MPEG-4 is a standard currently under development for the delivery of interactive multimedia across networks. As such, it is more than a single codec, and will include specifications for audio, video, and interactivity.
The video component of MPEG-4 is very similiar to H.263. It is optimized for delivery of video at Internet data rates. One implementation of MPEG-4 video is included in Microsoft's NetShow.
The rest of the MPEG-4 standard is still being designed. It was recently announced that QuickTime's file format will be used as a starting point.
From the National Association of Broadcasters (NAB) show:The MPEG-4 standard has been evolving very quickly. We've watched it go on the Internet, into 3G products and now, with this technology preview of H.264, we are going to watch it go to HD.
Unlike other codecs, H.264 is scalable, allowing content creators to write their content for everything from the newest 3G phones to HD, and everything in between.
As with MPEG-4 itself, H.264 is an open standard, which means that many different companies contribute to the process of evolving the codec into something the public sees on their computer or television.