Varying Audio Quality for Networked Multimedia Services and Tools

As a result of listening tests performed with users of multimedia applications we present constraints for a dynamic adaptation (scaling) of audio data streams to the available system and network resources. For the speech medium, any severe deformation of frequency characteristics should be avoided while shortening and expanding of speech pauses is suitable to cope with varying delays. For the music medium the best scaling algorithm is a smooth fade between quality levels. Scaling resulting in lower quality should be performed in multiple steps, while any approach can be chosen for higher quality scaling. It appears that six levels of quality are sufficient for scaling of music from high quality [compact disc (CD)] to very low quality (cellular phone), and vice versa. We propose enhancements to multimedia tools based on a Dynamic Quality of Service (QoS)-Centered Architecture, where the bit rate and scheduling of associated media streams are adapted dynamically, while taking into account the highest possible QoS for the user. These enhancements allow authors of multimedia applications to constrain the media content to the range in which scaling may be performed by the system. An alternate approach of using post-processors to include scaling information embedded in the data in the form of digital watermarks is also presented.

Print ISSN

0036-1682

Published

1997-12

Content type

Original Research

DOI

10.5594/J17161