[Hampshire] apt/dpkg question

I've been trying to revert some updates of ffmpeg and associated
libraries in Ubuntu as they appear to have completely broken sound and
video on my system. (No sound; and video plays very fast.)

While doing so I noticed that the dpkg logs said the upgrade was from
version xxx7.1 to xxx7.2
However synaptic shows that there is no 7.1 available, only a 7. So I
was wondering:
1. Why does the dpkg log say I upgraded from 7.1 and
2. is there an apt/dpkg command for listing the available versions of a
package

Thanks
Leo

PS Oh, and if anyone else lost media playback with that update and fixed
it could you let me know as google isn't helping yet and the reversion
has helped either :(