You may have to proxy the api since your users that make upload contributions ( of course ) won't be able to modify the profile. Probably easiest to have a few access control profiles for given times 5, 10, 15, etc. second previews.
The api for access controls is applied on a per entry basis. You can "add" new profiles with: http://www.kaltura.com/api_v3/testmeDoc/index.php?service=accessControlProfile
you can then assign an entry a base access control id from the baseEntry service: http://www.kaltura.com/api_v3/testmeDoc/index.php?service=baseEntry&action=update by populating field: baseEntry:accessControlId
Hope that helps.