Interoperable Master Format: Difference between revisions

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== Interoperable MediaMaster Format (IMF) ==

'''Interoperable Master Format (IMF)''' is a [[Container format (computing)|container format]] for the digital delivery and storage of finished audio-visual masters, including movies, episodic content and advertisements.

In IMF, each kind of [[Essence (media)|essence]] (video, audio, subtitles, etc.) is stored in individual media files (“Track Files”) and the instructions for synchronizing these media files are stored in a separate playlist file (“Composition Playlist”). This component-based approach allows the large media files to be reused across multiple playlists, each representing a different version of the content.

The IMF family of standards is maintained by [[Society of Motion Picture and Television Engineers|SMPTE]].<ref name=":0">{{Cite journal |date=August 2021 |title=OV 2067-0-2021 - SMPTE Overview Document - Interoperable Master Format |url=https://ieeexplore.ieee.org/document/9521128/ |journal=OV 2067-0-2021 |pages=1–4 |doi=10.5594/SMPTE.OV2067-0-2021}}</ref>. Its first edition was published in 2013.

= Architecture =

At the heart of IMF is the Composition, illustrated in the first image, which consists of a single Composition Playlist and a collection of Track Files. Each Composition corresponds to a single audio-visual master.

[[File:IMF_Composition.png|alt=An IMF Composition is defined by a Composition Play List|thumb|IMF ComposittionComposition]]

Each Track File contains a single kind of audio-visual essence corresponding to a single aspect of the presentation. For example, a first Track File might contain the primary video program while a second might contain Spanish stereo audio and a third English subtitles. Track Files use a constrained version of the MXF OP1a format <nowiki>[[Material Exchange Format]]</nowiki>.

The Composition Playlist is an [[XML]] document. It assembles the Track Files onto virtual tracks that are synchronized onto a timeline. It also contains metadata associated with that timeline.The combination of a Composition Playlist and the Track Files it references is called a Composition.

The primary benefit of separating the Composition Playlist from the Track Files is that a Track File can be reused across multiple Compositions as shown in the second image. Each compositionComposition represents a different version of an audio-visual work. Since different versions of a title typically differ in small ways and this component-based approach results in smaller files, fewer quality control passes and fewer resources expended foron mastringmastering the multiple versions. For example, a censored version of a movie might differ in only a few video frames from the original. Instead of having to deliver or store two largely identical versions, IMF allows the censored version to reuse the Track Files of the original version.

[[File:IMF_Track_File_Reuse.png|alt=IMF can re-use Track Files to minimize resource usage for versions of audio-viual works.|thumb|IMF Track File Reuse]]

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IMF is organized into:

* core constraints<ref name=":1" />., to which all IMF implementations conform;

* applications, which target specific use cases; and

* plug-ins, which contain optional technology that can be used across multiple applications.

The core constraints represent the bulk of the IMF standard, with applications and pluginsplug-ins introducing minimal variations. So far, the primary distinction between applications has been in the choice of video codecs.

The core constraints are specified in SMPTE ST 2067-2 (Core Constraints)<ref name=":1">{{Cite journal |date=May 2020 |title=ST 2067-2:2020 - SMPTE Standard - Interoperable Master Format — Core Constraints |url=https://ieeexplore.ieee.org/document/9097478/ |journal=ST 2067-2:2020 |pages=1–43 |doi=10.5594/SMPTE.ST2067-2.2020}}</ref>. An example of an applicationsapplication is Application #2E, which is specified in SMPTE ST 2067-21<ref name=":2">{{Cite journal |date=May 2020 |title=ST 2067-21:2020 - SMPTE Standard - Interoperable Master Format — Application #2E |url=https://ieeexplore.ieee.org/document/9097487/ |journal=ST 2067-21:20202021 |pages=1–34 |doi=10.5594/SMPTE.ST2067-21.2020}}</ref> and targets studio masters. One of the plugins is the Immersive Audio Bitstream Level 0 Plug-in, which is specified in SMPTE ST 2067-201<ref>{{Cite journal |date=January 2021 |title=ST 2067-201:2021 - SMPTE Standard - Immersive Audio Bitstream Level 0 Plug-in |url=https://ieeexplore.ieee.org/document/9343937/ |journal=ST 2067-201:2021 |pages=1–14 |doi=10.5594/SMPTE.ST2067-201.2021}}</ref> and adds support for immersive sound.

= Example uses =

IMF is specified by professional content creators for delivery of their content, including: BBC<ref>{{Cite web |title=TechnicalDeliveryStandardsBBCUHDiPlayerSupplement.pdf |url=https://www.dropbox.com/s/tkvwxksgy3izpca/TechnicalDeliveryStandardsBBCUHDiPlayerSupplement.pdf?dl=0 |access-date=2022-03-04 |website=Dropbox |language=en}}</ref>, Netflix<ref>{{Cite web |title=Netflix Branded Delivery Specifications v4.1 |url=https://partnerhelp.netflixstudios.com/hc/en-us/articles/214806618-Netflix-Branded-Delivery-Specifications-v4-1 |access-date=2022-03-04 |website=Netflix {{!}} Partner Help Center |language=en-US}}</ref> [6] and Disney<ref>{{Cite web |title=Disney Media Tech Specs |url=https://mediatechspecs.disney.com/production/naming-convention/naming-convention#/mastering/video/imf-master-packages |access-date=2022-03-04 |website=mediatechspecs.disney.com}}</ref>

= Supported essence =

IMF supports a wide range of audio-visual essence and metadata, including:

* ImageVideo up to 8192x6224 rasters, lossy and lossless compression, high-dynamic range, wide color gamut and stereoscopic 3D,<ref name=":2" />

* 24-bit 48 kHz channel-based sound, arranged in arbitrary configurations

* Immersive Audio Bitstream (IAB) immersive sound<ref>{{Cite journal |date=June 2019 |title=ST 2098-2:2019 - SMPTE Standard - Immersive Audio Bitstream Specification |url=https://ieeexplore.ieee.org/document/8752533/ |journal=ST 2098-2:2019 |pages=1–54 |doi=10.5594/SMPTE.ST2098-2.2019}}</ref>

* Subtitles and captions that conform to the TTML Profiles for Internet Media Subtitles and Captions 1.1 (IMSC 1.1) W3C Recommendation<ref>{{Cite web |title=TTML Profiles for Internet Media Subtitles and Captions 1.1 |url=https://www.w3.org/TR/ttml-imsc1.1/Overview.html |access-date=2022-03-04 |website=www.w3.org}}</ref><ref>{{Cite journal |date=May 2020 |title=ST 2094-40:2020 - SMPTE Standard - Dynamic Metadata for Color Volume Transform — Application #4 |url=https://ieeexplore.ieee.org/document/9095450/ |journal=ST 2094-40:2020 |pages=1–29 |doi=10.5594/SMPTE.ST2094-40.2020}}</ref>

== History ==

The need for IMF arose from various projects in the film and television industries<ref>{{Cite web |title=© 2011 AmberFin Limited Loose Coupling for Multipurpose Distribution Bruce Devlin Chief Technical Officer. - ppt download |url=https://slideplayer.com/slide/7416420/ |access-date=2022-04-01 |website=slideplayer.com}}</ref> that identified component -based working as a more efficient mechanism for handling the very large volumes of very large files created when delivering cinema and television content around the globe<ref>{{Cite web |last=Blog |first=Netflix Technology |date=2017-04-19 |title=The Netflix IMF Workflow |url=https://netflixtechblog.com/the-netflix-imf-workflow-f45dd72ed700 |access-date=2022-04-01 |website=Medium |language=en}}</ref>. With help from the [[Entertainment Technology Center]]<ref>{{Cite web |title=ETC |url=https://www.etcenter.org/imf-version-1-0-launches/ |access-date=2022-04-01 |website=www.etcenter.org}}</ref>, the [[Society of Motion Picture and Television Engineers|SMPTE]] created the first version of the standard in 2013. The IMF User Group (IMFUGIMF UG) was created by the [[Hollywood Professional Association]] shortly after and the IMFUGIMF UG fosters active discussions between content owners, technologists, logistics specialists and software providers on best current practise for delivering large volumes of localised content in a resource efficient way. The IMFUGIMF UG has created an IMF explainer in miultiple languages<ref>{{Cite web |title=EXPLAINER: Interoperable Master Format (IMF) – IMF UG |url=https://www.imfug.com/explainer/ |access-date=2022-04-01 |language=en-US}}</ref>.

== References ==