Selecting audio ports on Mac Pro’s in lab environments.

Michael — Mon, 01 Dec 2008 23:04:55 +0000

Where I work, Apple computers is the standard for Communications majors. That being said, we’ve got a few labs with Mac Pro’s and 13 individual editing suites. The edit suites provide the students with a cubical shunned away from the world by a sliding glass door allowing their video creativity juices to flow. In the labs, there is a desktop at the front of the room dedicated for the teacher with wall-mounted speakers and a projector. Although all this hardware looks great on the outside, one issue that came up was audio. Since the change to Intel chips, the three audio sources (headphone, audio speaker and line-out) which if you remember, would auto-switch based on what was plugged in, has now changed to three independent sources. What this means is if a user wants to make any changes to how audio gets routed they must make the change manually. To add to this issue, my environment consists of users logging in individually every time they use a machine whether it’s in a classroom or in an editing suite. If the audio changes were a global change, I wouldn’t be having this issue; but because it has a default value (front speaker jack) for each person that logs in, I’m stuck with another problem. Which if you are thinking, I’m leaving all my grunts and complaints about OSX’s “features” in a lab environment for another blog post.

Software named Soundsource made by Amoeba makes the change pretty simple by adding an icon on the toolbar. This is a pretty slick piece of software, but this still doesn’t fulfill the user login for teacher stations in the classrooms and the editing suites which have rear speaker input. You can suggesting plugging the speakers into the front plug, but give it a day and someone would have pulled it out.

In my search for solutions, I pondered if there was any way to change the audio configuration via command line. This would at least make it a viable option to use a launchd user agent once the user logs in. Scouring the internet, which I must say I do a pretty good job, I found a utility called Switchaudio. This small utility is just what I’ve been looking for. It adds a way to select the input or output audio sources from the available sources (as shown on the right). After this, everything else fell into place. I ended up putting this file in the /usr/bin directory to make the utility easily accessible. Then I created a launchd user agent using Lingon so whenever a user logs on, the output audio changes to whatever I want (in this case “Built-in Line Output”).

Lastly, to make the changes in the affected labs and 13 video editing suites, I made a package installer and pushed it out using Remote Desktop.

Pretty simple once I figured it out…

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Selecting audio ports on Mac Pro’s in lab environments.