Verifying a DVD

[Doug Hardie]

I am periodically backing up a bunch of files to DVD.  I use mkisofs to create the original image and growisofs to write it to a real DVD.  However, at that point I want to verify that the write was successful.  I tried using dd to read back in the DVD to a file.  Its interesting that the bs parameter must be at least 2048 or dd complains about a parameter error.  However, the big issues is that the original image file is shorter than the read file.  The difference is 10240  bytes.  This difference is the same for bs 2048, 10240, or 102400.  It appears that dd is adding one last block.  Is there a way to prevent this or remove that block?