MSF Tracks MAY be time-aligned. Those that are, are subject to the following requirements:
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Tracks advertised in the catalog as belonging to a common alternate group MUST be time-aligned.
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The render duration of the first media object of each equally numbered MOQT Group, after decoding, SHOULD have overlapping presentation time.
A consequence of this restriction is that an MSF receiver SHOULD be able to cleanly switch between time-aligned media tracks at group boundaries.
If time-aligned media tracks do not have overlapping presentation time at equally-numbered group boundaries, then an alternate mechanism, not defined by this specification, must be provided to the client to enable it to switch smoothly between time-aligned, but numerically dissimilar, Group IDs.