This guide will make use of the VoiceMeeter Banana software to split audio for the selective recording feature in Streamlabs OBS. For example, removing alert audio from your recording and allowing it to come through to you and your stream.
This guide builds on top of the Split Audio using VoiceMeeter Banana guide, so if you have not set up VoiceMeeter Banana yet, please follow that guide first to have the starting point for this guide.
Using both virual outputs of VoiceMeeter Banana
In addition to the initial set up, you also will be using the VoiceMeeter Aux Output (VB-Audio VoiceMeeter AUX VAIO), set as the Mic/Auxiliary Device 2. Your microphone can be set in the Mic/Auxiliary Device 3.
Browser Source Audio via OBS
The next thing to do is have audio from browser sources and widgets, such as the Streamlabs Alert box go through the audio system of Streamlabs OBS instead of having the output to the default playback device of Windows, mixing it with any other audio, such as the game audio.
To do this, open the properties of the browser source or widget and check Control Audio via OBS. For widgets, like the Alert Box widget, this is found under the “Source”. After this, you would need to monitor these sources in order to hear the audio again, more about this down below!
Set the Audio Monitoring Device
By default, the monitoring device is the same default playback device set in Windows, which would mean if you were to monitor any sources it would be mixed with any other audio and end up on the recording again. Set the Audio Monitoring Device found in the Advanced Settings of Streamlabs OBS to VoiceMeeter Aux Input (VB-Audio VoiceMeeter AUX VAIO). Now, game audio (default desktop) and monitored sources are separated from each other, each to one of the virtual inputs that VoiceMeeter Banana has to offer.
Advanced Audio Settings
Open the Advanced Audio Settings by clicking the ⚙️ icon above the Mixer in Streamlabs OBS. In here set the sources that you want to hear and be on stream only to “Monitor Only”. Furthermore, you would need to set the audio tracks, where track 1 will be used for the stream and additional tracks will be used for the recording.
In the following configuration the Alert Box is being monitored and the audio is not on the recording or stream. The stream will get the audio from VoiceMeeter Banana virtual output and the microphone (track 1). The recording will get the audio from the VoiceMeeter Banana virtual aux output (track 2), the microphone (track 3), and optionally the stream audio that includes other audio sources again (track 4).
Advanced Output Mode
In order to select which audio tracks you want to use for stream and recording, you would need to use the Advanced Output mode in the Output Settings of Streamlabs OBS. For Streaming select track 1 and under Recording check track; 2, 3, and 4. Make sure the Recording Format you selected supports multi-track recording, such as TS, MKV, or MP4.
Route audio with VoiceMeeter Banana
Back to VoiceMeeter Banana again where you will “patch” the audio from one of the inputs to one of the outputs, Virtual Output B1 is used for the stream and Virtual Aux Output B2 is used for the recording.
VoiceMeeter Banana has now both virtual inputs in use, the main would be the default desktop audio which usually contains game audio and the aux input contains monitored sources audio. The monitoring you want to “patch” only to A1 and B1, your headset and stream where the desktop audio you want to patch to A1, B1, and B2, your headset, the stream and recording.