Find Installed Audio Processing Objects in Registry

Audio Processing Objects (APOs) provide software-based digital signal processing for Windows audio streams. You can inspect both globally installed APOs and device-specific active processing objects using the Windows Registry Editor (Regedit). This guide details the exact registry paths required to view installed APO classes and their associated endpoint configurations.

1. View Globally Registered APOs

To view the complete list of system-registered APOs installed on Windows, navigate to the system class catalog:

Registry Path: HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AudioEngine\AudioProcessingObjects (Alternatively: HKEY_CLASSES_ROOT\AudioEngine\AudioProcessingObjects)

Under this key, each subkey is a GUID representing an installed APO component (such as Stream Effect, Mode Effect, or Endpoint Effect APOs). Selecting a specific GUID subkey allows you to inspect values such as: * FriendlyName: The descriptive name of the APO or its developer. * Copyright: Vendor or driver provider information. * MinInputConnections / MaxInputConnections: Channel configuration limits. * CLSID: COM class identifiers pointing to the underlying dynamic link library (DLL) registered in HKEY_CLASSES_ROOT\CLSID.

2. View Active APOs Assigned to Audio Endpoints

To check which APOs are assigned to specific playback or recording devices, check the Multimedia Device endpoint keys.

Registry Paths: * Render (Playback Devices): HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Render * Capture (Recording Devices): HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\MMDevices\Audio\Capture

Steps to Inspect Active APOs: 1. Expand the Render or Capture folder. 2. Select the specific device GUID folder. 3. Open the FxProperties subkey under the device GUID.

Inside FxProperties, the assigned APOs are listed under standard PKEY values: * Stream Effect (SFX): {d04e05a6-594b-4fb6-a80d-01af5eed7d1d},5 (or ,1 in legacy drivers) * Mode Effect (MFX): {d04e05a6-594b-4fb6-a80d-01af5eed7d1d},6 (or ,2 in legacy drivers) * Endpoint Effect (EFX): {d04e05a6-594b-4fb6-a80d-01af5eed7d1d},7

The string data contained in these values matches the registered APO GUIDs found in the global AudioProcessingObjects registry path.