Mobile Video Applications Research Articles

Power-efficient video encoding on resource-limited systems: A game-theoretic approach

Most mobile video applications are often deployed on battery-operated devices. With limited power supply, it is a challenging issue to support video applications with high resolution due to the complex functionality and high resource requirements. Thus, power-efficient design is important in computation intensive applications especially for mobile video terminals. Previous works on power-efficient control in video encoding systems focus on the low complexity design while typically ignoring the impact of scalable design by considering various power consumption involved in the encoding process. This paper is dedicated to developing a power-scalable video encoding (PSVE) strategy for energy-limited mobile terminals. PSVE can help the video encoding terminal to adjust its power consumption budget efficiently so as to enhance the power-scalable capability in mobile video terminals. This paper first establishes game theoretical analysis to model the power consumption problem as a bargaining problem. Then, the tradeoff between encoding effect and power consumption achieved by the use of game theory. The scalable and low power video encoding system based on Nash equilibrium solution is derived through the analysis on the power consumption and encoding effect. Experimental results demonstrate the efficiency of the proposed approach.

Learning experiences of mobile social media

In this paper, we describe how a mobile social video application (MoViE) was used to teach HCI concepts. The aims of the study were to study the success factors of mobile video blogging and future expectations of mobile video blogging in education. The learning activities in this experiment were analysed using the shared experience and activity framework. The results indicated that video blogging could be an effective method in HCI education. The students experienced social video services as useful learning tools. Mobile video blogging turned out to be a much more effective method of evaluating the students' level of understanding than traditional paper pencil tests.

Transform-Domain Rate-Distortion Optimization Accelerator for H.264/AVC Video Encoding

In H.264/AVC video encoding, rate-distortion optimization for mode selection plays a significant role to achieve outstanding performance in compression efficiency and video quality. However, this mode selection process also makes the encoding process extremely complex, especially in the computation of the rate- distortion cost function, which includes the computations of the sum of squared difference (SSD) between the original and reconstructed image blocks and context-based entropy coding of the block. In this paper, a transform-domain rate-distortion optimization accelerator based on fast SSD (FSSD) and VLC-based rate estimation algorithm is proposed. This algorithm could significantly simplify the hardware architecture for the rate-distortion cost computation with only ignorable performance degradation. An efficient hardware structure for implementing the proposed transform-domain rate-distortion optimization accelerator is also proposed. Simulation results demonstrated that the proposed algorithm reduces about 47% of total encoding time with negligible degradation of coding performance. The proposed method can be easily applied to many mobile video application areas such as a digital camera and a DMB (Digital Multimedia Broadcasting) phone.

A 1.2 V 4.5 mW 10 bit 8 MS/s cyclic-ADC for mobile video and sensor applications

A 10 bit 8 MS/s cyclic ADC without a dedicated sample and hold is presented. Op-amp sharing and a single ended reference buffer loaded with a resistive divider are used. For power saving the common-mode buffer was replaced by a simple low pass filter. The ADC consumes 4.5 mW and occupies 0.145 mm2. It is fabricated in a 130 nm 1.2 V CMOS process and achieves 57 dB SNDR for an 11 MHz input. The cyclic stage works with a 40 MHz clock which can be increased to 65 MHz where the effective number of bits is reduced to 8. A novel dynamic current switching technique is introduced to reduce the power consumption by 20%. The figure of merit (FOM) is about 0.37 pJ/conversion step.

Efficient two step edge based partial distortion search for fast block motion estimation

In video coding, block based full search motion estimation algorithm has been widely used, but it suffers from high computational requirements. In order to reduce the computations, this paper proposes a novel edge based partial distortion search (EPDS) algorithm which reduces the computation of each distortion measure by using partial distortion search. In this algorithm, the entire macroblock (MB) is divided into different sub-blocks and the calculation order of partial distortion is determined based on the edge strength of sub-blocks. This algorithm adaptively changes the early termination threshold for every accumulated partial sum of absolute difference. In the proposed method, only selected numbers of search points are considered for candidate motion vectors. An efficient early termination method, which is based on the dynamic threshold, is also proposed to decide whether a search point has met the rate-distortion (RD) cost criterion so that the best search point can be determined early. Simulation results show that the proposed method offers a remarkable improvement in computational speed when compared to full search (FS) and normalized partial distortion search (NPDS) algorithms. The proposed method is 115 times faster than FS, 10 times faster than NPDS and 2 times faster than the dual halfway stop NPDS (DHS-NPDS) on an average. PSNR degradation of the proposed algorithm is negligible and in the region of 0.01 dB. The proposed method can be easily applied to many mobile video application areas such as digital cameras and DMB (Digital Multimedia Broadcasting) phones.

Seamless handover and QoS provisioning for mobile video applications in an integrated WiMAX/MIP/MPLS architecture

Mobility management with QoS (Quality of Service) support is a major requirement for the success of next generation wireless networks. With this goal in mind, this paper proposes a new architecture that integrates Mobile WiMAX (WorldWide Interoperability for Microwave Access) with MIP (Mobile IP) and MPLS (Multiprotocol Label Switching) protocols as well as a mobility prediction algorithm to enable seamless handover. The anticipated handover technique provides service continuity based on information about the MN's (Mobile Node) location and speed, as well as the BS's (Base Station) signal strength. The proposed architecture is also enhanced from the traffic engineering mechanisms provided by the MPLS protocol.

An Advanced Total_Zeros Decoding Method Based on New Memory Architecture in H.264/AVC CAVLC

A new total_zeros decoding method based on efficient memory architecture for variable-length code tables (VLCTs) is proposed in this paper. In general, a large amount of memory accesses are required for context-based adaptive variable-length coding (CAVLC) decoding in the H.264/AVC standard. It is an important issue for low-power implementation of mobile video applications because the memory access function results in considerable power consumption. Some distinctive features in the VLCTs of the total_ zeros have been found through a careful analysis of the codewords. Efficient memory architecture and an advanced decoding are developed in order to remove redundant memory access. The simulation results show that the proposed method achieves an approximately 80%-90% memory access saving, compared with conventional decoding.

A dual‐band receiver front‐end using current‐mode passive mixer with digitally‐controlled oscillator in 90‐NM CMOS

AbstractThis work presents a receiver front‐end that targets mobile video applications, and integrates a dual‐band LNA, a current‐mode passive mixer, a reference Gilbert mixer, and a digitally‐controlled oscillator providing the quadrature LO signal for the mixers. The conversion gain and thermal noise performances of the current‐mode passive mixer are studied. Design tradeoffs among noise, linearity, and conversion gain are performed. Measured performance of the receiver front‐end shows a flicker noise corner of 70 kHz, a noise figure (NF) of 4.4 dB, an input third‐order intermodulation product (IIP3) of −2 dBm, and DCO phase noise of −128 dBc/Hz at 1‐MHz offset. The receiver consumes less than 24 mA of current in a 1.2‐V 90‐nm standard digital CMOS process. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2138–2142, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23587

“I would like to see the subtitles and the face or at least hear the voice”: Effects of picture ratio and audio–video bitrate ratio on perception of quality in mobile television

In new mobile video applications, the subjectively perceived visual and audiovisual qualities are critical factors in the wide audience adoption of mass products. The critical factors in mobile video coding are related to low bitrates, framerates and screen size of the devices. The first part of this study examined the effects of codecs, bitrates and picture ratio on the perceived visual video quality. In the second study, effects of two audio---video bitrate ratios are presented as factors in the perceived audiovisual video quality and the results are compared to the previous study that showed the content dependency in the audio---video bitrate ratio comparisons. In the results of the visual quality study, H.264 was rated as the most satisfying, but the quality was still not enough for text legibility and perceiving important details of image due to the QCIF picture ratio. The codec XviD was in generally experienced as worse than the H.264, but with the screen size SIF-SP with XviD codec was rated better with several contents. In the audiovisual study, the results also showed that in the low total bitrates the significance of audio is increased. However, the higher and lower bitrates had similar content dependent effects.

A Hardware Implementation of a Content-Based Motion Estimation Algorithm for Real-Time MPEG-4 Video Coding

Power efficiency and real-time processing capability are two major issues in today's mobile video applications. We proposed a novel Motion Estimation (ME) engine for power-efficient real-time MPEG-4 video coding based on our previously proposed content-based ME algorithm [8], [13]. By adopting Full Search (FS) and Three Step Search (TSS) alternatively according to the nature of video contents, this algorithm keeps the visual quality very close to that of FS with only 3% of its computational power. We designed a flexible Block Matching (BM) Unit with 16-PE SIMD data path so that the adaptive ME can be performed at a much lower clock frequency and hardware cost as compared with previous FS based work. To reduce the energy cost caused by excessive external memory access, on-chip SRAM is also utilized and optimized for parallel processing in the BM Unit. The ME engine is fabricated with TSMC 0.18 μm technology. When processing QCIF (15 fps) video, the estimated power is 2.88 [email protected] MHz (supply voltage: 1.62 V). It is believed to be a favorable contribution to the video encoder LSI design for mobile applications.

Optimizing mobile multimedia using SIMD techniques

Demand for mobile video applications is growing today in wireless handheld platforms. Optimizing instruction set architectures and employing SIMD techniques is a logical approach towards attaining higher performance in mobile multimedia applications. Intel® Wireless MMX� technology has been designed to accelerate mobile multimedia and applications processing in a power efficient manner. This paper provides an overview of Intel® Wireless MMX� technology, a 64-bit Single Instruction Multiple Data (SIMD) coprocessor for the Intel® XScale® microarchitecture, and the key features of the architecture that specifically enhance the multi-media performance. Tools and techniques for optimization are also described.

Accelerating Mobile Video: A 64-Bit SIMD Architecture for Handheld Applications

Providing quality mobile video applications in hand-held mobile devices requires increased computational capability. Using Single Instruction Multiple Data (SIMD) techniques to expose and accelerate the data parallelism inherent in video processing increases performance in handheld and wireless systems. The paper introduces a new 64-bit SIMD coprocessor of the Intel® XScale® microarchitecture which is optimized for low-power handheld applications. The architecture blends the SIMD media processing style with the capabilities of the XScale microarchitecture. This paper provides an overview of the architecture, its instruction set, programming model, the pipeline organization and functional units. The paper also describes how key features of architecture improve the performance of video applications as compared to a scalar implementation. The performance and power improvements based upon measured results are analyzed to show how the opportunities of power savings by reducing the frequency and voltage can be realized.

A sub-mW MPEG-4 motion estimation processor core for mobile video application

This paper describes a sub-mW motion estimation processor core for MPEG-4 video encoding. It features a gradient descent search (GDS) algorithm that reduces required computational complexity to 15 MOPS. The GDS algorithm combined with a sub-block search method upgrades picture quality. The quality is almost equal to that of a full search method. An SIMD datapath architecture optimized for the algorithm decreases a clock frequency and supply voltage. A dedicated three-port SRAM macro for image data caches of the processor is newly designed to reduce power consumption. It has been fabricated with 0.18-/spl mu/m five-layer metal CMOS technology. The VLSI processing QCIF 15-f/s video consumes 0.4-mW power at 0.85-MHz clock frequency with 1.0-V supply voltage. It is applicable to mobile video applications.

Mobile Video Qos Metrics

Video is an important issue in the latest generation of mobile networks that can provide enough bandwidth for video streaming and mobile video telephony applications. An adequate and accurate QoS evaluation of video is therefore needed. This article presents a practical set of QoS metrics for both objective and subjective measurement of video. Some of the objective metrics described is available in the ANSI and ITU standards, but they are here enriched by a set of nonstandard methods for QoS evaluation. Also included are standard subjective metrics for video quality assessment, as they complement the objective techniques. All of these methods can be used when implementing real-time mobile video applications, such as mobile videophones.

A combined source-channel video coding scheme for mobile channels

In this paper, we present a novel error resilient combined source-channel coding scheme suitable for mobile video applications. Several well-known methods from the areas of image and channel coding are combined to provide a system for transmitting low bit-rate video over mobile communication channels. The system is based on the use of Rate Compatible Punctured Convolutional codes that apply Unequal Error Protection to the H.263 source coder. An attempt at retaining synchronisation is made using the Error Resilient Entropy Coder to limit the propagation of bit errors in the macroblocks caused by the presence of burst errors in the mobile channel. Furthermore, the H.263 decoder has several error concealment methods to remove residual errors. Simulation results for the scheme are obtained for two QCIF sequences over Gaussian, Rayleigh and Rician channels using BPSK modulation.