Codecs attribute

The codecs attribute indicates the codecs used to encode the content referenced by all the Representation elements within an adaptation set.

The codecs attribute must be present on Representation elements or, preferably, on the AdaptationSet element. Additionally, if Preselection elements are used, the codecs attribute must be present on Preselection elements, as well.

For Dolby AC-4 bitstreams, the value element of the codecs attribute is created according to ETSI TS 103 190-2. The value consists of a dot-separated list of these four parts, of which the latter three are represented by two-digit hexadecimal numbers:
  • The fourCC ac-4
  • The bitstream_version, as indicated in the ac4_dsi()
  • The presentation_version, as indicated for presentations in the ac4_dsi()
  • The mdcompat parameter, indicating the compatibility level
For example, codecs="ac-4.02.01.03".

When the codecs attribute is used with the Preselection element, the attribute value must match the referenced Dolby AC-4 presentation in the ac4_dsi(), considering the highest compatibility level available in the associated representations.

When the codecs attribute is used with AdaptationSet elements that reference Dolby AC-4 bitstreams containing multiple presentations, the attribute value must match the Dolby AC-4 presentation with the lowest mdcompat value among all presentations where constituting components are fully contained in the referenced Dolby AC-4 bitstream.

When the codecs attribute is used with Representation elements, the compatibility level indicated in the codecs value must not exceed the level of the corresponding referencing Preselection elements or the parent AdaptationSet element.