Zdzisław Papir

Perceptual quality assessment for H.264/AVC compression

The paper proposes a No-Reference (NR) metric to objectively assess the H.264/AVC video quality. The proposed model takes into account the typical artefacts introduced by hybrid block-based motion compensated predictive video codecs as the one related to the H.264/AVC standard. More specifically, these artefacts are the blockiness introduced at the boundaries of each coded block and the temporal flickering due to different coding modes used for the same macroblock along the video sequence. Furthermore, a flickering metric for intra coded frames is also derived. The quality prediction accuracy of the proposed NR quality metric is validated over subjective data collected during a video subjective evaluation experiments. Moreover, the quality prediction accuracy is also compared with the one provided by the well known state-of-the-art Structural SIMilarity (SSIM) metric which works in a full-reference mode. The proposed metric achieves a higher Pearsons correlation coefficient with subjective scores than the one achieved by the SSIM metric.

Video Quality Assessment: Subjective testing of entertainment scenes

This article describes how to perform a video quality subjective test. For companies, these tests can greatly facilitate video product development; for universities, removing perceived barriers to conducting such tests allows expanded research opportunities. This tutorial assumes no prior knowledge and focuses on proven techniques. (Certain commercial equipment, materials, and/or programs are identified in this article to adequately specify the experimental procedure. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the program or equipment identified is necessarily the best available for this application.)

Assessing quality of experience for high definition video streaming under diverse packet loss patterns

Abstract This paper presents an approach for deriving a QoE model of High Definition video streaming in the presence of different patterns of packet losses. The goal was achieved by using the SSIM video quality metric, temporal pooling techniques and content characteristics. Subjective tests were performed in order to verify the proposed models. The impact of several network loss patterns on diverse video content was analysed. The paper also deals with the encountered difficulties and presents intermediate steps to give a better understanding of the final result. The research aims to evaluate the perceived performance of IPTV and video surveillance systems. The model has been evaluated in the Quality of Experience (QoE) domain. The final model is generic and shows high correlation with the subjective results.

Content driven QoE assessment for video frame rate and frame resolution reduction

Video bit rate reduction is very important for all video streaming applications. One possibility involves quantization domain and the majority of the work devoted to bit rate reduction focuses on this aspect only. The other possibility is to modify a video in time or space domain i.e. change the frames per second FPS rate or frame resolution FR. In this paper we present two no reference metrics mapping FPS rate and FR into MOS (Mean Opinion Scale). The performance of both models is significantly improved by incorporating content characteristics such as spatial information SI and temporal information TI. The impact on Quality of Experience (QoE) of both content characteristics is discussed with relation to the FPS rate and FR changes and general conclusions are drawn. The models were estimated and verified upon results of subjective experiments performed using video sequences of diverse spatial and temporal variability. The considered FPS rate was changed from 5 to 30 and the considered FR was changed from SQCIF to SD.

Evaluation of Quality Retaining Diagnostic Credibility for Surgery Video Recordings

The paper proves that it is possible to meet contradictory requirements of effective compression and diagnostic credibility, for long-lasting and low motion bronchoscopic recordings at compression ratios close to 100. As the main supporting assumption, it has been accepted that the content can be compressed as far as clinicians are not able to sense a loss of video diagnostic fidelity. Different market codecs were inspected by means of the combined subjective and objective tests.

Transient and stationary characteristics of a packet buffer modelled as an MAP/SM/1/b system

Abstract A packet buffer limited to a fixed number of packets (regardless of their lengths) is considered. The buffer is described as a finite FIFO queuing system fed by a Markovian Arrival Process (MAP) with service times forming a Semi-Markov (SM) process (MAP /SM /1/b in Kendall’s notation). Such assumptions allow us to obtain new analytical results for the queuing characteristics of the buffer. In the paper, the following are considered: the time to fill the buffer, the local loss intensity, the loss ratio, and the total number of losses in a given time interval. Predictions of the proposed model are much closer to the trace-driven simulation results compared with the prediction of the MAP /G/1/b model.

A no reference metric for the quality assessment of videos affected by exposure distortion

In the field of still and moving pictures digital imaging one of the most important factors affecting the quality of the acquisition is a correct exposure. This factor is especially important for video surveillance. It is particularly applicable in the case of CCTV cameras often operating in low-light conditions or blinded by an external light source. It is quite common that the lighting conditions are well below the adaptive capacity of a camera. Therefore, it is necessary to continuously monitor the level of exposure to determine image quality. It should be noted that the level of exposure is not expressed using quantitative parameters of acquisition (being sometimes meaningless from the perceived quality assessment point of view) but is measured directly on the image. The purpose of the presented research was to develop a No Reference (NR) metric assessing video Quality of Experience (QoE) affected with the exposure distortion. It was presumed that both over- and under-exposure degrade QoE, so the research task was to derive a proper mapping function between QoE and exposure. The presented exposure metric is unique and no similar research was found in the literature.

Compression evaluation of surgery video recordings retaining diagnostic credibility (compression evaluation of surgery video)

Wider dissemination of medical digital video libraries is affected by two correlated factors, resource effective content compression that directly influences its diagnostic credibility. It has been proved that it is possible to meet these contradictory requirements halfway for long-lasting and low motion surgery recordings at compression ratios close to 100 (bronchoscopic procedures were a case study investigated). As the main supporting assumption, it has been accepted that the content can be compressed as far as clinicians are not able to sense a loss of video diagnostic fidelity (a visually lossless compression).Different market codecs were inspected by means of the combined subjective and objective tests toward their usability in medical video libraries. Subjective tests involved a panel of clinicians who had to classify compressed bronchoscopic video content according to its quality under the bubble sort algorithm. For objective tests, two metrics (hybrid vector measure and hosaka Plots) were calculated frame by frame and averaged over a whole sequence.

OASIS Archive --- Open Archiving System with Internet Sharing

OASIS Archive project aimed at developing a system for the universal presentation of Media Art works independent of location. The goal was to establish a user-friendly search system in order to ensure the preservation and availability (sustainability) of cultural heritage in the field of Media Art. The metadata system interlinking databases of all participating institutions can be accessed by individual users (both researchers and general public) through an on-line interface, by multimedia archive servers engaged in exchange within a distributed system and by various play out media. Access permission is scalable depending on whether the access takes place within the system or from the outside.

Compression and distribution of panoramic videos utilising MPEG-7-based image registration

This paper describes an innovative compression method of panoramic images based on MPEG-7 descriptors. The proposed solution employs a detection of a series of individual video frame overlaps in order to produce concatenated panoramic images. The presented method is easy to implement even in simple devices such as low power consuming chipsets installed in remote cameras having limited power supplies. Under subjective tests it has been proved that the concatenation method allows for achieving lower transmission rates while sustaining picture quality.