WorthBroadcasting
What is a podcast?
Put most simply, a podcast is a means of broadcasting and receiving audio files (usually mp3s) whenever new files are released, without having to check a particular website on a regular basis. The advantages of this include the ability to keep track of a large number of podcasts from many different sources very easily.
This article will explain (first very simply, and then in more technical detail for the more geek minded) just what a podcast is and just what it isn't. To learn more about how to make a podcast, see our tutorials on Making Your Own Podcast and Recording Your Own Podcast.
Radio on demand
Podcasts have been likened to radio on demand. You can think of a podcast as a particular programme; that podcast then will consist of "episodes" released at intervals. The great thing about podcasts is that they automatically update their listeners whenever a new episode is released (you will notice that a great many radio programmes are now actually putting their shows out as podcasts).
What is not a podcast?
Some times you will see a webpage with words like "Download my podcast here" with a link to an mp3 file... this is emphatically not a podcast. A podcast is marked by the ability for you, its audience, to be notified when a new episode is released.
How!
At the heart of a podcast lies a file called an RSS feed. RSS refers to a family of file formats used to publish frequently updated content like blog entries, news headlines or podcasts. RSS can stand for "Really Simple Syndication", although depending on the format, it can also mean "RDF Site Summary" or "Rich Site Summary". Each time an entry is updated, or a new entry included, the file is changed. These changes are picked up by what whatever software is being used by the subscriber to track the changes.
RSS content can be read using software called an "RSS reader," "news reader" or an "aggregator." The user subscribes to a feed by entering the feed's link into the reader or by clicking an RSS icon in a browser that initiates the subscription process. The reader checks the user's subscribed feeds regularly for new content, downloading any updates that it finds.
Reading RSS Feeds
There are many applications for reading RSS feeds that are suitable for subscribing to podcasts. Some of these are web based, such as Google which will allow your to incorporate your newsfeeds into your own home page, and some are local applications. Mozilla Thunderbird, a popular email client, also incorporates a news reader as part of its suite of services. It really is a matter of personal preference which one you choose. Just as with email, web based solutions can suit those who access the internet from many different locations.
Delving Deeper
For those not interested in the arcane secrets of RSS formats and XML, read no further. But a general understanding of these formats and how they deliver data can help you understand a little bit more about how a podcast works. And a little bit more understanding can be no bad thing, right?
Geeky Stuff For Beginners
The RSS file used to create a podcast (or any news feed for that matter) is written in a language called XML (Extensible Markup Language), a simple format used to organise data for distribution across networks such as the internet. XML lends itself to structuring information where items can be categorised and sub-categorised. For example, we might want to classify our music collection.
<music>
</music>
The first <music> opens the category, the second (indicated by the /) closes it. Together, these two tags define the category and tell us that anything that falls between is an element of category.
<music>
<rock and pop>
<cd>
<artist>Meatloaf</artist>
<title>Bat Out Of Hell</title>
</cd>
</rock and pop>
<easy listening>
<easy listening>
</music>
and so on. This *is* hugely simplified, as elements can be given attributes and there are constraints on what forms a well structured document, but you should get the idea.
So when we define an RSS feed for a podcast we first tell whatever reader will be using our file just what type of code we are using
<?xml version="1.0" encoding="UTF-8"?>
and then go on to create information about the channel or the podcast itself
<channel>
<title>WorthBroadcasting</title>
<description>The lowdown of the use of internet media and social networking in campaigning strategies</description>
<link>http://www.worthbroadcasting.org</link>
<language>en-gb</language>
<copyright>Copyright 2007</copyright>
<lastBuildDate>Tue, 30 Oct 2007 11:30:00 +0000</lastBuildDate>
<pubDate>Tue, 30 Oct 2007 11:30:00 +0000</pubDate>
<docs>http://blogs.law.harvard.edu/tech/rss</docs>
<webMaster>admin@worthbroadcasting.org</webMaster>
note that the root element "channel" is still open. The next stage is to tell the reader just what the episodes consist of
<item>
<title>Interview with Head of eCampaigning at NCVO</title>
<link>http://www.worthbroadcasting.org/podcaster/episode_details.php?e=23</link>
<guid>http://www.worthbroadcasting.org/podcaster/play-e-test24.mp3</guid>
<description>A great opportunity to hear how the future of web2.0 is influencing current thinking in ecampaigning</description>
<enclosure url="http://www.worthbroadcasting.org/podcaster/play-e-test24.mp3" length="11779397" type="audio/mpeg"/>
<category>Podcasts</category>
<pubDate> Tue, 30 Oct 2007 11:30:00 +0000</pubDate>
</item>
and we have given all of the information needed to define the podcast episode. Each time we have a new episode, we simply add a new item with all the relevant details.
Finally, we close the file with the tag
</channel>
If we want to create an iTunes compatible feed, there are other elements that we need to use, but this gives the overall idea as to the data structure of a podcast.
