Search

This paper proposes a H.264 rate control method considering picture characteristics and buffer constraints. Selecting the optimum buffer size corresponding to each application's requirement gives better compression quality and functionality. However, conventional methods allocate the number of bits equally to each GOP and do not explicitly consider the buffer size, where picture quality might not be optimal and the buffer size is not optimally determined for applications. This paper provides a bit allocation method that reflects the picture characteristic of each frame while keeping the buffer transition compliant within a given size. In the proposed method, the number of bits to be generated is estimated from the complexity of each frame, and it is adjusted by a scaling coefficient newly introduced in this paper. Thus, the allocated number of bits reflects picture characteristics and fully complies with buffer constraints. Experimental results show that the proposed method improves picture quality and suppresses quality fluctuation.

This paper presents a QoS guaranteed MPEG-4 based live audio/video transmission system over broadband networks. By applying bandwidth adaptive rate control and error adaptive concealment methods, picture quality has been greatly improved under unstable network bandwidths with instantaneous packet loss.

We propose a fast logo insertion algorithm for MPEG compressed video. We employ compressed data domain logo insertion with an in-loop re-quantization process. We also adaptively use the MV (motion vector) and coding information of the input MPEG stream according to logo and non-logo regions. Experiments have shown that much faster and higher quality logo insertion is obtained compared with baseband domain insertion.

A fast motion estimation algorithm for digital video (DV) to MPEG-2 conversion is described. Since DCT information is available from DV data and 2/spl times/2 IDCT can be achieved by simple summation and subtraction operations, a low-resolution image is constructed and used for a coarse motion search. Then a fine search is performed using an extended two step search in the original image domain. The experimental results show that the proposed method is more than 160 times faster than the full search whereas the PSNR and search speed are greatly improved when compared with the conventional method.

In this paper we propose an unsupervised anchorperson detection algorithm from an MPEG coded TV program recorded for many hours. In order to extract news topic presentation shots, we employed several visual features such as motion, face, caption, and clothing on an MPEG DC image domain. In the experiment, it has been shown that news topics were successfully extracted from a recorded TV program for 24 hours.

A description is given of studies of source coding in the specialists group on coding for visual telephony in CCITT SG XV. Using a macro block approach, the source coding algorithm will have the capability of operating from 64 kb/s for videophone applications up to 2 Mb/s for high-quality videoconferencing applications. The authors describe the existing reference model and the evolution toward the latest reference model (RM5), which is going to be submitted for standardization. Theoretical information is provided and some examples for possible improvements are presented for the most important techniques used in the reference model, among which are quantization, variable block size, scanning classes, loop filter, entropy coding, multiple vs. single variable-length coding, and block-type discrimination. >

The base material currently used for optical fiber waveguides (optical fibers) is silica. By adding various impurities, properties required for optical transmissions are created. When these optical fibers are used in a particular environment, such as a nuclear reactor, damage caused by radiation from the source becomes a serious problem. It is well-established that when optical fibers are exposed to 60Co γ-rays, the attenuation of the signal through the fiber decreases (1–3). This is due to damage produced in the fiber by radiation. The nuclear reactor radiates not only γ-rays, but also thermal neutrons. However, the effect of the thermal neutron on optical fibers has not been established.