Podcasting: The latest buzz

Podcasting was created by former MTV VJ Adam Curry, along with programmer Dave Winer. Winer has been influential in the creation and promotion of blogging technologies, and wrote the RSS 2.0 specification (a standard for web logs and news feeds). Curry has been involved in radio programming and media technologies since his MTV days.

Curry was interested in delivering his radio show to as many people as possible. He recognized that iPods and similar devices were not just music players, but also a new platform to develop content for.

According to Curry, "We've been trained to think the only way you can fill your MP3 player is by either ripping your CD collection to it, or by purchasing music tracks from a few vendors. In reality you can fill up your MP3 players with audio files that contain anything you can record. A show, lecture, weather report, love letter... just like weblogs."

Winer's specification for RSS news feeds included the idea of an "enclosure". This allows any RSS news feed item to have an associated file, such as an MP3 audio file or a MPG video.

Curry wrote a small program, iPodder that automates the process of checking news feeds, downloading audio files and synchronizing them to an MP3 player. He also released his source code, which has seeded development and led to several alternate applications.

While there have been previous systems for downloading or synchronizing audio files, Podcasting is based on open and non-proprietary standards, which may help drive it to a larger audience. The success of Apple's iPod and other portable digital audio devices has also created a large audience for new content.

Creating a Podcast

A podcast is simply an XML file in RSS 2.0 format that containes URL references to audio file "enclosures".

RSS files are the language of blogging and news readers, and they can now be found at most news-oriented sites. RSS 2.0 is typically used to define a news feed "channel". A channel can contain "items", made up of a title, link, and description. When rendered as HTML, the title is usually rendered as a headline, the description as a summary paragraph, and the link as a hyperlink to the full article.

What makes an RSS channel a podcast is the incorporation of "enclosures" into the news items. Enclosures are normally optional sub-elements of news items. In a podcast, though, the enclosure element identifies the URL, the size and the type of the audio file associated with the news item.

By including a URL to an audio file, podcasts use RSS enclosures to turn a news feed into a XML feed of audio files.

Podcasting in Action

Some potential uses for RSS with audio enclosures:

* Daily radio shows;
* Audio-based web logs;
* Company news for sales reps/road warriors;
* TIVO-like time shifting of broadcasts;
* Audio book promotions, i.e., a free chapter to get you interested;
* Music aggregators

Podcasting is immature technology, but offers the potential of becoming a significant new platform for web content distribution.