How to Fix “Foo Out WASAPI” Errors in Windows Audio

Understanding “Foo Out WASAPI”: Troubleshooting GuideFooOut WASAPI (often referenced as “foo_out_wasapi”) is a popular output component used in Foobar2000 and other audio applications to deliver high-quality audio playback on Windows using the WASAPI (Windows Audio Session API) interface. It provides low-latency exclusive-mode playback, bit-perfect output, and advanced configuration options that audiophiles and professionals often require. This guide explains how WASAPI works, common problems with Foo Out WASAPI, step-by-step troubleshooting, configuration tips, and advanced diagnostics.

What is WASAPI and why use Foo Out WASAPI?

WASAPI is Microsoft’s modern audio API introduced with Windows Vista. It supports:

• Shared mode — audio streams are mixed by the system, which applies resampling and volume processing.
• Exclusive mode — the application has direct control of the audio device, allowing bit-perfect output with minimal latency.

Foo Out WASAPI is a third-party output component for Foobar2000 that leverages WASAPI’s capabilities to deliver:

• Bit-perfect playback in exclusive mode (no system resampling).
• Low-latency performance for real-time monitoring or DJing.
• Per-device configuration and advanced buffer controls.

Common issues and quick answers

• No sound after selecting Foo Out WASAPI — Often caused by incorrect device selection, exclusive mode conflicts, or driver issues. Check device choice and ensure the device isn’t used by another exclusive application.
• Crackling/popping — Buffer underruns or mismatched sample rates. Increase buffer size, enable shared mode, or set the player sample rate to match the hardware.
• Playback stutters only with certain files — File-specific sample rates or unusual bit depths may trigger automatic resampling or conversion problems. Verify codecs and convert to compatible formats if needed.
• Device unavailable / greyed out — The device may be disabled in Windows Sound settings or used exclusively by another app. Re-enable device or close the competing app.
• High CPU usage — Low buffer sizes and complex DSP chains can increase CPU load. Increase buffers or simplify DSP processing.

Step-by-step troubleshooting checklist

1. Confirm basics

   • Ensure Foobar2000 is up to date and foo_out_wasapi component is installed.
   • Restart Foobar2000 after installing or changing output components.
   • Reboot the system if device drivers were updated.

2. Verify Windows settings

   • Open Sound settings (Settings > System > Sound) and ensure the target device is enabled and set to the correct default if desired.
   • In Control Panel > Sound > Playback, right-click the device → Properties → Advanced. Note the “Default Format” sample rate/bit depth and whether exclusive mode options are checked.

3. Select the correct device in Foobar2000

   • Preferences > Playback > Output > Device: pick the intended WASAPI device. Try both the device name with “(WASAPI: Exclusive)” and the shared option to compare behavior.
   • If the device appears multiple times, pick the one that matches your intended mode (Shared vs Exclusive).

4. Test exclusive vs shared mode

   • Exclusive mode: Enables bit-perfect output but prevents other apps from using the device simultaneously. If issues appear, switch to shared mode to see if they disappear.
   • Shared mode: Uses system mixing and is more tolerant of mismatches.

5. Adjust buffer settings

   • In foo_out_wasapi preferences, increase buffer length if you hear pops/clicks. Typical values: start at 100–200 ms and adjust down if latency is critical.
   • If low-latency is required, try gradually reducing buffer size while monitoring stability.

6. Match sample rates

   • Ensure Foobar2000’s output sample rate (or the file’s native sample rate) matches the device’s supported rates. Avoid forced resampling unless necessary.
   • In Windows Sound Device Properties > Advanced, set Default Format to a common rate like 44100 Hz or 48000 Hz if unsure.

7. Disable enhancements and audio processing

   • In device Properties > Enhancements (or Spatial Sound), disable all enhancements and spatial audio that might introduce processing or conflicts.

8. Update or roll back drivers

   • Update the audio device driver from the manufacturer. For USB DACs, use the DAC vendor’s driver when available.
   • If problems began after a driver update, try rolling back to the previous driver.

9. Check for other exclusive apps

   • Close applications that might take exclusive control (games, other players, pro audio software). Use Task Manager to find suspect processes.

10. Test with simpler setups

    • Bypass DSPs, resamplers, or complex components in Foobar2000 to see if the issue persists.
    • Test with a different USB port/cable for external DACs.

Detailed troubleshooting examples

• Crackling only with high-resolution files

  • Cause: Device or driver cannot handle high sample rates in exclusive mode, or buffer too small.
  • Fix: Try switching to shared mode, increase buffer, or set Foobar2000 to downsample to a supported rate.

• No audio after switching to Exclusive

  • Cause: Another app holds exclusive access; device requires different sample format.
  • Fix: Close other apps; in Windows sound properties, ensure “Allow applications to take exclusive control” is checked/unchecked depending on behavior; try toggling it.

• Device doesn’t appear in Foobar2000

  • Cause: Device disabled, driver missing, or wasapi component not installed.
  • Fix: Re-enable in Windows Sound settings, reinstall drivers, confirm foo_out_wasapi is installed and enabled.

Advanced diagnostics

• Use Windows Event Viewer for driver-related errors (look under System logs).
• Use Process Explorer to inspect handles and which process is using the audio device.
• Use loopback testing: set the device as default and use another recorder to capture playback to verify the signal leaves the OS.
• For USB DACs, check power management settings and try different USB controllers (rear-panel ports on desktops).

Configuration tips for best results

• For bit-perfect playback: use exclusive mode, set device default format to match file rates when possible, and disable system enhancements.
• For stability across apps: use shared mode with moderately sized buffers (100–300 ms).
• For low-latency live monitoring: use exclusive mode with smaller buffers (30–80 ms) but only if your hardware/driver reliably supports it.
• Keep firmware and drivers of external DACs up to date.

When to seek help from device/vendor or Foobar2000 community

• Persistent issues after trying the above, especially if they occur only with certain hardware.
• If the DAC requires a custom driver or firmware update.
• If you suspect a bug in the foo_out_wasapi component — check Foobar2000 forums, GitHub issues (if applicable), or component changelogs.

Quick reference checklist

• Update Foobar2000 and foo_out_wasapi.
• Select correct WASAPI device and mode.
• Match sample rates; disable resampling if aiming for bit-perfect.
• Increase buffer on pops/crackles; decrease if latency too high and stable.
• Disable Windows audio enhancements.
• Update/rollback drivers; test different USB ports/cables.
• Close other apps that may take exclusive control.

If you want, I can:

• Provide step-by-step screenshots for Windows ⁄₁₁ settings.
• Suggest optimal foo_out_wasapi values for a specific DAC—tell me the model.