作者：
Werner, OBBC
Dept Res & Dev Surrey KT20 6NP England
An investigation on requantization for transcoding of video signals is carried out. Specifically, MPEG-2 compatible discrete cosine transform (DCT) intraframe coding is addressed. The aim of this work is twofold: firs...
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An investigation on requantization for transcoding of video signals is carried out. Specifically, MPEG-2 compatible discrete cosine transform (DCT) intraframe coding is addressed. The aim of this work is twofold: first, to provide a theoretical analysis of the transcoding problem, and second, to derive quantization methods for efficient transcoding based on the results of the analysis. The mean squared error (MSE) cost function is proposed for designing a quantizer with minimum distortion resulting in up to 1.3 dB gain compared with the quantizer used in the MPEG-2 reference coder TM5, However, the MSE quantizer leads in general to a larger hit rate and may therefore only be applied locally to blocks of sensitive image content. A better rate-distortion performance can be provided by the maximum a posteriori (MAP) cost function, In critical cases, the MAP quantizer gives a 0.4 dB larger signal-to-noise-ratio (SNR) at the same bit rate compared with the TM5 quantizer, The results are not limited to MPEG-2 and can be adapted to other coding schemes such as H.263 or JPEG.
This paper describes a scalable MPEG-2 bit-rate transcoder that scales from low complexity, resulting in moderate picture quality, to high complexity with much better quality. The algorithm presents a very fine grain ...
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This paper describes a scalable MPEG-2 bit-rate transcoder that scales from low complexity, resulting in moderate picture quality, to high complexity with much better quality. The algorithm presents a very fine grain scalability in terms of complexity, making this solution especially suitable for software implementations, in order to benefit from the available resources to increase picture quality. Picture quality degrades gracefully when the complexity of the algorithm is decreased.
Converting the Digital Video (DV) format for digital video cassette recorders into the MPEG-2 Intra coding is performed in the DCT domain to reduce conversion steps. To convert the 4: 1: 1 to the 4:2:2 chroma formats ...
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Converting the Digital Video (DV) format for digital video cassette recorders into the MPEG-2 Intra coding is performed in the DCT domain to reduce conversion steps. To convert the 4: 1: 1 to the 4:2:2 chroma formats and the 2-4-8 DCT mode to the 8-8 DCT mode, a matrix is multiplied by transformed data. Such multiplication enables parallel processing. And m_quant of the MPEG-2 TM5 rate control is computed in the DCT domain.
A JPEG Quality Transcoder (JQT) converts a JPEG image file that was encoded with low image quality to a larger JPEG image file with reduced visual artifacts, without access to the original uncompressed image. In this ...
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A JPEG Quality Transcoder (JQT) converts a JPEG image file that was encoded with low image quality to a larger JPEG image file with reduced visual artifacts, without access to the original uncompressed image. In this article, we describe technology for JQT design that takes a pattern recognition approach to the problem, using a database of images to train statistical models of the artifacts introduced through JPEG compression. In the training procedure for these models, we use a model of human visual perception as an error measure. Our current prototype system removes 32.2% of the artifacts introduced by moderate compression, as measured on an independent test database of linearly coded images using a perceptual error metric. This improvement results in an average PSNR reduction of 0.634 dB.
This article discusses the challenges in computer systems research posed by the emerging field of pervasive computing. It first examines the relationship of this new field to its predecessors: distributed systems and ...
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This article discusses the challenges in computer systems research posed by the emerging field of pervasive computing. It first examines the relationship of this new field to its predecessors: distributed systems and mobile computing. It then identifies four new research thrusts: effective use of smart spaces, invisibility, localized scalability, and masking uneven conditioning. Next, it sketches a couple of hypothetical pervasive computing scenarios, and uses them to identify key capabilities missing from today's systems. The article closes with a discussion of the research necessary to develop these capabilities.
In transcoding, simply reusing the motion vectors extracted from an incoming video bit stream may not result in the best quality. In this paper, we show that the incoming motion vectors become nonoptimal due to the re...
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In transcoding, simply reusing the motion vectors extracted from an incoming video bit stream may not result in the best quality. In this paper, we show that the incoming motion vectors become nonoptimal due to the reconstruction errors. To achieve the best video quality possible, a new motion estimation should be performed in the transcoder. We propose a fast-search adaptive motion vector refinement scheme that is capable of providing video quality comparable to that can be achieved by performing a new full-scale motion estimation but with much less computation. We discuss the case when some incoming frames are dropped for frame-rate conversions, and propose motion vector composition method to compose a motion vector from the incoming motion vectors. The composed motion vector can also be refined using the proposed motion vector refinement scheme to achieve better results.
THE CLARA PROTOTYPE ARCHITECTURE COLLOCATES ROUTING AND COMPUTATIONAL FUNCTIONALITY WITHIN A NETWORK, PROVIDING A SCALABLE, HIGH-PERFORMANCE COMPUTING SWITCH ROUTER FOR COMPUTATIONAL SERVICES. MULTIPLE OFF-THE-SHELF P...
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THE CLARA PROTOTYPE ARCHITECTURE COLLOCATES ROUTING AND COMPUTATIONAL FUNCTIONALITY WITHIN A NETWORK, PROVIDING A SCALABLE, HIGH-PERFORMANCE COMPUTING SWITCH ROUTER FOR COMPUTATIONAL SERVICES. MULTIPLE OFF-THE-SHELF PCS PROVIDE CLARA WITH COMPUTATIONAL POWER TO, FOR EXAMPLE, PERFORM REAL-TIME transcoding OF VIDEO WITH MINIMAL OVERHEAD.
This paper describes a new highly efficient deinterlacing approach based on motion estimation and compensation techniques. The proposed technique mainly benefits from the motion vector properties of zonal based algori...
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ISBN:
(纸本)0819439886
This paper describes a new highly efficient deinterlacing approach based on motion estimation and compensation techniques. The proposed technique mainly benefits from the motion vector properties of zonal based algorithms, such as the Advanced Predictive Diamond Zonal Search (APDZS) and the Predictive Motion Vector Field Adaptive Search Technique (PMVFAST), multihypothesis motion compensation, but also an additional motion classification phase where, depending on the motion of a pixel, additional spatial and temporal information is also considered to further improve performance. Extensive simulations demonstrate the efficacy of these algorithms, especially when compared to standard deinterlacing techniques such as the line doubling and line averaging algorithms.
This paper describes the new C64x DSP core including instruction set extensions that enhance performance for image and video processing. Key features include packed data processing and special instructions to accelera...
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ISBN:
(纸本)0819439916
This paper describes the new C64x DSP core including instruction set extensions that enhance performance for image and video processing. Key features include packed data processing and special instructions to accelerate algorithms such as motion estimation. Devices based on the C64x will be ideally suited for key target applications including video infrastructure and image analysis.
transcoding proxy strategy has been widely used as a means to reduce the delay in retrieving Web pages over wireless mobile data networks. However, this strategy has a serious drawback of being a potential point of fa...
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ISBN:
(纸本)0769509525
transcoding proxy strategy has been widely used as a means to reduce the delay in retrieving Web pages over wireless mobile data networks. However, this strategy has a serious drawback of being a potential point of failure or a bottleneck of the service. We developed a distributed proxy sewer system in which multiple proxy servers are installed at geographically dispersed locations and share the workloads among themselves by serving mobile hosts within assigned regions. A new handoff (HO) message protocol is proposed to enable handoffs between proxies as the mobile hosts move between regions. With this proxy sewer handoff protocol a client agent at the mobile host requests a proxy sewer to initiate handoff processing and two proxy servers synchronize distilled data for a HTTP session disconnected by the handoff.
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