VDO.Ninja logo OBS Plugin for VDO.Ninja

macOS audio-interface guide

Send Scarlett inputs 1–2 and 3–4 with VDO.Ninja

Chrome normally exposes only the first stereo pair of a multichannel interface. OBS 32.2 can select other CoreAudio input channels, and the OBS VDO.Ninja plugin can publish the resulting OBS mix without a browser capture path or paid virtual-audio software.

What the plugin supports: one OBS audio mix, encoded as one VDO.Ninja-compatible Opus stream. Route Scarlett 1–2 and 3–4 into that stereo mix in OBS. This solves a combined mic-and-piano feed; it does not deliver four discrete channels to the receiver.

1. Prepare OBS on the sender's Mac

  1. Use OBS Studio 32.2.x. The current prebuilt macOS VDO.Ninja plugin package is for Apple silicon; an Intel Mac requires a compatible source build.
  2. Connect and power on the Scarlett before opening OBS.
  3. In OBS -> Settings -> Audio, set Channels to Stereo.
  4. Disable the Scarlett as a global mic in Settings -> Audio if it is enabled there. The two scene sources below should be the only Scarlett captures, which avoids duplicate audio.

2. Create a stereo source for Scarlett inputs 1–2

  1. In Sources, select +, then Audio Input Capture.
  2. Create a new source named Scarlett Mic 1-2.
  3. Select the Scarlett under Device and turn off Enable Downmixing.
  4. Set OBS Channel 1 to Scarlett device channel 1.
  5. Set OBS Channel 2 to Scarlett device channel 2.

If the channel selectors do not appear immediately after selecting the Scarlett, click OK and reopen the source's Properties. OBS populates the channel list after the device has initialized.

3. Create a stereo source for Scarlett inputs 3–4

  1. Add another Audio Input Capture and create a new source.
  2. Name it Scarlett Piano 3-4 and select the same Scarlett device.
  3. Turn off Enable Downmixing.
  4. Set OBS Channel 1 to Scarlett device channel 3.
  5. Set OBS Channel 2 to Scarlett device channel 4.

Do not choose Add Existing: the mic and piano need separate source instances with different channel maps.

4. Put both sources on the streaming mix

  1. Open Advanced Audio Properties from the Audio Mixer.
  2. Enable Track 1 for both Scarlett sources. Disable Track 1 for any source you do not want to send.
  3. Set mic and piano levels while watching the OBS meters. Avoid clipping at the Scarlett and in OBS.
  4. If OBS uses Advanced Output mode, confirm Settings -> Output -> Streaming -> Audio Track is 1. Track 1 is also the normal Simple Output default.

5. Choose how to keep the two camera views

Keep both Ninja camera tabs Mute their outgoing microphones. Publish a third, OBS-based stream for the combined audio. The remote side can listen without receiving its video.
Use one OBS program feed Add both cameras to an OBS scene, arrange the desired layout, and let the plugin publish that scene plus the combined Scarlett audio as one stream.
Pair audio with one camera Put one camera in OBS with both audio sources, publish it through the plugin, and keep the second Ninja tab video-only.

Audio-only receiving link for the three-stream option

Configure Tools -> VDO.Ninja Studio with a unique stream ID such as PianoAudioMix, then start streaming. At the receiver, open: 

https://vdo.ninja/?view=PianoAudioMix&novideo

Add the same password or room parameters used by the publisher. The &novideo option tells the receiver not to request the OBS video track, reducing network and decode load.

6. Test before the performance

  1. Play only the mic into Scarlett 1–2 and verify only the mic source meter moves.
  2. Play only the piano into Scarlett 3–4 and verify only the piano source meter moves.
  3. Listen to the remote VDO.Ninja link and confirm both signals are present and balanced.
  4. Mute the two browser-tab microphones and confirm there is no doubling, echo, or comb filtering.
  5. Save the OBS scene collection and profile so the sender only needs to open OBS and start streaming later.

Current limits and future work

  • The plugin publishes one OBS streaming destination and one selected OBS audio track. It does not publish OBS tracks 1 and 2 as separate VDO.Ninja stream IDs at the same time.
  • The supported browser-compatible output is mono or stereo Opus. Sending a four-channel Opus packet is not a substitute for two independently controllable stereo feeds.
  • If separate mic and piano feeds are required at the receiver, the plugin would need an auxiliary-output feature: multiple simultaneous VDO.Ninja publishers, each with its own stream ID and OBS audio-track selection. That is a larger feature than multichannel device capture; OBS 32.2 already provides the device channel mapping used in this guide.

References