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Five Fun Ways to Play with Audio Hijack Pro

by Erica Sadun

I love my copy of Audio Hijack Pro. It's not little or shiny or white, but it's my most indispensable iPod accessory. I use it for so many things: capturing music, mixing audio, adding real-time sound effects, and more.

In this article, I'm going to share a few of my favorite ways to play with Audio Hijack Pro. These are not the only ways I use the program, but they're some of the more fun ones. They range from digitizing legacy music from my old long-playing vinyl albums to time-shifting radio shows to bypassing digital rights management and more.

Without further ado, here they are. My top five Audio Hijack Pro tricks:

1: Digitizing Legacy Music

I don't care how convenient and how easy it is to replace my legacy LPs and cassette tapes with higher-quality music from the iTunes store. I've already paid for my music and I'll keep playing that old stuff as long as I can. And, where possible, that music is going onto my iPod.

Enter Audio Hijack Pro. Its silence detection feature can digitize an entire album at once while automatically splitting it into individual tracks.

The Silence Monitor feature appears on the Recording pane. It allows you to select when to start a new file based on the kind of audio being played (analog or digital).

For legacy recording, choose Start New File (Analog) from the pop-up menu. This option starts a new file whenever a signal drop of -30db occurs for two seconds.

figure 1
Figure 1. The Silence Monitor automatically detects the pause between successive tracks.

I've tested this out with cassette playback, radio, and LPs. It's worked great for everything I've thrown at it, almost always splitting where it should, except for the one or two odd cases where a composer stuck a pause deliberately into a track.

Pseudo Stereo

figure 2 Figure 2. The MDA Stereo module creates pseudo-stereo audio files from mono sources.

Audio Hijack Pro comes bundled with a fair number of digital signal processing modules. One of these, the MDA Stereo filter, proves particularly handy when working with old mono audio.

MDA Stereo uses Haas delay and comb filtering to synthesize mono signals into stereo. It's not just doubled mono, and it sounds a lot better. By applying this filter while digitizing, you create pseudo-stereo audio files better suited for iPod playback.

To use this module, open the Effects pane. Click on any of the boxes and choose VST Effect -> MDA Stereo. Audio Hijack Pro adds the filter. It gets applied when you record.

Tip: Use silence detection when hijacking Internet radio sites, like the excellent (and newly ad-supported), to split the feed into individual tracks.

2: Recording Your Skype or iChat Conversations

You've just made an internet phone call to relatives overseas. Did you record it so you could share with your immediate family? Why not? Or how about that business chat you had with your immediate boss? Did you capture it so you could review it later and make sure you're on target with all her bullet points? Perhaps you should have.

Recording voice conversations isn't as easy as it might first appear. You need to record both your voice going out as well as your partner's voice arriving into your computer. And you want to hear both these sources blended at normal audio levels. Fortunately, Audio Hijack Pro can handle this complicated situation.

figure 3 Figure 3. The Application Mixer allows you to select a secondary application for audio mixing.

The secret lies in mixing the two audio streams with the Application Mixer effect. You'll need to start by launching Skype or iChat and then set up Audio Hijack Pro before placing your call. Here's how.

In Audio Hijack Pro, hijack your microphone normally as an Audio Device. This allows you to record your outgoing audio.

The real magic happens in the Effects pane. There, click on any of the empty squares and then select 4FX -> Application Mixer. A control panel opens.

Click Select and navigate to Skype (or iChat AV, depending on the program you're using), select it and click Choose. This sets the secondary application audio for the mix.

Click Hijack. The mixing starts instantly. When you Record, you'll capture audio from both sources. You're now ready to place your call.

Tip: The Crossfade slider lets you adjust the mix between the Source (your microphone) and the Application (Skype or iChat AV).

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3: Adding Sound Effects to Your Podcast

Audio Hijack Pro's Application Mixer effect does a lot more than just capturing two-party Skype conversations. It makes it possible for you to add some great special effects to podcasts.

For this, QuickTime Player has an advantage over iTunes: it lets you play and control more than one file at a time.

You'll need to set preferences to do this. Choose Quicktime Player -> Preferences and open the General settings. Uncheck "Play sound in frontmost player only" and check "Play sound when application is in background." These settings allow QuickTime Player both to handle multiple sounds and to continue playing when it's not the foreground application.

Organize your QuickTime windows. Load your favorite background tracks, bumpers (start- and end-of-segment music clips), and sound effects (laughs, applause, and so forth). Arrange them in a logical pattern around your screen. Make sure you've got all your sounds queued correctly so they'll start reliably when you need them.

figure 4
Figure 4. Set up your favorite background tracks and bumpers in QuickTime Player so you can easily access them while recording.

In Audio Hijack Pro, hijack your microphone. Plug in your headphones and redirect the output to them with the Input pane. You'll want to carefully monitor the mix between your sound effects and your voice.

figure 5 Figure 5. Raise the input to get the best voice strength for your mix.

In the Effects pane, add the Application Mixer. For this case, select QuickTime Player as your secondary application.

The input gain knob on the Application Mixer plug-in lets you strengthen your voice signal before the mix. Adjust this until you're satisfied with the quality of your sound balance. A good clear voice signal is essential for podcasting.

Once you're satisfied with your mix, you're ready to record. As you start the capture, turn your attention to QuickTime Player. Here, you can use your organized sounds to ornament your podcast.

Tip: Use your sounds to keep your podcast lively, building the pacing and audio experience you need.

4: Time-shift Radio Shows

Addicted to talk radio? Don't like to miss your regular fix of Car Talk or All Things Considered or Rush Limbaugh? Hook up a radio to your Mac and capture your fave radio shows in an iPod-friendly format. Use either a Mac-specific radio tuner solution or just connect a normal AM/FM radio into a Griffin iMic.

Audio Hijack Pro's Schedule feature allows you to automate recordings. Select a specific date and time or choose a repeating appointment, such as every Saturday at 10:00 a.m. At the time you specify, Audio Hijack begins its capture using the application and hardware you specify.

figure 6
Figure 6. Schedule options appear on the Input settings page for each application.

To help with timed recordings, you'll want to activate Schedule Helper. Choose Audio Hijack Pro -> Install Extras and click Install. Schedule Helper allows your timers to operate at all times, regardless of whether or not Audio Hijack Pro is open and your machine is awake. You'll need to authenticate with an Administrator password to do this upgrade.

Tip: Using an external radio? You'll need to keep it on and tuned. That way the signal's ready when Audio Hijack begins its recording.

5: UnDRM Your Music

It seems kind of wacky to record music from iTunes, but I end up doing that a lot. I like to be able to play the music I've already bought, particularly on my PocketPC when I go to the gym. I don't like seeing that "protected files cannot be converted to other formats" message.

figure 7
Figure 7. Grrrrrrr.

Audio Hijack Pro lets you hijack iTunes just like you'd hijack any other application. I just turn on the Silence Monitor, set my capture to medium MP3 (I am not, as you might have guessed, a big audiophile perfectionist) and play back my Purchased playlist.

A few minutes later, my music is ready and waiting for me.

Tip: Turn off your email and any other background programs while hijacking music to produce the cleanest captures. Hijacking can be processor intensive.

Final Thoughts

The tricks you just read about are just a sampling of what you can do with Audio Hijack Pro. I've been using the program for a few years now and find it amazingly helpful for all sorts of unexpected reasons. It's a fun, hacky kind of program that you can always find new uses for because it's a general handy tool rather than a narrow software solution.

Mac OS X only, $32 (trialware available), Rogue Amoeba

Erica Sadun has written, co-written, and contributed to almost two dozen books about technology, particularly in the areas of programming, digital video, and digital photography.

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