Read DVD image with dd until empty

I tested right now with an old Lubuntu 16.04.1 LTS amd64 iso file and DVD-disk that I burned when it was new (2016). I extracted from the DVD-disk with dd,

$ sudo dd if=/dev/sr0 of=dvd.img bs=4096
218880+0 poster in
218880+0 poster ut
896532480 byte (897 MB, 855 MiB) kopierade, 95,2247 s, 9,4 MB/s

and compared the result with my stored iso file,

$ ls -l lubuntu-16.04.1-desktop-amd64.iso /media/multimed-2/test/test0/temp/dvd.img
-rw------- 1 nio  1002 896532480 jul 20  2016 lubuntu-16.04.1-desktop-amd64.iso
-rw-r--r-- 1 root root 896532480 dec  7 12:25 /media/multimed-2/test/test0/temp/dvd.img

$ md5sum lubuntu-16.04.1-desktop-amd64.iso /media/multimed-2/test/test0/temp/dvd.img
d2d7edc41ea03998e267db607f92b40d  lubuntu-16.04.1-desktop-amd64.iso
d2d7edc41ea03998e267db607f92b40d  /media/multimed-2/test/test0/temp/dvd.img

$ sha256sum lubuntu-16.04.1-desktop-amd64.iso /media/multimed-2/test/test0/temp/dvd.img
1b91a43b0101e03b0890428d3e77198c0d35364cf35e38aaea2755d10ace26a7  lubuntu-16.04.1-desktop-amd64.iso
1b91a43b0101e03b0890428d3e77198c0d35364cf35e38aaea2755d10ace26a7  /media/multimed-2/test/test0/temp/dvd.img

As you can see, the sizes and the checksums match.