VoIP Hacks: Tips & Tools for Internet Telephony

Hack 36. From Podcasting to Skypecasting

With some simple recording tools, you can easily integrate Skypeand other VoIP calling softwareinto your podcasts.

Audio blogging, or podcasting, as it's called, is a form of amateur radio broadcasting that uses the Web as a means of distribution, just as blogging is a personal form of journalism that uses the Web for distribution. Podcasters record their broadcasts in MP3 audio files, and their audience downloads them for listening on a PC, iPod, or other portable MP3 player.

3.10.1. If You Build It, They Will Come

Creating cool content for podcasts isn't always easy. Without a broadcast license, it's not a simple thing to use (legally, anyway) copyrighted music in podcasts, since their distribution is heavily protected by the long legal arm of the Recording Industry Association of America (RIAA), the same folks who dumped millions into suing harmless teenagers who download Cold-play singles that sell for 99 cents apiece through iTunes. But I digress.

The point is that podcasts can get old really quickly unless you have a constant flow of good audio content, and this doesn't come easily. Fortunately, the talk format, which is stridently avoided by most of those downloading teenagers I mentioned earlier, is a content miracle. It won't get you in trouble with the RIAA, either.

But you don't need to have Rush Limbaugh's golden microphone or Howard Stern's subtle wit to master the talk format in your podcasts. You just need to be able to record your Skype (or MSN Messenger, or AIM) VoIP conversations, call them "interviews," and podcast them! You can also use your computer to record your traditional phone calls for podcast purposes, using tools like Phlink [Hack #15].

3.10.2. Mac Podcasting Tools

Using a tool like WireTap [Hack #23], grabbing the audio from a Skype conversation is a snap. Then it's just a matter of editing it down (the talk format isn't forgiving of coughing fits or belches) and converting it to MP3 format. Using Cacophony or GarageBand, you can insert the recorded interview into the middle of a podcast, or give it some bumper music just like the pro talkers.

Another cool app for recording audio from VoIP conversations on Mac OS X is Soundflower (http://www.cycling74.com/products/soundflower.html). This app actually lets you treat the output of any application as a sound input device in other applications, so you can use it to record Skype conversations and to process them later on so that they sound differently. With GarageBand, for instance, you can add reverb to a live sound input before adding it to the podcast. Or you can run it through EQ, compress it, or do a host of other cool stuff to it to whip it into shape for your own radio show.

Great for sound effects, GarageBand, in concert with Soundflower, could be the makings of the ultimate radio drama podcast. You can apply reverb, echo, and pitch shifting to sound inputs in GarageBand, taking your dramatic podcast to the Grand Canyon, or to a village of squeaky-talking munchkins as in The Wizard of Oz.

3.10.3. Windows Podcasting Tools

A great place to start on your quest to make the ultimate Skypecast is Total Recorder Standard Edition, a Windows shareware tool that you can grab from http://www.highcriteria.com/. Like its Mac counterpart, WireTap, Total Recorder lets you intercept audio from one or more channels, like the sounds from a Skype conversation, and save it to a file that you can integrate into your Skypecast.

As you can see in Figure 3-9, the creators of Total Recorder were thoughtful enough to create the "Record also input stream" option, which automatically mixes the microphone input channel with the sound output you're recording, simplifying the task of recording your Skypecast (that is, unless you don't want your voice to be heard during the interview). Once you've saved a WAV file with your interview, you can edit it into the rest of your podcast using Windows Sound Recorder or your favorite sound editor.

Then, if your editor doesn't support saving the whole thing as an MP3, you can run the finished WAV version through SoX (see Chapter 2 for a refresher on SoX) to make it ready for publishing to the Web:

$ sox my_skypecast.wav my_skypecast.mp3

Chances are that your Linux box already has SoX installed. If not, or if you don't have a Linux box, you can grab SoX for Windows at http://prdownloads.sourceforge.net/sox/sox12177.zip?download.

3.10.4. Three's a Crowd

One of Skype's knock-dead features is its multiparty conference-call support. Up to fifty participants can talk together, just like a traditional conference call. By recording a conference call, you can create a podcast-friendly "panel discussion." Even better, if you use Alex Rosenbaum's Skype Answering Machine software to greet callers while you're away [Hack #37], you can even use Skype to do the broadcasting, via the greeting the Skype Answering Machine plays for callers as they Skype you. Check out the next hack for the details.

3.10.5. Experiment Your Way to a Perfect Skypecast

A lot of variables are involved in recording a podcast. Many of the fundamental techniques of voice recording carry over from the radio broadcasting industry. The human voice is very dynamic. It's very quiet one moment, and very loud or boomy the next. Yet, the human ear prefers a much more controlled aural dynamicthat is, we'd rather listen to the human voice at a consistent volume level, especially when there's background noise. That's why professional radio broadcasts are compressed, or processed so that the quiet moments are louder and the loud moments are quieter. This way, the sound is at a much more consistent volume level (traditional phone calls work in much the same manner).

Microphones matter. A microphone with a windscreen (that afro-shaped sponge you see on news reporters' microphones) will reduce the unprofessional-sounding harshness caused when pronouncing the letters f and p. A microphone with a wide frequency response range will pick up more of your voice than a laptop's built-in mic or a cheap $9 USB mic. Of course, a good mic on your desk won't help your interviewee sound any better. They'll need a good mic, too.

Using different voice chat tools (iChat, Skype, Yahoo! Chat, etc.) will certainly deliver different levels of compression and equalization, and you might discover that you prefer one over the other. Using different post-processing tools (GarageBand, AcidPro, etc.) will afford you greater flexibility in making your podcast sound the way you want it to. But don't expect any of these applications to have the magical "podcast preset." You'll need to experiment until it sounds like what you think a broadcast should sound like. If you're talking a lot, listen to talk radio for inspiration (not only with respect to production, but also the subject matter).

3.10.6. See Also

• Podcasting Hacks (O'Reilly)