What a conversion would do to the frame sequence, judged against the options
as normalizeMedia will actually run them rather than as they were
written: leaving the rate unstated does not keep the source's timing here,
it takes the 30 hertz default.
A stated rate is only safe on a source that already runs at exactly that
rate. On anything else the conversion writes a different number of pictures
at different times, and a detection carrying a source frame index then names
a picture that was never at that position.
What a conversion would do to the frame sequence, judged against the options as normalizeMedia will actually run them rather than as they were written: leaving the rate unstated does not keep the source's timing here, it takes the 30 hertz default.
A stated rate is only safe on a source that already runs at exactly that rate. On anything else the conversion writes a different number of pictures at different times, and a detection carrying a source frame index then names a picture that was never at that position.