Human-Computer Interaction: Ergonomics and User Interfaces - Vol. 1

By Hans-Jörg Bullinger; Jürgen Ziegler | Go to book overview

On the Visual Quality of Still Images and of Low-
motion Talking Head Digital Videos

Peter J. Haubner
Institute of Applied Informatics and Formal Methods (AIFB)
University of Karlsruhe, Germany


1
Introduction

In order to achieve high fidelity performance when processing and displaying multimedia information consisting of text, still images, animations, video and audio, high data rates are needed in the order of some Mega-Bytes per second. This causes considerable transmission problems for the fastest computer devices and for today's networks. Therefore, the data rates have to be reduced, which, however, also reduces the perceived quality of the displayed information and leads to a loss in user acceptance.

Reduction of data rates can be achieved by compression. techniques or by scaling the multimedia file to a smaller window size, lower frame rate, lower resolution, lower colour depth or even by combinations of all of these measures. In an empirical study on tele-conferencing systems these possibilities of reducing data rates were evaluated in terms of perceived Visual Quality (VQ) and user acceptance. The goal of our study was to systematically investigate the influence of data rate reduction on perceived visual quality VQ and to gain statistically significant data and practical experiences from which guidelines for the ergonomic layout of "Talking Heads" and for other equivalent situations could be derived.


2
Empirical Study

2.1
Experimental Setup and Design

The experiments were carried out at a multimedia workplace in our HumanComputer Interaction Laboratory ( HCI-Lab), which enables to generate, to

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