Image Stream Transfer Using Real-Time Transmission Protocol

[Electrical Fan]

Even though we explore Image transport, ITP is a generic selectively reliable unicast Transport protocol with congestion control that can be customized for specific applications and formats. 1 Introduction Images constitute a significant fraction of traffic on the World Wide Web, e.g., according to a recent study, JPEGs account for 31% of bytes transferred and 16% of documents downloaded in a client trace [15]. The ability to transfer and render images on screen in a timely fashion is an important consideration for content providers and server operators because users surfing the Web care about interactive latency. At the same time, download latency must be minimized without compromising end to end congestion control, since congestion control is vital to maintaining the long term stability of the Internet infrastructure. In addition, appropriate reaction to network congestion also allows image applications to adapt well to available network conditions. The HyperText Transport Protocol (HTTP) [11] uses the Transmission Control Protocol (TCP) [31] to transmit images on the Web. While the use of TCP achieves both reliable data delivery and good congestion control, these come at a cost”interactive latency is often significantly large and leads to images being rendered in fits and starts rather than in a smooth way. The reason for this is that TCP is ill-suited to transporting latency sensitive images over loss prone net works where losses occur because of congestion or packet corruption. When one or more segments in a window of transmitted data are lost in TCP, later segments often arrive outoforder at the receiver. In general, these segments correspond to portions of an image that may be handled upon arrival by the application, but the in order delivery abstraction imposed by TCP holds up the delivery of these out of order segments to the application until the earlier lost segments are recovered. As a result, the image decoder at the receiver cannot process information even though it is available at the lower transport layer. The image is therefore rendered in bursts interspersed with long delays rather than smoothly. The TCP like in order delivery abstraction is appropriate for image encodings in which incoming data at the receiver can only be handled in the order it was transmitted by the sender. Some compression formats are indeed constrained in this manner, e.g., the Graphical Interchange Format, GIF [14] which uses lossless LZW compression [21, 43] on the entire image. However, while some compression formats are constrained in this manner, several others are not. Notable examples of formats that encourage out of order receiver processing include JPEG [42, 29] and the emerging JPEG2000 standard [20]. In these cases, a transport protocol that facilitates out of order data delivery allows the application to process and render portions of an image as they arrive improving the interactivity and perceived responsive ness of image downloads. Such a protocol also enables the image decoder at the receiver to implement effective error concealment algorithms on partially received portions of an image, further improving perceived quality


read the entire report
http://ieee-icnp2000/papers/2000-19.pdf

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see similar seminar like rtsp
http://tml.tkk.fi/Studies/Tik-110.300/19.../rtsp.html