Final Cut Pro does not like video that has been shot with an iPhone 4. I learned this shortly after getting my iPhone and shooting the Karpeles Manuscript Museum video a few weeks ago. I imported my iPhone-shot footage into FCP. I was skeptical I'd be able to do anything with it since it's H264 footage and FCP (still) doesn't handle that footage well. The picture was fine, actually. The problem was the audio -- in the form of a big red render bar, to be precise. What to do?
Thankfully, a benevolent soul (named Jeff Greenberg) has done two things:
First, he's explained the problem and the solution. Not surprisingly, it involves transcoding to ProRes.
Secondly, he's gone a step farther and created an iPhone 4-to-FCP compressor droplet for you.
To edit your iPhone footage in Final Cut Pro, all you have to do is download this file, drop your iPhone movies on the droplet, and import them when they're done rendering.
Perhaps we'll be able to expect better H264 in the new Final Cut Studio.
Whenever it's released, that is... Until it's released in June, this is the workaround (or one of them).