Rely on fair use to digitize sections of a film, as long as you weigh all four factors. In very rare cases, is may be appropriate to digitize an entire film under fair use. Read more in the Library Copyright Guide.
Be aware that:
You can't rely on section 110(1) of the Copyright Act while teaching remotely. This is what enables faculty to show entire films in the face-to-face classroom without permission.
Just because you or the Library owns a DVD does not provide legal permission to make a digital copy of the work.