It is unclear from the spec whether cloning a MediaStreamTrack preserves the subtype or not of the cloned track

[youennf]

It is unclear from the spec whether cloning a MediaStreamTrack preserves the subtype or not of the cloned track.
This can be tested for canvas tracks and cloning does preserve the subtype.
It might be good to add a note stating this intent in this spec.

[eladalon1983]

I think it should preserve the type, but the sub-type should be able to specify how state is handled, if that state was introduced by the sub-type. For example, a hypothetical sub-type called CroppableMediaStreamTrack should be able to specify that a clone is either also cropped or starts out uncropped. (Which choice it makes is out of scope; I only argue here that it should be up to the sub-type to make such a decision.)

[youennf]

I think it should preserve the type

Agreed.

it should be up to the sub-type to make such a decision.

Sounds good, my hope is that the default values of the sub type slots should hopefully be good enough in most cases so that nothing special is usually needed on sub type specs for cloning.

[alvestrand]

Note to self: Same issue exists with transfer (but that's not in this document).

[dontcallmedom]

re-assigning to @youennf based on #864 (comment)