After reading about the offer/answer mode of SDP, I think I've come to
the conclusion that there are no special considerations necessary for
AC-3. There are no parameter negotiations needed for an AC-3 decoder
since AC-3 was designed so that any AC-3 decoder will play any AC-3
stream. For example, a 2-channel decoder can naturally play a 2-channel
AC-3 content. But it is also, required to render a downmixed, 2-channel
version of any multichannel AC-3 content.
Will it satisfy your comment if I add a sentence that no special
considerations are needed for the offer/answer mode of SDP?