A picture quality control framework for MPEG video over ATM

This paper addresses the problem of transmission of digital Video communications over B-ISDN and provides a solution based on a good knowledge of both video system design and broadband networks capabilities. We propose a picture-oriented QoS control framework to ensure a high endto-end Quality of Picture (QoP) level for MPEG-encoded Video-On-Demand (VOD) applications carried over ATM networks. Our approach overcomes the difficulty imposed by random cell discarding due to the bursty and Variable Bit Rate transmission nature of compressed video, by using an accurate cell discrimination strategy and destination data recovery mechanisms. It is assumed that there are four hierarchical types of cell flows according to MPEG coding. Each flow has a different impact on the destination picture recovery process. Therefore, this scheme aims to minimize cell loss probability for critical data and thus, reduce the destination picture quality degradation, by adjusting the priority level of cells according to the carried data type. Despite these preventive measures, cell loss or errors may still occur. Therefore, complementary actions are cooperatively taken at the source and destination equipment (i.e., codecs), in conformity with the temporal requirements of MPEG video streams. In the one hand a fast cell-error detecting and recovery algorithm is proposed for protecting critical picture system information. In the other hand, a block-based bit interleaving schemes are designed to spatially disperse cell loss effect on reference frames. Finally, an extended AAL type 5 is presented to support such a high performance picture delivery framework.