In the way we'll use Loopback today it's best to think of it as a software pipe that pretends it has a hardware device on each end: audio input on one and audio output on the other. This lets you pass audio into it from one app and pull that same audio out of it from another. Many apps on your Mac have the ability to choose one device as their audio input. Very few have the ability to capture multiple audio devices, and even fewer can capture both audio devices and audio from applications themselves. This makes the seemingly-simple task of sharing both your microphone and, say, audio from QuickTime Player with someone on the other end of a Skype connection quite tricky.
Skype allows you to set one audio device as its “microphone.” The problem is QuickTime Player is not registered with your system as an audio device. It's just an app that plays through an audio device. To solve this we first have to capture QuickTime Player's audio, then we have to make it appear as though it's coming from an audio input device so that Skype will accept it. This is where using both Audio Hijack and Loopback together can create some magic.
First, we launch Loopback. By default it will create a very simple pass-through device (if you already have Loopback simply click “New Virtual Device”). Really the only thing I've changed from the defaults in the screenshot below is to give the Loopback pass-through device the name “Loopback-Skype Input.” That name is simply a label for my own reference, and doesn't affect its functionality.
Next, we launch Skype and set this newly-minted Loopback device as our “Microphone.”
Finally, we launch Audio Hijack and add both QuickTime Player and our Loopback device to a session. Once we activate that session by clicking the Start button in the lower-left corner, any audio from QuickTime Player will be played into our “Loopback-Skype Input” device. With Skype set to use that as its microphone, the person on the other end of the Skype call will hear our QuickTime audio!
Now let's say we want that person on the other end to hear both our QuickTime audio and our voice. Easy, we just add our microphone as an additional Source to our Audio Hijack session.
That's it! You've got a Skype call going and your guest can hear you and your audio. Unfortunately, you can only hear your guest, not yourself. No worries, though, if we take what we learned in our recent tip about monitoring ourselves and add the QuickTime/Loopback concept to that, we get a fully-functional Skype call that we can hear and record!
(Click the image for a larger view)
Now that's really it. Time to podcast!