dashdemux: add support for EssentialProperty and SupplementalProperty elements
Submitted by A Ashley
Link to original bug (#783547)
Description
The EssentialProperty and SupplementalProperty elements are used to signal information about an AdaptationSet, a Representation or a SubRepresentation.
SupplementalProperty elements provide additional information about an AdaptationSet, Representation or SubRepresentation. A DASH client can ignore any SupplementalProperty that it does not recognise.
EssentialProperty elements provide additional information about an AdaptationSet, Representation or SubRepresentation. A DASH client must skip any AdaptationSet, Representation or SubRepresentation that contains an EssentialProperty that it does not recognise.
According to the DASH specification, if EssentialProperty elements share the same id, processing any one of the EssentialProperty elements with the same value for id is sufficient.
Wojciech Przybyl provided a partial implementation of EssentialProperty elements in Bug 777441, however it did not provide support for attributes within these elements and does not include the logic around the id attribute.