Podcasting

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Figure 1. Steps in podcasting. Digital media files are created and made available to the internet using a file server. Audience members with internet access can find the podcast files using special software for reading podcast feeds and download the desired media files. A popular feature of podcasts is that they can be easily off-loaded from full-sized PCs to portable media players.

Welcome to the Wikiversity learning project for podcasting.

The term Podcast is most often used to refer to audio, but video and other media formats can also be distributed as podcasts. Regardless of the types of media transmitted, the common element of podcasting is use of a Web feed to make a list of digital files available to an audience. Audience members can use specialized software applications, web feed readers, to search for and view podcasts.

This learning project helps participants learn how to access existing podcasts and handle the digital media that you download from podcasts, create digital files that can be included in podcasts and make your own podcasts.

Digital media used in podcasts[edit]

There are a few digital media file types that are most commonly used in podcasts. In addition to emphasizing popular file types (such as MP3 audio), the discussion of file types (below) is guided by the biases of the Free Culture movement. Some file types are patented and in the past some patent holders have charged fees for the use of patented file types. In other cases, the details of a file format are kept secret, limiting the availability of software that can use the file format and allowing a company to sell compatible software at monopoly prices.

Some digital media file types are freely available for use without patents or other trade restrictions. Of particular interest are digital video file formats. The only video format allowed for upload to Wikimedia Foundation projects is the Ogg file format which is an Open source format. Software to allow you to play Ogg format audio and video files can be obtained at Xiph.Org Foundation website. Wikipedia maintains Help pages for the Ogg file format.

In addition to audio and video, other media types such as Portable Document Format (PDF) can be delivered by podcasting. For example, Wikinews has offered a PDF podcast.

Making digital media files for podcasts[edit]

Creating Ogg videos[edit]

To allow as many people to play video content as possible, it should be encoded into the open-source Theora format. The following are instructions on how to do so:

Mac OS X instructions[edit]

Mac PPC[edit]

This will not work on any Intel Mac, because ffmpeg2theora is not available in a Universal Binary (Note: version 17 says it is universal, but I get "Illegal instruction" when trying to use ffmpeg2theora on an Intel iMac). You should either follow these instructions on any G3, G4 or G5-based Macintosh, or use either Boot Camp or Parallels Workstation to convert the video under Microsoft Windows.

  1. Create the video that you would like to put online, using whatever software you would normally use. When you've finished, export the video.
  2. Download the free converter StreamClip, and open the file you wish to convert to Theora. Click the Play button to ensure that it plays correctly.
  3. Select "Export to Quicktime" from the File menu.
  4. In the new window, select "Sorenson Video 3 Compressor" from the Compression drop-down menu, and drag the Quality slider all the way to the right (100%). Ensure that Sound is set to "Uncompressed".
  5. Click "Make movie".
  6. Download ffmpeg2theora universal binary from here. Double click on the .zip file, which will extract the .pkg file. Double click on the .pkg file to install it. This will install a command-line application that can only be invoked from a Terminal window, using parameters. See (note on using the ffmpeg2theora command line application)
  7. Open up the Terminal application, which can be found in the Utilities folder in Applications (you can jump there by typing apple-shift-U from within the Finder). A few lines of text should appear, the last of which should say something like "davids-ibook-g4:~ username$".
  8. To test the installation was succesful, type "/usr/local/bin/ffmpeg2theora" (without quotes) and ENTER. You should see something similar to (this).
  9. Press the up arrow to bring back the last command, and go to the end of the line.
  10. Now, press the spacebar once to add a space, and copy and paste the following text into the Terminal window, without the quotes: "-o outputfilename.ogg -V 512 -K 48 -A 64 -c 2 -H 44100". Note: "-V 512 -K 48 -A 64 -c 2 -H 44100" are specifications for properties of the movie such as video and audio data rates. You do not need to specify these values; the default values are often fine.
  11. Add a space to the end of that line
  12. Finally, drag the video file that you created earlier onto the Terminal window. The text should now look something like this: "davids-ibook-g4:~ username$ /Users/dweeb/Desktop/ffmpeg2theora -o outputfilename.ogg -V 512 -K 48 -A 64 -c 2 -H 44100 /Users/dweeb/Desktop/Editing\ tutorial-large.mov"
  13. Press return. The video will now be converted into a file with the name outputfilename.ogg and in the same folder as the original file (not for me...you may have to search for it), but with the .ogg extension. It can be played using either VLC or MPlayer OS X.
  • Tip: If you have problems synchronizing the audio and video try using --sync
  • Note: With version 0.1.7 of the XiphQT QuickTime package, you can use iMovie to make ogg format videos. This may be all you need for some things, but there are very few controls. In iMovie, file menu, share, compress for setting to expert, then click share. If you set the export option to "movie to ogg" then it seems to only make a 720 x 480 pixel movie. I could not get a sharp image for fine text in screencasts. Other types of video and the audio seems good with the default settings.

Resources[edit]

See also[edit]

Tools for creating internet content
See also: Digital media workshop - Related discussion: Free content

External links[edit]