Represents the "B" entry of the media clip section mh/be dictionary object.

It is an optional entry defined as part of the PDF 1.0 specification.

It contains a MediaOffsetElement.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 278, page 496.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 289, page 621.

The B entry references the beginning offset dictionary for the clip section. The offset may be expressed as a time in seconds, a frame number, or a named marker in the media file.