For its own RealAudio, RealNetworks has adopted Advanced Audio Coding (AAC), part of the broader MPEG-4 standard (MP3 is a component of the MPEG-1 standard, and is strictly known as MPEG Audio Layer-3). Another strong supporter of AAC is Apple, which has chosen it for its iTunes service. AAC has been further developed (using the same techniques employed in MP3Pro) to create AACPlus.

Although MP3 is unchallenged as the first-generation music format, things are not so clear-cut for the next iteration. Rather than deploying AAC, Microsoft has developed its own, independent proprietary standard, the Windows Media Format, which covers video too.

To complicate matters further, Microsoft also supports the official industry formats for video, which are part of the umbrella MPEG-4 standard. However, Microsoft’s support is typically ambiguous: “While Microsoft continues to support the MPEG-4 standardization process, it is moving forward with the development of audio and video technologies that deliver superior quality and an end-to-end streaming solution for Microsoft customers.”

There is an official MPEG-4 site with information about MPEG-4, a FAQ and a more detailed introduction. Since part of the file format is based on Apple’s QuickTime, Apple is naturally a big fan of the standard for video as well as for audio, and provides some useful background resources. More generally, the Internet Streaming Media Alliance represents those companies supporting the standard (with Microsoft conspicuous by its absence).

As in so many other domains, post-MP3 video and audio standards in the commercial sector essentially come down to a choice between Microsoft and the rest. With the continuing roll-out of broadband, the bandwidth for video on demand is now in place; but until this format war is resolved, everyday VOD seems as far off now as it did ten years ago.

Glyn Moody welcomes your comments.