Podcasting - a Technical Overview
Welcome to this section!
In this section we will briefly explain the technology used in every step of the Podcasting process.
A little technological knowledge of the reader is expected. In case you run into an unknown term or abbreviation, please refer to the Glossary.
Steps in the Podcasting process:
- THE PODCASTERS SCRIPT
- Recording your Podcast
- Creating this Episodes Soundfile
- Creating the Feed
- Uploading
- The Missing Link
- Relaxing
- THE PODCAST LISTENERS SCRIPT
- Subscribing to the Feed
- Downloading
- Synchronizing with the Portable Player
- Enjoying
THE PODCASTERS SCRIPT
Recording your Podcast
With any kind of recording software you can create the piece of audio that, at the end of this process, will be called a Podcast Episode.
If you assemble your production from several kinds of audio files, like the song of a band and some sound effects, the highest quality should be chosen. In the next step, when the soundfile is being compressed for download purposes, low quality sound-input will become awful sound-output.
The format of the produced soundfile doesn't matter. When you have finished (editing and perfecting) your recording, you are ready for the next step, creating to sound file that will be put onto the Web.
Creating this Episodes Soundfile
The soundfile format of your Episode can be anything (as in mp3, aiff, wav, aac or another audio format), because the links you put in your Feed (the RSS 2.0 XML file) refers to both filename and - by the extension - file format. (More about this later in this section.) However, to make sure your audience can listen to you Podcast, the mp3-format is recommended.
When you've choosen the mp3 format (wise decision!), you'll have to make some decisions on the way the file is to be saved.
Options:
- mono/stereo
- variable speed or constant speed
- the number of kilo-bits-per-second (kbps)
Mono or Stereo
Depending on the recording, which should be either mono or stereo originally, you make your choice. If file-size is an issue, you might consider saving a stereo recording as a mono mp3-file, because that approximately saves about 50% file-size.
Variable or Constant Speed
Variable bit-rate (or VBR for short) can be handy for files with varying amounts of sound and silence, since silent moment are more compressed than "audio-rich" moments. Players on computers, like QuickTime, Windows Mediaplayer, WinAmp and others, can handle mp3-files with variable bit-speed. Howeever, cheaper or older portable mp3-players can not. Our advice; unless you want to exculde certain groups from your audience, stick to constant speed mp3 file format.
How many KBPS
Depending on the desired quality of sound you want to present to your audience, and the kind of content in your Podcast, the speed should be between 32 and 128 Kbps.
The lowest speed, 32 Kbps, can be used for speech-only newsflashes. The highest speed, 128 Kbps, can be used for high-quality sound with lots of music. The best test is to save your production at several bitrates and decide what's best for your show.
Creating the Feed
A soundfile without a Feed is just a soundfile. A soundfile with a Feed, well, that's a Podcast!
A Feed is a textfile that describes the Podcast, the various Episodes the Podcast consists of, and the links to the audiofiles and related images (if applicable).
These links, pointing to other files, are called enclosures. The Podcasts feeds adhere to the RSS 2.0 standard file-format, and are written in XML.
A simplified Feed of a Podcast with one Episode looks like this:
<?xml version="1.0" encoding="UTF-8"?>
<rss>
<channel>
<title>- PPP - The Podcast Platform Podcast !</title>
<subtitle>The Podcast about Podcasting</subtitle>
<summary>Each episode we tell you about new developments in the Pod-o-sphere. Ranging from new Podcasts you can listen to, to tips and tricks for Podcast Producers.</summary>
<language>en-us</language>
<image href="http://www.podcastplatform.com/images/podcast-logo.png" />
<item>
<title>PPP no 1: the first Podcast Platform Podcast</title>
<subtitle>"What is Podcasting", explained in simple terms!</subtitle>
<summary>In this episode we explain what a Podcast is, the benefits of Podcasting compared to radio, and we give you some examples of popular Podcasts.</summary>
<enclosure url="http://www.podcastplatform.com/podcast/ppp_001.mp3" length="19907210" type="audio/mpeg" />
<guid>http://www.boppod.com/podcast/boppod/boppod%23001.mp3</guid>
<pubDate>Thu, 08 Dec 2005 12:00:00 +0100</pubDate>
</item>
</channel>
</rss>
The combination of the Feed (with enclosures)and the related audio-files, is what forms the Podcast.
Uploading
The next step is to put the Feed and the audio-file (the mp3) onto the Web. This can be done by using a simple FTP-program. When the files are uploaded the files can be downloaded, but nobody knows yet where to look for them.
The Missing Link
Depending if you have your own webspace (you have a website hosted at your ISP) or you are using a hosting-company specialising in feeds (like Feedburner), you either create a link on your website, or your hosting-company does that for you. The link is accompanied by the all-to familiar orange XML-logo.
Now your Podcast can be found!
Relaxing
You've done it! Congratulations! You just made your Podcast Episode available to the World.
Time to lean back, take a half-liter bottle of Grolsch from your fridge and relax.
THE PODCAST LISTENER'S SCRIPT
Subscribing to the Feed
The Podcast Listener, brought to your Podcast by browsing through tens of entries in a Podcast Directories (like Podcast Alley), has the ability to subscribe to your Feed by means of a Podcatcher (like Juice or iTunes).
This piece of software registers the url of the Feed (the subscription), and automatically checks the content of the Feed at regular intervals whenever you are online. This all happens in the background, and does not require any addition action from the Podcast Listener from the moment he or she subscribed to the Feed.
The same happens in newreaders, checking for newsflashes (textual content).
Downloading
The moment a new entry (item + enclosure) is found in the Feed, the Podcatcher software automatically downloads the related enclosures, and updates the information in you Podcast-list with the info it found in the Feed (title + sub-title + summary).
And surprise, without doing anything you just received the latest episodes of your favorite Podcasts. You can now listen to them on your computer.
Synchronizing with the Portable Player
Additionally, you might prefer listening to your Podcasts on the go. If you move your latest Podcasts to your portable mp3-player, a process called synchronizing, you can listen to your Podcasts when you want, where you want and as many times as you want.
Enjoying
And now it's time to go to your favorite spot on the beach (or on the mountain) and press Play...
You read it, you understand it. And now, go do something creative with all that knowledge!
The PLATFORM TEAM
;-)