There are various facilities for utilizing the data which enhance the basic recorded material; namely the selection of segments, the addition of annotations, and the post-processing and analysis of data. Furthermore, as the data sets are real-time multimedia, they are rather large. To enable the flexible use of the recorded data and to enable access to these large data sets, the concept of the real-time multimedia index has been devised.
These indexes allow access to the source streams in a multitude of ways. The primary index used is created when a stream is originally recorded. For each source of a media, the incoming data will be saved together with an entry in this index. Each index entry contains a reference to the data, the time it arrived at the recorder, and a reference to some meta-data, which will initially be empty. At the end of a recording, each source will have a stream of data and a stream of index entries. It is the editing client which allows the user to manipulate these indexes in order to gain the flexibility required. For example, the user can add a text annotation to any part of the recording, and the server will attach this to the source stream in the relevant place in the index by updating the meta-data field of an index entry.
These indexes are different but complementary to Rowe's indexes [#!rowind!#] which are used in his Continuous Media Player. His indexes are for content categorisation and are used to aid users in searching particular material in the database. For example, in Rowe's system the user might ask: List all videos about dinosaurs, and the system would search the category index for dinosaur. Similar work in the categorisation area has been done by Niblack et al, who build indexes based on the colour, the texture, and the shape of the content [#!nibla!#] Also complementary is the work by Hampapur on Video Data Management Systems [#!hampa!#] Other kinds of index devised have been used for finding the site at which material is held in a distributed multimedia system.
The index is one of the main design concepts and they allow access to the multimedia data in a multitude of ways. When a stream is originally recorded is index is created . This is called the primary index and used for access to the stream of data. For each source of a media, every component of the incoming data will be saved together with an entry in the primary index.
An important factor of indexes is that the kind of data being indexed is not important nor is its size nor its frequency. Implementors can write specialised recorders and players for each specific data kind, all of which utilize, but are independent of the index itself.
Next: Index Approach and Implementation Up: Recording Previous: Speed and Delay Jon CROWCROFT