In this paper, the authors propose a novel method to measure the perceived picture quality of H.264 coded video based on hybrid no reference framework. The latter term means that the proposed model uses only receiver-side information for objective video quality assessment, but analyzes both the compressed bitstream and baseband signals of the decoded picture to improve the estimation accuracy of the subjective quality. The proposed method extracts quantizer-scale information from the bit-stream along with two spatiotemporal image features from the baseband signal, which are integrated to express the overall quality using the weighted Minkowski metric. A computer simulation shows the proposed method can estimate the subjective quality at a correlation coefficient of 0.909 whereas the PSNR metric, which is referred to as a benchmark, correlates the subjective quality at a correlation coefficient of 0.773.

This paper presents a novel method to represent a real 3D world using IBR (Image-based Rendering) technology. The major achievement is realization of "walk-through" experience, in which audiences can see the scene of sport games as if they were the player, while the conventional IBR method cannot provide such an experience. The key idea is a newly introduced framework "locally divided ray space" to capture the ray inside the scene. Consequently, the proposed algorithm can generate a virtual image inside the scene using multiple real images captured from outside. In this paper, the outline of the proposed method as well as the possible demonstration at the conference venue is described.

In this paper, we propose two novel methods for arbitrary listening-point generation for 3D audio-video (3DAV) integration in a large-scale multipoint cameras and microphones system with abilities to process, and display information of any recorded 3D scene in realtime. With this system, users are able to control their own viewpoint/listening-point position, freely. Arbitrary listening-point can be generated by either (i) ray-space representation of sound wave field (i.e. source sound independent) for multi frequency layers, or (ii) acoustic transfer function estimation (i.e. source sound dependent) and blind separation of sources of sounds. Arbitrary viewpoint generation is based on ray-space method, which is enhanced by using multipass dynamic programming for geometry compensation. Integration is done by either (i) ray-space representation of sound wave and image together, or (ii) integrating each camera video signal and acoustic transfer function of the same location as integrated 3DAV data. The prototype system of integrated audio-visual viewer achieves both good image and sound qualities with 15 frames/second.

In IP-based TV distribution, coding degradation is sometimes evident in critical scenes because the bit rate for compression is rather low. Prefiltering is an effective countermeasure since it replaces the coding noise with the degradation more difficult to detect visually, though it has the drawback that excessive smoothing might occur. This paper proposes a scene-adaptive method to control a prefilter separate from the encoder. By calculating block-wise motion-compensated predictive error variances and correlation coefficients, it estimates the coding noise as well as the potential improvement by prefiltering each frame, realizing a control scheme which performs prefiltering only when effective

In Japan, a terrestrial digital broadcasting service for cellular phone will start for the first time in the world in April, 2006. We already prototyped a cellular phone terminal with terrestrial digital broadcasting function. The evaluation result indicated the need of a quick recovery mechanism for packet loss error of broadcasted data. In addition, an efficient mechanism for developing collaborated applications which fully utilize the both-way communication capability of the broadcasting service with cellular phones as the uplink is expected. However simply transmitting the audience's information (e.g. user account information, channel selection and his/her location) via the cellular phone may cause traffic burden on the cellular network. In this paper we propose a new packet loss recovery mechanism which uses the cellular network for retransmitting the lost packets. Next, we propose a gateway architecture for upload information to reduce the traffic from the terminals to solve the second issue. We demonstrate the effectiveness of these mechanisms through the evaluation using the prototype terminal. We also show the detail implementation of the prototype terminal.

Digital terrestrial broadcasting in Japan specifies a service profile not only for fixed receivers in the home, but also for personal mobile terminals such as acellular phones and PDAs. Services for personal mobile terminals are expected to become more attractive with sufficient functionality and flexibility by utilizing the network connectivity of mobile terminals. In order to verify the possibilities of digital television broadcasting (DTV) services for personal mobile terminals and clarify technical problems at the commercial level, we developed a prototype mobile terminal capable of receiving digital terrestrial broadcasting in addition to the Internet. This paper describes the assumed DTV service for personal mobile terminals and the technical architecture of the developed mobile terminal with regard to the hardware and the software. Several experiments using the developed mobile terminal were conducted and the performance was evaluated.

Although free viewpoint images can be synthesized using reference images with their depth maps, the quality of the output images can be degraded because of lack of information on occluded regions in the same frame. We previously proposed a high quality free viewpoint Video on demand system using a background buffer updated dynamically. However, this method cannot interpolate regions where depth changes continuously such as ground since the background buffer is like a plane. As a solution to this problem, in this paper we propose a new method using a "curved background buffer" to achieve higher quality of output images.

Appropriate rate control plays a very important role in encoding motion pictures under the constant bit-rate. One of the requirements for rate control is minimizing temporal fluctuations in picture quality, which may cause flicker artifacts. To satisfy the requirement, some methods for MPEG-1 and MPEG-2 have been proposed. However, these methods cannot be applied to the H.264 encoding algorithm based on R-D optimization since they require the DCT coefficients and the accurate output bit amount for each quantization parameter of a current picture in advance. To overcome the problem, we propose a rate control method to satisfy the requirement in the H.264 encoding algorithm by introducing approximations to estimate the bit amount and the distortion.

For contribution and primary distribution of television, i.e., television transmission to broadcasting stations, parallel transmission links that include codecs are often set up for reliability. However, this configuration still faces the following issues: 1) during normal periods, the reserve link is totally wasted and 2) when a failure occurs, the disrupted signal continues to be transmitted until the system switches to the reserve link. In addition, in digital video transmission, automatic assessment of received video quality is an important issue. To address these issues, the authors developed a processing system for parallelly transmitted video signals, which mainly consists of the following three elements: 1) when both links are normal, outputting the average signal of both links reduces compression coding noise and improves picture quality compared to only one link (efficiency); 2) comparison of the pictures from the two links enables failure detection in either link, to switch to the normal link (support of failure detection); and 3) comparison of the two normally decoded pictures enables evaluation of picture quality (automatic coding noise evaluation). This unique system improves the reliability and operational efficiency of conventional parallel video transmission links.

Motion JPEG2000 has been developed as a new video coding standard for motion pictures, utilizing the still image coding standard JPEG2000. Motion JPEG2000 specifies a normative bitstream syntax that the decoder must recognize and allows flexible selection of detailed coding parameters at the encoder. The compression performance largely depends, therefore, on the encoder design. However, the simple implementation of JPEG2000 encoder might cause picture quality degradation due specifically to wavelet image coding of interlaced TV signals and unsatisfactory bit assignments. That degradation might then become conspicuous in subjective picture quality especially during low bit-rate coding. To overcome this problem, we investigated an optimal design for a Motion JPEG2000 encoder that can be used for primary distribution applications of HDTV programs, assuming that the available bit-rate is approximately 50 Mbps. Our study introduces advanced key technologies not yet recognized officially. Coding experiments using those technologies confirmed that a significant coding gain was achieved versus conventional encoding schemes.

This paper proposes a novel CT image coding concept named LOI which stands for level of interest and coding methods based on that concept. The well-known ROI (region of interest) coding gives priority to pixels in particular regions of an image when encoding or decoding the image. Similarly, LOI coding gives priority to the pixels having a particular pixel level. LOI is ideal for coding of CT images and offers remarkably high coding efficiency. This paper proposes two types of LOI coding methods. One type is the floating point method and the other is the integer method. This paper verifies that the both types improve coding efficiency of pixels in the LOI window. This paper also shows that adequate image quality is obtained even if the viewing window is different from the LOI window.

Presenting images from a free viewpoint is a promising interactive video application. Though reference images from one viewpoint and their depth maps are often used to render free viewpoint images, picture quality degradation may occur because of lack of information in background regions that are occluded by foreground regions. In this paper an interpolation method for free viewpoint images using multilayered dynamic background buffers is proposed. In the proposed method, the buffers, updated using the reference images divided in each frame, are used to store the background regions and the output images are interpolated by the background buffers. Since the background buffers are created and updated using only the reference images and their depth maps, additional information on the background buffers is not required for the interpolation. The effectiveness of the proposed method was evaluated by several simulation experiments.

This paper proposes novel techniques for reducing tiling artifacts and encoding time which are two of the largest problems with the JPEG2000 encoder. The proposed method detects tiling artifacts during the coding process and reduces them automatically using tile-boundary adaptive post-quantization. It also provides a higher speed JPEG2000 coding process. This accelerated performance was obtained by predicting the truncation points using the entropy of wavelet transform coefficients prior to the arithmetic coding. This encoding method also requires no additional processing in the decoder. In the experiment, it was subjectively confirmed that tiling artifacts were greatly reduced and that the coding process was considerably accelerated.

MPEG-2 is an international standard specifying a normative bitstream syntax that decoders must recognize and that allows flexible selection of detailed coding parameters at the encoder. The compression performance is therefore largely dependent on the encoder design and the difference in coded picture quality is present even among encoders developed by different codec makers at identical bit-rates. Conventional MPEG-2 encoders were also designed for high picture quality transmission at an adequate bit-rate, and the overhead portion occupancy in a coded bitstream can be ignored in the final picture quality. However, the unexpected increase in overhead portion occupancy might cause fatal picture quality degradation at extremely low bitrates. To overcome this problem, we investigated an optimal design for an MPEG-2 encoder for use in HDTV digital terrestrial broadcasting where the available bit-rate is limited to less than 0.2 bit/pixel. In our study, advanced key technologies which have not been clearly recognized until now were introduced into possible optimization points, picture type selection macroblock coding mode selection and rate control, and a significant coding gain versus conventional encoding schemes was confirmed in coding experiments.

This paper proposes the tile size conversion method for the wavelet image transcoding gateway and a set of methods to reduce the tile boundary artifacts caused by the conversion.In the wavelet image coding system represented by JPEG2000, pictures are usually divided into one or more tiles and each tile then transformed separately. On low memory terminals such as mobile terminals, some decoders are likely to have limits on what tile sizes they can decode. Assuming a system using these limited decoders, methods were investigated for converting the tile size quickly and automatically at the gateway when image data with a non-decodable tile size is received at the gateway from another system. Furthermore, tile boundary artifacts reduction methods are investigated. This paper proposes a basic method, which creates a tiled wavelet coefficient sequence from a non-tiled wavelet coefficient sequence. This paper also verifies the validity of the proposed scheme by implementing it with a 5x3 reversible filter and a 9x7 irreversible filter.

A new hybrid coding method for transmitting videoconferencing images at a bit rate 384 kbits/s is proposed. Considering the characteristics of motion-compensated interframe prediction errors for typical videoconferencing scenes, a filter is introduced to separate pulsive components on which conventional discrete cosine transform (DCT) coding method does not work well. These separated pulsive components are coded by using scalar quantization (SQ). The remainder are DCT coded. For DCT coefficients, an adaptive coding method based on the classification of DCT coefficients is applied in order to improve the coding performance. Since the proposed method employs both DCT coding and SQ of prediction errors, it is named "DCT/SQ coding method." Experimental results show that the DCT/SQ coding method is effective to reduce so-called mosquito effects, and thus it can improve the quality of decoded images.