What Is iPhone 4's FaceTime Video Chat?

Steve Jobs usually saves the meatiest bit if keynotes for the end. But WWDC's "One More Thing" was a little tame: FaceTime, a video chat system for iPhone 4. So, what's special about FaceTime, and how does it work?

First, let's get this out of the way: Yes, FaceTime is just video chat, similar to what the HTC Evo demonstrated last week, and not unlike what my British LG slider from 2006 could pull off, over 3G. But regardless, video chat hitting the iPhone is a big deal. Here's what we know:

...It only works over Wi-Fi...

For now! Though Jobs says they're working with carriers to get networks up to speed to support cellular video calling later.

...with both the front and rear cameras...

Though I suppose those entail drastically different use scenarios. (Front-facing camera for "hello, this is my face!; rear camera for "hey, look at this!")

...It's an open standard...

Meaning that other manufacturers could tap into the protocol if they want to. It's kind of like a standalone network, in a way; like a Skype, or an iChat. (Presumably, iChat is too loaded of a name for a industry wide standard, so they went with something brand-neutral, like FaceTime.) Says MacRumors:

[FaceTime is]Based on many open standards, h.264, AAC, SIP, STUN, TURN, ICE, RTP, SRTP, Apple going to standards body tomorrow to make FaceTime an open industry standard.

SIP? I guess Apple just build their own little VoIP network, sort of!

...but it's only available for the iPhone 4 at launch.

People may groan a bit at what seems like a smallish technological step, but this lays a lot of groundwork. First, it means that within a few years, the one of the most popular handsets in the world will support video calling, which is still relative rare. It also means that Apple competitors will likely speed up their development on competing techs. It also means that Apple could potentially expand video chat to all kinds of platforms , that we could see it in Mac OS and elsewhere, and even on Android. It's effectively an open VoIP network, meaning that all-purpose chat clients, like iChat, could easily integrate it in the future, assuming Apple opens development for non-mobile software.

Then again, that's just Apple's hope - they don't yet own video chat, so FaceTime could just as easily become as marginal tech as a dominant one.

Thanks to GDGT for the photo, and fantastic liveblog, and MacRumors for their coverage. For more on iPhone 4, here's our complete coverage.