We analyze 20 large sets of actual variable-bit-rate (VBR) video data, generated by a variety of different codecs and representing a wide range of different scenes. Performing extensive statistical and graphical tests, our main conclusion is that long-range dependence is an inherent feature of VBR video traffic, i.e., a feature that is independent of scene (e.g., video phone, video conference, motion picture video) and codec. In particular, we show that the long-range dependence property allows us to clearly distinguish between our measured data and traffic generated by VBR source models currently used in the literature. These findings give rise to novel and challenging problems in traffic engineering for high-speed networks and open up new areas of research in queueing and performance analysis involving long-range dependent traffic models. A small number of analytic queueing results already exist, and we discuss their implications for network design and network control strategies in the presence of long-range dependent traffic. >

Long-range dependence in variable-bit-rate video traffic

To represent an image of high perceptual quality with the lowest possible bit rate, an effective image compression algorithm should not only remove the redundancy due to statistical correlation but also the perceptually insignificant components from image signals. In this paper, a perceptually tuned subband image coding scheme is presented, where a just-noticeable distortion (JND) or minimally noticeable distortion (MND) profile is employed to quantify the perceptual redundancy. The JND profile provides each signal being coded with a visibility threshold of distortion, below which reconstruction errors are rendered imperceptible. Based on a perceptual model that incorporates the threshold sensitivities due to background luminance and texture masking effect, the JND profile is estimated from analyzing local properties of image signals. According to the sensitivity of human visual perception to spatial frequencies, the full-band JND/MND profile is decomposed into component JND/MND profiles of different frequency subbands. With these component profiles, perceptually insignificant signals in each subband can be screened out, and significant signals can be properly encoded to meet the visibility threshold. A new quantitative fidelity measure, termed as peak signal-to-perceptible-noise ratio (PSPNR), is proposed to assess the quality of the compressed image by taking the perceptible part of the distortion into account. Simulation results show that near-transparent image coding can be achieved at less than 0.4 b/pixel. As compared to the ISO-JPEG standard, the proposed algorithm can remove more perceptual redundancy from the original image, and the visual quality of the reconstructed image is much more acceptable at low bit rates.

A perceptually tuned subband image coder based on the measure of just-noticeable-distortion profile

Source modeling and performance issues are studied using a long (30 min) sequence of real video teleconference data. It is found that traffic periodicity can cause different sources with identical statistical characteristics to experience differing cell-loss rates. For a single-stage multiplexer model, some of this source-periodicity effect can be mitigated by appropriate buffer scheduling and one effective scheduling policy is presented. For the sequence analyzed, the number of cells per frame follows a gamma (or negative binomial) distribution. The number of cells per frame is a stationary stochastic process. For traffic studies, neither an autoregressive model of order two nor a two-state Markov chain model is good because they do not model correctly the occurrence of frames with a large number of cells, which are a primary factor in determining cell-loss rates. The order two autoregressive model, however, fits the data well in a statistical sense. A multistate Markov chain model that can be derived from three traffic parameters is sufficiently accurate for use in traffic studies. >

Statistical analysis and simulation study of video teleconference traffic in ATM networks

The authors survey a number of important research topics in ATM (asynchronous transfer mode) networks. The topics covered include mathematical modeling of various types of traffic sources, congestion-control and error-control schemes for ATM networks, and priority schemes to support multiple classes of traffic. Standard activity for ATM networks and future research problems in ATM are also presented. It is shown that the cell-arrival process for data sources can be modeled by a simple Poisson process. However, voice sources or video sources require more complex processes because of the correlation among cell arrivals. Due to the effects of high-speed channels, preventive control is more effective in ATM networks than reactive control. Due to the use of optical fibers in ATM networks, the channel error rate is very small. The effects of propagation delay and processing time become significant in such high-speed networks. These fundamental changes trigger the necessity to reexamine the error-control schemes used in existing networks. Due to the diversity of service and performance requirements, the notion of multiple traffic classes is required, and separate control mechanisms should be used according to the traffic classes. The priority scheme is shown to be an effective method to support multiple classes of traffic. >

Survey of traffic control schemes and protocols in ATM networks

The applications of discrete cosine transform (DCT)-based image- and video-coding methods in the asynchronous transfer mode (ATM) environment are considered. Coding and reconstruction mechanisms are jointly designed to achieve a good compromise among compression gain, system complexity, processing delay, error-concealment capability, and reconstruction quality. The Joint Photographic Experts Group (JPEG) and Motion Picture Experts Group (MPEG) algorithms for image and video compression are modified to incorporate block interleaving in the spatial domain and DCT coefficient segmentation in the frequency domain to conceal the errors due to packet loss. A new algorithm is developed that recovers the damaged regions by adaptive interpolation in the spatial, temporal, and frequency domains. The weights used for spatial and temporal interpolations are varied according to the motion content and loss patterns of the damaged regions. When combined with proper layered transmission, the proposed coding and reconstruction methods can handle very high packet-loss rates at only a slight cost in compression gain, system complexity, and processing delay. >

Coding and cell-loss recovery in DCT-based packet video

Basic characteristics of variable-rate video coders applied to asynchronous transfer mode (ATM) transmission are described Burstiness of video information is evaluated for conference-type scenes using various coding algorithms Three measures (distribution, autocorrelation, and coefficient of variation) are introduced to evaluate burstiness Video sources are modeled and characterized by the autoregressive process and coefficient of variation Video quality improvement achieved with variable rate transmission is evaluated using signal-to-noise ratio (SNR) and subjective ratings An improvement of 5-10 dB in temporal SNR and 1 rank in mean opinion score are reported >

Basic characteristics of variable rate video coding in ATM environment

International real-time streaming of 4K digital cinema

In this paper, we will present a survey of the all-digital super high definition (SHD) image specifications currently under development by the authors to support this type of media integration. We will discuss specification requirements, encoding and support technologies, and present a survey of signal processing systems. Especially, we will focus on the NOVI-II experimental system which was created to develop signal processing architectures for all-digital SHD image processing, as well as to evaluate compression schemes for SHD images. Of course, any discussion of media integration cannot fail to touch on hypermedia, so we will also examine the relationship of hypermedia to super high definition images.

All-digital super high definition images

Real time switching and streaming transmission of uncompressed 4K motion pictures

We introduce a study investigating the impact of high frame rate videos on viewer's eye blink frequency. A series of videos with varying combinations of motion complexities and frame rates were shown to participants, while their eye blinks were counted with J!NS MEME (smart eye wear). Lower frame rates and lower motion complexity caused higher blink frequencies, which are markers for stress and emotional arousal.

Naohisa Ohta

Papers

Basic characteristics of variable rate video coding in ATM environment

International real-time streaming of 4K digital cinema

All-digital super high definition images

Real time switching and streaming transmission of uncompressed 4K motion pictures

In the Eye of the Beholder: The Impact of Frame Rate on Human Eye Blink