I'm sorry for my utter ignorance, but I'm having an issue where my video is flickering constantly. I guessed it to be an interlacing issue, but added FCP's de-interlace filter on it, and it didn't help. Anyone have a guess, or could point me a guide or something?
Finding the cause of flickering video can be tricky. It's not unheard of for interlacing to be involved (making it worse than it would be on a progressive scan), but it's not usually the cause. More likely are things like filming under fluorescent lights or filming off a computer screen - juggling the shutter speed at the time can usually minimise it, but it's tricky to fix if it's recorded with flicker.
More technical details and a link to a clip of the problem material might generate more of a response here, without it you're not going to get much more than guesses.
If by flickering you mean the lights or lighting appear to be flickering then that does sound like the issue I get when shooting on the wrong shutter speed for the situation on a HDSLR. I don't know a cure I'm afraid, just the prevention.