UsacConfig/UsacDecoderConfig
This element contains all further information required by the decoder to interpret the bitstream. In particular the SBR resampling ratio is signalled here and the structure of the bitstream is defined here by explicitly stating the number of elements and their order in the bitstream
usacElementType: Defines the USAC channel element type of the element
channelConfigurationIndex
(value)
implies element order (expected channel config order)