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Audio signal modeling and processing based on sparse representation:
Complex NMF and composite autoregressive model
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Although audio signals generated by real-world sources are observed as
what seems to be extremely varied waveforms, one can realize by focusing
on a particular space or feature that they are actually composed of only
a limited number of basic components, as for example the phoneme units
such as /a/ or /i/ in human speech, or the semitone units in a piano
performance. In this research, we explore under this hypothesis a new
paradigm in the audio signal processing area based on the so-called
sparse representation approach, which can learn autonomously the
previously unknown basic elements of a signal. We have proposed so far
two signal analysis methods based on the above concept, complex NMF and
the composite autoregressive model.
Mystery of perception -action affects perception-
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Perceiving own body state and motion is very important for our daily life behavior. This "body perception" has been proposed to be formed through integration of sensory, such as somatic and visual, information in the brain. We recently found, however, that motor command information for action is also involved in body perception. When sensory information becomes unreliable (e.g., when numbness in a limb happens) during action, motor command information is utilized to compensate the sensory unreliability. Such a finding can lead to development of a novel interface based on human action-perception interaction mechanisms.
Standardization of Lossless Audio Coding and Archival Format
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We have made significant contributions to the establishment of lossless audio coding standard MPEG-4 ALS ＊(ISO/IEC 14496-3). In addition, we have designed a package file format for archival system, which is one of the most important applications of lossless coding. Recently, the format has been established as MPEG-A PA-AF＊＊(ISO/IEC 23000-6) as well as the associated reference software.
These two standards, individually or jointly, will be used for various applications including long-term archival system and preservation, transmission, editing and playback of high quality audio signals, making use of the merits of the international standard. For further details, click here.
＊ALS：Audio Lossless Coding
＊＊PA-AF: Professional Archival Application Format
Tracking multiple objects and simultaneous learning of their movement patterns
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Many surveillance cameras have been installed in our daily life, and they watch various kinds of behaviors performed by various people.
However, most of such information about the recorded scenes is buried in storages because we don't have enough human resources to watch all the recorded movies.
We developed a new statistical model which is able to not only track multiple targets in the scenes, but also to learn and recognize movement patterns of targets (walk right, run upper left, etc...) in a research of time series data mining. Capability of the understanding and recognition about scenes grows according to the amount of movies the system has been fed.
Please visit
this page to find more information.
Dynamical Information Processing Systems (DIPS)
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The world around us is full of complex and unpredictable behavior, such as water churning in a stream, electrons tumbling along a wire and human behavior itself. In our research we aim to model and harness complex dynamical behavior for use in information and communication technologies. One example is the use of complex dynamics in lasers for information security applications. Laser light beams with complex fluctuations can be generated and controlled by taking the light from a laser and reflecting some of it back inside the laser. By combining advanced methods from physics and information theory, we have developed methods to harness these laser beam fluctuations so that they can be used as physical random number generators to generate passwords and secret keys for secure data communications. Recently we showed that semiconductor lasers can be used to generate random numbers at very high rates. In collaboration with an experiment group at Takushoku University, we demonstrated the continuous generation of random bits at the word's fastest rate of 1.7 Gbps. This achievement was reported in the research journal Nature Photonics Vol.2, No.12 (2008) pp. 728-732, where it was called "The world's fastest dice".
For further details, click here.
