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Table of Contents for A/V Content

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Use Case

Like books, A/V content can be divided into parts that constitute a unit of interest. It is important to provide users with easy access to these individual units so the structure of an A/V item is represented in a table of contents to facilitate navigation given that jumping to a specific point using only the player slider is hard.

Opera is a form of theatre in which music has a leading role. A recording of an opera is a good example of structured A/V: an opera is composed of acts; an act is composed of scenes; a scene may include multiple arias. Ranges are well suited to model the hierarchy of the components of an opera.

Implementation Notes

Implementation is similar to Book Chapters except that nesting may be deeper.

Ranges in the structure target different portions of the same Canvas using temporal media fragments (e.g. “t=0,100”). This is in contrast to the Book Chapters recipe where each Range targets a different Canvas using spatial media fragments.

A media fragment specifying the Canvas temporal dimensions for a Range does not need the end time to be explicitly specified when it coincides with the end time of the Canvas itself, as exemplified here for Atto Secondo.

Restrictions

Leaf Range nodes in a structure are played linearly so they should be contiguous, since gaps will cause silent moments resulting in poor user experience.

Example

The opera covers the whole length of the Canvas and is divided into two Ranges for the two acts. Atto Primo has a Range for the prelude and first song and then a Range for the remainder of the act. Atto Secondo has not been subdivided into Ranges for simplicity of this example.

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