As I understand it launchpad uses .po files for translation. The .srt files which totem (and other media players) use is not something we can directly import into launchpad for translation. I could file a bug against launchpad (if that's the best thing to do, to see if we can get .srt files supported in Rosetta. This would definitely make translation easier.

Also, have a look at the conversation I started on my blog:- http://popey.com/Multi-lingual_Video_and_Audio