Product Quantization (PQ) search and its derivatives are popular and successful methods for large-scale approximated nearest neighbor search. In this paper, we review the fundamental algorithm of this class of algorithms and provide executable sample codes. We then provide a comprehensive survey of the recent PQ-based methods.
We present a liver surgery simulator using full-HD autostereoscopic displays. We have developed two kinds of autostereoscopic displays to keep on showing a full-HD 3D image to a viewer who moves freely in front of the display. One is a 3D display based on time-division multiplexing directional backlight and the other is a 3D display based on time-division multiplexing parallax barrier. We have applied the developed simulator using the 3D displays with different specifications to the education of medical students. The result of the questionnaires suggests that 3D visualization is effective and that reduction of crosstalk plays an important role to promote medical use of 3D displays.
Digital signage (DS) is becoming well accepted as a ubiquitous medium that can deliver and display various types of information by specifying the location and time. In this paper, we put our focus on the following two directions of DS development: (1) Networked DS: networking displays to form a large-scale open DS network that allows content providers to submit contents, and schedule, deliver, and display the contents at the right place and time, (2) Context-aware DS: displaying contents appropriate to the current status of people, places, and objects around the display, that is, changes in context. This paper gives an overview of the research being done on these issues, specifically, content scheduling, real-time content adaptation, and context sensing. Finally, some of the future challenges will be discussed.
In a telework scenario, the lack of informal communications, such as impromptu meetings, is a hard-to-solve problem for those who work at home over the long term. To facilitate informal communication, a system called media space provided an always-on audiovisual connection between distributed workers. Moreover, recent studies suggested that telepresence robots featuring audiovisual capabilities like media space are effective for informal communication. However, in practical use, various problems exist. Therefore, in this paper, we survey the systems of media space and telepresence robots concerning the advantages, problems, and solutions. We also discuss the unresolved issues and required investigations. One of the unresolved issues is that a stationary or desktop robot has a difficulty in initiating informal communication because it cannot move around the office. To tackle the issue, we introduce our experiment suggesting that a robot emulating the social greeting process actually promotes informal communication compared with no emulation.
Recently, to provide a low-latency mobile computing platform, Mobile Edge Computing (MEC) is proposed. In this paper, we first summarized the feature capabilities of MEC, such as content distribution and caching, computational offloading and multimedia Internet of Things (IoT). Then, to understand recent research efforts of multimedia MEC, we briefly highlight the research efforts in terms of above three capabilities: how to achieve edge caching in video distribution, how to schedule computational offloading to the cloud and how the communication quality degradation affects to the user experience of multimedia IoT. Finally, we addressed the emerging research issues of multimedia MEC to improve reliability and robustness of multimedia MEC.
A lot of new broadcasting services using communication channels have been developed and structures of conventional content distribution and broadcasting services have been gradually changed. For example, broadcasting services were not bi-directional, but now, TV sets have Internet connection. This means that bi-directional and enriched broadcasting services may be possible. Content copyright protection is an issue also in such services. Several protection techniques have been applied for the purpose, but often broken. In addition, according to the change of the service structures, new security requirements have arisen and new security technologies are required. New security technologies developed to improve the current ones and to meet the requirements of new services are described in this paper. Moreover, trends in state-of -the-art studies and future outlook are described.
This paper presents recent advances in biometric recognition, where we focus on face, fingerprint and iris recognition, which are major research topics on biometric recognition. We summarize the research trend of face, fingerprint and iris recognition over the past decade. This paper also presents our activities of biometric recognition. Our approach employs the phase information obtained by Discrete Fourier Transform (DFT) of images. The phase information preserves the inherent features of the image, and its correlation function, called phase correlation or Phase-Only Correlation (POC), gives us both the good similarity measure for biometric recognition and the translational displacement for image registration. Our approach of using phase information has been successfully applied to fingerprint, face, iris, palmprint, finger knuckle and dental recognition. Among them, we present some interesting results of palmprint recognition, finger knuckle recognition and dental recognition.
Collaborative reception has been proposed to improve frequency utilization efficiency in wireless networks. This paper proposes adaptive configuration of forward channels that selects not only terminals to forward received signals to the destination terminal but also higher frequency bands for the forward links. We propose adaptive terminal selection algorithms to implement the proposed adaptive configuration of forward channels. The proposed adaptive configuration based on the algorithms achieves higher frequency utilization efficiency than fixed configurations. While the proposed two algorithms attain similar frequency utilization efficiency, one of the algorithms, so called, a complexity-reduced selection algorithm reduces the computational complexity to almost 1/200 of the other of the optimum selection algorithm.
A superposed multicarrier transmission scheme is known to improve frequency utilization eﬃciency where several systems share spectrum without any spectrum spreading techniques. In the superposed multicarrier transmission scheme forward error correction (FEC) coding is in general applied so that the eﬀects of interference caused by superposition of spectrum is mitigated by error correction capability. Thus, the superposed multicarrier transmission scheme is eﬀective under cognitive environments where several wireless systems share the same frequency band. The superposed multicarrier transmission scheme is also expected in broadcasting where wireless communications are also used and can be interfered by other wireless systems. In the superposed multicarrier transmission scheme, to reduce the eﬀects of interference by exploiting the capability of FEC, initial log likelihood ratio (LLR) should be set appropriately. Setting LLR correctly requires several information including interference power on each subcarrier, which are not known in general. We have developed several techniques to estimate the information includ- ing interference required for the superposed multicarrier transmission scheme. This paper introduces the superposed multicarrier transmission scheme. This paper also introduces some of our techniques proposed for the superposed multicarrier transmission scheme.
In order to realize next generation digital terrestrial television broadcasting (DTTB) systems, the currently deployed Integrated Services Digital Broadcasting Terrestrial (ISDB-T) is still essential due to the spectrum-scarcity. This paper proposes a layered division multiplexing (LDM) scheme to simultaneously transmit ISDB-T stream and a secondary data stream over a common frequency band. The next generation DTTB system can be obtained by combining the ISDB-T and the secondary data streams. In the proposed scheme, we deploy the primary layer for transmission of ISDB-T signal and the secondary layer for transmission of secondary data stream both employed space time block coding. In addition, we only adopt partial LDM to reduce the interference between two systems, since the transmission capacity of the secondary layer exceeded the minimum requirement due to reuse of primary layer.
Content distributed by broadcast and multicast services is often encrypted (scrambled) to protect copyrighted material. When any cryptanalysis of the current cryptographic scheme used in such services is found, the scheme must be updated. However, the scheme cannot be updated suddenly because a lot of subscribers have receivers with the current scheme. We have previously proposed two cryptographic scheme updating methods. The two methods have trade-off relationship between security and transmission bit rate. However, our security analysis was insufficient. We revisit the security analysis on the methods. In addition, we show a new strong attack against the methods and we evaluate the security against the new attack. As a result, we show that, even if the new attack is implemented in a pirate receiver (PR), its probability to reconstruct content in real-time is very small and that the proposed methods are secure against such a new attack from the viewpoint of service quality. Totally, we show the update methods are practical and secure.
We propose a flicker-free method for video captured at a 120-Hz frame frequency and a 100-Hz illumination intensity variation frequency by using interlaced scanning and an electrical shutter to broadcast video during the 2020 Olympic Games in Tokyo. We found from the results of image simulation that the human eye cannot identify the decrease in vertical resolution of images with interlaced scanning when they are displayed at a 120-Hz frame frequency. We found that flicker in video captured with the flicker-free method was suppressed to less than one-twentieth of the flicker with 120-Hz progressive scanning as a result of implementation. The sensitivity of the prototype camera head with the flicker-free method also became 1.2 times higher than that with 120-Hz progressive scanning. The 120-Hz flicker-free method could be adopted in a fieldprogrammable gate array of the prototype camera head that has already been developed with a 120-Hz frame frequency.
In this paper, we propose a method of emotion monitoring using physiological signals such as RR intervals and blood volumes obtained by analyzing hemoglobin concentrations from facial color images. Emotion monitoring has great potential in areas such as market research, safety, medical and robot systems. The most popular method of emotion monitoring uses physiological signals. However, it is difficult to apply the commonly used methods in practice because special instruments such as electrodes or laser speckle flowgraphy are required to obtain physiological signals. The proposed method uses a simple RGB camera. Using 27 features calculated from the physiological signals obtained from facial RGB images, we classified five emotional states, amusement, anger, disgust, sadness and surprise, with 94% accuracy.