![]() |
|||
![]()
|
![]() |
![]() Click Here! |
![]() |
Quantitative QOS Parameters End-to-end quality of service (QOS) in videoconferencing and visual collaboration is defined as the level of satisfaction a user has with a given session. It is a function of many independent and interdependent factors (e.g., window size, processor speed, network bandwidth), which together influence frame rate, bit depth, image clarity and resolution, audio clarity, lip synchronization, and latency. In contrast to conventional data applications in which data transmission is bursty, digital video and audio applications require continuous data transmission. In IP environments, precise bit rates during the transmission vary. In the following list, the factors influencing bit rates (bandwidth) during videoconferencing and collaborative computing are presented as a function of the media (i.e., video, audio, and data):
The central processor, any additional compression/decompression (codec) circuits, network infrastructure, and the users network connection directly affect these quantitative factors. Qualitative QOS Experience Depending on the quantitative parameters, the users experience with multimedia (which is a combination of audio, video, and data) may be qualitatively different. Exhibit 5-2-2 is intended to help readers understand the interdependence of various quality of service parameters in time-dependent streaming media.
The users experience with bidirectional, live video and visual collaboration over any network can be expressed quantitatively and qualitatively; in general, though, the objective is to reproduce a live meeting or conversation. For the interaction to be as close to natural as possible, it is especially important that both (or all) users in a videoconference experience a uniformly low latency (minimum delay). Any variation in the frame rate between points is perceived as jitter. Poor synchronization between lips and audio is also distracting. Thus, the most important factors in the users qualitative experience of a videoconferencing system are:
All these quality of service concepts are critical to the readers overall understanding of the pros and cons of selecting IP networks for videoconferencing. PROS/CONS OF VIDEOCONFERENCING OVER IP NETWORKS Founders of the Internet were academics driven by four guiding principles:
Internet protocols have withstood the test of multiple applications at the user interface, new operating systems in end-points, and ever-changing transport media in the physical layers (e.g., SONET, ATM). For videoconferencing and visual collaboration, there are fundamental principles that determine bandwidth use in any session.
|
![]() |
|
Use of this site is subject certain Terms & Conditions. Copyright (c) 1996-1999 EarthWeb, Inc.. All rights reserved. Reproduction in whole or in part in any form or medium without express written permission of EarthWeb is prohibited. Please read our privacy policy for details. |