MXF

The Material eXchange Format, SMPTE 377M, is aimed at the exchange of program material between file servers, video recorders, editing systems, tape streamers and digital archives, etc. It is a container, or wrapper, format that supports a variety of differently coded streams of essence (images and sound), together with metadata describing the material in the MXF file.

There are ten Operational Patterns defined by SMPTE standards. The main nine are the intersections along two-axes describing Item (segment) versus Package (complexity). This gives the combinations of 1) Single Item, 2) Playlist Items and 3) Edit Items against a) Single Package, b) Ganged Packages and c) Alternate Packages. By far the most common is OP-1a – Single Item, Single Package – which contains a single flat clip. The tenth operational pattern is OP-Atom which is used by Panasonic P2.

Bridging file and streaming transfers, MXF helps move material between AAF file-based post production and streaming program replay using standard networks. This set-up extends the reliable essence and metadata pathways of both formats to reach from content creation to playout. The MXF body carries the content. It can include compressed formats such as MPEG and DV as well as uncompressed video and can contain an interleaved sequence of picture frames, each with audio and data essence plus frame-based metadata. There are other scenarios where, for example, P2 MXF files contain a single essence track with no interleaving and no frame-based metadata. Also Panasonic AVC Long-G MXF files do interleave but not per-frame; instead they interleave partitions (chunks) of a constant duration, typically about 10 seconds. It is perfectly valid for MXF files to be metadata-only and this has no bearing on the operational pattern; for example, AS-02 bundles always contain a metadata-only version MXF file that references separate essence MXF files.

See also: AAF, AMWA

Website: www.pro-mpeg.org