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Interoperable Master Format (IMF)

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name Interoperable Master Format (IMF)
Description

IMF, the file extension and acronym for the Interoperable Master Format, is defined by the ST 2067 family of SMPTE (Society of Motion Picture and Television Engineers) standards in order to streamline the management and processing of multiple versions of primary or "master" audiovisual content, such as feature films, short-form content, television or episodic content, advertisements, and more to be "efficiently represented, managed, played back, processed and transformed on file-based systems." IMF is designed to facilitate the internal or business-to-business (B2B) distribution chain and is not intended to function as the mechanism for final delivery to the end consumer. Note: See General for details about the use of the term "master" and alternative options including "primary" in SMPTE publications and in this document as well as the rationale for "IMF_Package" as the short name instead of "IMF".

IMF draws its inspiration from the Digital Cinema Initiative Distribution Package (DCP) which is a set of encrypted files representing digital moving image content packaged for shipment to theaters. The two formats are not directly related from a standards perspective but the concepts of a packaged set of all the track files, a separate XML packing list and other housekeeping files for B2B distribution is the same.

Conceptually, an IMF package (known as an IMP) is not a single file although it may be delivered as one ZIP archive file. An IMP is a bundle of components for a piece of media content including all the audio and video essence along with full metadata including, if applicable, subtitles and captions. Each component is treated as a separate and individual asset. The flexibility of an IMP is that it allows for these assets to be combined in various ways to create different versions of the content in a Composition, such as the theatrical cut for a specific country or an airline edit.

IMP/IMF packages can vary but typically comprises:

MXF OP1a file containing

  • image track(s) which current implementations include options for lossless or lossy JPEG2000 or ProRes
  • audio track(s) which can be Broadcast Wave or Multichannel (Dolby Atmos or 5.1 Surround). Each Audio Track File is intended to carry a single soundfield group. If the audio that is to be carried consists of more than one soundfield group, then each is carried in its own Audio Track File(s).
  • Timed Text (TTML) track files for captions and subtitles (optional)
  • Ancillary data track files for VBI (vertical blanking interval) and/or ANC (ancillary) data contained in source material (optional)
  • Caption Description Packet (CDP) Track File for CEA-708 captions and CEA-608 data (optional)

Additional IMF components are:

  • 1 Asset Map XML file which provides a mapping between UUIDs (universally unique identifiers) and actual filenames
  • 1 Packing List (PKL) XML file which provides general information including file sizes and hash or fixity values for all other files contained in the IMP
  • 1 or more Composition Playlist (CPL) XML file(s) which specify how media components (audio, video, timed text, etc) are assembled on a timeline to compile specific content representations. The CPL also lists technical metadata for the EssenceDescriptors that are present within the SegmentList (Playlist).- see below for more details
  • Output Profile List (OPL) which may include optional Volume Index and Output Profile List XML files.

For an example IMF file using the RDD 59-1:2022 - SMPTE Registered Disclosure Doc - Interoperable Master Format — Application DPP (ProRes), see the BBC example via Dropbox (and linked from within RDD 59-1).

Production phase Final-state for use in a distribution chain; may also serve as a middle-state format for archiving.
Relationship to other formats
    Contains MXF_OP1a, MXF Operational Pattern 1a (OP1a)
    Contains XML, XML (Extensible Markup Language). Used for mandatory Asset Map and Packing List
    May contain ZIP_PK, ZIP File Format (PKWARE)
    May contain MXF_OP1a_JP2_LL, MXF File, OP1a, Lossless JPEG 2000 in Generic Container
    May contain Apple_ProRes_422_HQ, Apple ProRes 422 High Quality. As of December 2023, Apple ProRes 422 HQ is the video track requirement for IMPs for the BBC iPlayer to conform to RDD 59-1:2022 - SMPTE Registered Disclosure Doc - Interoperable Master Format — Application DPP (ProRes).
    May contain MXF File, OP1a, Lossy JPEG 2000 in Generic Container. As of December 2023, both Warner Brothers and Netflix use this implementation as part of SMPTE ST 2067-21:2023 - Interoperable Master Format — Application #2E. Although there is an entry reserved for this format, it is not described in detail at this time.
    May contain PCM, PCM, Pulse Code Modulated Audio. Identified in Disney specification as of January 2024.
    May contain LPCM, Linear Pulse Code Modulated Audio (LPCM)
    May contain WAVE_BWF_LPCM_1, Broadcast WAVE File Format, Version 1, with LPCM Audio. IMF does not specify a version of Broadcast WAVE. Identified in Warner Brothers IMF specification as of January 2024.
    May contain WAVE_BWF_LPCM_2, Broadcast WAVE File Format, Version 2, with LPCM Audio. IMF does not specify a version of Broadcast WAVE. Identified in Warner Brothers IMF specification as of January 2024.
    May contain Immersive Audio Bitstream (IAB). With Dolby Atmos for Immersive Audio. Not described separately at this time. Defined by ST 2098-2:2022 - SMPTE Standard - Immersive Audio Bitstream Specification
    May contain Dolby Atmos. With IAB codec for Immersive Audio. Not described separately at this time.

Local use Explanation of format description terms

LC experience or existing holdings The Library of Congress has Interoperable Master Format files as part of submissions to the Packard Campus of the National Audio-Visual Conservation Center, most notably from a pilot project with Netflix.
LC preference

The Library of Congress Recommended Formats Statement (RFS) lists IMF as a preferred format for file-based video.


Sustainability factors Explanation of format description terms

Disclosure Fully disclosed through non-proprietary open standards developed and maintained by the Society of Motion Picture and Television Engineers (SMPTE).
    Documentation IMF is documented in a series of standards documents through SMPTE (available at no cost as of May 2021): ST 2067-2:2020 - SMPTE Standard - Interoperable Master Format — Core Constraints, ST 2067-3:2020 - SMPTE Standard - Interoperable Master Format — Composition Playlist, ST 2067-5:2020 - SMPTE Standard - Interoperable Master Format — Essence Component and ST 2067-21:2020 - SMPTE Standard - Interoperable Master Format — Application #2E (the implementation used by Netflix and Warner Brothers for HDR). In addition, RDD 59-1:2022 - SMPTE Registered Disclosure Doc - Interoperable Master Format — Application DPP (ProRes) defines the implementation using ProRes 422 HQ in use by the BBC.
Adoption

IMF is highly adopted as a packaging format in broadcast environments. It is required as a delivery specification for Netflix, Warner Brothers (both with JPEG2000 lossy) as well as for UHD programs in the BBC iPlayer (with ProRes 422 HQ), for Disney Master Packages and Distribution Packages.

    Licensing and patents None identified. ST 2067-2:2020 and ST 2067-21 state "At the time of publication no notice had been received by SMPTE claiming patent rights essential to the implementation of this Engineering Document. However, attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights." Comments welcome.
Transparency The Packing List will be transparent and describe the general file but the essence tracks themselves may not be. Like a ZIP file, the IMF exists to support the movement of data. The encryption method for non-interleaved MXF frame-wrapped tracks is defined in SMPTE 429-6:2006. The algorithm and mode for the KLV encrypted triplets is defined in the Cipher Algorithm metadata item within the Cryptographic Context Set. The default is Advanced Encryption Standard (AES) cipher as defined by NIST SP 800-38a.
Self-documentation

The Packing List identifies each file, includes file-integrity checks ("hash") for each file, as well as a public key and digital signature that is part of the overall security system. Optional "MIC" (media content integrity) hash values can be created at the KLV triplet level using a structure which parallels that for encryption defined in SMPTE 429-6:2006. The MIC value within the KLV triplet is calculated only on the V portion of triplet - not the K and L.  The hash algorithm type is defined in the "MIC Algorithm" metadata item within the Cryptographic Context Set. The default algorithm is SHA-1. The actual hash value is stored on the "MIC" metadata item within the Encrypted Triplet Variable Length Pack.

Accessibility Features

The IMF/IMP (Interoperable Master Format / Package) offers good accessibility support, enabling alternate audiovisual description across a number of track options specifically for use by assistive technology, including: Timed text track file (SMPTE ST 2067-2:2020, 5.4), Caption Description Packet (CDP) Track File (SMPTE ST 2067-2:2020, 5.6), Timed Text Virtual Tracks (Caption Description Packet (CDP) Track File, 6.3). See the specification for more technical information related to these features.

See W3C's Making Audio and Video Media Accessible for more general information about accessible sound and moving image media.

External dependencies See MXF.
Technical protection considerations

SMPTE 2067-2 states that assets can be encrypted with or without authentication required and that "such mechanisms are outside the scope of this specification."

In addition, "when the Signature element of the IMF Packing List is present, digital certificates in the signer’s certificate chain shall conform to the provisions of SMPTE ST 430-2."


Quality and functionality factors Explanation of format description terms

Moving Image
Normal rendering See MXF.
Clarity (high image resolution) See MXF.
Functionality beyond normal rendering See MXF.
Sound
Normal rendering See MXF.
Fidelity (high audio resolution) See MXF.
Multiple channels See MXF.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension See note.  IMF packages may be contained within ZIP archive files.
Internet Media Type See related format.  See XML for mediatype for Composition Playlist as defined by SMPTE ST 2067-3
Internet Media Type See related format.  See MXF for mediatype of essence track files as defined by SMPTE ST 2067-2
Pronom PUID See note.  No PUID as of December 2023 but this is to be expected as an IMF a package of several related files.
Wikidata Title ID Q63859043
See https://www.wikidata.org/wiki/Q63859043

Notes Explanation of format description terms

General

A note about the term "master". In 2020, the SMPTE Committee on Diversity, Equity, and Inclusion (DEI) published a statement (Engineering Documents from SMPTE Will Replace Offensive Terminology with Alternative Language) that the "SMPTE Standards Community has recently updated one of its Administrative Guidelines (AG 16) which governs the style of standards and engineering documents. The guidelines identify four offensive terms and provides a multitude of substitutes to use in place of each." Master is included in this list of offensive terms with alternative terms offered as substitute including "primary". This document will use the term "master" when referring to the current published title of the SMPTE standard and in direct quotations. Otherwise, the term "primary" will be used.

A note about naming entries in this resource. Typically, entries are named after format extensions which in this case would be "IMF". However, there is a preexisting entry for the Internet Message Format (IMF) so the short name for Interoperable Master Format is "IMF_Package".

 
History The IMF specifications underwent significant revisions in 2020 to resolve editorial and technical issues. SVG provides a helpful summary: "Specific changes to SMPTE ST 2067-2 IMF Core Constraints include added support for IMSC 1.1 timed text, added support for Forced Narrative timed text sequences, and definition of asset identification for Sidecar Composition Map assets. Audio Virtual Tracks have been made optional. Additional CPL Markers have been included in SMPTE ST 2067-3 IMF Composition Playlist, and a provision in SMPTE ST 2067-5 IMF Essence Component was altered to eliminate a conflict with a provision in ST 2067-201. The ST 2067-21 IMF Application #2E has been revised so that it incorporates the provisions of both ST 2067-20 and ST 2067-21, consolidating provisions from SD to UHD formats for IMF mastering with JPEG 2000. For end users, this revision to Application #2E is most significant, as it eliminates some of the variability between various essence files, in turn increasing the likelihood that files will work “out of the box.” Because SMPTE made no major changes affecting backward compatibility, existing files should continue to work as expected."

Format specifications Explanation of format description terms


Useful references

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Last Updated: 05/14/2024