What is IChat?
iChat is an AOL Instant Messenger (AIM), ICQ and Jabber client for Mac OS X. Using a Jabber-like protocol and Bonjour for user discovery, it also allows for LAN communication. iChat's AIM support is fully endorsed by AOL, and uses their official implementation of the AIM OSCAR protocol. Using a Jabber transport, iChat users may also integrate their MSN and Yahoo! contacts into the Jabber pane, so only one instant messenger program is needed on a Mac.
It bears a brushed metal interface and uses speech bubbles and pictures that some advocates claim personify the online chatting experience. With iChat, green (available), yellow (idle), and red (away) dots can be seen next to the name of each connected user on the buddy list.
In June 2003, Apple Computer announced iChat AV Public Beta, a new version of iChat that added voice and video chat capabilities. It also introduced the iSight camera, designed specifically for use with iChat AV. These capabilities are based on the industry-standard, but not yet widely adopted, Session Initiation Protocol (SIP) for video chat and audio chat. The final version of the software was shipped with Mac OS X v10.3 and became available separately on the same day for users of Mac OS X v10.2 for 29.95USD. Apple eventually discontinued sale of iChat AV separately; it can now only be acquired through OS X or with a new Mac.
In February 2004, America Online introduced AOL Instant Messenger (AIM) version 5.5 for Windows-PC users. This version allowed video (but not voice) chats over the AIM protocol and was compatible with Apple's iChat AV. On the same day, Apple released iChat AV 2.1 Public Beta to allow Mac OS X users to video conference with AIM 5.5 users.
In June 2004, Steve Jobs revealed that the next version of iChat AV (commonly called iChat 3) would be included with Mac OS X v10.4 (Tiger). iChat 3 supports up to four people in a video conference and ten people in an audio conference. Additionally, video conferencing uses H.264/AVC, which offers better quality than the H.263 codec used in previous versions. This release also supports the Jabber protocol (which can be directly used to connect to Google Talk and indirectly be used to connect to users of services including Yahoo! Messenger and MSN Messenger as well). However, support is limited as it does not support several common Jabber/XMPP features like account creation, service discovery and full Multi-User Chat support. Despite initial rumors that the client would support tabbed browsing for multiple chat windows (a popular feature available on almost all third-party clients), the released version did not, puzzling many users.
ChatFX is a third-party add-on for iChat that enhances functionality, adding special video effects created by the Quartz Composer application included in Apple's free Developer Tools. ChatFX changes the video in a video conference through use of Quartz Composer compositions. Special video effects like bluescreen, distort, display of desktop, sobel, comicbook, ghost, etc. come with ChatFX but an unlimited number of effects are possible by creating new compositions in Quartz Composer.
Chax is a free, third-party add-on for iChat that enhances functionality, including autoreconnect, tabbed windows, and auto-accept of messages and file transfers. Chax also prevents iChat from pausing audio-video (AV) chat when also transferring files. The ability to animate buddy icons, which is absent in iChat, can also be added through Chax. It was developed by Kent Sutherland and is similar in functionality to AIM+ and DeadAIM, which added similar features to the Windows version of AOL's AIM client.