SMPTE 390M-2004

This standard defines the specialized operational pattern atom or OP-Atom for the storage and exchange of an MXF file with a tightly defined structure for a single item of essence described by a single essence track. It defines the operating restrictions, structural metadata objects and individual attributes that shall be applied to the MXF file format specification to achieve interoperability when exchanging a single item of audio-visual material. Operational pattern atom is intended to satisfy the demands of applications where there is a requirement for exchange of material and associated metadata together in a single file with an open and standardized format, yet also a demand a simple, predictable, layout with minimum scope for variation. OP-Atom is specifically intended for applications where each essence track is held separately. Operational pattern atom provides for a subset of MXF features. The provisions of OP-Atom may make it unsuitable for certain applications, in these cases a generalized operational pattern or a different specialized operational pattern should be used. In all cases, the suitability of this pattern needs to be judged on a per-application basis. Some specific areas to consider are: OP-Atom is optimized for applications where the record (file creation) process is completed before a playout (file read) process is started. Therefore, it may be unsuitable in applications where the record/playout (file creation/file reading) processes occur concurrently. This operational pattern places a full index table in the footer which, with VBR essence, may make it impossible to use as a streaming format where stream delivery requires advanced knowledge of frame boundaries. With VBR essence, it also requires the (possibly very large) index table to be stored separately until the file recording ends. Each OP-Atom file holds a single track of essence data therefore many applications will need an external mechanism to synchronize essence among multiple files. This standard does not define such a synchronization method; however, it does include an annex detailing a method of informatively recording synchronization among files created as a group.