User:Mrmxf/sandbox

Interoperable Master Format

Filename extension	.xml
Developed by	SMPTE
Initial release	29 August 2013 (2013-08-29)
Latest release	SMPTE ST 2067:2021 12 October 2020 (2020-10-12)
Type of format	Container format
Container for	Audiovisual material, rich metadata
Open format?	Yes
Free format?	Yes

Interoperable Media Format (IMF)

Interoperable Master Format (IMF) is a 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 (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 SMPTE. 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.

IMF Composittion

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 [https://en.wikipedia.org/wiki/Material_Exchange_Format].

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 composition 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 for mastring 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.

IMF Track File Reuse

Specifications

IMF is specified in the ST 2067 family of standards managed by SMPTE.

IMF is organized into:

• core constraints., 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 plugins 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). An example of an applications is Application #2E, which is specified in SMPTE ST 2067-21 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 and adds support for immersive sound.

Example uses

IMF is specified by professional content creators for delivery of their content, including: BBC, Netflix [6] and Disney.

Supported essence

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

• Image up to 8192x6224 rasters, lossy and lossless compression, high-dynamic range, wide color gamut and stereoscopic 3D,
• 24-bit 48 kHz channel-based sound, arranged in arbitrary configurations
• Immersive Audio Bitstream (IAB) immersive sound
• Subtitles and captions that conform to the TTML Profiles for Internet Media Subtitles and Captions 1.1 (IMSC 1.1) W3C Recommendation

History

The need for IMF arose from various projects in the film and television industries 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. With help from the Entertainment Technology Center, the SMPTE created the first version of the standard in 2013. The IMF User Group (IMFUG) was created by the Hollywood Professional Association shortly after and the IMFUG fosters active discussions between content owners, technologists, logistics specialists and software providers on how to deliver large volumes of high quality localiosed content in a resource efficient way. The IMFUG has created an IMF explainer in miultiple languages that helps users understand how the standard works.