Anastasios Kourtis

Quantified PQoS assessment based on fast estimation of the spatial and temporal activity level

This paper presents a novel method for fast and quantified estimation of the Perceived Quality of Service (PQoS) for MPEG-4 video content, encoded at constant bit-rates. Taking into account the instant PQoS variation due to the Spatial and Temporal (S–T) activity within a given MPEG-4 encoded content, this paper introduces the Mean PQoS (MPQoS) as a function of the video encoding rate and the picture resolution, and exploits it as a metric for objective video quality assessment. The validity of this metric is assessed by comparing PQoS experimental curves to the theoretical benefit functions vs. allocated resources. Based on the proposed metric, and taking into account the qualitative similarity between theoretical and experimental curves, the paper presents a prototype method for pre-encoding PQoS assessment based on the fast estimation of the S–T activity level of a video signal.

A Theoretical Framework for End-to-End Video Quality Prediction of MPEG-based Sequences

This paper presents a novel theoretical framework for end-to-end video quality prediction of MPEG-based video sequences. The proposed framework encloses two discrete models: (i) A model for predicting the video quality of an encoded signal at a pre-encoding stage and (ii) A model for mapping QoS-sensitive network parameters (i.e. packet loss) to video quality degradation. The efficiency of both the discrete models is experimentally validated, proving by this way the accuracy of the proposed framework.

Evaluation of video quality based on objectively estimated metric

Multimedia applications and especially encoded video services, are expected to play a major role in the 3rd generation (3G) and beyond mobile communication systems. Given that future service providers are expected to provide video applications at various price and quality levels, quick and economically affordable methods for preparing/encoding the offering media at various qualities are necessary to be developed. This paper presents a method for objective evaluation of the perceived quality of MPEG-4 video content, based on a quantification of subjective assessments. Showing that subjectively derived perceived quality of service (PQoS) vs. bit rate curves can be successfully approximated by a group of exponential functions, the proposed method exploits a simple objective metric, which is obtained from the mean frame rate vs. bit rate curves of an encoded clip. The validity of this metric is assessed by comparing subjectively derived PQoS results to the corresponding ones, which come from the proposed objective method, showing that the proposed technique provides satisfactory PQoS estimation.

A framework for end-to-end video quality prediction of MPEG video

This paper proposes, describes and evaluates a novel framework for video quality prediction of MPEG-based video services, considering the perceptual degradation that is introduced by the encoding process and the provision of the encoded signal over an error-prone wireless or wire-line network. The concept of video quality prediction is considered in this work, according to which the encoding parameters of the video service and the network QoS conditions are used for performing an estimation/prediction of the video quality level at the user side, without further processing of the actual encoded and transmitted video content. The proposed prediction framework consists of two discrete models: (i) a model for predicting the video quality of an encoded signal at a pre-encoding stage by correlating the spatiotemporal content dynamics to the bit rate that satisfies a specific level of user satisfaction; and (ii) a model that predicts primarily the undecodable frames (and subsequently the perceived quality degradation caused by them) based on the monitored averaged packet loss ratio of the network. The proposed framework is experimentally tested and validated with video signals encoded according to MPEG-4 standard.

Dynamic bandwidth allocation in DVB-T networks providing IP services

The combination of high capacity, signal robustness, and worldwide acceptance have made digital terrestrial broadcasting (DVB-T) one of todays more promising technologies, while newly adopted standards support the integration of digital television programs and data services within a single multiplex, offered to both stationary and mobile end users. The paper addresses the issue of optimal bit rate allocation among DTV and IP services within the DVB-T multiplex, and demonstrates a novel configuration providing real-time sharing of the available bandwidth via an algorithm based on service hierarchy and perceptual quality assessment. The architecture and performance of a fully functional DVB-T testbed developed on this concept is also presented.

Shot boundary detection without threshold parameters

Automatic shot boundary detection is a field, where many techniques and methods have been proposed and have claimed to perform reliably, especially for abrupt scene cut detection. However, all the proposed methods share a common drawback: the necessity of a threshold value, which is used as a reference for detecting scene changes. The determination of the appropriate value or the dynamic reestimation of this threshold parameter remains the most challenging issue for the existing shot boundary detection algo- rithms. We introduce a novel method for shot boundary detection of discrete cosine transform (DCT)-based and low-bit-rate encoded clips, which exploits the perceptual blockiness effect detection on each frame without using any threshold parameter, therefore mini- mizing the processing demands required for algorithm

Quantifying TV white space capacity: quantifying tv white space capacity:

The so-called TV white spaces (TVWS) are locally underutilized portions of the terrestrial TV bands and occur as a by-product of the digital switchover taking place in most countries across the globe. Thanks to the very good characteristics of the TV bands in terrestrial radio communications, the exploitation of TVWS for local- or regional-area wireless license-exempt networking, under a carefully established regulatory framework, is a very attractive prospect. This article presents a generic methodology for determining the actual capacity of white spaces using a geolocation-based approach, that is, dynamic assignment of radio resources to TVWS networks according to their geographical location. This methodology is applied in a case study investigating a sample area in southeastern Europe and unveils a significant amount of access capacity that can be unleashed via TVWS exploitation.

Unidirectional lightweight encapsulation: performance evaluation and application perspectives

Multi Protocol Encapsulation (MPE) is today the dominant method for encapsulating IP data into the MPEG-2 Transport Stream so they can be conveyed over digital television platforms (DVB or ATSC). Unidirectional Lightweight Encapsulation (ULE) is a new alternative to MPE, providing simplicity, efficiency and configurability. This paper presents the principle and benefits of ULE, approaches the issues associated with its adoption and compares it against MPE through extensive performance measurements in a fully functional testbed under IPv4 and IPv6 load. It also proposes, implements and demonstrates the combination of MPEG-4/H.264, IPv6 and ULE as the most efficient and flexible protocol stack for next-generation transmission of digital video over Digital Television networks

Joint assessment of Network- and Perceived-QoS in video delivery networks

Given the increasing number of IP streaming video customers, service providers are seeking an efficient way to monitor in real time the offered quality of service, as perceived by each end user. Since real-time video quality assessment via image processing algorithms is quite bandwidth- and processing-power-demanding, a feasible alternative could be to monitor the Network-level Quality of Service (NQoS) and associate it with the Perceived QoS (PQoS). This article presents a network-agnostic framework for the joint assessment of N- and P-QoS, with the aim of correlating these two parameters for a specific network and service configuration. This framework/architecture is implemented with open source software tools and is being demonstrated in an actual WiMAX streaming video distribution platform.

ADAMANTIUM project: Enhancing IMS with a PQoS-aware multimedia content management system

IMS entails novel business opportunities for pioneering and emerging multimedia services, such as IPTV and VoIP video call applications. However, this strong commercial interest on this promising convergent IMS environment is balanced by the lack of efficient user/customer-centric network management mechanisms. ADAMANTIUM proposes an IMS-compatible multimedia content management system (MCMS) focused on performing dynamic cross layer adaptations for optimization of the user experience in terms of perceptual quality for media services. This multimodal management system will be applied in an integrated and coherent way along all the network layers and delivery-chain nodes based on a user/customer-centric approach rather than a typical engineering one.