SVDA

The Scalable Video Distributed Architecture (SVDA) is, generally speaking, an environment that introduces enormously large storage capacity devices into multimedia environments. In modern multimedia environment there is a tendency of moving the responsibility of storing and delivering video data onto video servers. Such a solution has a lot of well-known advantages: clients don't need to be equipped with large discs, a video stored on a video server can be delivered at the same moment to many clients and thus the need of keeping the same data at many places is refused, etc. The solution presented by this system follows the idea. Furthermore, it enhances the functionality of video servers by adding third-party devices that can save video files on its low access time, but large storage capacity devices.

Digital video can be very large: a one-hour video encoded in the MPEG-1 format at 1.5Mbps requires about 0,7 GB; using MPEG-2 format for a one-hour video involves about 3,5 GB storage space. It is still too much for the newest hard discs: e.g. a computer fit up with 50 MB storage capacity can hold only 15 hours of MPEG-2 stream. Considering the fact that clients are usually interested in several, the most up-to-date pieces of video, it is worth taking into account that the rest of the files can be stored on low access time, but large storage capacity devices and migrated into a video server when a client wishes to watch them.

This is what the SVDA does: it gives the whole functionality of a video server (delivering and recording video streams) and additionally extends storage capacity by almost unlimited number of bytes (for the current implementation it is up to 3 terabytes). When a user wants to watch a film, which is not stored on a video server, they specify at what time they want to watch it and the system takes the responsibility of making a video accessible for playing at the indicated time.

• A user has a transparent view of the whole file system that is made accessible by the SVDA system. It has no idea where the files are actually stored: on which video or archive server. All that the user knows is whether it is possible to stream a film promptly, or the film must be requested to be streamed.
• At least one video and archive server must be used. The video server must give the network access to its resources, so all the file transfer operations might be performed through the network. The archive server must provide a large storage capacity and, as a video server, give the network access to its resources.
• The whole environment must be modular, scalable and hardware-independent. The CORBA middleware must be used to meet all this requirements.
• The system must be designed in the way that accepts all the new solutions that might appear on the IT-market in the future.
• It must be possible to access the system 'from anywhere, anytime, by anyone on anything'. It implies the use of the Java technology for a client layer of the system. The system cannot be limited only to the Java platform, thus all the others solutions for the client layer must be acceptable, too.

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