EFFECT OF BIT-RATE VARIATION OF THE BASE LAYER ON THE PERFORMANCE OF 2-LAYER VIDEO CODECS

Three different versions of a two-layer video coding technique are considered. In the first method the generated bit rate of both layers are variable (VBR-VBR). The second method employs a smoothing buffer and a control mechanism to produce a constant bit rate at the base layer, but that of the second layer is still variable (CBR-VBR). The third method is similar to the second method but the base layer rate within the buffer size is made variable (Semi-CBR-VBR). The performance of these methods under the coding efficiency and their interactions with ATM networks are investigated. It is shown that the second layer under VBR-VBR has the minimum network delay and loss, while at the base-layer, CBR-VBR has the best performance. Both layers under Semi-CBR-VBR method have all the advantages of the other two methods without having their disadvantages. The Semi-CBR-VBR codec does not need network policing and hence is an ideal candidate for ATM networks.