tailieunhanh - Nén Video thông tin liên lạc P4

Compressed video streams are intended for transmission over communication networks. With the advance of multimedia systems technology and wireless mobile communications, there has been a growing need for the support of multimedia services such as mobile teleconferencing, telemedicine, mobile TV, distance learning, etc., using mobile multimedia technologies. These services require the real time transmission of video data over fixed and mobile networks of varying bandwidth and error rate characteristics | Compressed Video Communications Abdul Sadka Copyright 2002 John Wiley Sons Ltd ISBNs 0-470-84312-8 Hardback 0-470-84671-2 Electronic 4 Error Resilience in Compressed Video Communications Introduction Compressed video streams are intended for transmission over communication networks. With the advance of multimedia systems technology and wireless mobile communications there has been a growing need for the support of multimedia services such as mobile teleconferencing telemedicine mobile TV distance learning etc. using mobile multimedia technologies. These services require the real time transmission of video data over fixed and mobile networks of varying bandwidth and error rate characteristics. Since the coded video data is highly sensitive to information loss and channel bit errors the decoded video quality is bound to suffer dramatically at high channel bit error ratios BER . This quality degradation is exacerbated when no error control mechanism is employed to protect coded video data against the hostility of error-prone environments. A single bit error that hits a coded video stream could lead to disastrous quality deterioration for extended periods of time. Moreover the temporal and spatial predictions used in most of the video coding standards today render the coded video stream rather more vulnerable to channel errors. This vulnerability is represented by the rapid propagation of errors in both time and space and the quick degradation of the reconstructed video quality. To mitigate the effects of channel errors on the decoded video quality error-handling schemes must be efficiently applied at both the video encoder and decoder. Since real-time video transmissions are sensitive to time delays the issue of re-transmitting the erroneous video data is totally ruled out. Therefore other forms of error control strategy must be employed to mitigate the effects of errors inflicted on coded video streams during transmission. Some of these error control schemes .