Podcasting/Vodcasting: Distributing Your Audio and Video Files Via the Web
Intro to RSS
We are now armed with the knowledge of what Podcasting and XML are. Now we will finally get to put that knowledge to good use to make our Podcast. The hard part isn't over yet, unfortunately, but now we're getting to the fun parts (remember that this is all on a relative scale).
Consider the following example of a perfectly valid Podcast feed:Our first Podcast RSS feed, podcast.rss:
Note how we are now naming our file with the .rss file extension. We can use .xml if we wish, but since we are using RSS specifically, it is more appropriate to use RSS's extension.
Adding the First Episode
The podcast.rss file we have thus far gives us the Title of our Podcast, the URL link to our main page (the home page for our Podcast ), and a phrase or sentence to describe our Podcast. The good people at Harvard (who also maintain RSS 2.0 in addition to XML) say that every valid RSS feed must have exactly one (no more; no less) <channel> which of course must be closed
Therefore, what we have so far is all that RSS requires. But in order to add the functionality of a Podcast (i.e. listing episodes), we will need to add some code to bring us up to:Our Podcast RSS feed, podcast.rss, with one episode:
The <item> tag
We have added the <item> tag and a few other tags to give us more information about that item. You can think of <item> as being like <episode>. Each episode will get its own <item>.
The <enclosure> tag
Remember from a while ago how we said that each and every tag in XML (and thus in RSS) must have an accompanying closing tag? This is both true and not-true (interestingly enough). It wouldn't make sense for some tags to have a closing tag, and the <enclosure> tag is one of them. In order for this to make sense to the Pod Catcher (and so our file conforms to the XML and RSS standards), we add a /> (preceded by a space) to the end of the enclosure tag to tell the Pod Catcher that it shouldn't expect it to be closed later.
Notice that the enclosure is left with empty attributes url, length, and type. Each of these attributes needs some explanation before we start giving them values.
The url attribute takes the full url to the actual file we would like to podcatcher to download for this episode. Please note that it must start with http:// or http:// or some other protocol. Simply putting the www. without the protocol will not work.
The length attribute is probably the trickiest. You need to find the length of your podcast, not in minutes and seconds, but in bytes.
- If you are comfortable with the UNIX shell, you can use the ls -l (l as in a lower-case L) command to see a file's size in bytes.
- If you are on a Windows machine, right-click on your Podcast file and select Properties. A window will appear and will show you the size in bytes of your file.
- If you are on a Macintosh, Control+Click (or right-click) on your Podcast file and select "Get Info." The size of your file in bytes is located in the "General" tab of the Info Window that pops up.
The included screen shots indicate different file sizes for the same file, but this is a factor of how the different operating systems downloaded this particular Podcast episode from the iTunes directory. Your file size will be specific to whatever operating system you used to create and upload the file. For this reason, you should always check your file sizes on whatever computer you're using to upload the Episodes.
Depending on your operating system, you may be given the file size with commas to make it easier to read. For our purposes we will delete the commas when putting this number into the size attribute.
The final attribute, type, is where you input the kind of file the podcast episode is. For audio files this will be the the MIME type. In general, the .mp3 format will have be of type "audio/mpeg."
MIME Types and You
|File Extension||MIME Type|
Included is a table for the most commonly-used MIME types associated with Podcasts. If your file type isn't listed, you can go to WebMaster's Toolkit (opens in a new window) to get an expanded list. (Please note that the University of Washington is in no way affiliated with WebMaster's Toolkit and is not responsible for any content thereon.)
MIME stands for "Multipurpose Internet Mail Extensions." When you send something as an attachment to an email, the email program actually takes all of the binary data from the attachment and throws it at the end of the message. The MIME type associated with the attachment tells the recipient's computer how to interpret the binary data.
True, we are not using email for our Podcast, but this idea has made its way onto the Internet. Every sort of file out there has an associated MIME type that gives the computer information about what kind of file it is. We humans can commonly tell what program opens what file just by its extention, but computers often need more than this. Such is the case with our Podcast Episodes. While it technically is possible to have a MIME type that's different than the extension (e.g. putting the PDF MIME type for a .mp3 file), this would have unpredictable results. We tend to think of MIME types and file extensions as being one-to-one (i.e. for every file extension there is exactly one MIME type and vice-versa). This is not always the case, but we can think of it as such for the purposes of Podcasting.
The <description> tag
...should include a brief description (ideally less than 255 characters) of your Podcast. You should not use any special characters. That is, limit yourself to letters, numbers and basic punctuation ( . , " ' ). HTML is not allowed. There is an analogous tag that will allow for HTML, but it is specific to just iTunes. We will cover it later.
Putting it All Together
Adding this information about URL, Length and, and Type, we have a final Podcast RSS feed:Our (now complete) Podcast RSS feed, podcast.rss, with one episode:
Now you would be able to save this file to a public server and subscribe to your Podcast via iTunes or your favorite Pod Catcher. We're left with a pretty boring Podcast, however. It only has one episode, it's not listed on any Podcast directories, and there's no more information like its category, relevant album art, or "show notes." the next page will show you how to add a new episode (a fairly straight-forward process). After that, we'll get into the more iTunes-specific RSS tags that allow us to give Apple's widely popular Pod Catcher (and thus a large number of subscribers) more information.