chapter 8-multimedia over internet
TRANSCRIPT
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
● No product shipping
● No customer service
concerns
● Make money while you
sleep
● The world at your doorstep
● Minimal risk
● High income potential
Multimedia Over IP Multicast Network
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 example, 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
Multimedia Services & Applications
Video Streaming
Interactive Multimedia Applications
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
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.