I've been asked several times how I create the RealAudio portion of SIGPC. Authoring streaming media content for Web delivery sounds like a rather complicated task. In fact, it's relatively easy.

Recording RealAudio

After I write the text version of each article, I then record it as a Windows .WAV file. I use a headset combination that has both earphones and a boom microphone. This is plugged directly into the audio-input jack on my computer. I use a simple sound editor to post-process the recorded audio, removing background noises and generally cleaning up the recording. I then save the edited file back to disk.

One problem with .WAV files is that they quickly become very large. For about 8 minutes of recording time, the file balloons to over 45 megabytes. It is for this reason that I use an external SCSI disk to store the .WAV files.

The .WAV files are then converted to RealAudio format using Real's Real Producer Plus G2. This is the commercial version of their free Real Producer G2 product. The G2 moniker indicates that this program is a member of their second generation streaming media product line. The conversion between .WAV and .RM (Real Media) files is automatic. The resultant .RM file is much smaller than the original .WAV file: a reduction from 45 megabytes to about 800 kilobytes.

[back to the top]

Putting RealAudio on the Web

The RealAudio files are part of the same collection of files that belong to specific articles. To upload media files to a Web site, I use the same technique as any other HTML file: webpost. The files are transferred automatically when I transfer the rest of the content.

The links on the Web pages for RealAudio files are in fact to .RAM files. These are simple redirections that point the Real Player to the actual .RM file. The RealPlayer program is launched by the user's browser as a helper application, and the Web server begins streaming the audio.

For example, the HTML code used in this page to launch the RealAudio version of this article is as follows:

For truly high-fidelity audio, Real files should be streamed from a RealMedia server. However, I stream the files using regular HTTP, in part because the audio is relatively undemanding mono. Using a proper RealMedia server becomes more important when you are streaming video, when the server has to maintain many streams simultaneously, or when you want to take advantage of some of the special capabilities of the G2 technology. For example, "SureStream" is a feature that creates a single RealMedia file for playback at several bandwidths, from 28.8K to 10Mbps, automatically.

[back to the top]

Real Experiments

At the University of California, Riverside, I've been conducting a few other Real experiments. I'm recording my lectures for the "CS180: Introduction to Software Engineering" undergraduate course and then placing the lecture online in RealAudio format. I use a regular pocket recorder, which records onto miniature tapes that can hold 60 minutes per side in extended mode. I then use the same Real Publisher Plus G2 program to transcribe the recording from the tape into RealAudio in real time.

Although the resultant audio quality is not very high, this low-tech and low-cost approach to distance learning has proven quite popular. I also place my slides online at the course Web in Acrobat format after the lecture. This means students can follow along with the complete presentation at their leisure.

More recently, I've been testing Microsoft's NetShow streaming media technology. I haven't placed any material online yet in NetShow format though, mainly because RealAudio commands a larger market share. Most users already have the RealAudio application or plugin available on their computers. Newer streaming media techniques are becoming available, such as Geo Interactive's Java applet-based WebRadio. It remains to be seen how successful any of these alternate streaming media formats will be.

Next quarter I may use a digital video camera to record my lectures in streaming audio and video for later playback. Now that would be the real thing.

[back to the top]