ATM網路中視訊傳輸之流量控制

Abstract

本論文所要探討的是關於壓縮後的影像在ATM網路上傳輸的問題，藉由使 用動態影像壓縮的標準--MPEG壓縮法和網路傳輸速率的管制--LEAKY BUCKET POLICING，我們討論編碼器所應有的限制以及編碼器與網路的流 量控制。因為ATM網路具有提供可變傳輸位元率的彈性，若網路能盡量配 合影像壓縮所產生的變化位元率的要求，則在網路的接收端可獲得較佳的 影像品質。本論文提出一種聯合協調編碼器和網路速率的方法，在符合網 路的要求下能得到最大的效益。 This thesis examines the problem of video transport over ATM networks using MPEG-based video compression coder. The constraints on the traffic of a MPEG-based codec in ATM environment are investigated and the interactions between the codec and the network are exploited. ATM networks, as proposed by CCITT as the solution for the future B-ISDN, will provide high flexibility of variable bit-rate (VBR) video service. And the policing function has been introduced to monitor some traffic characteristics of any connection in order to protect the networks. By integrating network source-policing into the VBR encoder, the available network bandwidth can be better utilized. According to a commonly proposed ATM network-user contract, the effect of encoder rate-control for the leaky bucket channel is examined. With the considerations of ATM cell loss, a 2-layered coding scheme is applied to keep picture quality high.