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This paper addresses the problem of how to efficiently manage the power consumption while preserving high visual quality performance in video coding for pervasive video applications. We define an optimization problem that corresponds to the minimization of both the power consumption and video distortion of a video encoder. A joint rate-complexity-distortion(R-C-D) model is developed to capture and control the general R-C-D behavior of video coding. Based on the analysis of the proposed model, optimization strategies are developed to achieve good video quality while maximizing the battery service life. We demonstrate how the observations and optimization strategies can be utilized in a practical parameterized encoder under various preferences of quality and power. We perform simulations on an instruction set simulator to exhibit the effectiveness of the proposed scheme.

A novel sulfonated diamine, 1,2-dihydro-2-(3-sulfonic-4-aminophenyl)-4-[4-(3-sulfonic-4-aminophenoxy)-phenyl]-phthalazin-1-one(S-DHPZDA), was successfully synthesized and two series of six-membered sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), S-DHPZDA, and nonsulfonated diamines DHPZDA or 4,4′-diaminodiphenyl ether (ODA). The chemical structure of the S-DHPZDA and the SPIs were characterized by 1H NMR and FT-IR. Tough, brownish and transparent membranes were cast from SPIs’ solution in NMP. The water uptake, swelling ratio, chemical and thermal stability, hydrolytic and oxidative stability as well as proton conductivity of these new polymers were investigated systematically. Compared with Nafions, the obtained SPI membranes have onset decomposed temperatures of these two series SPIs were above 318 °C and decomposed temperature of main chain were 565 °C and excellent dimension stabilities on similar IECs. Introduction of phthalazinone moieties had improved the copolyimides’ solubility in polar aprotic organic solvents like m-cresol, NMP, DMSO, DMF etc. The SPIs had high proton conductivity (σ) in the order of magnitude of 10−3 to 10−2 S cm−1 depending on the degree of sulfonation (DS) of the polymers.

In this work, sulfonated poly(phthalazinone ether nitrile ketone)/boron phosphate (SPPENK/BPO4) composite membranes with BPO4 content from 10 to 30 wt.% were prepared from SPPENK matrix, tripropylborate (C3H7O)3B and phosphoric acid (H3PO4) via an in situ process. The composite membranes were characterized using X-ray diffraction, FT-IR and TGA, which revealed the interaction between the sulfonic acid groups of SPPENK and BPO4. The SPPENK/BPO4 composite membranes showed excellent thermal, oxidative and hydrolytic stabilities. The swelling ratios of composite membranes were about 5.0%, which was similar to that of SPPENK membrane. Proton conductivity of the composite membranes was studied under 100% relative humidity conditions up to 95 °C. A five-fold increase in proton conductivity was observed for the composite membrane with 30 wt.% BPO4.

In this work, sulfonated poly(phthalazinone ether)s (SPPENK, SPPESK and SPPBEK) were synthesized by direct aromatic nucleophilic polycondensation reaction. H-bonded composite membranes were prepared from SPPENK, SPPESK and SPPBEK, respectively, and polyetherimide (PEI). Both of compounds were dissolved in N-methylpyrrolidone (NMP), and tough membranes were obtained by casting from NMP solution with 9:1 mass ratio of sulfonated poly(phthalazinone ether)s/PEI. These H-bonded composite membranes all showed better thermal, oxidative and mechanical stabilities than corresponding pure sulfonated polymers membranes. The H-bonded composite membranes had high proton conductive ranging from 0.02 to 0.06 S/cm at 95 °C. All membranes showed an increase in proton conductivities with temperature elevation. The swelling ratio of H-bonded composite membranes was lower than that of pure membranes.

To provide basic video services and applications in 3G wireless networks, two video coding formats, H.263 baseline and MPEG-4 visual simple profile, are commonly adopted in different forms for various usage scenarios. To ensure interoperability between these cases, we propose efficient compressed domain algorithms for transcoding between MPEG-4 visual simple profile and H.263 baseline, and among MPEG-4 visual simple profile coding modes. Experimental results show that our suggested algorithms provide significant complexity reduction and quality improvement, in terms of PSNR, compared to the spatial domain approach. Being the first complete work on transcoding between all kinds of MPEG-4 visual simple profile and H.263 baseline bit streams, we believe this work provides valuable solutions for various 3GPP (3rd generation partnership project) compliant video services and applications).

Mobile devices performing video coding and streaming over wireless and pervasive communication networks are limited in energy supply. To prolong the operational lifetime of these devices, an embedded video encoding system should be able to adjust its computational complexity and energy consumption as demanded by the situation and its environment. To analyze, control, and optimize the rate-distortion (R-D) behavior of the wireless video communication system under the energy constraint, we develop a power-rate-distortion (P-R-D) analysis framework, which extends the traditional R-D analysis by including another dimension, the power consumption. Specifically, in this paper, we analyze the encoding mechanism of typical video coding systems, and develop a parametric video encoding architecture which is fully scalable in computational complexity. Using dynamic voltage scaling (DVS), an energy consumption management technology recently developed in CMOS circuits design, the complexity scalability can be translated into the energy consumption scalability of the video encoder. We investigate the R-D behavior of the complexity control parameters and establish an analytic P-R-D model. Both theoretically and experimentally, we show that, using this P-R-D model, the video coding system is able to automatically adjust its complexity control parameters to match the available energy supply of the mobile device while maximizing the picture quality. The P-R-D model provides a theoretical guideline for system design and performance optimization in mobile video communication under energy constraints.

In this paper, we consider the problem of MPEG-4 visual simple profile to H.264/AVC baseline profile (BP) transcoding. An efficient transcoding algorithm with fast mode selection and motion vector refinement is proposed. The proposed algorithm exploits the side information from the decoding stage to predict the coding modes and MVs of H.264/AVC BP coding. The proposed algorithm consists of two parts: INTRA macroblocks (MBs) transcoding and INTER MBs transcoding. By reusing the side information during the decoding stage, these techniques provide significant complexity reduction, when compared with the fully spatial domain approach.

Exploitation of redundancies for superior coding efficiency is one of the major research issues in multi-view video coding (MVC). However, this incurs extra computation, counteracting the benefit gained from coding efficiency. This paper exploits inter-view correlations among video objects and background to lower the prediction complexity while achieving high coding efficiency in MVC. We propose an effective object-based scheme that utilizes video object information obtained from the coded base view. This information assists to predict disparity vectors and motion vectors in enhancement views (EVs) by employing object registration and warping. This leads to high compression and low-complexity coding scheme for EVs. The proposed scheme provides higher coding efficiency when compared to the segmentation-free scheme, while achieving lower computational complexity.

Joint histogram is the only quantity required to calculate the mutual information (MI) between two images. For MI based image registration, joint histograms are often estimated through linear interpolation or partial volume interpolation (PVI). It has been pointed out that both methods may result in a phenomenon known as interpolation induced artifacts. In this paper, we implemented a wide range of interpolation/approximation kernels for joint histogram estimation. Some kernels are nonnegative. In this case, these kernels are applied in two ways as the linear kernel is applied in linear interpolation and PVI. In addition, we implemented two other joint histogram estimation methods devised to overcome the interpolation artifact problem. They are nearest neighbor interpolation with jittered sampling with/without histogram blurring and data resampling. We used the clinical data obtained from Vanderbilt University for all of the experiments. The objective of this study is to perform a comprehensive comparison and evaluation of different joint histogram estimation methods for MI based image registration in terms of artifacts reduction and registration accuracy.

This paper presents a novel multistage motion estimation (ME) scheme called content adaptive search technique (CAST). The proposed scheme consists of four stages: motion vector field (MVF) prediction, block-based segmentation, motion parameter extraction, and adaptive search strategy. Through pre-processing the MVF of the previous reference frame in the first three stages, CAST extracts the motion parameters for each region. The 4th stage is a combination of various techniques including MV prediction, search area decision and an adaptive fast search algorithm that is adjusted by a mathematical model for the block distortion surface (BDS). Experiment shows that the proposed scheme improves the visual quality, while yielding a faster speed, comparing with the other predictive ME algorithms.

Motion estimation is a multistep process that encompasses techniques such as motion vector prediction, determination of search range and search patterns, and identification of termination criteria. Each of these techniques has several diversions that may suit a particular set of video characteristics. It would be hard to conceive a universal algorithm that can perform well for all kinds of video contents. However, if important characteristics of a video sequence can be identified and utilized for adjusting various steps of motion estimation, one can design an adjustable algorithm that can tune its parameters to suit the video at hand. A multistage motion estimation algorithm that includes a pre-stage for analyzing the motion characteristics of a video sequence online is proposed. This stage predicts the motion vector field (MVF) from the previous coded frame, and clusters macroblocks into background and foreground regions based on the predicted MVF. The information from the pre-stage are passed on to the next stage, which includes a mathematical model for block distortion surface to estimate the distance from the current search point to the global optimal position. This allows the motion estimation stage to adjust its search strategies accordingly. The search is performed on a precise area according to the statistical properties of the motion vector prediction error, separately for foreground and background regions. The proposed algorithm, including the pre-stage, is fast and, therefore, is suitable for online and real-time encoding. Extensive simulation results obtained for several video sequences affirm the effectiveness of the proposed algorithm. The self-tuning property enables the algorithm to perform well for several types of benchmark sequences, yielding better video quality without exceeding the time complexity as compared to the other predictive motion estimation algorithms.

The embedded motion compensation model of the new H.264/AVC video coding standard dramatically increases the computational complexity of motion estimation. We propose a fast motion estimation algorithm using a hierarchical motion intensity structure to lower the computational complexity of the motion estimation in H.264/AVC. The proposed algorithm is mainly based on a multi-level motion intensity structure. It determines the motion intensity at three levels and, accordingly, uses different motion estimation techniques to find a more accurate, and faster, motion vector (MV). Experimental results show that the proposed algorithm provides promising performance in terms of the computational speedup and video reconstruction quality.

For video coding in futuristic ubiquitous environments, how to efficiently manage the power consumption while preserving high video quality is crucial. To address the above challenge elegantly, we formulate a multiple objective optimization problem to model the behavior of power-distortion-optimized video coding. Though the objectives in this problem are incommensurate and in conflict with one another. By assessing the performance trade-offs as well as the collective impact of power and distortion, we propose a joint power distortion control strategy (JPDC), in which the power and distortion are jointly considered. After the analysis on the approach of solving the problem statically, we utilize a sub-optimal “greedy” approach in the JPDC scheme. Each complexity parameter is adjusted individually. The system starts coding at the highest complexity level, and will automatically migrate to lower/higher level until the performance improvement gets saturated, leading to the optimal operation point. We perform simulations to demonstrate the effectiveness of the proposed scheme. Our results show that the proposed JPDC scheme is aware of the power constraint as well as the video content, and achieves significant power savings with well-perceived video quality. Such a feature is particularly desirable for futuristic video applications.

This paper proposes a median-bias fast priority search algorithm for motion estimation. The main characteristic of the proposed algorithm is that it adapts a priority median-bias search pattern enabling the identification of locations with higher probability of finding the motion vector. Moreover, based on the history of motion vectors, the algorithm includes a robust region detection technique to avoid unnecessary searches in the static background region. A minimum-distortion based analytical threshold is proposed to stop the search quickly when a "good enough" motion vector is achieved. Experimental results show that by using the proposed algorithm, the speed and accuracy of motion estimation are improved compared with the conventional approaches.

In wireless communication networks, an important issue that must be addressed is the limited energy supply of a mobile device, especially in wireless video applications. In this paper, we develop a parametric video encoding architecture, which is fully scalable in power consumption, and establish the power-rate-distortion (P-R-D) model of the video encoding system. Both theoretically and experimentally, we show that by using this P-R-D model, the encoding system is able to automatically adjust its complexity control parameters to match the available energy supply of the mobile device while maximizing the picture quality. The P-R-D model provides a theoretical guideline for system design and performance optimization in wireless video communication under power constraint.