Podcasting: Technical Specification

Podcasting requires several steps:
  1. Creating your first episode, which can be an audio recording, video, or even a text document. Supported file formats include .m4a, .mp3, .mov, .mp4, .m4v, and .pdf.
  2. Posting your episode file(s) on a server with a publicly accessible URL.
  3. Creating an RSS feed (an XML file) that:
    1. conforms to the RSS 2.0 specification
    2. includes the recommended iTunes RSS tags,
    3. contains pointers to your episode.
  4. Posting the RSS file on a server.
  5. Submitting the URL for your RSS feed to iTunes.
The remainder of this document focuses on technical aspects of preparing your RSS feed.
Testing Your Feed

When you have created your RSS feed and posted it to a server with a publicly addressable URL (i.e., not behind a firewall), you should test your feed to see if it works with iTunes:

Launch iTunes.
In the Advanced menu, select Subscribe to Podcast.
Enter your feed URL in the text box and click OK.
iTunes displays your Podcast playlist, which shows all of the podcasts to which you have subscribed. Next to the new podcast subscription, you should see an orange circle, which indicates that iTunes is downloading your most recent episode. When the orange circle disappears, you should be able to see your podcast title, a list of all the episodes referenced in your feed, and a check next to the most recent episode, indicating that it has been successfully downloaded. Double-click on the episode to play it in iTunes. If you can successfully play the episode, then your feed is working and you can submit your podcast to iTunes.

If the orange circle is replaced by an “i" in a black circle, iTunes encountered a problem with your feed or episode. You should troubleshoot your episode and feed before submitting it. Please do not submit your feed until you can successfully subscribe using the Advanced menu.

Submitting Your Podcast to iTunes
If you can successfully subscribe to your feed using the Advanced menu in iTunes, you’re ready to submit your feed:

  1. Launch iTunes.
  2. In the left navigation column, under Inside the Music Store, click on the Podcasts link to go to the Podcasts page.
  3. In the left column of the Podcasts page, click on the Submit a Podcast link.
  4. Follow the instructions on the Submit a Podcast page.
Note that you will need a valid iTunes account, and you will need to be logged into iTunes. If you are not logged in, iTunes will prompt you to do so before accepting your submission. By requiring you to log in, iTunes increases the likelihood of valid contact information for each submission. Your credit card will not be charged for submission of a podcast.

If you have created an RSS feed with all of the recommended iTunes tags, you will see a summary page immediately after you submit your feed URL. If you have not included <language>, <itunes:category>, and <itunes:explicit> tags in your feed, you will see a second screen prompting you for this information. Please note that you can change this information at a later date by including the tags in your feed. Your RSS feed is considered the current and authoritative source for information about your podcast.

The Queue

After your podcast is submitted, it is placed in a queue, where iTunes staff check it for problems. Your podcast may be rejected for a variety of reasons, including but not limited to:

Technical problems, usually the lack of episodes or the inability to download or play episodes. These problems can almost always be avoided by testing your feed using Subscribe to Podcast in the Advanced menu prior to submission.
Apparent misuse of copyrighted material or other violation of third party rights.
In general, if there’s something that you want to convey about your feed, please do so in the summary field in your RSS feed, not in the content of an episode.

Normally, podcasts that are added to the iTunes directory will appear first in iTunes search, and later in iTunes browse. Appearing in the browse category that you specified can take up to two days. The image associated with your podcast may also require additional time to appear, because images are edge-cached by iTunes and must propagate across the caching servers.

Adding Episodes

Whenever you create a new podcast episode, you should add a new <item> section to your podcast feed. The iTunes directory will list the episode the next time it reads your feed. The order in which the episodes appear is based on the pubDate for each item, with the most recent episodes appearing at the top of the list.

By default, the iTunes directory reads every feed once per day. However, you can control this rate using the < ttl> tag (see below). Note that this tag affects the iTunes directory but not what existing subscribers see in their iTunes client. The client picks up new episodes based on the preferences set by the user.

Changing Your Feed URL

Podcasters occasionally need to move their feed from one location to another. In this case, you should not remove your feed. If possible, you should set your web server to return a 301 error and redirect when receiving a request for the old feed. Doing so will cause both the iTunes Music Store and the iTunes clients that have subscribed to your podcast to pick up the new feed URL. Be sure to maintain the redirect for at least two weeks to ensure that most subscribers have attempted to download your most recent episode and have thereby received the new URL.

If you don’t know how to return an HTTP 301, you can use the <itunes:new-feed-url> tag described in the iTunes RSS Tags section below. The tag will cause the iTunes music store to be updated with the new feed URL, but it will not inform iTunes clients of the new location. You may choose to include an audio note in your podcast, informing your subscribers that your podcast has changed locations. After adding the tag, be sure to keep your feed running at the old URL for at least 48 hours.

Tracking Usage

Please note that iTunes does not provide usage statistics. Some podcasters have created mechanisms for tracking the number of times that each episode has been downloaded. iTunes does not provide support in how to track downloads, but the following notes may be helpful:

302s will be followed to a depth of 5 redirects and will not update the feed URL in the directory.
The URL before the GET-style form values (before the first ?) must end in a media file extension (e.g. mp3). To work around this, the feed provider can alter their URL from this:
to this:
Notice how it says load.mp3 instead of load.php. It should be possible to accomplish this via various means, such as web server rewrites. iTunes looks at the extension of the path part of the url, i.e. the part before the"?".

Creating Video Podcasts

Although iTunes can play a variety of .mp4, .m4v, and .mov video formats, video iPods require more specific formats. By following the steps in the Creating Video for iPod tutorial, QuickTime 7 Pro will automatically create an .m4v file containing H.264 video and AAC audio that is optimized for iPod. iPod can play the following video formats:

H.264 video
File formats:
.m4v, .mp4, and .mov
Video: Up to 768 kbps, 6400 x 480, 30 frames per second (fps), Baseline Profile up to Level 1.3
Audio: AAC-LC up to 160 kbps, 48 Khz, stereo audio

MPEG-4 video
File formats:
.m4v, .mp4, and .mov
Video: Up to 2.5 mbps, 640 x 480, 30 fps, Simple Profile
Audio: AAC-LC up to 160 kbps, 48 Khz, stereo audio

An Example Feed

<?xml version="1.0"?>
<rss xmlns:itunes="http://www.itunes.com/DTDs/Podcast-1.0.dtd" version="2.0">
<title>New Hope Christian Fellowship O'ahu</title>
<itunes:author>Pastor Wayne Cordeiro</itunes:author>
<description>Pastor Wayne Cordeiro is Senior Pastor of New Hope Christian Fellowship in Honolulu, Hawaii; one of the nation’s fastest growing churches. Since opening it's doors in September of 1995, Since then New Hope has grown to over 12,000 in weekend attendance with 8,500 of those being first-time decisions.</description>
<itunes:subtitle>New Hope's Weekly Podcast. Featuring Pastor Wayne Cordeiro and Pastor Elwin Ahu</itunes:subtitle>
<itunes:summary>Pastor Wayne Cordeiro is Senior Pastor of New Hope Christian Fellowship in Honolulu, Hawaii; one of the nation’s fastest growing churches. Since opening it's doors in September of 1995, Since then New Hope has grown to over 12,000 in weekend attendance with 8,500 of those being first-time decisions.</itunes:summary>
<copyright>New Hope Christian Fellowship O'ahu</copyright>
<itunes:name>Peter Thourson</itunes:name>
<title>New Hope Christian Fellowship O'ahu</title>
<itunes:link rel="image" type="video/jpeg" href="http://www.enewhope.org/media/podcast.jpg">New Hope Christian Fellowship</itunes:link>
<lastBuildDate>Sun, 29 Jan 2005 9:32:54 GMT</lastBuildDate>
<title>When You Feel Absolutely Helpless</title>
<description>Pastor Wayne Cordeiro</description>
<pubDate>Sun, 29 Jan 2006 21:00:00 GMT</pubDate>
<enclosure url="http://www.enewhope.org/media/mp3/W0605.mp3" length="26079152" type="audio/mpeg"/>
<title>What do Kids Need?</title>
<description>Pastor Dave Barr</description>
<pubDate>Sun, 22 Jan 2006 21:00:00 GMT</pubDate>
<enclosure url="http://www.enewhope.org/media/mp3/W0604.mp3" length="24965934" type="audio/mpeg"/>



Common Mistakes

Wrong <pubDate> Format
The date and time format in <pubDate> must conform to RFC 2822.

The date must be “day-of-week, day month year". The time must be in 24 hour format (no AM or PM) and must include the time zone offset.

<! — date and time not in RFC 2822 format — >
<pubDate>7/6/2005 1:00:00 PM</pubDate>

<! — valid date and time format — >
<pubDate>Wed, 6 Jul 2005 13:00:00 PDT</pubDate>
<pubDate>Wed, 6 Jul 2005 13:00:00 -0700</pubDate>

Failure to Escape Ampersands
<! — illegal xml — >
<title>Food & Wine</title>

<! — valid xml — >
<title>Food &amp; Wine</title>

Using HTML Named Character Entities
<! — illegal xml — >
<copyright>&copy; 2005 John Doe</copyright>

<! — valid xml — >
<copyright>&#xA9; 2005 John Doe</copyright>

Technical Specifications for podcasting with iTunes taken from Apple's Developer Center: http://www.apple.com/itunes/podcasts/techspecs.html