Describe process for ripping discs were dd fails

diff --git a/misc/ripping.md b/misc/ripping.md
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@@ -34,6 +34,12 @@ See <https://diskprices.com/>.
 
 ### Video
 
-`pv` seems to be enough to create ISO.
+You can use `dd` to rip DVD and Blu-ray.
+However, `dd` can fail on some disks, perhaps due to damage or copy protection.
+[This post on unix.stackexchange describes a trick that works](https://unix.stackexchange.com/a/642790):
+
+* Start playback of the disc using [VLC media player](https://www.videolan.org/vlc/)
+* Run a command like `ddrescue -n -b2048 -K1M /dev/sr0 x.iso x.map`
+* After `ddrescue` starts running, pause playback.
 
 [FindVUK](http://fvonline-db.bplaced.net/) has the keys to rip Blu-ray discs.