[M4IF Technotes] Sub-part of a presentation

[Richard Shields]

Section 13.2.3.4 of 14496-1 mentions that a file that contains an IOD in the
esds atom but no BIFS track is a sub-part of a presentation.  Given that, is
it possible to create a file that is a sub-part of a presentation where the
file contains both video and audio streams?  Since the IOD cannot include a
video stream and an audio stream because of section 8.7.1.2 one would need
to create an OD stream to create objects for each media type.  But, 8.7.1.4
indicates that an OD cannot contain an OD stream without a BIFS stream.  So,
if you include an BIFS stream in the IOD to comply with 8.7.1.4 then it is
no longer a sub-part of a presentation.  Am I misinterpreting the
specifications?
Other related questions:
Can an iods atom contain multiple OD's?  13.2.3.4 seems to indicate that it
can only contain one.
Can an iods atom contain OD commands?
Is it valid to have an IOD that doesn't refer to any elementary streams?  I
have seen this in some .mp4 files but it does not seem to follow 8.6.4.
Thanks,
Richard