Wrapper Formats

Wrapper formats are used to combine more granular elements of audiovisual content such as images and audio. A Digital Cinema Package (DCP) is essentially a wrapper format and depends in part on MXF. These wrapper formats are more often used for distribution or delivery but may be useful for archives if there is a need for keeping granular elements together in a package for conformance or ease of use.  Archivists may preserve the separate elements separately and also maintain assets in wrapper formats. MXF created a structure based on OAIS models to contain both assets and metadata among other components.

  • Media eXchange Format (MXF, SMPTE 377) — A container format developed for the interchange of professional digital video and audio media with associated data and metadata. An introduction to MXF is here. A subset of MXF developed for the archiving of moving images by the U.S. Library of Congress is defined by SMPTE RDD 48.
  • Interoperable Master Format (IMF) — A wrapper format in significant use in the entertainment industry to maintain complex moving-image file-based assets in one place.
  • Digital Cinema Package (DCP) — The format used to project digital moving images in theaters, created by the Digital Cinema Initiatives (DCI) consortium of the major Hollywood studios. Keeping a DCP in your preservation archive if your job is archiving feature films can be a helpful reference tool in the future. In current restoration workflows a 35mm print made at the time of release is often used for color and creative decision reference to help inform restoration decisions.  Keeping unencrypted DCPs is an approach often followed by archives.

An important issue for digital preservation is how to organize the massive amount of data in the archive of a feature. This data can be parsed into types of primordial and workflow units (camera data, VFX, graphics, titling and other imagery, audio, editorial matrices), but it still represents a massive amount of data in diverse file formats and configurations.

Two proposals for the systematic organization of archival data have been advanced. The first is the Archive eXchange Format (AXF) advanced by Brian Campanotti and standardized as SMPTE ST 2034-1 and ISO/IEC 12034-1 (not to be confused with the Appearance Exchange Format, AxF). AXF was championed by Front Porch Digital, which was later acquired by Oracle. It is not clear how widely the format has been adopted for cinema archives. For more information, see Archive eXchange Format (AXF) – An Open Standards-Based Approach to Long Term Content Archiving and Preservation, Archive eXchange Format, AXF: An Open Format for Universal Content Transport, Storage and Long Term Preservation, and axf.io.

More recently, SMPTE has published SMPTE ST 2067-50, Interoperable Master Format — Application #5 ACES, which defines the use of IMF to wrap images encoded in the ACES format for delivery and archiving.  For more information, see Introducing IMF Application #5 “ACES” and IMF Delivery Schema.