Streaming Audio Between Macs

Airplay you say? Between Macs, not an Airport Express or Apple TV. Airtunes you say? Well… I’m watching videos and streaming the audio to a different computer because it’s connected to the awesome speakers. And the lag… 2.5 seconds. Seriously.[1] Shairport? Same problem. Banana TV? Abandoned. And they have audio quality issues. And I could run down another half dozen systems that didn’t even work.

So, Mac to Mac, audio only. Fortunately, a friend of mine dug up this blog, which links to another blog that no longer exists. But it does provide a high-level overview, and I’m here to bring the step-by-step back.

Things you’ll need:

Sending Mac

  1. Install Soundflower (and reboot) and AU Lab
  2. Set System Audio to Soundflower (probably 2 channel) (System Preferences -> Audio -> Output)
  3. Run AU Lab
  4. Under the Stereo In/Stereo Out configuration, set the Input to SoundFlower and the Output to Built-in Output. Create document
  5. Under the Output, there’s an Effects dropdown. Set that to AUNetSend. Optionally configure a name, port, or password. Also, select Audio Quality. Both of my computers are on a gigabit LAN, so I’m streaming 24 Bit Apple Lossless with no problems.

Receiving Mac

  1. Run AU Lab
  2. Under the Stereo In/Stereo Out configuration, set the input to None and the output to Built-in Output. Create document
  3. Go to the “Edit” menu (as in menu bar) and select Add Audio Unit Generator. Choose AUNetRecieve
  4. In the new window, the share name you created earlier should appear. Select it and press Select Host and then Connect. If “Status” is “Connected”, you can close this window (you can bring it back by selecting the Generator and going to Edit -> Edit Selected Generator)
  5. Make sure the window with your Generator and Output says “Audio Engine Running” at the bottom. If it doesn’t click it to start it

Bam! High quality, low latency audio streaming between Macs. Rock out :)


This solution seems to accumulate lag too over several hours :(. No idea why. Resetting the AUNet connection from either end resolves it though (on the sender, you can edit the AUNetSend effect and click “Disconnect” and then “Connect” again). It should last through a movie at least. Well… maybe not LotR extended edition…

[1]Support says they’ll be rewriting the audio subsystem eventually. After they do something with Windows…
Thanks to this site, which got me most of the way here

About Bion

I'm a software developer at Modo Payments, a mobile payment provider. When I'm not hacking away the office, you I'm usually at home hacking on something else. Or practicing Aikido. Anyway, I just post things here that Google couldn't help me with, so maybe it'll help you in the future. Since you're reading this, I guess it worked :)
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