3. Capturing mixes

The obs-asio plugins allows capture of audio inputs of your ASIO device. Normally output audio is not available to capture with the exception of hardware implemented loopback channels (outputs which are copied by the device to an input). This feature is often a complete toss up depending on the device, and is made in general more confusing / frustrating to deal with especially since daws list these output channels and may make it seem they can be read from. Normally however these output channels are 0'd (muted) out so that applications like daws can write audio. This is doubly confusing if you've spent time looking at the asio standard and the asio api giving access seemingly to the output buffers directly. To avoid people getting as confused and frustrated as we were when finding this out, we simply do not list output channels. TLDR; if we were to list output channels, you'd likely be yelling at us that output channels don't work, and unfortunately you'd be exactly right.

For anyone however looking to capture outputs, all is not lost. You can absolutely work around this, and so we'll leave an example of how here. To do this we abuse virtual asio audio drivers to route output back to an asio device as an input. Doing this effectively creates a mock loopback channel. The following tutorial explains how to use Reaper's rearoute. Many professional daws and audio software have a similar feature.

0. Install Reaper and make sure ReaRoute is ticked in the install options (it's optional by default).
1. Create tracks and make your mixes in Reaper.
2. On the track you want to capture with obs-studio, click on the Route button
   
3. The Route panel appears.
4. Select the dropdown Menu Add new hardware output....
   Add a Rearoute output (in the screenshot, it's a stereo output to ReaRoute 3+ reaRoute 4).
5. In obs-studio, create an Asio Input source
6. Select the ReaRoute channels 3 and 4
7. Check that audio is streaming from Reaper to obs-studio in the volume meter: