Can I use dd to make an ISO of a DVD that is only as large as the data on the DVD?

I am starting to make backups of my movie DVDs at home. I am using DD to make ISO images of my DVD as follows: dd if=/dev/dvd of=~/dvd/abc.iso However, even though the content of the DVD is only, for example, 5.4GB (I check this with du -sh), the resulting image is still 7GB, so it seems as if it is making an ISO image of the entire disc, even the unused portion. Is there a way to make an ISO backup of the DVD using dd that is only as large as the used portion of data on the disc?