Multimedia Over Internet

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Multimedia Over IP Multicast Network

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.

Multimedia Data Streaming

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.

Web Information System Architecture

Interactive Web Pages

Interactive Multimedia Applications

Multimedia Services & Applications

Video Streaming

Interactive Multimedia Applications

● 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.

Collaborative Work

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.

Multimedia Messaging System

MMS Network Architecture

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.