the need of performing any transform at the encoder. In order to generate the side information, the decoder adaptively chooses spatial or temporal information, based on the local estimate of the correlation noise. Simulations on test sequences demonstrate that a coding gain of up to +1.8 dB can be obtained with respect to the case that generates the side information by motion interpolation only.
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feedback channel in Pixel Domain wyner ziv video coding myths and realities
European Signal Processing Conference, 2006Co-Authors: Catarina Brites, Joao Ascenso, Fernando PereiraAbstract:Wyner-Ziv (WZ) video coding - a particular case of distributed video coding (DVC) - is a new video coding paradigm based on two major Information Theory results: the Slepian-Wolf and Wyner-Ziv theorems. Recently, practical WZ video coding solutions were proposed with promising results. Many of the solutions available in the literature make use of a feedback channel (FC) to perform rate control at the decoder. In this context, this paper intends to analyse the impact of this feedback channel, notably through a number of metrics such as the frequency the feedback channel is used as well as its associated rate. It is also presented a study on the evolution of the decoded frames quality as more parity bits are requested via feedback channel. Those measures are important since they allow characterizing the usage of the feedback channel, and have never been presented in the literature.
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improving turbo codec integration in Pixel Domain distributed video coding
International Conference on Acoustics Speech and Signal Processing, 2006Co-Authors: Marco Dalai, Riccardo Leonardi, Fernando PereiraAbstract:The field of distributed video coding (DVC) theory has received a lot of attention in recent years and effective encoding techniques have been proposed. In the present work the framework of Pixel Domain Wyner-Ziv coding of video frames is considered, following the scheme proposed in A. Aaron et al. (2002). Some key frames are supposed to be available at the decoder while other frames are Wyner-Ziv encoded using turbo codes; at the decoder motion compensated interpolation between the key frames is performed in order to construct the side information for the Wyner-Ziv frame decoding. In this paper an improved model for the correlation noise between the side information frame and the original one is proposed. It is shown that modeling the nonstationary nature of the noise leads to substantial gain in the rate-distortion performance. Furthermore, by considering the memory of the noise, we show that some further gain can be obtained by placing an interleaver before the turbo codec so as to spread the correlation noise all over the frame
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intra mode decision based on spatio temporal cues in Pixel Domain wyner ziv video coding
International Conference on Acoustics Speech and Signal Processing, 2006Co-Authors: Marco Tagliasacchi, A Trapanese, Stefano Tubaro, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed source coding principles have been recently applied to video coding in order to achieve a flexible distribution of the complexity burden between the encoder and the decoder. In this paper we elaborate on a Pixel based Wyner-Ziv video codec that shifts all the complexity of the motion estimation phase to the decoder, thus achieving light encoding. We observe that the correlation noise statistics describing the relationship between the frame to be encoded and the side information available at the decoder is not spatially stationary. For this reason we introduce a mode decision scheme either at the encoder or at the decoder in such a way that when the estimated correlation is weak we opt for intra coding on a block-by-block basis. Both spatial and temporal criteria are used to determine whether a block is better intra coded or not.
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extrapolating side information for low delay Pixel Domain distributed video coding
Lecture Notes in Computer Science, 2005Co-Authors: Luis Natario, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed Video Coding (DVC) is a new video coding approach based on the Wyner-Ziv theorem. Unlike most of the existing video codecs, each frame is encoded separately (either as a key-frame or a Wyner-Ziv frame) which results in a simpler and lighter encoder since complex operations like motion estimation are not performed. The previously decoded frames are used at the decoder to estimate the Wyner-Ziv frames – the frames are coded independently but jointly decoded. To have a low-delay codec, the side information frames (estimation of the Wyner-Ziv frames to be decoded) must be extrapolated from past frames. This paper proposes a robust extrapolation module to generate the side information based on motion field smoothening to provide improved performance in the context of a low-delay Pixel-Domain DVC codec.
Joao Ascenso - One of the best experts on this subject based on the ideXlab platform.
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exploiting spatial redundancy in Pixel Domain wyner ziv video coding
International Conference on Image Processing, 2006Co-Authors: Marco Tagliasacchi, A Trapanese, Stefano Tubaro, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed video coding is a recent paradigm that enables a flexible distribution of the computational complexity between the encoder and the decoder building on top of distributed source coding principles. In this paper we focus on the scenario where most of the complexity is shifted to the decoder, thus achieving light encoding. We elaborate on a well known Pixel based Wyner-Ziv architecture and we improve its coding efficiency by exploiting both spatial and temporal correlation at the decoder side, without the need of performing any transform at the encoder. In order to generate the side information, the decoder adaptively chooses spatial or temporal information, based on the local estimate of the correlation noise. Simulations on test sequences demonstrate that a coding gain of up to +1.8 dB can be obtained with respect to the case that generates the side information by motion interpolation only.
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feedback channel in Pixel Domain wyner ziv video coding myths and realities
European Signal Processing Conference, 2006Co-Authors: Catarina Brites, Joao Ascenso, Fernando PereiraAbstract:Wyner-Ziv (WZ) video coding - a particular case of distributed video coding (DVC) - is a new video coding paradigm based on two major Information Theory results: the Slepian-Wolf and Wyner-Ziv theorems. Recently, practical WZ video coding solutions were proposed with promising results. Many of the solutions available in the literature make use of a feedback channel (FC) to perform rate control at the decoder. In this context, this paper intends to analyse the impact of this feedback channel, notably through a number of metrics such as the frequency the feedback channel is used as well as its associated rate. It is also presented a study on the evolution of the decoded frames quality as more parity bits are requested via feedback channel. Those measures are important since they allow characterizing the usage of the feedback channel, and have never been presented in the literature.
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intra mode decision based on spatio temporal cues in Pixel Domain wyner ziv video coding
International Conference on Acoustics Speech and Signal Processing, 2006Co-Authors: Marco Tagliasacchi, A Trapanese, Stefano Tubaro, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed source coding principles have been recently applied to video coding in order to achieve a flexible distribution of the complexity burden between the encoder and the decoder. In this paper we elaborate on a Pixel based Wyner-Ziv video codec that shifts all the complexity of the motion estimation phase to the decoder, thus achieving light encoding. We observe that the correlation noise statistics describing the relationship between the frame to be encoded and the side information available at the decoder is not spatially stationary. For this reason we introduce a mode decision scheme either at the encoder or at the decoder in such a way that when the estimated correlation is weak we opt for intra coding on a block-by-block basis. Both spatial and temporal criteria are used to determine whether a block is better intra coded or not.
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motion compensated refinement for low complexity Pixel based distributed video coding
Advanced Video and Signal Based Surveillance, 2005Co-Authors: Joao Ascenso, Catarina Brites, F PereiraAbstract:Distributed video coding (DVC) is a new coding paradigm that enables to exploit video statistics, partially or totally at the decoder. A particular case of DVC, Wyner-Ziv coding, deals with lossy source coding with side information at the decoder and allows a shift of complexity from the encoder to the decoder, theoretically without any penalty in the coding efficiency. The Wyner-Ziv solution here described encodes each video frame independently (intraframe coding), but decodes the same frame conditionally (interframe decoding). At the decoder, and compensation tools are responsible to obtain an accurate interpolation of the original frame using previously decoded (temporally adjacent) frames. This paper proposes a novel approach to improve the performance of Pixel Domain Wyner-Ziv video coding by using a motion compensated refinement of the decoded frame and use it as improved side information. More precisely, upon partial decoding of each frame, the decoder refines its motion trajectories in order to achieve a better reconstruction of the decoded frame.
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extrapolating side information for low delay Pixel Domain distributed video coding
Lecture Notes in Computer Science, 2005Co-Authors: Luis Natario, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed Video Coding (DVC) is a new video coding approach based on the Wyner-Ziv theorem. Unlike most of the existing video codecs, each frame is encoded separately (either as a key-frame or a Wyner-Ziv frame) which results in a simpler and lighter encoder since complex operations like motion estimation are not performed. The previously decoded frames are used at the decoder to estimate the Wyner-Ziv frames – the frames are coded independently but jointly decoded. To have a low-delay codec, the side information frames (estimation of the Wyner-Ziv frames to be decoded) must be extrapolated from past frames. This paper proposes a robust extrapolation module to generate the side information based on motion field smoothening to provide improved performance in the context of a low-delay Pixel-Domain DVC codec.
Catarina Brites - One of the best experts on this subject based on the ideXlab platform.
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exploiting spatial redundancy in Pixel Domain wyner ziv video coding
International Conference on Image Processing, 2006Co-Authors: Marco Tagliasacchi, A Trapanese, Stefano Tubaro, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed video coding is a recent paradigm that enables a flexible distribution of the computational complexity between the encoder and the decoder building on top of distributed source coding principles. In this paper we focus on the scenario where most of the complexity is shifted to the decoder, thus achieving light encoding. We elaborate on a well known Pixel based Wyner-Ziv architecture and we improve its coding efficiency by exploiting both spatial and temporal correlation at the decoder side, without the need of performing any transform at the encoder. In order to generate the side information, the decoder adaptively chooses spatial or temporal information, based on the local estimate of the correlation noise. Simulations on test sequences demonstrate that a coding gain of up to +1.8 dB can be obtained with respect to the case that generates the side information by motion interpolation only.
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feedback channel in Pixel Domain wyner ziv video coding myths and realities
European Signal Processing Conference, 2006Co-Authors: Catarina Brites, Joao Ascenso, Fernando PereiraAbstract:Wyner-Ziv (WZ) video coding - a particular case of distributed video coding (DVC) - is a new video coding paradigm based on two major Information Theory results: the Slepian-Wolf and Wyner-Ziv theorems. Recently, practical WZ video coding solutions were proposed with promising results. Many of the solutions available in the literature make use of a feedback channel (FC) to perform rate control at the decoder. In this context, this paper intends to analyse the impact of this feedback channel, notably through a number of metrics such as the frequency the feedback channel is used as well as its associated rate. It is also presented a study on the evolution of the decoded frames quality as more parity bits are requested via feedback channel. Those measures are important since they allow characterizing the usage of the feedback channel, and have never been presented in the literature.
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intra mode decision based on spatio temporal cues in Pixel Domain wyner ziv video coding
International Conference on Acoustics Speech and Signal Processing, 2006Co-Authors: Marco Tagliasacchi, A Trapanese, Stefano Tubaro, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed source coding principles have been recently applied to video coding in order to achieve a flexible distribution of the complexity burden between the encoder and the decoder. In this paper we elaborate on a Pixel based Wyner-Ziv video codec that shifts all the complexity of the motion estimation phase to the decoder, thus achieving light encoding. We observe that the correlation noise statistics describing the relationship between the frame to be encoded and the side information available at the decoder is not spatially stationary. For this reason we introduce a mode decision scheme either at the encoder or at the decoder in such a way that when the estimated correlation is weak we opt for intra coding on a block-by-block basis. Both spatial and temporal criteria are used to determine whether a block is better intra coded or not.
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motion compensated refinement for low complexity Pixel based distributed video coding
Advanced Video and Signal Based Surveillance, 2005Co-Authors: Joao Ascenso, Catarina Brites, F PereiraAbstract:Distributed video coding (DVC) is a new coding paradigm that enables to exploit video statistics, partially or totally at the decoder. A particular case of DVC, Wyner-Ziv coding, deals with lossy source coding with side information at the decoder and allows a shift of complexity from the encoder to the decoder, theoretically without any penalty in the coding efficiency. The Wyner-Ziv solution here described encodes each video frame independently (intraframe coding), but decodes the same frame conditionally (interframe decoding). At the decoder, and compensation tools are responsible to obtain an accurate interpolation of the original frame using previously decoded (temporally adjacent) frames. This paper proposes a novel approach to improve the performance of Pixel Domain Wyner-Ziv video coding by using a motion compensated refinement of the decoded frame and use it as improved side information. More precisely, upon partial decoding of each frame, the decoder refines its motion trajectories in order to achieve a better reconstruction of the decoded frame.
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extrapolating side information for low delay Pixel Domain distributed video coding
Lecture Notes in Computer Science, 2005Co-Authors: Luis Natario, Joao Ascenso, Catarina Brites, Fernando PereiraAbstract:Distributed Video Coding (DVC) is a new video coding approach based on the Wyner-Ziv theorem. Unlike most of the existing video codecs, each frame is encoded separately (either as a key-frame or a Wyner-Ziv frame) which results in a simpler and lighter encoder since complex operations like motion estimation are not performed. The previously decoded frames are used at the decoder to estimate the Wyner-Ziv frames – the frames are coded independently but jointly decoded. To have a low-delay codec, the side information frames (estimation of the Wyner-Ziv frames to be decoded) must be extrapolated from past frames. This paper proposes a robust extrapolation module to generate the side information based on motion field smoothening to provide improved performance in the context of a low-delay Pixel-Domain DVC codec.
Bernd Girod - One of the best experts on this subject based on the ideXlab platform.
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Transform-Domain Wyner-Ziv codec for video
2015Co-Authors: Anne Aaron, Shantanu Rane, Eric Setton, Bernd GirodAbstract:In current interframe video compression systems, the encoder performs predictive coding to exploit the similarities of successive frames. The Wyner-Ziv Theorem on source coding with side information available only at the decoder suggests that an asymmetric video codec, where individual frames are encoded separately, but decoded conditionally (given temporally adjacent frames) could achieve similar efficiency. We propose a transform-Domain Wyner-Ziv coding scheme for motion video that uses intraframe encoding, but interframe decoding. In this system, the transform coefficients of a Wyner-Ziv frame are encoded independently using a scalar quantizer and turbo coder. The decoder uses previously reconstructed frames to generate side information to conditionally decode the Wyner-Ziv frames. Simulation results show significant gains above DCT-based intraframe coding and improvements over the Pixel-Domain Wyner-Ziv video coder
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transforms for high rate distributed source coding
Asilomar Conference on Signals Systems and Computers, 2003Co-Authors: David Rebollomonedero, Anne Aaron, Bernd GirodAbstract:We extend high-rate quantization theory to distributed source coding for the case in which the rate is the conditional entropy of the quantization index given the side information. This theory is applied to orthonormal block transforms for distributed source coding. A formula for the optimal rate allocation and an approximation to the optimal transform are derived. We implement a transform-Domain Wyner-Ziv video coder that encodes frames independently but decodes them conditionally. Experimental results show a rate-distortion improvement with respect to the Pixel-Domain coder by using the discrete cosine transform.
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watermarking of uncompressed and compressed video
Signal Processing, 1998Co-Authors: Frank Hartung, Bernd GirodAbstract:Abstract In this paper, methods for embedding additive digital watermarks into uncompressed and compressed video sequences are presented. The basic principle borrows from spread spectrum communications. It consists of addition of an encrypted, pseudo-noise signal to the video that is invisible, statistically unobtrusive, and robust against manipulations. For practical applications, watermarking schemes operating on compressed video are desirable. A method for watermarking of MPEG-2 encoded video is presented. The scheme is a compatible extension of the scheme operating on uncompressed video. The watermark is generated exactly in the same manner as for uncompressed video, transformed using the discrete cosine transform (DCT) and embedded into the MPEG-2 bit-stream without increasing the bit-rate. The watermark can be retrieved from the decoded video and without knowledge of the original, unwatermarked video. Although an existing MPEG-2 bit-stream is partly altered, the scheme avoids visible artifacts by addition of a drift compensation signal. The proposed method is robust and of much lower complexity than a complete decoding process followed by watermarking in the Pixel Domain and re-encoding. Fast implementations exist which have a complexity comparable to a video decoder. Experimental results are given. The scheme is also applicable to other hybrid transform coding schemes like MPEG-1, MPEG-4, H.261, and H.263.
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digital watermarking of mpeg 2 coded video in the bitstream Domain
International Conference on Acoustics Speech and Signal Processing, 1997Co-Authors: Frank Hartung, Bernd GirodAbstract:Embedding information into multimedia data, also called watermarking, is a topic that has gained increased attention. For video broadcast applications, watermarking schemes operating on compressed video are desirable. We present a scheme for robust watermarking of MPEG-2 encoded video. The watermark is embedded into the MPEG-2 bitstream without increasing the bit-rate, and can be retrieved even from the decoded video and without knowledge of the original, unwatermarked video. The scheme is robust and of much lower complexity than a complete decoding process followed by watermarking in the Pixel Domain and re-encoding. Although an existing MPEG-2 bitstream is partly altered, the scheme avoids visible artifacts by adding a drift compensation signal. The scheme has been implemented and the results confirm that a robust watermark can be embedded into MPEG encoded video which can be used to securely transmit arbitrary binary information at a data rate of several bytes/second. The scheme is also applicable to other hybrid coding schemes like MPEG-1, H.261, and H.263.
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digital watermarking of raw and compressed video
Digital Compression Technologies and Systems for Video Communications, 1996Co-Authors: Frank Hartung, Bernd GirodAbstract:Embedding information into multimedia data is a topic that has gained increasing attention recently. For video broadcast applications, watermarking of video, and especially of already encoded video, is interesting. We present a scheme for robust interoperable watermarking of MPEG-2 encoded video. The watermark is embedded either into the uncoded video or into the MPEG-2 bitstream, and can be retrieved from the decoded video. The scheme working on encoded video is of much lower complexity than a complete decoding process followed by watermarking in the Pixel Domain and re-encoding. Although an existing MPEG-2 bitstream is partly altered, the scheme avoids drift problems. The scheme has been implemented and practical results show that a robust watermark can be embedded into MPEG encoded video which can be used to transmit arbitrary binary information at a data rate of several bytes/second.
John Cosmas - One of the best experts on this subject based on the ideXlab platform.
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embedded side information refinement for Pixel Domain wyner ziv video coding towards umts 3g application
International Conference on Multimedia and Expo, 2007Co-Authors: John CosmasAbstract:This paper presents a new approach to Pixel Domain Wyner-Ziv (PDWZ) video coding by using weighted motion compensated refinement (WMCR) embedded into turbo decoder to efficiently optimize side information. The proposed system is designed by combining a relatively simple interpolation model for initial side information plus embedded refinement process to achieve better performance of system as a whole. In order to explore practical application of PDWZ in wireless environment, we adopt the 3GPP standardized turbo codec as Slepian-Wolf codec in PDWZ system. Experimental results showed that the proposed system have noticeable improvement in RD performance and reduced complexity of whole system.
