I received a DVD home movie from a friend with a PC.
He had burned consumer format (VIDEO_TS et al) onto a DVD+R disk.
The disk would not play in my consumer player, and would
read on my Panther iMac, but would not reliably play with the DVD Player App.

I attempted to use this hint to make a copy onto Apple DVD-R media (which my consumer player likes just fine.)

What I probably SHOULD have done was used Disk Utility to make an image copy, and then used Disk Utility to burn the image. (But I'd momentarily spazzed and forgotten to try that.)

dd if=/Volumes/myDVD of=myDVDcopy.img bs=2048
did not work. It created a file which was the mount point, not the data.

I saw that /dev/disk1 was mounted on that mount point.

dd if=/dev/disk1 of=myDVDcopy.img bs=2048
did not work. It complained that disk1 was busy.

Going into Disk Utility and unmounting myDVD, and THEN
dd if=/dev/disk1 of=myDVDcopy.img bs=2048
worked! Then I ejected the DVD using Disk Utility.
I then used Disk Utility to burn myDVDcopy.img onto Apple
DVD-R media which my consumer player indeed played just fine.

I won't say Disk Utility works for image copy of DVD's until I try it. In this case, I thought the list would benefit from my experience using dd for DVD, and how I had to amend the instructions to get them to work.