Constant bitrate (CBR) encoding of media streams can result in either reduced quality of complex scenes or wasted storage space during simple scenes. VBR encoding on the other hand allocates bits where they are most needed, resulting in a more uniformly high visual or aural quality. The disadvantage of the VBR technique is that it results in bursty network traffic and uneven resource utilization when streaming media. Our techniques focuses on smoothing VBR media transmissions without a priori knowledge of the actual bitrate. Hence, our technique can be applied to (a) live streams and (b) stored streams without requiring any server side pre-processing.
Our technique called Multi-Threshold Flow Control (MTFC) utilizes multi-level buffer thresholds at the client side that trigger feedback information sent to the server. This technique can be applied to both live captured streams and stored streams without requiring any server side pre-processing. We have implemented this scheme in our continuous media server Yima and verified its operation across real world LAN and WAN connections. The results show smoother transmission schedules than any other previously proposed online technique.
Real-Time Digital Storage and Playback of Multiple Independent Streams.
The many different streams of video and audio data are stored and played back from the system developed at IMSC. The goal of the Yima project is to design and develop an end-to-end architecture for real-time storage and playback of several high quality digital media streams through heterogeneous, scalable and distributed servers utilizing shared IP networks (e.g., Internet). The system consists of 1) a , high performance, and real-time media server, 2) a real-time network streaming paradigm and 3) several video and audio clients.
SCADDAR: An Efficient Randomized Technique to Reorganize
Description:
This technology is a new scalable storage architecture called
SCADDAR (SCAling Disks for Data Arranged Randomly.)
SCADDAR uses a pseudo-random placement technique to place data across a set of disks in order to achieve load balancing. The random locations can always be regenerated using a standard pseudo-random number generator and the same seed value. This approach efficiently redistributes only a small amount of data when scaling the storage to ensure load balancing.
Advantages
- disks Block movement minimized.
- Does not require a directory for storing block locations.
- Computes the new locations of blocks on-the-fly for each block access.
- Maintains randomized block placement for successive scaling operations, which in turn preserves load balancing of the.
Applications
- Storage devices.
- continuous media servers.
- video conferencing.
- video-on-demand .
- streaming video/audio.
- Storage Area Networks (SAN).
- Direct Attached Storage (DAS).
Explanation:
Scalable storage architectures allow for the addition of disks to increase storage capacity and/or bandwidth. This is an important requirement for continuous media servers for two reasons. First, multimedia objects are ever increasing in size, numbers and bandwidth requirements. Second, magnetic disks are continuously improving in capacity and transfer rate. In its general form, disk scaling also refers to disk removals when either capacity needs to be conserved or old disk drives are retired. There are two basic approaches to scatter the blocks of a continuous media object on multiple disk drives: random and constrained placement. Assuming random placement, our optimization objective is to redistribute a minimum number of media blocks after disk scaling. This objective should be met under two restrictions. First, uniform distribution and hence a balanced load should be ensured after redistribution. Second, the redistributed blocks should be retrieved at the normal mode of operation in one disk access and through low complexity computation. We propose a technique that meets the objective, while we prove that it also satisfies both restrictions. The SCADDAR approach is based on using a series of REMAP functions which can derive the location of a new block using only its original location as a basis.
Adding one storage node to a four node cluster results in a minimal movement of data with the SCADDAR algorithm. Only 20% of the data need to be moved from each old node to the new node.
Real-Time Streaming Protocol
RTSP features
_ “rough” synchronization (fine-grained a RTP sender reports)
_ virtual presentations = synchronized playback from several servers
a command timing
_ load balancing using redirection at connect, during stream
_ supports any session description
_ device control a camera pan, zoom, tilt
_ caching: similar to HTTP, except “cut-through”
RTSP operation
RTSP functionality
_ first, get presentation description
_ unicast
_ multicast, client chooses address
_ multicast, server chooses address (NVOD)
_ independent of stream file format a subsets or combinations of
files
conference participant: “invite” to conference, controlled by several
people
live streaming: ability to add media
one session = single time axis
RTP has important properties of a transport protocol: it runs on end systems, it provides demultiplexing. It differs from transport protocols like TCP in that it (currently) does not offer any form of reliability or a protocol-defined flow/congestion control. However, it provides the necessary hooks for adding reliability, where appropriate, and flow/congestion control. Some like to refer to this property as application-level framing (see D. Clark and D. Tennenhouse, "Architectural considerations for a new generation of protocols", SIGCOMM'90, Philadelphia). RTP so far has been mostly implemented within applications, but that has no bearing on its role. TCP is still a transport protocol even if it is implemented as part of an application rather than the operating system kernel.
APPLICATIONS
- Video-on-demand
- News-on-demand
- E-commerce
- Distance learning
- Corporate training
- Scientific visualization
1)Video-on-demand :-
Almost every home has a television today. It offers programmes from a number of available channels and is very simple to use. The Cable TV (CATV) makes it possible to choose programmes from large number of channels. Then became video rental business in combination with a video recorder, which provides customers to select movies when they will. This service may be called video on demand.
Nowadays Video-on-Demand (VoD) includes much wider services and opportunities. Today s technology allows telecommunication network operators to offer such services as home shopping, games, and movies on demand. These services should have a competitive pri ce comparing to the video rental, and customers do not need to travel for the services. These possibilit ies have been reached by the development of the telecommunication and electronic industry. The capacity of a hard disk has doubled almost every year at near-constant cost. The useful compression ratio for video has been increased considerably, MPEG-format ted video can be transported at a bit rate of few Mbit/s. The digital signal processing techniques permit the transport of a few Mbit/s over existing copper wires for a distance of a few kilometres. Finally, Asynchronous Transfer Mode (ATM) systems allow the switching of any reasonable bit rate to a single or multiple customers among a large number of connected customers. However, today s transmission bandwidth is large only downstream towards the customer with narrow upstream bandwidth. But upstream bandwidth will also become wider in the future, then interactivity between the customer and the service provider will increase.
This new technology is being developed all the time, because Video-on-Demand has so many different applications to offer to the custo mers and economical possibilities have been seen. Many companies, organisations and universities are developing products and standards. Both cable TV and telephone operators invest to their networks and have some trials in Video-on-Demand. To finance the required investments, higher consumer volumes must be reached from residential side instead of business side that is running ahead in the development of technology. The battle is hard, and it is getting harder all the time. So some companies have establis hed business relationships to get their knowledge and resources together. In addition, they may avoid some regulation restrictions before telecommunication markets are opened to everyone.
Interactive services
The current TV broadcasting will meet a fundamental change by interactive video delivery services. Many TV stations broadcast their programmes simultaneously to users, who select one channel of the available channels to view at a particular time. In contr ast, by an interactive system much wider selection of programmes become available at any time.
Types of interactive services
Based on the level of interactivity, interactive services can be classified into several categories. The following categories are collected from an article written by Thomas D.C. Little and Dinesh Venkatesh from Boston University Broadcast (No-VoD) services similar to broadcast TV, in which the user is a passive participant and has no control over the session.
Pay-per-view (PPV) services in which the user signs up and pays for specific programming, similar to existing CATV PPV services.
Quasi Video-on-Demand (Q-VoD) services, in which users are grouped based on a threshold of interest. Users can perform at the simplest level temporal control activities by switching to a different group.
Near video-on-demand (N-VoD) services in which functions like forward and reverse are simulated by transitions in discrete time intervals (on the order of 5 minutes). This capability can be provided by multiple channels with the same programming skewed in time.
True Video-on-Demand (T-VoD) services, in which the user has complete control over the session presentation. The user has full-function VCR (virtual VCR) capabilities, including forward and reverse play, freeze, and random positioning. T-VoD needs only a single channel per customer; multiple channels become redundant.
PPV services are the easiest to implement, and T-VoD systems are the most difficult to implement. PPV and Q-VoD are services like watching movies. In these cases, a local controller, set-top-box, can filter multiple channels to achieve the service. T-VoD requires a bi-directional signal from the user to a centralised controller.
Interactive services cover a wide range of services from movies-on-demand to distance learning. Some of the basic interactive multimedia services are listed below in Table 1.
2)Scientific visualization
What is Scientific Visualization?
Scientific visualization, sometimes referred to in shorthand as SciVis, is the representation of data graphically as a means of gaining understanding and insight into the data. It is sometimes referred to as visual data analysis. This allows the researcher to gain insight into the system that is studied in ways previously impossible.
What it is not- It is important to differentiate between scientific visualization and presentation graphics. Presentation graphics is primarily concerned with the communication of information and results in ways that are easily understood. In scientific visualization, we seek to understand the data. However, often the two methods are intertwined.
From a computing perspective, SciVis is part of a greater field called visualization. This involves research in computer graphics, image processing, high performance computing, and other areas. The same tools that are used for SciVis may be applied to animation, or multimedia presentation, for example.
As a science, scientific visualization is the study concerned with the interactive display and analysis of data. Often one would like the ability to do real-time visualization of data from any source. Thus our purview is information, scientific, or engineering visualization and closely related problems such as computational steering or multivariate analysis. The approaches developed are general, and the goal is to make them applicable to datasets of any size whatever while still retaining high interactivity. As an emerging science, its strategy is to develop fundamental ideas leading to general tools for real applications. This pursuit is multidisciplinary in that it uses the same techniques across many areas of study..
Conclusions and Future Work
In this study we presented an evaluation of Yima which addresses the complete endto-end issues of storing, retrieving, and delivering isochronous media types over IP networks. We described the architecture that is based on a scalable multi-disk, multi-node server and an MPEG-4 capable client. We introduced a mechanism to stream variable bit rate media in a simple yet flexible way via the industry standard protocols RTP and RTSP. We demonstrated the feasibility of streaming near NTSC-quality video and audio (compressed via MPEG-4 and MPEG-1 Layer 3 algorithms) to residential locations over current broadband connections (ADSL). In the near future, we plan to scale up our prototype to more nodes and evaluate its
scalability and fault-tolerance with a large number of different clients and media types as well as enable multiple retransmissions.
- part: Continuous Media Server
- part: property of Continuous Media Server
- part: Features of Continuous Media Server
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