Trickle ICE questions?

I apologize if these were already covered in one of the drafts, but I could
not find the answer to those questions.

Imagine the following situation, that I want to enable TURN use for audio
but not for video. Let's first assume the case without bundle. ICE agent
creates two m-lines with initial (I assume local) candidate sets one
intended for audio and another for video. When reflexive and relayed
candidates are discovered, onicecandidate call back is called. How do I
specify that reflexive candidate for one m-line should not be used? Keep in
mind that simply not sending it to the remote party is no enough since if
the connectivity check will be delivered to remote party through this
reflexive candidate it will be added to the candidate set. Should we have
something similar to setLocalDescription for each trickle ICE candidate set?

In case of bundle, how do I specify that turn should be used for one and
not the other? While we are at it, how can I find out if media flows
through the relayed candidate and how would I know when this changes?

Another question, in case of trickle ICE and constraint being set to use
only relayed candidates, should offer or answer generation be delayed until
at least one relayed candidate is discovered for each m-line or should SDP
with no candidates for an m-line be generated? If it is the later, what
would this look like?
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Roman Shpount