Last year I "attended" a briefing with a few Apple representatives while sitting in my office chair in Seattle. They were in Cupertino, and thanks to the video chat capabilities of iChat AV, we had a face-to-face conversation. But since there were three of them, they had to crowd into the frame by sitting behind each other so that I could see them all.
If we have a similar briefing now, I'll have a much clearer picture of each person. iChat AV 3.0, included in Mac OS X 10.4 Tiger, can now handle video chats of up to four people (you and three others), with potentially better image quality than before. This capability comes with a price, however, as some Macs aren't capable of participating.
Multi-Person Chats -- The multi-person video chat is one of the snazziest-looking new features of Tiger, which is why Apple has included screenshots of it in action on most of the company's advertisements I've seen. When two people are chatting, iChat AV 3.0 uses the same appearance as in iChat AV under Panther: you appear in a small corner window, and the other person occupies the rest of the window.
But as soon as you add a third person, your participants appear on planes angled in 3D, as if you had set up two LCD screens. (The Audio and Video status buttons in iChat's Buddy List show up as stacked icons to indicate that a person is running iChat AV 3.0 and is capable of multi-person chats.) A fourth person added appears on a similar plane, but facing straight-on. The idea is that you're all sitting around a conference table, and Apple enhances the illusion by providing surface reflections below each person's plane; I have to admit that I spent most of my first multi-person video chats staring at the reflections, which update in real time.
Unlike the previous version, not just anyone can start a multi-person video chat. The originating computer performs much of the video encoding and audio-video synchronization, leading to stringent hardware requirements: a Mac with at least dual 1 GHz PowerPC G4 processors, or one with a PowerPC G5 CPU, along with 384 Kbps of Internet bandwidth. Unfortunately, that rules out Apple's entire laptop line as video chat initiators.
Participation in a multi-person video chat is less demanding: you need at least a 1 GHz PowerPC G4 or a dual 800 MHz PowerPC G4-based Power Mac - along with 100 Kbps of Internet bandwidth. iChat AV also supports video chat with Windows users running the latest version of AIM (AOL Instant Messenger), but only one to one, not for multi-person chats.
As advertised by Apple, the video quality is improved due to iChat's use of the H.264 video codec, but the quality also depends on the connection and the hardware involved. Slower connections appear blurrier than faster ones; that isn't necessarily a bad thing, as iChat is sacrificing fine detail in favor of more fluid motion (see the image at the second URL above for an example).
iChat AV 3.0 also features audio chats of up to 10 people, which doesn't carry the same hardware and connection demands. Hosting a 10-person conference requires a Mac running a 1 GHz G4, dual 800 MHz G4, or G5 processor and a 128 Kbps Internet connection. Participation in an audio chat needs any G3, G4, or G5 processor and a 56 Kbps connection.
Miscellaneous Changes -- The multi-person chats are the star attractions, but iChat AV 3.0 includes a number of other noticeable changes. It's easier to switch among several iChat or AIM accounts using a new Switch To item under the iChat menu. You can set a profile that describes you when other people view your information from their Buddy Lists by choosing Change My Profile from the Buddies menu; previously, you had to launch the AIM application to edit this field.
Speaking of switching, iChat includes a preference that dictates what the program should do when you use Fast User Switching to go to another user, either to log out of iChat (the old method), or to change your status to Away. If you are away, and someone chats you up anyway, you can set iChat to fire back with a reply (either your custom status message or "Auto-reply: I am away from my computer" if set to the default Away status).
The Groups feature is also improved, with a more comprehensible interface. I never bothered with groups before, but now I can arrange my buddies according to affiliations (such as a TidBITS group), which appear under banner headings in the Buddy List.
For companies looking to secure their instant message traffic, iChat AV 3.0 now supports Jabber, which can encrypt messages. You can sign onto existing Jabber servers, or use the Jabber-based iChat Server included with Mac OS X 10.4 Server.
Apple also incorporated a popular third-party feature into iChat. In addition to Available and Away status messages, you can choose to display the title and artist of the song currently playing in iTunes (which I used to use iChat Status for). Clicking an arrow at the right edge of the status message takes you to that song in the iTunes Music Store if you want to sample (or buy) music your friends are playing.
Video Future -- I use iChat every day for text-chatting with friends and colleagues, and only occasionally chatting via audio or video. Although the new multi-person video chatting capability is cool, I'm curious to see how often people end up using it. Still, it does provide an inexpensive, built-in way to participate in video conferences, something that formerly required more expensive, often proprietary services to accomplish.