The Composition section discussed how multiple versions of a Composition may be created while sharing essence carried in select Track Files. In the DCP section, the concept of a single Composition Package was presented for the carriage of multiple Compositions. A Composition Package can be used to efficiently carry multiple versions of a title.
It is often desirable, however, to distribute title versions as separate DCPs. In such cases, a parent Composition will carry the complete version of a title, and one or more child Composition versions are created, designed to share select Track Files of the parent. When all of the CPLs and essence Track Files are present in common data storage, the playback system will have everything it needs to play each version of the title. But all of the files needed to play a child Composition will not be present in the DCP that carries it. A mechanism is needed to properly manage the distribution of parent and child Compositions.
In practice, the parent Composition is given the label “Original Version,” or “OV” package, and carried in its own DCP. Each child Composition is given the label “Version File” or “VF” package, and also carried in its own DCP. When the parent OV package and associated child VF packages are loaded onto a digital cinema server, all of the files needed to play the various Composition versions are present and ready to play.
The illustrations below depict the two methods available for distributing multiple Compositions that share Track Files.
Using a single Composition Package:
Using multiple DCPs:
Both distribution packaging methods, when fully loaded into the digital cinema server, lead to the same result, allowing both Composition versions to be played, as illustrated below.