Several techniques exist for surround sound, including Ambisonics, VBAP, WFS, and pair-wise panni... more Several techniques exist for surround sound, including Ambisonics, VBAP, WFS, and pair-wise panning. Each of the systems have strengths and weaknesses but Ambisonics has long been favored for its extensibility and for being a complete solution, including both recording and playback. But Ambisonics has not met with great critical or commercial success despite having been available in one form or another for many years. Some observers have gone so far as to suggest that Ambisonics can’t work. The present work is intended to provide an analysis of the performance of Ambisonics according to various psychoacoustic mechanisms in spatial hearing such as localization.
An earlier paper [1] examined the performance of "Classic" horizontal Ambisonic surroun... more An earlier paper [1] examined the performance of "Classic" horizontal Ambisonic surround sound systems with speakers arranged in regular polygons or as diametrically opposite pairs. We extend the work to non-traditional Ambisonic systems; ITU-R BS775 5.0 layouts supposedly used for domestic surround sound and also non-optimal decode, where the speaker array does not correspond to the decoder. Our interest is in simple enhancements possible with present day technology that could benefit the listener at home.
Optimal Ambisonic reproduction requires two different filter types, one to implement dual-band de... more Optimal Ambisonic reproduction requires two different filter types, one to implement dual-band decoding and a second to compensate for the near-field effect of having the loudspeakers close to the listener. We present the theory, design, and implementation of both types of filters. They comprise key components of a full Ambisonic decoder engine written completely in FAUST. The FAUST digital signal processing specification language was selected for the implementation so the filters may be easily incorporated into many different plugins and decoder engines.
Implementation of Ambisonic reproduction systems is limited by the number and placement of the lo... more Implementation of Ambisonic reproduction systems is limited by the number and placement of the loudspeakers. In practice, real-world systems tend to have insu!cient loudspeaker coverage above and below the listening position. Because the localization experienced by the listener is a nonlinear function of the loudspeaker signals it is di!cult to derive suitable decoders analytically. As an alternative, it is possible to derive decoders via a search process in which analytic estimators of the localization quality are evaluated at each search position. We discuss the issues involved and describe a set of tools for generating optimized decoder solutions for irregular loudspeaker arrays and demonstrate those tools with practical examples.
Google, Inc. (search). SIGN IN SIGN UP. An experimental evaluation of projective invariants. Auth... more Google, Inc. (search). SIGN IN SIGN UP. An experimental evaluation of projective invariants. Authors: Christopher Coelho, Aaron Heller, Joseph L. Mundy, David A. Forsyth, Andrew Zisserman, 1992 Article. Bibliometrics. · Downloads ...
In this paper we discuss the motivation, design, and analysis of ambisonic decoders for systems w... more In this paper we discuss the motivation, design, and analysis of ambisonic decoders for systems where the vertical order is less than the horizontal order, known as mixedorder Ambisonic systems. This can be due to the use of microphone arrays that emphasize horizontal spatial resolution or speaker arrays that provide sparser coverage vertically. First, we review Ambisonic reproduction criteria, as defined by Gerzon, and summarize recent results on the relative perceptual importance of the various criteria. Then we show that using full-order decoders with mixedorder program material results in poorer performance than with a properly designed mixed-order decoder. We then introduce a new implementation of a decoder optimizer that draws upon techniques from machine learning for quick and robust convergence, discuss the construction of the objective function, and apply it to the problem of designing two-band decoders for mixed-order signal sets and nonuniform loudspeaker layouts. Results...
In earlier papers, the present authors established the importance of various aspects of Ambisonic... more In earlier papers, the present authors established the importance of various aspects of Ambisonic decoder design: a decoding matrix matched to the geometry of the loudspeaker array in use, phase-matched shelf filters, and near-field compensation. These are needed for accurate reproduction of spatial localization cues, such as interaural time difference (ITD), interaural level difference (ILD), and distance cues. Unfortunately, many listening tests of Ambisonic reproduction reported in the literature either omit the details of the decoding used or utilize suboptimal decoding. In this paper we review the acoustic and psychoacoustic criteria for Ambisonic reproduction, present a methodology and tools for “black box” testing to verify the performance of a candidate decoder, and present and discuss the results of this testing on some widely used decoders.
Ambisonic reproduction systems are unique in their ability to separately reproduce the pressure a... more Ambisonic reproduction systems are unique in their ability to separately reproduce the pressure and velocity components of recorded audio signals. Gerzon proposed a theory of localization in which the human auditory system is presumed to localize using the direction of the velocity vector in the reproduced sound at low frequencies, and the energy vector at high frequencies. An Ambisonic decoder has the energy and velocity vectors coincident. These are the directions of the apparent source when the listener can turn to face it. Separately optimizing the low-frequency and mid/high-frequency operation of the reproduction system can optimize localization where the listener cannot turn to face the apparent source. We test the localization of horizontal-only Ambisonic reproduction systems using various test signals to separately evaluate low-frequency and mid-frequency localization.
In this Automatic Population of GeospatialDatabases (APGD) overview paper, we describeour progres... more In this Automatic Population of GeospatialDatabases (APGD) overview paper, we describeour progress in developing and evaluating a genericcontext-based architecture (which we call the BOSfor the Battlespace Observer System) and algorith-mic techniques to radically reduce the human effortrequired to extract cartographic features, especiallyroads and buildings, from aerial and satelliteimagery. We also describe progress in supportingthe DARPA APGD community by constructingverified and well-documented datasets and evalu-ation procedures to allow interested researchers toexperimentally evaluate their extraction techniquesin a common framework. Our APGD Communityoriented activities are accessible at SRI’s APGDweb site, http://www.ai.sri.com/~apgd,and the APGD “Virtual Laboratory,”http://www.ai.sri.com/~apgd/vl.In a formal April1998presentation,we successfullydemonstrated the “end-to-end” extraction of all the This work was sponsored by the Defense Advanced Re-search Projects Agency under c...
We present extensions to the Ambisonic Decoder Toolbox to efficiently design periphonic decoders ... more We present extensions to the Ambisonic Decoder Toolbox to efficiently design periphonic decoders for non-uniform speaker arrays such as hemispherical domes and multilevel rings. These techniques include modified inversion, AllRAD, and spherical Slepian function-based decoders. We also describe a new backend for the toolbox that writes out full-featured decoders in the Faust DSP specification language, which can then be compiled into a variety of plugin formats. Informal listening tests and performance measurements indicate that these decoders work well for speaker arrays that are difficult to handle with conventional design techniques. The computation is relatively quick and more reliable compared to nonlinear optimization techniques used previously.
We describe a system for converting RADIUS site models into a Web-accessible form. Once converted... more We describe a system for converting RADIUS site models into a Web-accessible form. Once converted, the site models can be downloaded and viewed with standard, off-the-shelf Web browsers. Site models themselves are represented in the Virtual Reality Modeling Language (VRML). Each feature in the site model is cross-linked to a Web page that describes that feature in more detail, including image chips and collateral information. A demonstration of work described in this paper is accessible via the URL http://www.ai.sri. com/˜connolly/pathfinder.
For millions of people with swallowing disorders, preventing potentially deadly aspiration pneumo... more For millions of people with swallowing disorders, preventing potentially deadly aspiration pneumonia requires following prescribed safe eating strategies. But adherence is poor, and caregivers' ability to encourage adherence is limited by the onerous and socially aversive need to monitoring another's eating. We have developed an early prototype for an intelligent assistant that monitors adherence and provides feedback to the patient, and tested monitoring precision with healthy subjects for one strategy called a "chin tuck." Results indicate that adaptations of current generation machine vision and personal assistant technologies can effectively monitor chin tuck adherence, and suggest feasibility of a more general assistant that encourages adherence to a range of safe eating strategies.
The RADIUS Common Development Environment pulls together many diverse functions into an integrate... more The RADIUS Common Development Environment pulls together many diverse functions into an integrated whole. The main goal of the environment is to provide a system to do interactive modeling of 3-dimensional scenes from multiple images, as well as, providing ...
Proceedings 1992 IEEE Computer Society Conference on Computer Vision and Pattern Recognition, 1992
The concepts and design issues that provide the basis for the I 2F (image interpretation foundati... more The concepts and design issues that provide the basis for the I 2F (image interpretation foundations) system are described. The I2F system combines object-oriented design for machine vision software and constraint-based geometric modeling into a flexible and effective system for automatic template-guided visual inspection. Object-oriented design for 2-D geometry-based image analysis is discussed, and results from processing experimental X-ray data
Several techniques exist for surround sound, including Ambisonics, VBAP, WFS, and pair-wise panni... more Several techniques exist for surround sound, including Ambisonics, VBAP, WFS, and pair-wise panning. Each of the systems have strengths and weaknesses but Ambisonics has long been favored for its extensibility and for being a complete solution, including both recording and playback. But Ambisonics has not met with great critical or commercial success despite having been available in one form or another for many years. Some observers have gone so far as to suggest that Ambisonics can’t work. The present work is intended to provide an analysis of the performance of Ambisonics according to various psychoacoustic mechanisms in spatial hearing such as localization.
An earlier paper [1] examined the performance of "Classic" horizontal Ambisonic surroun... more An earlier paper [1] examined the performance of "Classic" horizontal Ambisonic surround sound systems with speakers arranged in regular polygons or as diametrically opposite pairs. We extend the work to non-traditional Ambisonic systems; ITU-R BS775 5.0 layouts supposedly used for domestic surround sound and also non-optimal decode, where the speaker array does not correspond to the decoder. Our interest is in simple enhancements possible with present day technology that could benefit the listener at home.
Optimal Ambisonic reproduction requires two different filter types, one to implement dual-band de... more Optimal Ambisonic reproduction requires two different filter types, one to implement dual-band decoding and a second to compensate for the near-field effect of having the loudspeakers close to the listener. We present the theory, design, and implementation of both types of filters. They comprise key components of a full Ambisonic decoder engine written completely in FAUST. The FAUST digital signal processing specification language was selected for the implementation so the filters may be easily incorporated into many different plugins and decoder engines.
Implementation of Ambisonic reproduction systems is limited by the number and placement of the lo... more Implementation of Ambisonic reproduction systems is limited by the number and placement of the loudspeakers. In practice, real-world systems tend to have insu!cient loudspeaker coverage above and below the listening position. Because the localization experienced by the listener is a nonlinear function of the loudspeaker signals it is di!cult to derive suitable decoders analytically. As an alternative, it is possible to derive decoders via a search process in which analytic estimators of the localization quality are evaluated at each search position. We discuss the issues involved and describe a set of tools for generating optimized decoder solutions for irregular loudspeaker arrays and demonstrate those tools with practical examples.
Google, Inc. (search). SIGN IN SIGN UP. An experimental evaluation of projective invariants. Auth... more Google, Inc. (search). SIGN IN SIGN UP. An experimental evaluation of projective invariants. Authors: Christopher Coelho, Aaron Heller, Joseph L. Mundy, David A. Forsyth, Andrew Zisserman, 1992 Article. Bibliometrics. · Downloads ...
In this paper we discuss the motivation, design, and analysis of ambisonic decoders for systems w... more In this paper we discuss the motivation, design, and analysis of ambisonic decoders for systems where the vertical order is less than the horizontal order, known as mixedorder Ambisonic systems. This can be due to the use of microphone arrays that emphasize horizontal spatial resolution or speaker arrays that provide sparser coverage vertically. First, we review Ambisonic reproduction criteria, as defined by Gerzon, and summarize recent results on the relative perceptual importance of the various criteria. Then we show that using full-order decoders with mixedorder program material results in poorer performance than with a properly designed mixed-order decoder. We then introduce a new implementation of a decoder optimizer that draws upon techniques from machine learning for quick and robust convergence, discuss the construction of the objective function, and apply it to the problem of designing two-band decoders for mixed-order signal sets and nonuniform loudspeaker layouts. Results...
In earlier papers, the present authors established the importance of various aspects of Ambisonic... more In earlier papers, the present authors established the importance of various aspects of Ambisonic decoder design: a decoding matrix matched to the geometry of the loudspeaker array in use, phase-matched shelf filters, and near-field compensation. These are needed for accurate reproduction of spatial localization cues, such as interaural time difference (ITD), interaural level difference (ILD), and distance cues. Unfortunately, many listening tests of Ambisonic reproduction reported in the literature either omit the details of the decoding used or utilize suboptimal decoding. In this paper we review the acoustic and psychoacoustic criteria for Ambisonic reproduction, present a methodology and tools for “black box” testing to verify the performance of a candidate decoder, and present and discuss the results of this testing on some widely used decoders.
Ambisonic reproduction systems are unique in their ability to separately reproduce the pressure a... more Ambisonic reproduction systems are unique in their ability to separately reproduce the pressure and velocity components of recorded audio signals. Gerzon proposed a theory of localization in which the human auditory system is presumed to localize using the direction of the velocity vector in the reproduced sound at low frequencies, and the energy vector at high frequencies. An Ambisonic decoder has the energy and velocity vectors coincident. These are the directions of the apparent source when the listener can turn to face it. Separately optimizing the low-frequency and mid/high-frequency operation of the reproduction system can optimize localization where the listener cannot turn to face the apparent source. We test the localization of horizontal-only Ambisonic reproduction systems using various test signals to separately evaluate low-frequency and mid-frequency localization.
In this Automatic Population of GeospatialDatabases (APGD) overview paper, we describeour progres... more In this Automatic Population of GeospatialDatabases (APGD) overview paper, we describeour progress in developing and evaluating a genericcontext-based architecture (which we call the BOSfor the Battlespace Observer System) and algorith-mic techniques to radically reduce the human effortrequired to extract cartographic features, especiallyroads and buildings, from aerial and satelliteimagery. We also describe progress in supportingthe DARPA APGD community by constructingverified and well-documented datasets and evalu-ation procedures to allow interested researchers toexperimentally evaluate their extraction techniquesin a common framework. Our APGD Communityoriented activities are accessible at SRI’s APGDweb site, http://www.ai.sri.com/~apgd,and the APGD “Virtual Laboratory,”http://www.ai.sri.com/~apgd/vl.In a formal April1998presentation,we successfullydemonstrated the “end-to-end” extraction of all the This work was sponsored by the Defense Advanced Re-search Projects Agency under c...
We present extensions to the Ambisonic Decoder Toolbox to efficiently design periphonic decoders ... more We present extensions to the Ambisonic Decoder Toolbox to efficiently design periphonic decoders for non-uniform speaker arrays such as hemispherical domes and multilevel rings. These techniques include modified inversion, AllRAD, and spherical Slepian function-based decoders. We also describe a new backend for the toolbox that writes out full-featured decoders in the Faust DSP specification language, which can then be compiled into a variety of plugin formats. Informal listening tests and performance measurements indicate that these decoders work well for speaker arrays that are difficult to handle with conventional design techniques. The computation is relatively quick and more reliable compared to nonlinear optimization techniques used previously.
We describe a system for converting RADIUS site models into a Web-accessible form. Once converted... more We describe a system for converting RADIUS site models into a Web-accessible form. Once converted, the site models can be downloaded and viewed with standard, off-the-shelf Web browsers. Site models themselves are represented in the Virtual Reality Modeling Language (VRML). Each feature in the site model is cross-linked to a Web page that describes that feature in more detail, including image chips and collateral information. A demonstration of work described in this paper is accessible via the URL http://www.ai.sri. com/˜connolly/pathfinder.
For millions of people with swallowing disorders, preventing potentially deadly aspiration pneumo... more For millions of people with swallowing disorders, preventing potentially deadly aspiration pneumonia requires following prescribed safe eating strategies. But adherence is poor, and caregivers' ability to encourage adherence is limited by the onerous and socially aversive need to monitoring another's eating. We have developed an early prototype for an intelligent assistant that monitors adherence and provides feedback to the patient, and tested monitoring precision with healthy subjects for one strategy called a "chin tuck." Results indicate that adaptations of current generation machine vision and personal assistant technologies can effectively monitor chin tuck adherence, and suggest feasibility of a more general assistant that encourages adherence to a range of safe eating strategies.
The RADIUS Common Development Environment pulls together many diverse functions into an integrate... more The RADIUS Common Development Environment pulls together many diverse functions into an integrated whole. The main goal of the environment is to provide a system to do interactive modeling of 3-dimensional scenes from multiple images, as well as, providing ...
Proceedings 1992 IEEE Computer Society Conference on Computer Vision and Pattern Recognition, 1992
The concepts and design issues that provide the basis for the I 2F (image interpretation foundati... more The concepts and design issues that provide the basis for the I 2F (image interpretation foundations) system are described. The I2F system combines object-oriented design for machine vision software and constraint-based geometric modeling into a flexible and effective system for automatic template-guided visual inspection. Object-oriented design for 2-D geometry-based image analysis is discussed, and results from processing experimental X-ray data
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