Detailed information on the Windows Audio device insert driver (also known as APO). What APO stands for, how to set it up, and why is it a good alternative to the Virtual Windows audio driver (WASAPI).
In this article:
- Audio Processing Object
- Setting up with Windows audio device insert (APO)
- Essential questions answered
Audio Processing Object (APO)
Audio processing objects (APOs) provide digital signal processing (DSP) for Windows audio streams. Similar to plugins in DAW, an APO insert is an object hosted in Windows Audio Engine.
Once an Output Preset is created in the SoundID Reference app (with the APO driver selected), the APO is inserted directly into the Windows Audio Engine to calibrate the system output. This means that SoundID Reference doesn't require a virtual audio device for this driver type.
Similar to ASIO drivers, APO offers low-latency performance of 7-10ms. Note that the APO insert is a WASAPI-type driver and cannot be used or applied to ASIO-exclusive devices.
Setting up with Windows audio device insert (APO)
With the SoundID Reference app launched, add an output device and select the driver type that the SoundID Reference app will use for audio signal processing:
- Click on Add new output > WASAPI
- Select your audio interface from the list below
- Driver type: Windows audio device insert (APO)
- Wait for the APO to be applied: ⓘ Applying APO > ☑ APO has been applied
- Make sure the Windows Sound output is assigned to the same output device/channels as used for your APO preset in SoundID Reference
NOTE! The APO can take up to 1 minute to load when creating the preset. Wait for the 'APO has been applied' dialog for confirmation.
If experiencing any issues during this step, refer to this article: "APO can't be applied" error [WIN]
IMPORTANT! Make sure your audio interface is selected in Windows Sound as the APO is assigned to the audio interface (there is no SoundID Reference virtual audio device with this driver type).
Essential questions answered
Can I use the APO driver to calibrate my DAW output?
Technically, this is possible. If your DAW can be configured to Direct Sound, WASAPI, or other Windows APIs the APO driver should receive the audio signal and calibrate it. Otherwise, the APO driver has been designed and developed as a systemwide driver.
Can I configure the APO driver in the SoundID Reference?
No, the APO insert driver cannot be further configured inside the SoundID Reference app. Should you require to apply any changes, these will take place inside the audio interface control software and affect the audio interface directly.