Takuya Fujihashi

UMSM: A Traffic Reduction Method on Multi-View Video Streaming for Multiple Users

Multi-view video consists of multiple video sequences captured simultaneously by multiple closely spaced cameras and enables users to freely change their viewpoints by playing different video sequences. Therefore, the transmission bitrate of multi-view video requires more bandwidth than conventional multimedia. In order to reduce the bandwidth requirement, User Dependent Multi-view Video Transmission (UDMVT), which is based on Multi-view Video Coding (MVC), has been proposed for single users. In UDMVT, the same frames are encoded into different versions for each user, which increases the transmission bitrate for multiple users because of the redundant transmission of overlapping frames. In order to address this problem, we proposed User dependent Multi-view video Streaming for Multi-users (UMSM). UMSM possesses two characteristics: overlapping frames required by multiple users are transmitted only once by multicast while un-overlapping frames required by each user are transmitted by unicast and offset of video requests between multiple users is aligned so as to maximize the area of overlapping frames. UMSM achieves a low transmission bitrate of multi-view video for multiple users by means of combining these characteristics. To investigate the effect of users view switching on traffic reduction, we design three types of view-switching models, namely, scanning model, random model, and watching model. Simulation results obtained using benchmark test sequences provided by MERL reveal that UMSM decreases the transmission bitrate by 80.6% on average for five users, as compared to MVC, when users gaze a viewpoint for a while after switching views in order to search an attractive viewpoint.

Traffic Reduction for Multiple Users in Multi-view Video Streaming

Multi-view video consists of multiple video sequences captured simultaneously from different angles by multiple closely spaced cameras. It enables the users to freely change their viewpoints by playing different video sequences. Transmission of multi-view video requires more bandwidth than conventional multimedia. To reduce the bandwidth, UDMVT (User Dependent Multi-view Video Transmission) based on MVC (Multi-view Video Coding) has been proposed for single user. In UDMVT, for multiple users the same frames are encoded into different versions for each user, which increases the redundant transmission. For this problem, this paper proposes UMSM (User dependent Multi-view video Streaming for Multi-users). UMSM possesses two characteristics. The first characteristic is that the overlapped frames that are required by multiple users are transmitted only once using the multicast to avoid unnecessary duplication of transmission. The second characteristic is that a time lag of the video request by multiple users is adjusted to coincide with the next request. Simulation results using benchmark test sequences provided by MERL show that UMSM decreases the transmission bit-rate 55.3% on average for 5 users watching the same multi-view video as compared with UDMVT.

Wireless Multi-View Video Streaming with Subcarrier Allocation by Frame Significance.

When an access point transmits multi-view video over wireless networks with multiple subcarriers, errors occur in low quality subcarriers. The errors cause a significant degradation of video quality. The present paper proposes Significance based Multi-view Video Streaming with Subcarrier Allocation (SMVS/SA) for the maintenance of high video quality. SMVS/SA transmits a significant video frame with a high quality subcarrier to minimize the effect of the errors. Evaluations using MERLs benchmark test sequences reveal that SMVS/SA achieves a slight degradation of video quality. For example, SMVS/SA improves video quality by 8.0 [dB] compared to standard H.264/AVC MVC when the maximum packet loss ratio of each subcarrier is 10 %.

Improvement of Community Bus Operation Management System

We renovated the community bus operation management system which is operated in Tsushima area of Ehime Prefecture Uwajima City. The bus operation management system was developed in 2013. It is possible to grasp the bus location and the number of passengers by using the application installed on the tablet and the web application. However, it did not satisfy the necessary functions for the system. In this paper, we interviewed the problems of the current situation from customers and organized the problems of customers. We reflected systematic problems in the design of the system and developed a more satisfying system for customers.

Utilizing Tablets in an Ideathon for University Undergraduates

This paper discusses utilizing tablets during an ideathon for university undergraduates. When holding an ideathon, we had to meet some requirements such as appropriate and prompt team organization. Tablets were distributed to students and faculty members in order to meet those requirements. Tablets were used for organizing teams, answering a survey, sharing files, and using the Internet. As a result, we received positive evaluations from students in the survey conducted after the ideathon.

Development of Seawater Temperature Announcement System for Quick and Accurate Red Tide Estimation

Fisheries researchers who predict the occurrence of red tides want to be able to visualize the seawater temperature information measured using the marine buoy in a form that can be handled easily for researchers in order to improve the prediction accuracy. In this research, we develop a system to visualize measured seawater temperature information. In the system, it is possible to display latest seawater temperature information and time change of seawater temperature in the form of tables and graphs by using a web application. In addition, it is possible to download the sea water temperature information collected in the past into the csv format file. With this system, researchers can predict the occurrence of red tide at an early stage because seawater temperature information becomes easier to handle.

Quality improvement and overhead reduction for soft video delivery

Soft video delivery, i.e., analog video transmission, has been proposed to provide graceful video quality in unstable wireless channels. However, existing analog schemes need to transmit a significant amount of metadata to a receiver for power allocation and decoding operations. It causes large overheads and quality degradation because of rate and power losses. To reduce the overheads while keeping high video quality, we propose a new analog transmission scheme. Our scheme exploits a Gaussian Markov random field for modeling video sequences to significantly reduce the required amount of metadata, which are obtained by fitting into the Lorentzian function. Our scheme achieves not only reduced overhead but also improved video quality, by using the fitting function and parameters for metadata. Evaluations using several test video sequences demonstrate that our proposed scheme reduces overheads by 97 % with 3.4 dB improvement of video quality compared to the existing analog video transmission scheme.

Experimental Throughput Analysis in Screen-Camera Visual MIMO Communications

Screen-camera communication, which uses a liquid crystal display (LCD) screen and camera image sensors, has been an attractive variant of visible light communications (VLC) since display and camera have been equipped with in various mobile devices. To improve transmission rates, we investigate the impact of nonlinear channel equalization and nonbinary channel coding as well as high-order modulation schemes. Equalization techniques can reduce the effect of channel impairments, such as color mixing. Nonbinary coding improves reliability of high-order modulation and thus increases the transmission rate. Experimental evaluations using an LCD screen and camera demonstrate that our proposed scheme achieves 3.6-2.4 times higher transmission rates compared to existing schemes for a communication distance of 40-100 cm.

A Novel Segment Scheduling Method for Multi-View Video Using Progressive Download

Progressive download for multi-view video delivery is one of promising techniques to provide immersive and interactive experiences to users. In conventional multi-view video systems, a user downloads videos of all viewpoints of one content to realize smooth view switching. However, it causes increase of video traffic, and thus low video quality within an available download rate. To download only a desired viewpoint is another approach for reduction on volume of video traffic. However, playback stalls occur after view switching. The stalls induce low users satisfaction for applications. In this paper, we aim at two objectives: 1) to achieve reduction on video traffic and 2) to achieve reduction on the number of playback stalls. To this end, we propose a new multi-view video delivery scheme for progressive download. The main idea of the proposed scheme is that the user only downloads potential videos, which are potentially played back by the user, to realize both traffic reduction and smooth view switching. In addition, we propose two download scheduling algorithms to prevent playback stalls even in a low download rate. The first algorithm prevents stalls in frequent view switching cases while the other prevents stalls in gazing cases. Evaluations using Joint Multi-view Video Coding (JMVC) encoder and multi-view video sequences show that the proposed method reduces video traffic by 55.1% compared with a simulcast scheme. In addition, the proposed method decreases the number of playback stalls during video playback by 86.0% compared with a request and response scheme.

High Quality Multi-path Multi-view Video Transmission considering Path Priority Control

Multi-view video is one of promising techniques for future video services. In multi-view video delivery, transmitted video frames are highly vulnerable for losses during transmission. When a video frame in a certain camera is lost, the effect of the loss may propagate to the subsequent video frames in the same camera and video frames in the neighbor cameras. This is referred to as multi-view error propagation. To improve the loss resilience, some multi-path-based video transmission schemes have been proposed for multi-view video delivery. The existing transmission schemes assume that each transmission path has the same packet loss characteristic and thus do not account for the path diversity. However, each transmission path often has different loss characteristic, e.g., loss-free and loss-prone. To exploit the path diversity for high video quality, we propose two multi-view video transmission schemes. The first scheme utilizes features of multi-view video encoding. Specifically, reference, i.e., important, video frames are transmitted over lossfree transmission path while the other video frames are transmitted over loss-prone transmission paths. The second scheme utilizes decoding operation of multi-view video. In this case, a sender sends odd video frames over loss-free transmission path and exploits decoding operations for transmissions of even video frames. Evaluations show that our proposed scheme improves video quality (in terms of Peak Signal Noise Ratio) by 3 dB compared to existing transmission schemes when loss rate of transmission paths is 10%. In addition, our scheme achieves 1 MB lower video traffic in the same environment.