You used growisofs, i assume. Afaik it does not close DVD+R even if option -dvd-compat or -dvd-video is given.
??? -dvd-compat or -dvd-video do close the disk! Well, if used already at 1st recording. There is code that prevents you from closing the disk *if* 1st recording was not performed with -dvd-compat [or -dvd-video]. This is done for reasons discussed in "Compatibility: caveat lector" on dvd+rw-tools page. Point is that if you perform 1st recording without -dvd-compat and leave the disk open, then lead-out pointer points at the outer edge. This means that DVD-ROM units that try to calibrate at lead-out vicinity will be forced to virgin surface and fail. Just closing such disk will leave you with *nothing* you would be able to do to improve its compatibility in such DVD-ROM units. This is why growisofs refuses to just close open disk and -M /dev/cdrom=/dev/zero is advised to be used instead. Point is that -M /dev/cdrom=/dev/zero ensures that whole surface is recorded and above mentioned calibration is not performed on virgin surface. Reasoning basically is "even if more time consuming, it's better than nothing left to do." Once again, this applies if 1st session was recorded without -dvd-compat or -dvd-video. If 1st session is recorded with -dvd-compat, then disk is closed at once [and unit burns lead-out pointer to point at the end of 1st session and not out-most edge]. A.