Издательство Kluwer, 2004, -381 pp.
Mode communications technology has become a part of our daily experience and has dramatically changed the way we live, receive education, work, and relate to each other. Nowadays, communications are already fundamental to smooth functioning of the contemporary society and our individual lives. The expeditious growth in our ability to communicate was one of the most revolutionary advancements in our society over the last century, particularly the last two decades.
In recent progress of the communication revolution, we observe four technical developments that have altered the entire landscape of the telecommunication marketplace. The first is the proliferation of data transfer rate. Thanks to technological breakthroughs in fiber optics, the data transfer rate was boosted from around 100 Mbps (Megabits per second) for one single fiber at the beginning of the 1980s to today’s 400 Gbps (Gigabits per second). The capacity of optical fiber has increased by a factor of four thousand in just twenty years, exceeding Moore’s law (which describes the growth in the number of transistors per square inch on integrated circuits.) The second is the ubiquity of packet switched networks driven by the ever-growing popularity of the Inteet and the World-Wide Web. The invention of the Inteet and the World-Wide Web created a common platform for us to share highly diverse information in a relatively unified manner. Ubiquitous packet switched networks make the world more intertwined than ever from an economical, cultural, and even political perspective. Compared to conventional circuit switched networks, packet switched networks are more cost effective and more efficient. Furthermore, adding new services and applications is obviously easier and more flexible on packet switched networks than on circuit switched networks. As a result, the convergence of circuit and packet switched networks has emerged and the trend will continue into the future. The third is the wide deployment of wireless communications. A decade ago most people barely knew of wireless personal communications. In those days, it was basically a techie’s vision. But today, it is no longer an electrical engineer’s dream. Wireless communications has been well accepted by the public and its business is growing bigger every day and everywhere. The wireless communications technology has evolved from first-generation analog systems to second-generation digital systems, and will continue advancing into its third generation, which is optimized for both voice and data communication services. The last but not least significant development is the escalating demand for broadband access through such connections as digital subscriber line (DSL) or cable to the Inteet. Broadband access enables a large number of prospective bandwidth-consuming services that will potentially make our work more productive and our leisure more rewarding. These developments are shaking the foundations of the telecommunications industry and it can be foreseen that tomorrow’s communications will be carried out over fast, high-capacity packet-switched networks with mobile, broadband access anytime and anywhere.
Packet switched networks so far have achieved great success for transferring data in an efficient and economical manner. Data communications have enabled us to acquire timely information from virtually every coer of the world. Our intuition may tell that the faster a network could be, the more favorable it becomes. But there is a lack of perceived benefit from paying more to gain another further quantum leap to even faster networks. We believe that it is more imperative and more urgent to introduce innovative communication services that keep up with the aforementioned four developments in communication technologies. Multimedia communications for telecollaboration (for example teleconferencing, distant leaing, and telemedicine) over packet switched networks is one of the most promising choices. The features that it introduces will more profoundly enhance peoples’ life in the way they communicate, and will bring remarkable values to service providers, enterprises, and end-users.
For a collaboration, full-scale interaction and a sense of immersion are essential to put the users in control and to attain high collaborative productivity in spite of long distances. In this case, not only messages would be exchanged, but also experiences (sensory information) need to be shared. Experiences are inherently composed of a number of different media and advanced multimedia technologies are crucial to the successful implementation of a telecollaboration system. The desire to share experiences has been and will continue to be the motivating factor in the development of exciting multimedia technologies. Multimedia communication differs from traditional communication modes in that it is no longer constrained by one given medium. It selects appropriate media according to the content and combines messages and experiences together. With enriched experiences, remote environments can be reproduced as faithfully as possible so that local users can make full use of both their binaural hearing and binocular vision. Such an immersive interface makes it easier to determine who is talking and helps understand better what is being discussed, particularly when there are multiple participants. Full-scale interaction differentiates collaboration from exhibition although both are possibly powered by multimedia. Interaction establishes two channels of information flow from and to a user, which makes communication more effective. This can be well recognized by considering the effectiveness of a lecture with and without allowing the audience to raise questions. Full-scale interaction and a sense of immersion are indeed the two most important features of collaboration, and we cannot afford to intentionally sacrifice them anymore in building next-generation communication systems.
Evidently, the most powerful way to conduct full-scale interaction and to create a sense of immersion in telecollaboration is with both visual and audio properly involved. But due to space limitation and the authors’ expertise, this book will focus exclusively on the processing, transmission, and presentation of audio and acoustic signals in multimedia communications for telecollaboration. The ideal acoustic environment that we are pursuing is referred to as immersive acoustics, which demands at least full-duplex, hands-free, and spatial perceptibility. As a result, we confront remarkable challenges to address a number of complicated signal processing problems, but at the same time possess tremendous opportunities to develop more practically useful and more computationally efficient algorithms. These challenges and opportunities will be detailed in the following section.
Introduction.
Speech Acquisition and Enhancement.
Differential Microphone Arrays.
Spherical Microphone Arrays for 3D Sound Recording.
Subband Noise Reduction Methods for Speech Enhancement.
Acoustic Echo Cancellation.
Adaptive Algorithms for MIMO Acoustic Echo Cancellation.
Double-Talk Detectors for Acoustic Echo Cancelers.
The WinEC: A Real-Time Hands-Free Stereo Communication System.
Sound Source Tracking and Separation.
Time Delay Estimation.
Source Localization.
Blind Source Separation for Convolutive Mixtures: A Unified Treatment.
Audio Coding and Realistic Sound Stage Reproduction.
Audio Coding.
Sound Field Synthesis.
Virtual Spatial Sound.
Mode communications technology has become a part of our daily experience and has dramatically changed the way we live, receive education, work, and relate to each other. Nowadays, communications are already fundamental to smooth functioning of the contemporary society and our individual lives. The expeditious growth in our ability to communicate was one of the most revolutionary advancements in our society over the last century, particularly the last two decades.
In recent progress of the communication revolution, we observe four technical developments that have altered the entire landscape of the telecommunication marketplace. The first is the proliferation of data transfer rate. Thanks to technological breakthroughs in fiber optics, the data transfer rate was boosted from around 100 Mbps (Megabits per second) for one single fiber at the beginning of the 1980s to today’s 400 Gbps (Gigabits per second). The capacity of optical fiber has increased by a factor of four thousand in just twenty years, exceeding Moore’s law (which describes the growth in the number of transistors per square inch on integrated circuits.) The second is the ubiquity of packet switched networks driven by the ever-growing popularity of the Inteet and the World-Wide Web. The invention of the Inteet and the World-Wide Web created a common platform for us to share highly diverse information in a relatively unified manner. Ubiquitous packet switched networks make the world more intertwined than ever from an economical, cultural, and even political perspective. Compared to conventional circuit switched networks, packet switched networks are more cost effective and more efficient. Furthermore, adding new services and applications is obviously easier and more flexible on packet switched networks than on circuit switched networks. As a result, the convergence of circuit and packet switched networks has emerged and the trend will continue into the future. The third is the wide deployment of wireless communications. A decade ago most people barely knew of wireless personal communications. In those days, it was basically a techie’s vision. But today, it is no longer an electrical engineer’s dream. Wireless communications has been well accepted by the public and its business is growing bigger every day and everywhere. The wireless communications technology has evolved from first-generation analog systems to second-generation digital systems, and will continue advancing into its third generation, which is optimized for both voice and data communication services. The last but not least significant development is the escalating demand for broadband access through such connections as digital subscriber line (DSL) or cable to the Inteet. Broadband access enables a large number of prospective bandwidth-consuming services that will potentially make our work more productive and our leisure more rewarding. These developments are shaking the foundations of the telecommunications industry and it can be foreseen that tomorrow’s communications will be carried out over fast, high-capacity packet-switched networks with mobile, broadband access anytime and anywhere.
Packet switched networks so far have achieved great success for transferring data in an efficient and economical manner. Data communications have enabled us to acquire timely information from virtually every coer of the world. Our intuition may tell that the faster a network could be, the more favorable it becomes. But there is a lack of perceived benefit from paying more to gain another further quantum leap to even faster networks. We believe that it is more imperative and more urgent to introduce innovative communication services that keep up with the aforementioned four developments in communication technologies. Multimedia communications for telecollaboration (for example teleconferencing, distant leaing, and telemedicine) over packet switched networks is one of the most promising choices. The features that it introduces will more profoundly enhance peoples’ life in the way they communicate, and will bring remarkable values to service providers, enterprises, and end-users.
For a collaboration, full-scale interaction and a sense of immersion are essential to put the users in control and to attain high collaborative productivity in spite of long distances. In this case, not only messages would be exchanged, but also experiences (sensory information) need to be shared. Experiences are inherently composed of a number of different media and advanced multimedia technologies are crucial to the successful implementation of a telecollaboration system. The desire to share experiences has been and will continue to be the motivating factor in the development of exciting multimedia technologies. Multimedia communication differs from traditional communication modes in that it is no longer constrained by one given medium. It selects appropriate media according to the content and combines messages and experiences together. With enriched experiences, remote environments can be reproduced as faithfully as possible so that local users can make full use of both their binaural hearing and binocular vision. Such an immersive interface makes it easier to determine who is talking and helps understand better what is being discussed, particularly when there are multiple participants. Full-scale interaction differentiates collaboration from exhibition although both are possibly powered by multimedia. Interaction establishes two channels of information flow from and to a user, which makes communication more effective. This can be well recognized by considering the effectiveness of a lecture with and without allowing the audience to raise questions. Full-scale interaction and a sense of immersion are indeed the two most important features of collaboration, and we cannot afford to intentionally sacrifice them anymore in building next-generation communication systems.
Evidently, the most powerful way to conduct full-scale interaction and to create a sense of immersion in telecollaboration is with both visual and audio properly involved. But due to space limitation and the authors’ expertise, this book will focus exclusively on the processing, transmission, and presentation of audio and acoustic signals in multimedia communications for telecollaboration. The ideal acoustic environment that we are pursuing is referred to as immersive acoustics, which demands at least full-duplex, hands-free, and spatial perceptibility. As a result, we confront remarkable challenges to address a number of complicated signal processing problems, but at the same time possess tremendous opportunities to develop more practically useful and more computationally efficient algorithms. These challenges and opportunities will be detailed in the following section.
Introduction.
Speech Acquisition and Enhancement.
Differential Microphone Arrays.
Spherical Microphone Arrays for 3D Sound Recording.
Subband Noise Reduction Methods for Speech Enhancement.
Acoustic Echo Cancellation.
Adaptive Algorithms for MIMO Acoustic Echo Cancellation.
Double-Talk Detectors for Acoustic Echo Cancelers.
The WinEC: A Real-Time Hands-Free Stereo Communication System.
Sound Source Tracking and Separation.
Time Delay Estimation.
Source Localization.
Blind Source Separation for Convolutive Mixtures: A Unified Treatment.
Audio Coding and Realistic Sound Stage Reproduction.
Audio Coding.
Sound Field Synthesis.
Virtual Spatial Sound.