Podcasting/Vodcasting: Distributing Your Audio and Video Files Via the Web
From our last lesson, we have the following podcast.rss file:
What we'd like to do now, however, is add more episodes. While this process is mostly straight-forward, there are a lot of opportunities to make small errors. Pod Catchers are highly unforgiving--if you get completely stumped on why your feed isn't working, there is no pride lost in starting over.
Existence and Uniqueness
When we have more than one episode, the notion of existence and uniqueness comes up. We won't go into it too heavily, but the basic idea is that we need to keep track of what's old and has simply changed and what's new. Since we may get new Subscribers after we've published subsequent Episodes, we leave information in our XML file about the older episodes to offer the ability to download old content. The problem of existence and uniqueness then is posed by the desire to tell new content from changed old content.
The answer, of course, is obvious: IDs! We give each Episode its own ID that we can *never* change, and then we are free to change absolutely anything else about the XML file that references it. When posed to a group of people, many suggested that we simply use an Episode's web address (URL) as the ID, but then what happens if we want to move the file to a new server or to a new folder? The same thing goes for using the Episode's Title: we may wish to change it in the future. While there is no standardized way of giving your Episodes IDs, using a combination of sequential numbers and the date works well. The following might be a list of IDs for monthly Podcast Episodes
"Where does this ID go?", you might ask. The confession, then, is that there are (quite) a few tags you might not know about yet. Many are specific to just iTunes and other PodCatchers (and we will cover the most useful ones on a later page), but the next few tags are applicable to all PodCatchers (and RSS Readers for that matter).
The <guid> Tag
After all that talk about existence and uniqueness theory, we finally get to apply it with the <guid> tag. GUID stands for Globally Unique Identifier, and its purpose is to assign what is like a social security number to your Podcast Episodes.
An example of the <guid> tag in action would be:
There must be a <guid> tag inside each item, or many Podcatchers will only 'see' the first episode.
We are almost done with <guid>. Before we move on, we need to add one attribute and property to it--the isPermaLink property. A PermaLink is a static URL in a dynamic directory structure. Because some Podcasters use an Episode's PermaLink as its ID, there is support in PodCatchers for this. Since we are not including the Episode's URL, we will just leave this as false.
Given this, we are now up to:
You can now simply copy/paste iterations of the above text multiple times and replace the respective values as necessary to add new episodes. Doing so, we arrive at another completed Podcast Feed:
An Important Note
Up until this point, the order of tags has not mattered so long as we haven't broken the nesting rules discussed with XML. That is, the <title> tag could have appeared before the <link> tag and so on. Order doesn't appear to matter. However, iTunes and most other PodCatchers will list <item>s in the order that they appear in the feed's code (which is why we've put episode 3 above episode 2 and 2 above 1 in the code). Next we will learn some extraneous (i.e. not completely necessary but sometimes useful) tags including one that will allow us to change the order.
At this point, you really really can stop with this tutorial. You know how to set up your feed and add new episodes. If you know how to upload to your Dante (or other FTP site), you can save what you have so far and run with it without worrying about anything we've purposefully left out.
We will devote another two pages to more RSS tags to add new features to our Podcast (such as episode descriptions a/k/a shownotes, "album art", and a slew of iTunes-specific features). Then we will cover validators to be sure our feed is free of errors before posting it. Then we will refresh you on how to upload to the webserver and the basics of HTML and linking to your Podcast on your website. After this, we will cover listing your Podcast on various Podcast directories (including the iTunes Music Store). And then last (and perhaps least) we will introduce a few Podcast feed Generators and tracking services that will do the hard work for you and let you more accurately track your Subscriber statistics. Finally we will give you the HTML and some free icons and buttons you can use to link to your podcast on your website.