We address the delivery of composite multimedia documents, namely Web pages, over the Internet to clients with diverse resources and capabilities. We do so by adapting the multimedia content to meet the client device ...
详细信息
We address the delivery of composite multimedia documents, namely Web pages, over the Internet to clients with diverse resources and capabilities. We do so by adapting the multimedia content to meet the client device characteristics. We model the adaptation process as a resource allocation problem in a generalized rate-distortion framework. In this framework, we address the issue of both multiple media types in a Web document and multiple resource types at the client. We extend this framework to allow prioritization on the content items in a Web document. We illustrate our content adaptation technique with a Web server that adapts multimedia news stories to clients as diverse as workstations, PDAs and cellular phones.
In MPEG, the input pictures can be coded in three different types, I, P and B. The three pictures require quite different numbers of bits because of different natures of their temporal processing. Hence, an intelligen...
详细信息
In MPEG, the input pictures can be coded in three different types, I, P and B. The three pictures require quite different numbers of bits because of different natures of their temporal processing. Hence, an intelligent bit allocation strategy should assign a target rate for a picture according to the picture's type. Furthermore, for a given bit budget, the types of other pictures should also be taken into consideration. This implies a requirement of a prior knowledge of the picture organization (GOP). This requirement is not a problem for encoder as encoder can plan ahead the types of the pictures. A transcoder however has no such a priori knowledge about a picture's type before actually processing the picture. This creates a difficulty in bit allocation for transcoder. This paper proposes a novel rate control scheme for MPEG transcoder that requires no a priori knowledge of the picture types. The experiments indicate that the picture target rates determined by the proposed rate control with and without a priori knowledge of the picture types are very close.
A realtime software MPEG transcoder has been developed. Novel motion vector reuse and SIMD optimization techniques are introduced to accelerate the transcoder without any quality degradation. Mean absolute error appro...
详细信息
A realtime software MPEG transcoder has been developed. Novel motion vector reuse and SIMD optimization techniques are introduced to accelerate the transcoder without any quality degradation. Mean absolute error approximation criteria are employed in the reuse technique to refine scaled motion vectors. The developed transcoder on a Pentium II 266 MHz machine runs 2.5 times as fast as realtime, when scaling an MPEG-1 bitstream to half size.
The deployment of information appliances is predicted to exceed that of personal computers in the next few years. However, due to the wide range of communication, processing, storage and display capabilities of inform...
详细信息
The deployment of information appliances is predicted to exceed that of personal computers in the next few years. However, due to the wide range of communication, processing, storage and display capabilities of information appliances, the multimedia content on the Internet needs to be adapted before it can be efficiently delivered to these devices. We present content adaptation framework (CAF), a general framework for customizing Internet content for diverse client devices. The system first analyzes the content to be customized. Next, a variety of transcoders generate multi-resolution, multimodal versions of the content. The transcoded versions of the multimedia content are represented in a novel multi-modal, multi-resolution representation hierarchy called the InfoPyramid. Finally, a selection module uses an extended rate-distortion framework to pick the best content versions from the InfoPyramid while meeting the client device characteristics and resources. The content adaptation system can be deployed at various nodes in the Internet topology, such as at the server, at the client device or at an intermediate proxy. We present examples of proxy and server content adaptation systems based on CAF. Based on the content adaptation framework, we present a description scheme for multimedia and Internet content. This description scheme enables universal access to content. It has been proposed to various standards bodies.
Video transcoding techniques offer the possibility of matching coded video to transmission channels of lower capacity by reducing the bit rate of compressed bit streams. In this paper we propose a new frequency domain...
详细信息
Video transcoding techniques offer the possibility of matching coded video to transmission channels of lower capacity by reducing the bit rate of compressed bit streams. In this paper we propose a new frequency domain video transcoder for bit rate reduction of compressed bit streams. A motion compensation (MC) loop, operating in the frequency domain, is used for drift compensation at reduced computational complexity. We derive approximate matrices for fast computation of the MC blocks in the frequency domain. By using the Lagrangian optimisation in calculating the best quantiser scales for transcoding, we show that transcoded pictures from a high quality bit stream are better than those encoded from original frames at the same reduced bit rates.
The ability to manipulate the temporal dependencies in coded video data is important for a number of compressed domain video processing tasks. This paper formulates the general problem and examines it in the context o...
详细信息
The ability to manipulate the temporal dependencies in coded video data is important for a number of compressed domain video processing tasks. This paper formulates the general problem and examines it in the context of MPEG. This is used to develop a method for performing frame conversions in MPEG coded video data. These frame conversions are used to develop compressed-domain video processing algorithms for performing temporal mode conversion, frame-by-frame reverse play, and frame-accurate splicing.
transcoding is regarded as a down conversion process, where the bit rate of a compressed video bit stream is reduced according to a given constraint. Based on a transcoding architecture, previously developed by the au...
详细信息
transcoding is regarded as a down conversion process, where the bit rate of a compressed video bit stream is reduced according to a given constraint. Based on a transcoding architecture, previously developed by the authors, an optimal transcoder in a rate-distortion sense is proposed. It is shown that the basic architecture provides the necessary support for measuring the global transcoding distortion to be minimised under the optimisation algorithm. The experimental results show that, optimally transcoded pictures have a better quality than those encoded from the original video material, using a standard encoder at the same bit rates. This paper shows that compressed video can be further compressed with a good efficiency.
An extremely efficient MPEG-2 video transcoding method is proposed, which has a low buffer requirement and results in a low-delay. Most importantly, the proposed method does not need the computational intensive motion...
详细信息
ISBN:
(纸本)0780343719
An extremely efficient MPEG-2 video transcoding method is proposed, which has a low buffer requirement and results in a low-delay. Most importantly, the proposed method does not need the computational intensive motion estimation. Simulation results demonstrate that the proposed approach results in very consistent video quality and maintains the buffer level effectively.
This paper discusses the problem of transcoding H.263-based video streams. Two different models for transcoding are examined, rate reduction and resolution reduction. Results will show that the computational complexit...
详细信息
This paper discusses the problem of transcoding H.263-based video streams. Two different models for transcoding are examined, rate reduction and resolution reduction. Results will show that the computational complexity of the basic transcoding model can be reduced for each model by, on average, 39% and 23% without significant lose in quality. Comparisons with the scaleable coding model are also shown.
This paper discusses the problem of transcoding as it may occur in, for instance, the following situation. Suppose a satellite transmits an MPEG-compressed video signal at say 9 Mbit/s. This signal must be relayed at ...
详细信息
This paper discusses the problem of transcoding as it may occur in, for instance, the following situation. Suppose a satellite transmits an MPEG-compressed video signal at say 9 Mbit/s. This signal must be relayed at a cable head end. However, since the cable capacity is only limited, the cable head end will want to relay this incoming signal at a lower bit-rate of, say, 5 Mbit/s. The problem is how to convert a compressed video signal of a given bit-rate into a compressed video signal of a lower bit-rate. The specific transcoding problem discussed in this paper is referred to as bit-rate conversion. Basically, a transcoder used for such a purpose will consist of a cascaded decoder and encoder. It is shown in the paper that the complexity of this combination can be significantly reduced. The paper also investigates the loss of picture quality that may be expected when a transcoder is in the transmission chain. The loss of quality as compared to that resulting in the case of transmission without a transcoder is studied by means of computations using simplified models of the transmission chains and by means of using computer simulations of the complete transmission chain. It will be shown that the presence of two quantizers, i.e. cascaded quantization, in the transmission chain is the main cause of extra losses, and it will be shown that the losses in terms of SNR will be some 0.5-1.0 dB greater than in the case of a transmission chain without a transcoder.
暂无评论