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.
Even if these wrapper formats are often used for distribution or delivery, they may be useful for archives with the need for keeping granular elements together in a package for conformance or ease of use. The MXF format allows archivists to preserve separate elements independently, and also maintain assets in wrapper formats since it is based on OAIS models that can contain both assets and metadata. Here are three types of wrapper formats:
- 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 has been 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 for displaying digital moving images in theaters created by the Digital Cinema Initiatives (DCI), consortium of the major Hollywood studios. It can be helpful to keep a DCP in your preservation archive if you are archiving feature films in the future. Current restoration workflows often use a 35mm print made at the time of release as a reference for color and creative decisions. For this reason, archives frequently preserve an unencrypted Digital Cinema Package in their digital storage.
A relevant issue for digital preservation is organizing massive amount of data in the archive of a feature. Although this data can be broken down into many sorts of fundamental and process units, such as camera data, VFX, graphics, titling and other visuals, audio, and editorial matrices, it still constitutes a significant amount of data in several file formats and configurations.
Two proposals for the systematic organization of archival data have been advanced:
- 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, that was championed by Front Porch Digital and 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.
- 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 storage. For more information, see Introducing IMF Application #5 “ACES” and IMF Delivery Schema.