Running spcacat....

$ /usr/local/bin/spcacat
Spcaview version: 1.1.4 date: 27:11:2005 (C) mxhaard@magic.fr
video /dev/video0
ERROR opening V4L interface

Googling the above error shows lots of people have run into the same problem, for various reasons. Not sure what the problem is in my case, but it will be the next thing I tackle.