The Digital Fact Book - Quantel

FragmentationThe scattering of data over a (disk) store caused by many recording and deletion operations.Generally this will eventually result in store access becoming slow – a situation that is notacceptable for video recording or replay. The slowing is caused by the increased time neededto access randomly distributed data or free space. With such stores de-fragmentation routinesarrange the data (by copying from one part of the disk to another) so that it is quickly accessiblein the required order for replay. Clearly any change in replay, be it a transmission runningorder or the revision of an edit, could cause further fragmentation.Disk tracksFFragmented dataDe-fragmentationDe-fragmented dataStores capable of true random access, such as Quantel’s sQ server are able to play framesin any order at video rate, and never need de-fragmentation.See also: Consolidation, FrameMagicFrameMagicQuantel term describing an advanced form of the management of video in a server.This covers much ground but basically offers the practical goals of guaranteeing realtimeaccess to any frame for all video connections (simultaneous true random access) andavoiding the deletion of any material by one user that is partly or wholly used by another.This is achieved by implementing a number of basic design criteria, including realtime randomaccess to any frame, storing video material as a series of individual frames, rather thanlonger video files, as well as an on-board realtime database management system which,among other things, tracks who is using what material. FrameMagic is implemented inQuantel’s sQ servers.See also: Delta Editing89