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Multimedia Over Internet. Growth of Internet. No production cost Low cost infrastructure No fees for joining or licenses to buy Choice of products and services No sales experience needed No employees required No expensive accounts needed. No inventory to carry No order processing
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Growth of Internet No production cost Low cost infrastructure No fees for joining or licenses to buy Choice of products and services No sales experience needed No employees required No expensive accounts needed • No inventory to carry • No order processing • No product shipping • No customer service concerns • Make money while you sleep • The world at your doorstep • Minimal risk • High income potential
Delivering Real-time Multimedia over Internet framework for transporting real-time Internet video includes two components: congestion control and error control Congestion control consists of rate control, rate-adaptive encoding, and rate shaping Error control consists of forward error correction (FEC), retransmission, error resilience, and error concealment QoS issues are bandwidth, delays and loss of data
Heterogeneity Network Environment Network heterogeneity and Receiver heterogeneity Network heterogeneity refers to the subnetworks in the Internet having unevenly distributed resources (e.g., processing, bandwidth, storage, and congestion control policies). Receiver heterogeneity means that receivers have different or even varying latency requirements, visual quality requirements, and/or processing capability.
Heterogeneity Network Environment Network-centric approach: Routers/switches in the network are required to provide QoS support to guarantee bandwidth, bounded delay, delay jitter, and packet loss for video applications (e.g., integrated services, or differentiated services). End-system based approach: Control techniques to maximize the video quality without any QoS support from the transport network. The integrated solutions is based on both transport (use of control/processing techniques without regard of the specific video) and compression perspectives (employing signal processing techniques with consideration of the video semantics).
Heterogeneity Network Environment Congestion Control: Bursty loss and excessive delay are caused by network congestion Reduce packet loss and delay Rate control matches the rate of the video stream to the available network bandwidth. Rate-adaptive video encoding or rate shaping is required. Rate control is from the transport perspective, while rate-adaptive video encoding is from the compression perspective; rate shaping is in both transport and compression domain.
Heterogeneity Network Environment Error Control Four types: Forward error correction (FEC), retransmission, error resilience, and error concealment. FEC adds redundant information to a compressed video bit stream so that the original video can be reconstructed the in presence of packet loss. Three kinds of FEC: channel coding; source coding-based FEC; joint source/channel coding.
Internet Multimedia Applications Classes of multimedia applications Streaming Stored Multimedia Data Applications Clients request on-demand data (for example, compressed audio or video files) which is stored on servers. One to many streaming of real-time data applications Similar to ordinary broadcast of radio and television, except the transmission takes place over the Internet. Real-time interactive multimedia applications Allows people to use audio/video to communicate with each other in real-time
Multimedia Data Streaming Significant improvement over the download-and-play approach to multimedia file distribution Allows the data to be delivered to the client as a continuous flow with minimal delay before playback can begin Streaming is a server/client technology that allows live or pre-recorded data to be broadcast in real time Multimedia applications such as news, education, training, entertainment, advertising, and a host of other uses Streaming enables the Internet or company Intranet as a new broadcast medium for audio and video.
Multimedia Data Streaming Example: If there are 100 requests for a video stream compressed at 28.8 Kbps, the server would require at least a 3 Mbps connection. The Encoding Station and the Video Streaming Server can be one single system. However, unless hardware encoding is used, this would typically be for a situations requiring limited performance (e.g. a single input stream and a small number of viewer requests). Even so, it would still require a fairly high-performance system. It is much more common to have two separate systems.
Unicast vs. IP Multicast Streaming delivery techniques: Unicast and Multicast. Unicast: Computers establish two-way, point-to-point connections. Client computer can communicate with the computer supplying the multimedia stream. Each client that connects to the server receives a separate stream, which rapidly uses up network bandwidth. IP Multicast: One computer sends a single copy of the data over the network and many computers receive that data. Only a single copy of the data is sent across the network, which preserves network bandwidth. It is connectionless; clients have no control over the streams they receive
Web Multimedia Information Systems Web Process Organizing entity that determines a set of activities and specifies their relations Activity Process step, which participates in the fulfillment of an overall objective. An agent who satisfies the required skills and rights (paradigm of role) fulfilled it. Activities Synchronization Temporal preconditions to define a temporal order between activities, Alternatives to let the user decide on the media to use for a specific purpose, Parallelism between activities what is especially useful in the case of collaborative work.
Flexible scheduling based on a finite set of channels available to all viewers A set of channels are multicast to all viewers tuned to the respective channel. Viewers may watch a program playing on any channel or make a request for something of their own choosing. Viewers' requests are scheduled on one of the jukebox's channels using scheduling criteria like minimum waiting time, etc. A schedule of currently playing and scheduled programs, updated in real-time, is available to all viewers. Viewers can watch any program, including those scheduled by others, by tuning to the appropriate channel.
Jukebox Policies Content-based scheduling Limitations may be imposed based on the content Service provider scheduling A service provider may have a desire or obligation to schedule certain programs at certain times Limited viewer input A service provider may want to blunt the ability of individual viewers to control what programs are playing
Jukebox - Architecture Scheduling control: The scheduler receivers viewer requests, performs scheduling, controls the video server, and provides a schedule of programs to all viewers. Video server: The video server transmits audio/video streams into the network Network: The network must provide an effcient multicast facility and have sufficient bandwidth to meeting viewer quality expectations Receivers: Receivers must be able to receive, decode, and display an audio/video stream.
Collaboration Work Client: A client can send some session requests to a session server to create or join the session so that it can take part in some meeting. Media Server: A media server is a RTP Channel for audio and video communication between clients. Session Server: The session server is the core of the XGSP, which can accept request of various clients and organize the video conference.
MMS Operation Sending Messages: A user sends a message by having its MMS-UA submit the message to its home MMS-RS. Receiving Messages: Upon reception of a message, the recipient MMS-RS verifies the recipient profile and generates a notification to the recipient MMS-UA. Message Adaptation: Within a request for delivery of a message, the recipient MMS-UA can indicate its capabilities, e.g., a list of supported media types and media formats, for the recipient MMS-RS.t Delivery Reports: If a delivery report has been requested by the originator MMS-UA and if the recipient MMS-UA did not request a delivery report not to be generated, the recipient MMS-RS generates a delivery report and delivers the delivery report to the originator MMS-RS.
