WASAPI

WASAPI (Windows Audio Session API) is the default audio interface in Windows and the default choice for WATCHOUT audio devices. It uses Windows' shared audio engine: many applications can play to the same sound output at the same time, and Windows mixes their output together. WASAPI is the right choice for built-in sound chips, USB audio interfaces, and most consumer hardware where you do not need the lowest possible latency and other applications may need to share the device.

For lower latency on the same hardware, see WASAPI Exclusive. For professional interfaces with a manufacturer ASIO driver, see ASIO.

Configuring a WASAPI Device

To add a WASAPI audio device:

  1. In the Devices window, click Add → Audio Device.
  2. Set Node to the machine that hosts the physical audio device.
  3. Set Device Type to WASAPI.
  4. Choose the physical audio device from the Device dropdown. Use default to follow the Windows default audio device. Click Refresh if a newly connected interface does not appear.
  5. Pick the Channels count supported by the device (typically 2 for stereo, more for multi-channel interfaces).
  6. Pick the Format — sample rate and bit depth (for example 48000Hz, 16 bit).
  7. Enable the device with the heart icon.

Properties

PropertyBehavior
DeviceThe Windows audio device. The dropdown lists every WASAPI-visible interface on the node, plus a default entry that tracks the Windows default.
ChannelsChannel count as reported by the device. Limited to what the device supports — for built-in audio this is usually 2.
FormatSample rate and bit depth, presented as one combined choice (for example 48000Hz, 16 bit). WASAPI converts on the fly if the format does not match the device's native mode, at the cost of an extra resample. Pick the device's native format for the cleanest path.
LatencyThe ±100 ms manual offset described in Audio Devices → Latency. WASAPI's intrinsic buffering is set by Windows and is typically 10–30 ms — fine for most show audio but noticeable for tightly-synced live performance.

When to Use WASAPI

  • Built-in sound hardware on the node.
  • USB sound devices and consumer audio interfaces without an ASIO driver.
  • Two WATCHOUT services need to share the same physical audio device — for example, the audio renderer playing the show out of one direction of the device while the LTC Bridge captures timecode from the other direction. WASAPI is shared at the Windows-mixer level, so both services coexist without conflict. See Sharing a Card with Audio Input for the full compatibility table.

When Not to Use WASAPI

  • If the show needs WATCHOUT to own the sound output and bypass the Windows mixer, use WASAPI Exclusive or ASIO.
  • If you have a multi-channel card that WASAPI splits into several stereo-pair devices and the show needs the channel groups to phase-lock (multi-channel music, surround mixes), use ASIO so all channels share a single clock.
  • If audio is going to professional gear on the network, use Dante Audio.

Troubleshooting

For WASAPI symptoms and fixes (empty device list, distorted audio, latency, no sound), see Audio Issues → WASAPI.

  • Audio Devices — shared model and the bus routing matrix.
  • WASAPI Exclusive — lower-latency alternative on the same hardware.
  • ASIO — for professional interfaces with vendor drivers.
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