WASAPI Exclusive
WASAPI Exclusive is Windows' exclusive-access mode for the WASAPI interface. Where regular WASAPI lets several applications share a sound output through the Windows mixer, exclusive mode hands the playback side of the device directly to one application — WATCHOUT — and lets it bypass the shared mixer.
The exclusivity applies to the render endpoint (the playback side). The capture endpoint of the same physical device is a separate endpoint and can still be opened by another process at the same time — useful for setups where WATCHOUT plays audio out while another service captures from the same card; see Sharing a Card with Audio Input below.
The cost of exclusive mode is that no other application can play through the device's render endpoint while WATCHOUT holds it, and the format must match the device's native mode exactly.
Configuring a WASAPI Exclusive Device
- In the Devices window, click Add → Audio Device.
- Set Node to the machine that hosts the physical audio device.
- Set Device Type to WASAPI exclusive.
- Choose the physical audio device from the Device dropdown. The default entry is available but exclusive mode behaves more predictably when you pin the device by name.
- Pick the Channels count supported by the device.
- Pick the Format — must match a format the device supports natively (no on-the-fly resampling in exclusive mode).
- Enable the device with the heart icon. Once enabled, the device is locked to WATCHOUT.
Properties
The properties are the same set as WASAPI (Device, Channels, Format, Latency), but two behaviors differ:
- Format must be native — exclusive mode does not convert. If you pick a format the hardware doesn't support exactly, the device fails to open. Use the format dropdown to pick from the device's reported native modes.
- Render endpoint is locked while enabled — other Windows applications cannot play through the device. Browsers, Teams, system sounds, and Windows alerts either silently fail or get redirected to another device while WATCHOUT holds it. The capture endpoint (microphone / line-in side) of the same device is independent and not locked.
When to Use WASAPI Exclusive
- You need lower latency than WASAPI Shared, but the device has no ASIO driver.
- The node is dedicated to WATCHOUT and no other application needs the audio device.
- You want deterministic format handling — no Windows resampling between WATCHOUT and the hardware.
When Not to Use WASAPI Exclusive
- The node also runs other applications that need to play through the same device (e.g. an operator station that also runs a control surface or video conferencing).
- You need WATCHOUT to share an ASIO card with another process that opens ASIO on the same card — ASIO is typically single-client per driver instance, so two processes cannot share it. Use plain WASAPI or WASAPI Exclusive on the playback side instead.
Sharing a Card with Audio Input
WATCHOUT's LTC Bridge reads timecode from an audio input on the node. The bridge runs as a separate process from the audio renderer that plays the show. If both services need to use the same physical audio device — playback from the renderer, timecode capture from LTC Bridge — the interface choice on each side determines whether they can coexist:
| Renderer side | LTC Bridge side | Can they share the same card? |
|---|---|---|
| WASAPI Shared | Any of WASAPI / WASAPI Exclusive / ASIO | Yes — the Windows mixer arbitrates. |
| WASAPI Exclusive | WASAPI / WASAPI Exclusive | Yes — the render endpoint is locked by the renderer, the capture endpoint is opened independently by LTC Bridge. |
| WASAPI Exclusive | ASIO | Often no — ASIO typically opens both directions of the driver and claims the whole instance, so the WASAPI Exclusive playback fails to start. |
| ASIO | Any | No if both target the same ASIO driver — ASIO is single-client. Whichever process opens the driver first wins; the second errors. Use a separate physical audio device for the other side, or switch one side to WASAPI / WASAPI Exclusive. |
If you need timecode capture and playback on the same physical audio device and the device has an ASIO driver you'd rather use, the safest pattern is: WASAPI Exclusive on the playback side, WASAPI (shared or exclusive) on the LTC Bridge side. Reserve ASIO for devices that are dedicated to one direction only.
Troubleshooting
For WASAPI Exclusive symptoms and fixes (device fails to enable, other apps lose audio, latency), see Audio Issues → WASAPI Exclusive.
Related
- WASAPI — shared-mode alternative; coexists with other apps.
- ASIO — usually lower latency on professional interfaces.
- Audio Devices — shared properties and the bus routing matrix.