Hi.
Sorry for late bidding. This is very difficult or might not possible because playing-time is something which has to be "simulated" on server to get true 30-seconds.
If you could however accept percentage (instead of timing) then you might want to look at this page: [login to view URL] It might work only on .WEBM videos at the moment since my server has very limited capacity. It will play only the 10% part of complete video, from the start.
I haven't tested it fully for .MP4 videos, but I'm afraid these are the only 2 types of videos which are HTML5 and can be supported.
What do you think?
Err, also... may I know what licensing plugin you were talking about?
Hendra