Valter Roesler

Proposta Brasileira de Metadados para Objetos de Aprendizagem Baseados em Agentes (OBAA)

This paper presents the Agent Based Learning Objects - OBAA standard proposal. The main goal of the research was to establish a standardized specification of the technical and functional requirements of learning objects that should allow the interoperability of the contents between Web and Digital TV environment, supporting accessibility and pedagogical issues. In this proposal it has been explored the convergence among the multiagent systems, LO and ubiquitous computing technologies, allowing the authoring, storage and recovery of LO in varied contexts and through different digital platforms. The result of this research was the definition of the OBAA proposal containing the requirements, specifications and architectures that will compose the Brazilian standard for the management, transmission, storage, search, editing and use of LO that can be distributed and used in an integrated manner within the Web platforms, mobile devices and Digital TV.

A Tutorial on H.264/SVC Scalable Video Coding and its Tradeoff between Quality, Coding Efficiency and Performance

The evolution of digital video technology and the continuous improvements in communication infrastructure is propelling a great number of interactive multimedia applications, such as real-time video conference, web video streaming and mobile TV, among others. The new possibilities on interactive video usage have created an exigent market of consumers, which demands the best video quality wherever they are and whatever their network support is (Schwarz et al., 2006). On this purpose, the transmitted video must match the receiver’s characteristics such as the required bit rate, resolution and frame rate, thus aiming to provide the best quality subject to receiver’s and network’s limitations. Besides, the same link is often used to transmit to either restricted devices such as small cell phones, or to high-performance equipments, e.g. HDTVworkstations. In addition, the stream should adapt to wireless lossy networks (Ohm, 2005). Based on this reasoning, these heterogeneous and non-deterministic networks represent a great problem for traditional video encoders which do not allow for on-the-fly video streaming adaptation. To circumvent this drawback, the concept of scalability for video coding has been lately proposed as an emergent solution for supporting, in a given network, endpoints with distinct video processing capabilities. The principle of a scalable video encoder is to break the conventional single-stream video in a multi-stream flow, composed by distinct and complementary components, often referred to as layers (Huang et al., 2007). Figure 1 illustrates this concept by depicting a transmitter encoding the input video sequence into three complementary layers. Therefore, receivers can select and decode different number of layers – each corresponding to distinct video characteristics – in accordance with the processing constraints of both the network and the device itself. The layered structure of any scalable video content can be defined as the combination of a base layer and several additional enhancement layers. The base layer corresponds to the lowest supported video performance, whereas the enhancement layers allow for the refinement of A Tutorial on H.264/SVC Scalable Video Coding and its Tradeoff between Quality, Coding Efficiency and Performance 1

Hardware integrated quantization solution for improvement of computational H.264 encoder module

The computational module of several MPEG-based video encoders, which includes the known algorithms of Discrete Cosine Transform, Hadamard Transform and Quantization, is widely used to identify and compress spatial redundancy in intra (raw input) or inter (computed residue) data pixel matrices. For some modern multimedia applications, like high definition (HD H.264/AVC) or scalable (H.264/SVC) encoder solutions, the demand for fast module implementations becomes critical. Practical experiments indicate that, inside a H.264 computational module, the quantization module normally represents a real bottleneck for fast hardware implementations. Considering that we propose a complete integrated solution of H.264 computational module, which incorporates the direct and inverse algorithms of Discrete Cosine Transform, Hadamard and Quantization with minimal communication delays. Also in this paper it is presented a practical study, considering distinct levels of parallelism for the quantization to demonstrate its influence in order to optimize global encoder complexity and performance. All proposed alternatives were designed using hardware description language VHDL and implemented into commercial FPGA boards to obtain experimental results.

A new multimedia synchronous distance learning system: the IVA study case

This paper presents an innovative distance learning system named IVA (Interactive Video and Audio) which allows users to access video content, from any electronic device with enough processing capability and resources, aiming an ubiquitous application (anytime and anywhere) through synchronous or asynchronous communication. The paper raises and discusses real issues about multipoint multimedia transmission, taking into account adaptation to differnt devices and different networks. The paper also discusses the implemented solutions to overcome the faced problems. The papers main focus is on live video transmission to many heterogeneous receivers, as this is the application which demands most resources from devices and network.

Motivating people to perform better in exergames: competition in virtual environments

Repetitive indoor exercises as running on a treadmill or cycling on an exercise bike use to be tedious, meanwhile immersive virtual environments can bring a greater incentive especially when combined with other sources of motivation such as competition. In this work we introduce Running Wheel, an exergame with both single player and competitive modes with real time capture of heartbeat rhythm and speed of the treadmill. Two hypotheses were tested: (a) there is difference between users that ran with the competitive mode versus the single player mode; and (b) there is difference in performance depending on the kind of competitor picked. We evaluated the system with 12 volunteers which performed at least 6 jogging sessions. Results show that participants got strongly motivated and most of them tried to overcome their limitations and overtake others which in turn led to more effort, perceived by an increase in heartbeat rhythm.

Subjective video quality assessment applied to scalable video coding and transmission instability

This paper presents a study of subjective quality of scalable video sequences, coded using the scalable extension of the H.264 standard (SVC). A group of experiments was performed to measure, primarily, the effects that the transmission instability has in the video quality and the relationship between the three scalability methods (spatial, temporal and quality) in terms of subjective quality. The decisions taken to model the tests were based on layered transmission systems that use protocols for adaptability and congestion control. To run the subjective assessments we used the ACRHRR methodology and recommendations given by ITU-R Rec. BT.500 and ITU-T Rec. P.910. The results show that the instability modeled does not cause signifficant alterations on the overall video quality when compared to a stable video and that temporal scalability usually produces videos with worse quality than spatial and quality scalabilities, the latter being the one with the better quality.

Highly Efficient Transforms Module Solution for a H.264/SVC Encoder

The computational-intensive demands of H.264 video encoder normally imply to the use of high performance hardware solutions like dedicated multimedia DSP or programmable logic devices. These demands can be even more critical when it is necessary to implement a H.264/SVC (Scalable Video Coding) solution, an emergent encoder standard that provides the generation of flexible and adaptive multi-layer streams. The complexity of a SVC encoder increases proportionally with number of configured layers, introducing new challenges to multimedia market. In this work we propose an efficient hardware module, responsible for the transform algorithms (Hadamard and DCT) of a SVC encoder, processing up eight samples per clock. The proposed module take into account specific memory demands in order to produce an optimized solution with respect to encoder performance and complexity, aiming to reach a realizable SVC encoder.

Avaliaçao subjetiva de qualidade aplicada à codificaçao de vídeo escalável

This paper presents a subjective video quality study of video sequences coded using the scalable extension of the H.264 standard (SVC). A group of experiments was performed to measure, primarily, the effects of transmission instability and the influence of the three scalability methods (spatial, temporal and quality) on the video quality. The definitions were based on a layered transmission system using protocols for adaptability and congestion control. To run the subjective assessment we used the ACR-HRR methodology and recommendations given by ITU-R Rec. BT.500 and ITU-T Rec. P.910. The results show that instability does not causes significant alterations on the overall video subjective quality and that the temporal scalability usually presents far lower subjective quality than spatial and quality scalabilities.

Proposal of an improved motion estimation module for SVC

In October 2007 ITU-T and MPEG organizations published the Scalable Video Coding (SVC) specification as an addendum to the H.264 standard. Basically SVC enables H.264 video encoders to support temporal, spatial and SNR scalability. This new functionalities lead to more flexibility on bandwidth management and robustness against packet losses. It is therefore more suitable for heterogeneous multimedia applications like IPTV and mobile networks. However implementations of SVC specification are still limited due the augmented computational complexity. One of the most critical SVC algorithms is the motion estimation module, which allows identification of extra intra and inter-layer redundancies. The great computation demand of this module is responsible for the large SVC encoder latency time, restraining its use in real-time applications. We propose in this paper a new motion estimation approach specially designed to reduce memory accesses and data comparisons in order to increase performance. Experimental results prove significant gains in speed (up to 6 times faster) with small effects on quality (less than 0.2 dB).

Quality analysis of scalable video coding on unstable transmissions

This paper presents a study of quality on scalable video sequences coded using the scalable extension of the H.264 standard (SVC). A group of experiments was performed to measure, primarily, the effects that transmission instability has in the quality of the videos and the relationship among three scalability methods (spatial, temporal and quality) in terms of quality. A set of experiments was performed to measure the subjective quality using the ACR-HRR methodology and recommendations from ITU-R Rec. BT.500 and ITU-T Rec. P.910. The results show that the amount of instability is not as important as just the presence of instability, that video quality can be deteriorated due to instability and that temporal scalability usually produces videos with worse quality than spatial and quality scalabilities.