Computationally efficient 3D orientation (3DO) tracking using gyroscope angular velocity measurem... more Computationally efficient 3D orientation (3DO) tracking using gyroscope angular velocity measurements enables a short execution time and low energy consumption for the computing device. These are essential requirements in today's wearable device environments, which are characterized by limited resources and demands for high energy autonomy. We show that the computational efficiency of 3DO tracking is significantly improved by correctly interpreting each triplet of gyroscope measurements as simultaneous (using the rotation vector called the Simultaneous Orthogonal Rotation Angle, or SORA) rather than as sequential (using Euler angles) rotation. For an example rotation of 90 • , depending on the change in the rotation axis, using Euler angles requires 35 to 78 times more measurement steps for comparable levels of accuracy, implying a higher sampling frequency and computational complexity. In general, the higher the demanded 3DO accuracy, the higher the computational advantage of using the SORA. Furthermore, we demonstrate that 12 to 14 times faster execution is achieved by adapting the SORA-based 3DO tracking to the architecture of the executing low-power ARM Cortex ® M0+ microcontroller using only integer arithmetic, lookup tables, and the small-angle approximation. Finally, we show that the computational efficiency is further improved by choosing the appropriate 3DO computational method. Using rotation matrices is 1.85 times faster than using rotation quaternions when 3DO calculations are performed for each measurement step. On the other hand, using rotation quaternions is 1.75 times faster when only the final 3DO result of several consecutive rotations is needed. We conclude that by adopting the presented practices, the clock frequency of a processor computing the 3DO can be significantly reduced. This substantially prolongs the energy autonomy of the device and enhances its usability in day-today measurement scenarios.
Abstract Multimedia and streaming applications are getting more and more important in 3G networks... more Abstract Multimedia and streaming applications are getting more and more important in 3G networks and will be an important part of the future 4G networks. In this article, after introducing 3G and 4G concepts and architectures, multimedia support in these network ...
Real-time biomechanical feedback (BMF) is a relatively new area of research. The potential of usi... more Real-time biomechanical feedback (BMF) is a relatively new area of research. The potential of using advanced technology to improve motion skills in sport and accelerate physical rehabilitation has been demonstrated in a number of studies. This paper provides a literature review of BMF systems in sports and rehabilitation. Our motivation was to examine the history of the field to capture its evolution over time, particularly how technologies are used and implemented in BMF systems, and to identify the most recent studies showing novel solutions and remarkable implementations. We searched for papers in three research databases: Scopus, Web of Science, and PubMed. The initial search yielded 1167 unique papers. After a rigorous and challenging exclusion process, 144 papers were eventually included in this report. We focused on papers describing applications and systems that implement a complete real-time feedback loop, which must include the use of sensors, real-time processing, and con...
The aim of the present study was to determine if an inertial measurement unit placed on the metat... more The aim of the present study was to determine if an inertial measurement unit placed on the metatarsal part of the foot can provide valid and reliable data for an accurate estimate of vertical jump height. Thirteen female volleyball players participated in the study. All players were members of the Republic of Serbia national team. Measurement of the vertical jump height was performed for the two exemplary jumping tasks, squat jump and counter-movement jump. Vertical jump height estimation was performed using the flight time method for both devices. The presented results support a high level of concurrent validity of an inertial measurement unit in relation to a force plate for estimating vertical jump height (CMJ t = 0.897, p = 379; ICC = 0.975; SQJ t = −0.564, p = 0.578; ICC = 0.921) as well as a high level of reliability (ICC > 0.872) for inertial measurement unit results. The proposed inertial measurement unit positioning may provide an accurate vertical jump height estimate ...
Interfaces enable the interaction and exchange of information between a system and a user. In the... more Interfaces enable the interaction and exchange of information between a system and a user. In the case of auditory interface, the information is presented with different types of sounds. Auditory interfaces can be used for input or output and can complement or replace visual interfaces. Although nowadays technology shapes our lives in many ways, in some cases, our lifestyle requires more than the technical devices are designed for. Mobility is the major paradigm of our times; nevertheless, many of our mobile devices, like mobile phones or personal digital assistants (PDAs), fail to meet the demands arising from the variety of mobile situations. Often the user interfaces on mobile devices are simply a simplified version of the desktop computer interfaces, using the same metaphors and methods of interaction. But due to their miniaturization, mobile devices have limited input and output capacities which make the traditional interaction based on the Windows Icons Menus Pointers (WIMP) p...
IP multimedia subsystem (IMS) represents a standardized next-generation reference system to provi... more IP multimedia subsystem (IMS) represents a standardized next-generation reference system to provide an overlay global open service delivery platform (SDP) that enables provisioning of converged multimedia
This paper reports on a user study of simulated cell phone use in a driving simulator. The main q... more This paper reports on a user study of simulated cell phone use in a driving simulator. The main questions we were seeking to answer were concerning the effectiveness and efficiency of the auditory interfaces in comparison to a standard visual interface. In our experiment we tested two audio interfaces; one with many spatial audio sources and one with a single source. These were compared against a visual interface. Both of the auditory interfaces were as effective as each other but they were not better than the visual interface. However users made more errors while using the visual interface than in the two audio conditions. So although both types of interface were as effective as each other the visual interface was less efficient as it distracted strongly from the primary driving task.
This article studies the suitability of smartphones with built-in inertial sensors for biofeedbac... more This article studies the suitability of smartphones with built-in inertial sensors for biofeedback applications. Biofeedback systems use various sensors to measure body functions and parameters. These sensor data are analyzed, and the results are communicated back to the user, who then tries to act on the feedback signals. Smartphone inertial sensors can be used to capture body movements in biomechanical biofeedback systems. These sensors exhibit various inaccuracies that induce significant angular and positional errors. We studied deterministic and random errors of smartphone accelerometers and gyroscopes, primarily focusing on their biases. Based on extensive measurements, we determined accelerometer and gyroscope noise models and bias variation ranges. Then, we compiled a table of predicted positional and angular errors under various biofeedback system operation conditions. We suggest several bias compensation options that are suitable for various examples of use in real-time bio...
The IEEE Region 8 EUROCON 2003. Computer as a Tool.
Generating spatial sound and playing it through headphones is demanding task, since two important... more Generating spatial sound and playing it through headphones is demanding task, since two important factors, ILD-Inter-aural Level Difference and ITD-Inter-aural Time Difference, need to be taken into consideration. The problem can be solved by the use of Head Related Transfer Functions (HRTF) which represent a set of empirically measured functions, one for each spatial direction. The complete reconstruction of HRTF is possible through the use of Finite Impulse Response (FIR) filters with 512 coefficients each. Since the spectrum of HRTF consists of distinctive maximums and minimums, the spectrum could be approximated by the use of resonators and notch filters. The approximation of the complete spectrum (20 Hz-20 kHz) could be done by the use of six resonators and one notch filter. Our approach to spatial sound generation using HRTF created by the use of recursive (IIR) filters presents a practical and computationally effective solution. It also indicates a way to uniformly model all factors connected to spatial sound perception.
First International Conference on Advances in Computer-Human Interaction, 2008
In this paper we evaluate the safety of the driver when using an embedded communication device wh... more In this paper we evaluate the safety of the driver when using an embedded communication device while driving. As a part of our research, four different tasks were preformed with the device in order to evaluate the efficiency and safety of the drivers under three different conditions: one visual and two different auditory conditions. In the visual condition, various menu items were shown on a small LCD screen attached to the dashboard. In the auditory conditions, the same menu items were presented with spatial sounds distributed on a virtual ring around the user's head. The same custom-made interaction device attached to the steering wheel was used in all three conditions, enabling simple and safe interaction with the device while driving. The auditory interface proved to be as fast as the visual one, while at the same time enabling a significantly safer driving and higher satisfaction of the users. The measured workload also appeared to be lower when using the auditory interfaces.
Auditory navigation in virtual acoustic space is a well-known aid for helping blind people orient... more Auditory navigation in virtual acoustic space is a well-known aid for helping blind people orient in space. Methods used for generating virtual acoustic space are also useful in reproduction of realistic sounds in surrond audio systems, video games, etc. In order to design an ...
— Sorting is extensively used in many applications. Predominantly, comparison based sequential so... more — Sorting is extensively used in many applications. Predominantly, comparison based sequential sorting algorithms are used. High speed computing is also driving the quest for ever faster sorting. Sorting networks executing parallel sorting and dataflow computational paradigm are offered as a possible solution. Sorting networks are briefly explained, Details are given for the Bitonic merge sort algorithm, which we used in our experiments. Sorting was implemented on an entry model of the Maxeler dataflow supercomputing systems. We employed different testing scenarios. Results show, that for a small size array of 128 numbers, the speedup, comparing to the fastest sorting algorithm on a CPU, achieves factor of 16. Moving to more advanced Maxeler systems, we expect to be able to sort larger arrays and achieve much greater speedups.
ABSTRACT Lightweight Directory Access Protocol is a communication protocol which enables the acce... more ABSTRACT Lightweight Directory Access Protocol is a communication protocol which enables the access to online directories. As it is the case with the majority of free client software, the user is merely able to explore the directory, but can not change its content. The necessary software to administrate LDAP directory can be bought, but it is usually not compliant with the needs of users. Our interface module runs on ASP server and works as a converter between HTML and LDAP protocol. With the use of our model the user can access his directory, administrate it or change its content merely by using a standard internet browser. It was developed to simplify the use of LDAP protocol and the access to LDAP directory for various users.
The synthesis of spatial sound which is played through the headphones can be done by the use of H... more The synthesis of spatial sound which is played through the headphones can be done by the use of Head Related Transfer Functions (HRTF). The latter describe the changes in the sound wave as it propagates from a spatial sound source to the human eardrum. The functions ...
2009 Second International Conferences on Advances in Computer-Human Interactions, 2009
Abstract In this paper we evaluate two different auditory interfaces for word processing applica... more Abstract In this paper we evaluate two different auditory interfaces for word processing application. The interfaces are in the form of hierarchical menu structures and use spatial sounds in two different spatial configurations. The first menu - AH - has a ring shaped horizontal ...
This paper focuses on design and development of four different types of auditory interfaces as ... more This paper focuses on design and development of four different types of auditory interfaces as well as the user study with visually impaired and blind computer users. The interfaces represent the hierarchical menu structure of a Windows based application and use spatial sounds ...
The paper gives an overview of the new features of web technologies. The general idea of the new ... more The paper gives an overview of the new features of web technologies. The general idea of the new version of HTML (Hyper Text Markup Language), i.e. HTML5, and other tools presented in this paper is the formal specification and the establishment of uniform solutions for technologies and functionalities which have already been in use through various hacks and plug-ins proposed by web developers. Many of these functionalities will now be implemented in browsers. The applications can access these functionalities through newly defined application programming interfaces. The latter include support for multimedia, dynamic graphic rendering, geolocation, multithreading, local data storage etc. HTML5 also introduces semantic markup, which can be used for marking the document structure as well as its elements and data. The new version of HTML enforces strict separation of the page content from its style. The styling can only be done using CSS (Cascading Style Sheets) language. The new CSS version, i.e. CSS3, has a modular structure, in which different modules define different styling features. The development cycles of the individual modules are independent as well as their support and implementation in various browsers.
Computationally efficient 3D orientation (3DO) tracking using gyroscope angular velocity measurem... more Computationally efficient 3D orientation (3DO) tracking using gyroscope angular velocity measurements enables a short execution time and low energy consumption for the computing device. These are essential requirements in today's wearable device environments, which are characterized by limited resources and demands for high energy autonomy. We show that the computational efficiency of 3DO tracking is significantly improved by correctly interpreting each triplet of gyroscope measurements as simultaneous (using the rotation vector called the Simultaneous Orthogonal Rotation Angle, or SORA) rather than as sequential (using Euler angles) rotation. For an example rotation of 90 • , depending on the change in the rotation axis, using Euler angles requires 35 to 78 times more measurement steps for comparable levels of accuracy, implying a higher sampling frequency and computational complexity. In general, the higher the demanded 3DO accuracy, the higher the computational advantage of using the SORA. Furthermore, we demonstrate that 12 to 14 times faster execution is achieved by adapting the SORA-based 3DO tracking to the architecture of the executing low-power ARM Cortex ® M0+ microcontroller using only integer arithmetic, lookup tables, and the small-angle approximation. Finally, we show that the computational efficiency is further improved by choosing the appropriate 3DO computational method. Using rotation matrices is 1.85 times faster than using rotation quaternions when 3DO calculations are performed for each measurement step. On the other hand, using rotation quaternions is 1.75 times faster when only the final 3DO result of several consecutive rotations is needed. We conclude that by adopting the presented practices, the clock frequency of a processor computing the 3DO can be significantly reduced. This substantially prolongs the energy autonomy of the device and enhances its usability in day-today measurement scenarios.
Abstract Multimedia and streaming applications are getting more and more important in 3G networks... more Abstract Multimedia and streaming applications are getting more and more important in 3G networks and will be an important part of the future 4G networks. In this article, after introducing 3G and 4G concepts and architectures, multimedia support in these network ...
Real-time biomechanical feedback (BMF) is a relatively new area of research. The potential of usi... more Real-time biomechanical feedback (BMF) is a relatively new area of research. The potential of using advanced technology to improve motion skills in sport and accelerate physical rehabilitation has been demonstrated in a number of studies. This paper provides a literature review of BMF systems in sports and rehabilitation. Our motivation was to examine the history of the field to capture its evolution over time, particularly how technologies are used and implemented in BMF systems, and to identify the most recent studies showing novel solutions and remarkable implementations. We searched for papers in three research databases: Scopus, Web of Science, and PubMed. The initial search yielded 1167 unique papers. After a rigorous and challenging exclusion process, 144 papers were eventually included in this report. We focused on papers describing applications and systems that implement a complete real-time feedback loop, which must include the use of sensors, real-time processing, and con...
The aim of the present study was to determine if an inertial measurement unit placed on the metat... more The aim of the present study was to determine if an inertial measurement unit placed on the metatarsal part of the foot can provide valid and reliable data for an accurate estimate of vertical jump height. Thirteen female volleyball players participated in the study. All players were members of the Republic of Serbia national team. Measurement of the vertical jump height was performed for the two exemplary jumping tasks, squat jump and counter-movement jump. Vertical jump height estimation was performed using the flight time method for both devices. The presented results support a high level of concurrent validity of an inertial measurement unit in relation to a force plate for estimating vertical jump height (CMJ t = 0.897, p = 379; ICC = 0.975; SQJ t = −0.564, p = 0.578; ICC = 0.921) as well as a high level of reliability (ICC > 0.872) for inertial measurement unit results. The proposed inertial measurement unit positioning may provide an accurate vertical jump height estimate ...
Interfaces enable the interaction and exchange of information between a system and a user. In the... more Interfaces enable the interaction and exchange of information between a system and a user. In the case of auditory interface, the information is presented with different types of sounds. Auditory interfaces can be used for input or output and can complement or replace visual interfaces. Although nowadays technology shapes our lives in many ways, in some cases, our lifestyle requires more than the technical devices are designed for. Mobility is the major paradigm of our times; nevertheless, many of our mobile devices, like mobile phones or personal digital assistants (PDAs), fail to meet the demands arising from the variety of mobile situations. Often the user interfaces on mobile devices are simply a simplified version of the desktop computer interfaces, using the same metaphors and methods of interaction. But due to their miniaturization, mobile devices have limited input and output capacities which make the traditional interaction based on the Windows Icons Menus Pointers (WIMP) p...
IP multimedia subsystem (IMS) represents a standardized next-generation reference system to provi... more IP multimedia subsystem (IMS) represents a standardized next-generation reference system to provide an overlay global open service delivery platform (SDP) that enables provisioning of converged multimedia
This paper reports on a user study of simulated cell phone use in a driving simulator. The main q... more This paper reports on a user study of simulated cell phone use in a driving simulator. The main questions we were seeking to answer were concerning the effectiveness and efficiency of the auditory interfaces in comparison to a standard visual interface. In our experiment we tested two audio interfaces; one with many spatial audio sources and one with a single source. These were compared against a visual interface. Both of the auditory interfaces were as effective as each other but they were not better than the visual interface. However users made more errors while using the visual interface than in the two audio conditions. So although both types of interface were as effective as each other the visual interface was less efficient as it distracted strongly from the primary driving task.
This article studies the suitability of smartphones with built-in inertial sensors for biofeedbac... more This article studies the suitability of smartphones with built-in inertial sensors for biofeedback applications. Biofeedback systems use various sensors to measure body functions and parameters. These sensor data are analyzed, and the results are communicated back to the user, who then tries to act on the feedback signals. Smartphone inertial sensors can be used to capture body movements in biomechanical biofeedback systems. These sensors exhibit various inaccuracies that induce significant angular and positional errors. We studied deterministic and random errors of smartphone accelerometers and gyroscopes, primarily focusing on their biases. Based on extensive measurements, we determined accelerometer and gyroscope noise models and bias variation ranges. Then, we compiled a table of predicted positional and angular errors under various biofeedback system operation conditions. We suggest several bias compensation options that are suitable for various examples of use in real-time bio...
The IEEE Region 8 EUROCON 2003. Computer as a Tool.
Generating spatial sound and playing it through headphones is demanding task, since two important... more Generating spatial sound and playing it through headphones is demanding task, since two important factors, ILD-Inter-aural Level Difference and ITD-Inter-aural Time Difference, need to be taken into consideration. The problem can be solved by the use of Head Related Transfer Functions (HRTF) which represent a set of empirically measured functions, one for each spatial direction. The complete reconstruction of HRTF is possible through the use of Finite Impulse Response (FIR) filters with 512 coefficients each. Since the spectrum of HRTF consists of distinctive maximums and minimums, the spectrum could be approximated by the use of resonators and notch filters. The approximation of the complete spectrum (20 Hz-20 kHz) could be done by the use of six resonators and one notch filter. Our approach to spatial sound generation using HRTF created by the use of recursive (IIR) filters presents a practical and computationally effective solution. It also indicates a way to uniformly model all factors connected to spatial sound perception.
First International Conference on Advances in Computer-Human Interaction, 2008
In this paper we evaluate the safety of the driver when using an embedded communication device wh... more In this paper we evaluate the safety of the driver when using an embedded communication device while driving. As a part of our research, four different tasks were preformed with the device in order to evaluate the efficiency and safety of the drivers under three different conditions: one visual and two different auditory conditions. In the visual condition, various menu items were shown on a small LCD screen attached to the dashboard. In the auditory conditions, the same menu items were presented with spatial sounds distributed on a virtual ring around the user's head. The same custom-made interaction device attached to the steering wheel was used in all three conditions, enabling simple and safe interaction with the device while driving. The auditory interface proved to be as fast as the visual one, while at the same time enabling a significantly safer driving and higher satisfaction of the users. The measured workload also appeared to be lower when using the auditory interfaces.
Auditory navigation in virtual acoustic space is a well-known aid for helping blind people orient... more Auditory navigation in virtual acoustic space is a well-known aid for helping blind people orient in space. Methods used for generating virtual acoustic space are also useful in reproduction of realistic sounds in surrond audio systems, video games, etc. In order to design an ...
— Sorting is extensively used in many applications. Predominantly, comparison based sequential so... more — Sorting is extensively used in many applications. Predominantly, comparison based sequential sorting algorithms are used. High speed computing is also driving the quest for ever faster sorting. Sorting networks executing parallel sorting and dataflow computational paradigm are offered as a possible solution. Sorting networks are briefly explained, Details are given for the Bitonic merge sort algorithm, which we used in our experiments. Sorting was implemented on an entry model of the Maxeler dataflow supercomputing systems. We employed different testing scenarios. Results show, that for a small size array of 128 numbers, the speedup, comparing to the fastest sorting algorithm on a CPU, achieves factor of 16. Moving to more advanced Maxeler systems, we expect to be able to sort larger arrays and achieve much greater speedups.
ABSTRACT Lightweight Directory Access Protocol is a communication protocol which enables the acce... more ABSTRACT Lightweight Directory Access Protocol is a communication protocol which enables the access to online directories. As it is the case with the majority of free client software, the user is merely able to explore the directory, but can not change its content. The necessary software to administrate LDAP directory can be bought, but it is usually not compliant with the needs of users. Our interface module runs on ASP server and works as a converter between HTML and LDAP protocol. With the use of our model the user can access his directory, administrate it or change its content merely by using a standard internet browser. It was developed to simplify the use of LDAP protocol and the access to LDAP directory for various users.
The synthesis of spatial sound which is played through the headphones can be done by the use of H... more The synthesis of spatial sound which is played through the headphones can be done by the use of Head Related Transfer Functions (HRTF). The latter describe the changes in the sound wave as it propagates from a spatial sound source to the human eardrum. The functions ...
2009 Second International Conferences on Advances in Computer-Human Interactions, 2009
Abstract In this paper we evaluate two different auditory interfaces for word processing applica... more Abstract In this paper we evaluate two different auditory interfaces for word processing application. The interfaces are in the form of hierarchical menu structures and use spatial sounds in two different spatial configurations. The first menu - AH - has a ring shaped horizontal ...
This paper focuses on design and development of four different types of auditory interfaces as ... more This paper focuses on design and development of four different types of auditory interfaces as well as the user study with visually impaired and blind computer users. The interfaces represent the hierarchical menu structure of a Windows based application and use spatial sounds ...
The paper gives an overview of the new features of web technologies. The general idea of the new ... more The paper gives an overview of the new features of web technologies. The general idea of the new version of HTML (Hyper Text Markup Language), i.e. HTML5, and other tools presented in this paper is the formal specification and the establishment of uniform solutions for technologies and functionalities which have already been in use through various hacks and plug-ins proposed by web developers. Many of these functionalities will now be implemented in browsers. The applications can access these functionalities through newly defined application programming interfaces. The latter include support for multimedia, dynamic graphic rendering, geolocation, multithreading, local data storage etc. HTML5 also introduces semantic markup, which can be used for marking the document structure as well as its elements and data. The new version of HTML enforces strict separation of the page content from its style. The styling can only be done using CSS (Cascading Style Sheets) language. The new CSS version, i.e. CSS3, has a modular structure, in which different modules define different styling features. The development cycles of the individual modules are independent as well as their support and implementation in various browsers.
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Papers by Sašo Tomažič