On Media Data Structures for Interactive Streaming in Immersive Applications Interactive media streaming is the communication paradigm where an observer periodically requests new desired subsets from the streaming sender in realtime, upon which the sender sends the appropriate media data, corresponding to the received requests, for immediate decoding and display. This is in contrast to noninteractive media streaming, e.g., TV broadcast, where the entire media set is compressed and delivered to the observer before the observer interacts with the data (such as switching TV channels). Examples of interactive streaming abound in different media modalities: interactive browsing of JPEG2000 images, interactive light field or multiview video streaming, etc. Interactive media streaming has the obvious advantage of bandwidth efficiency: only the media subsets corresponding to observeru0027s requests are transmitted. This is important when an observer only views a small subset out of a very large media data set during a typical streaming session. The technical challenge is how to structure media data such that good compression efficiency can be achieved by exploiting correlation among media subsets (thus inducing a particular decoding order if correlation is exploited during encoding), while providing sufficient flexibility for the observer to freely navigate the media data set in hisher desired unique order. In this overview paper, we survey different proposals in the literature that simultaneously achieve the conflicting objectives of compression efficiency and decoding flexibility.

Interactive browsing of 3D environment over the internet In this paper, we describe a system for wandering in a realistic environment over the Internet. The environment is captured by the concentric mosaic, compressed via the reference block coder (RBC), and accessed and delivered over the Internet through the virtual media (Vmedia) access protocol. Capturing the environment through the concentric mosaic is easy. We mount a camera at the end of a level beam, and shoot images as the beam rotates. The huge dataset of the concentric mosaic is then compressed through the RBC, which is specifically designed for both high compression efficiency and justintime (JIT) rendering. Through the JIT rendering function, only a portion of the RBC bitstream is accessed, decoded and rendered for each virtual view. A multimedia communication protocol  the Vmedia protocol, is then proposed to deliver the compressed concentric mosaic data over the Internet. Only the bitstream segments corresponding to the current view are streamed over the Internet. Moreover, the delivered bitstream segments are managed by a local Vmedia cache so that frequently used bitstream segments need not be streamed over the Internet repeatedly, and the Vmedia is able to handle a RBC bitstream larger than its memory capacity. A Vmedia concentric mosaic interactive browser is developed where the user can freely wander in a realistic environment, e.g., rotate around, walk forwardbackward and sidestep, even under a tight bandwidth of 33.6 kbps.