Podcasting and Streaming Audio
Streaming audio and podcasting are different ways to provide the same audio files to users.
Streaming is when you want to starting listening right away without having to wait for the entire file or broadcast to download to your computer.
Podcasting means subscribing to an on-line broadcast. Typically, you want to have the broadcast files downloaded to your computer so you can listen to them at your leisure. A podcatcher is the software client program on your computer which you use to subscribe to podcasts and which then handles the chore of monitoring those podcasts and downloading them as new broadcasts become available. Some programs have built-in podcatchers, such as iTunes (a multi-function audio program) and Firefox (a Web browser).
Streaming is older, so we will cover it in detail first.
Streaming media -- from Wikipedia
Streaming audio/video from a web server -- a how-to guide with examples
There are two ways to do streaming. The full-fledged way is with a streaming server. Taking RealAudio as an example, as the content provider, you create a RealAudio file (.ra or .rm) which contains multiple copies of the recording, each at a different resolution. There is a "stub file" with the extension .ram, which contains the URL for the RealAudio server and identifies the particular RealAudio file to play. The RealAudio streaming server (which runs as part of your Web site) and the RealAudio player (A.K.A., ReaOne, which runs on the listener's computer) repeatedly communicate with each other concerning the user's connection speed and the current traffic conditions. As the conditions change, the server switches among the resolutions contained in the file to compensate.
The benefit is that the user automatically hears the highest quality audio which is suitable for their connection speed and traffic conditions. Notice that this "highest quality" may change more than once before the end of the file or broadcast.
A drawback is that this method often costs extra money or may not available from your Web hosting service.
Streaming Without a Server
The "simple" way to do streaming is possible because most modern media
players can do a form of streaming on their own. That is, they can
start playing an audio file without having to download the entire file
first when there's no streaming server on the Web site. The simplest
way to do this, from the standpoint of your HTML code, is with the
appropriate stub file for the media type you're using. As mentioned
above, for RealAudio, it has the extension .ram; in this case, the
file contains a normal (and complete) URL to the RealAudio file (e.g.,
http://www.YourSiteNameHere.com/podcast_01.rm). For MP3 files, the
extension is .m3u (yes, an MP3 playlist) (and the URL it contains
might be, for example,
Benefits include no extra cost and no additional server software.
One drawback is that, if you want to have multiple resolutions, to support different connection speeds, you have to provide them separately, with separate links, labeled so the user can distinguish them.
Problems with Both Methods
Whether or not either of the methods works for the user depends on how they have their computer and browser configured. Three real-life examples:
- One PC is set up so that, when the owner clicks on a link to an .m3u file, Firefox passes that file to Winamp, which then contacts the Web site for the MP3 file and then starts streaming it.
- On another PC, when the owner clicks on an m3u link in Internet Explorer (IE), IE opens a pane with the Windows Media Player plug-in, which streams the MP3 file.
- On a third, apparently misconfigured PC, when the owner clicks on an m3u link in IE, they get an error message.
If you want to see concrete examples, here are links to two sites. The first site contains MP3 files of speech and associated PDF files, and is updated weekly. (They are also podcast.) The second site has ReadVideo files in two resolutions, for low and high-bandwidth connections.
Podcasting -- from Wikipedia
RSS Validator -- checks to see that your RSS feed uses valid XML
http://www.howtopodcast.org/ -- Once upon a time, this contained useful tutorial instructions, but, as of the end of September 2006, it has been replaced by an "under construction" sign.
Same as the first example above for streaming. The site contains MP3 files of sermons and associated PDF files with notes for the sermons, and it is updated weekly. These are also podcast. The information about each sermon, both the audio and PDF files, is stored in a database. This database is used to generate both the regular HTML page and the XML RSS feed page. As a programmer, the LibriVox volunteer who created this page learned to write RSS-type XML so he could get the RSS feed to update automatically, since the database already existed when he added podcasting to the site.