Re: Install dependencies automatically from backports.

[Anthony DeRobertis <aderobertis@metrics.net>]

A good way to troubleshoot these problems (and an aide in writing 
pinning files as well) is "apt-cache policy".

~$ apt-cache policy
Package files:
⋮
 500 http://www.debian-multimedia.org/ wheezy/main amd64 Packages
     release v=None,o=Unofficial Multimedia Packages,a=testing,n=wheezy,l=Unofficial Multimedia Packages,c=main
     origin www.debian-multimedia.org
⋮


In that, you can see the priority (500), and the various fields you can 
pin based on.