Book vs Sheet

An image file fed into OMR software contains one or several images. Typically PDF and TIFF formats support the notion of multi-image files while, for example, JPEG or PNG formats can deal only with single-image files.

For Audiveris, using the metaphore of a physical book made of several sheets of paper, this physical containment is modeled as one Book instance (corresponding to the input file) and a sequence of one or several Sheet instances (one sheet corresponding to one image).

Note that a sheet image may contain no music. This happens for example for a title or illustration or simply a blank sheet. In that case, the sheet will later be recognized as "invalid" (from the OMR point of view) and flagged as such.

A (super-) Book instance could recursively contain (sub-) Book instances, although this feature is not fully implemented yet.