Is sending multiple audio codecs on same RTCRtpSender supported?

Hi all,

Imagine the following (crazy) scenario, where you want to send OPUS and
PCMA on the same RTCRtpSender (obviously on different ssrcs as they have
different clock rates).

Is it assumed that this SHALL be supported by all browsers implementing
ORTC?

I think we should explicitly set it in the spec if this shall be supported
or it is forbidden. If I have this kind of doubt in the SDP O/A world I
have tons of RFCs I can search for the answer, but with the ortc params
there is no other source of information I can look for.

Best regards
Sergio