Language attribute

The language indicated by the lang attribute of the Preselection or AdaptationSet elements should match the language of the referenced Dolby AC-4 presentation.

The language of a Dolby AC-4 presentation is indicated by the language_tag_bytes of the ac4_substream_group_dsi structure (within the ac4_dsi_v1 structure), which is typically tagged as dialogue or complete main in the corresponding content_classifier.

In case an adaptation set is referenced by more than one Preselection element, the lang attribute should not be present at the AdaptationSet element, but only on the Preselection elements. In this case, the value of the lang attribute on each Preselection element must correspond to the language of its associated presentation. If the lang attribute needs to be present at the AdaptationSet element as well, the value must correspond to the language of the Dolby AC-4 presentation that is refered to by the codecs attribute of the AdaptationSet.