Multimedia applications such as video streaming and mobile TV are emerging as the most promising applications over wireless networks. The increased coding efficiency and network friendly architecture of the latest vid...
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ISBN:
(纸本)9781424416523
Multimedia applications such as video streaming and mobile TV are emerging as the most promising applications over wireless networks. The increased coding efficiency and network friendly architecture of the latest video coding standard H.264/AVC has facilitated the delivery of coded video content to wireless users. However, wireless networks allow lower transmission bit-rates than wired networks while the display resolution of mobile devices is generally smaller than that of standard definition (SD) TV. This calls for fast bit-rate reduction techniques through video transcoding that can deliver the best video quality to the mobile receiver while adhering to the bit-rate constraints of the wireless network. In this paper, we present a bit-rate estimation model that speeds up the transcoding process by predicting the transcoded video bit-rate for different spatial resolution reduction ratios and quantization steps. We demonstrate that, on average, our proposed model can accurately estimate the bit-rate of the transcoded video to within 5% of the actual bit-rate of the transcoded video.
This paper proposes a designing framework for downsampling compressed images/video frames with arbitrary ratio in the discrete cosine transform (DCT) domain. We first derive a set of DCT-domain down-sampling methods w...
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ISBN:
(纸本)9781424414833
This paper proposes a designing framework for downsampling compressed images/video frames with arbitrary ratio in the discrete cosine transform (DCT) domain. We first derive a set of DCT-domain down-sampling methods which can be represented by a linear transform with double-sided matrix multiplication (LTDS) in the DCT domain, and show that the set contains a wide range of methods with various complexity and visual quality. Then, based on a pre-selected spatial-domain method, we formulate an optimization problem for finding an LTDS to approximate the given spatial domain method for achieving the best trade-off between the visual quality and the complexity. By selecting a spatial-domain reference method with the popular Butterworth lowpass filtering and bicubic interpolation, the proposed framework discovers LTDSs with better visual quality and lower computational complexity as saving 20%similar to 70% execution time when compared with state-of-the-art methods in the literature.
In this paper, we present a spatial resolution reduction transcoding architecture for H.264/AVC, which extends open-loop transcoding with a low-complexity compensation technique in the reduced-resolution domain. The p...
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ISBN:
(纸本)9781424417650
In this paper, we present a spatial resolution reduction transcoding architecture for H.264/AVC, which extends open-loop transcoding with a low-complexity compensation technique in the reduced-resolution domain. The proposed architecture removes visual artifacts from the transcoded sequence, while keeping complexity significantly lower than more traditional cascaded decoder-encoder architectures. The refinement step of the proposed architecture can be used to further improve rate-distortion performance, at the cost of additional complexity. In this way, a dynamic-complexity transcoder is rendered possible.
One objective in MPEG-2 to H.264 transcoding is to improve the H.264 compression ratio by using more accurate H.264 motion vectors. Motion re-estimation is by far the most time consuming process in video transcoding, ...
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ISBN:
(纸本)9781424414833
One objective in MPEG-2 to H.264 transcoding is to improve the H.264 compression ratio by using more accurate H.264 motion vectors. Motion re-estimation is by far the most time consuming process in video transcoding, and improving the searching speed is a challenging problem. We introduce a new transcoding scheme that uses the MPEG-2 DCT coefficients to predict the block size partitioning for H.264. Performance evaluations have shown that, for the same rate-distortion performance, our proposed scheme achieves an impressive reduction in the computational complexity of more than 82% compared to the full range motion estimation used by H.264.
transcoding is required to enable interoperability between Push to talk over Cellular (PoC) clients with incompatible capabilities (e.g. between a PoC client supporting the AMR speech codec and another supporting EVRC...
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ISBN:
(纸本)9780769533339
transcoding is required to enable interoperability between Push to talk over Cellular (PoC) clients with incompatible capabilities (e.g. between a PoC client supporting the AMR speech codec and another supporting EVRC). Although the Open Mobile Alliance (OMA) recognizes the need for transcoding in the PoC application, no solution is provided by the standard to enable it. In this paper, we present a transcoding system for real-time multi-user PoC sessions. The solution is centralized at the Controlling PoC Function which manages session control operations and the flow of media streams to enable transcoding. to be performed in a distinct transcoding server (TS). There are several advantages to this solution, such as scalability, applicability to all PoC group session scenarios, compatibility with existing PoC specifications, and transparency for existing PoC clients.
In this paper, we discuss motion-refined rewriting of single-layer H.264/AVC streams to SVC streams with multiple quality layers. First, we elaborate on techniques we developed for efficient rewriting of residual data...
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In this paper, we discuss motion-refined rewriting of single-layer H.264/AVC streams to SVC streams with multiple quality layers. First, we elaborate on techniques we developed for efficient rewriting of residual data from H.264/AVC to SVC. We investigate if rate-distortion performance can further be improved by extending these architectures with motion refinement techniques, which exploit the inter-layer motion prediction mechanisms available in SVC. For optimum performance, we discuss a fast rate-distortion technique based on Lagrangian relaxation. Although motion refinement in the transform-domain leads to extra distortion in the bitstream, we show that our rate-distortion model successfully takes into account both base and enhancement layer rate and distortion during optimization. Implementation results show that motion-refined rewriting in the transform domain can increase rate-distortion performance, with gains of up to 0.5 dB for the SVC base layer. The presented rewriting architectures significantly reduce the computational complexity when compared to reencoding, with a speed-up by a factor of forty or more, even in the case of motion refinement. (C) 2011 Elsevier Inc. All rights reserved.
High performance SIMD text processing using the method of parallel bit streams is introduced with a case study of UTF-8 to UTF-16 transcoding. A forward transform converts byte-oriented character stream data into eigh...
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ISBN:
(纸本)9781595939609
High performance SIMD text processing using the method of parallel bit streams is introduced with a case study of UTF-8 to UTF-16 transcoding. A forward transform converts byte-oriented character stream data into eight parallel bit streams. Decoding, validation and computation of UTF-8 indexed UTF-16 bit streams are performed using bit-parallel logic and shifting operations. Conversion from UTF-8 indexing to UTF-16 indexing is performed using parallel bit deletion. The inverse transform is applied to yield high and low UTF-16 byte streams which are then merged. Combined with optimization techniques for blocks of ASCII data, speed-ups of 3 to 25 times are achieved on commodity processors compared with optimized byte-at-a-time code. Further applications of the method of parallel bit streams to bulk text processing applications are briefly discussed along with future prospects for the combination of intraregister and intrachip parallelism on multicore processors.
Expansion in 3G cellular coverage and the emergence of more powerful mobile devices has increased demand for massively scalable mobile video delivery. The rapid adoption of the third screen as a primary screen for vid...
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Expansion in 3G cellular coverage and the emergence of more powerful mobile devices has increased demand for massively scalable mobile video delivery. The rapid adoption of the third screen as a primary screen for video has highlighted inefficiencies in the mobile delivery ecosystem and scalability issues in the mobile delivery infrastructure. This article provides an overview of the current mobile content delivery ecosystem and discusses the expanding role of HTTP-based mobile video delivery. A new class of HTTP-based mobile delivery protocols seeks to address existing quality and scalability issues by simplifying and standardizing mobile video delivery. This article shows how segment-based delivery has enabled HTTP-based live streaming and dynamic bitrate adaptation while increasing scalability through the use of existing CDN infrastructure.
Existing media providers such as YouTube and Hulu deliver videos by turning it into a progressive download. This can result in frequent video freezes under varying network dynamics. In this paper, we present CloudStre...
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ISBN:
(纸本)9781424499212
Existing media providers such as YouTube and Hulu deliver videos by turning it into a progressive download. This can result in frequent video freezes under varying network dynamics. In this paper, we present CloudStream: a cloud-based video proxy that can deliver high-quality streaming videos by transcoding the original video in real time to a scalable codec which allows streaming adaptation to network dynamics. The key is a multi-level transcoding parallelization framework with two mapping options (Hallsh-based Mapping and Lateness-first Mapping) that optimize transcoding speed and reduce the transcoding jitters while preserving the encoded video quality. We evaluate the performance of CloudStream on our campus cloud testbed.
Comparing numerical performance between different languages does not only mean comparing different number-word systems, but also implies a comparison of differences regarding culture or educational systems. The Czech ...
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Comparing numerical performance between different languages does not only mean comparing different number-word systems, but also implies a comparison of differences regarding culture or educational systems. The Czech language provides the remarkable opportunity to disentangle this confound as there exist two different number-word systems within the same language: for instance, "25" can be either coded in non-inverted order "dvadsetpat" [twenty-five] or in inverted order "patadvadset" [five-and-twenty]. To investigate the influence of the number-word system on basic numerical processing within one culture, 7-year-old Czech-speaking children had to perform a transcoding task (i.e., writing Arabic numbers to dictation) in both number-word systems. The observed error pattern clearly indicated that the structure of the number-word system determined transcoding performance reliably: In the inverted number-word system about half of all errors were inversion-related. In contrast, hardly any inversion-related errors occurred in the non-inverted number-word system. We conclude that the development of numerical cognition does not only depend on cultural or educational differences, but is indeed related to the structure and transparency of a given number-word system. (C) 2011 Elsevier Ltd. All rights reserved.
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