Interoperable Master Format: Difference between revisions

Revision as of 18:55, 20 May 2022

Revision as of 20:37, 20 May 2022

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Each Track File contains a single kind of 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 [[Material Exchange Format]]<ref name=":1" />

The Composition Playlist is an [[XML]] document<ref>{{Cite journal |date=May 2020-05 |title=ST 2067-3:2020 - SMPTE Standard - Interoperable Master Format — Composition Playlist |url=https://ieeexplore.ieee.org/document/9097510/ |journal=ST 2067-3:2020 |pages=1–35 |doi=10.5594/SMPTE.ST2067-3.2020}}</ref>. It assembles the Track Files<ref>{{Cite journal |date=May 2020-05 |title=ST 2067-5:2020 - SMPTE Standard - Interoperable Master Format — Essence Component |url=https://ieeexplore.ieee.org/document/9099734/ |journal=ST 2067-5:2020 |pages=1–15 |doi=10.5594/SMPTE.ST2067-5.2020}}</ref> 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 on mastering 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.