Windows Audio Driver vs. WASAPI

1
votes

I'm right now reading the microsoft documentation about drivers and core audio apis. At the moment I'm still confuse which way to go to achieve what I need. I have an audio application which is Standalone and coded with framework JUCE in C++. And I need to build a Windows solution that would capture the audio stream that is going to an audio endpoint device to use it as an input of my audio application.

  • This stream must have an unaltered volume: always 1.0 (no matter if the hardware volume is changed or muted).
  • I must be able to choose between the different endpoint devices, for exemple if I have an external soundcard that is plugged, my audio application should be able to intercept and copy the stream that is going to that external soundcard, or do the same for the stream that is going to the built-in speakers.
  • The idea is to capture the output streams before they are modified by hardware volume modifications, and make a copy of them routed to my application without changing the output routing and behaviour.

The microsoft documentation is very furnished, but even if the WASAPI provides a lot of ways to capture and stream from audio endpoint devices, I'm not sure it is possible to get an unaltered volume, as it will always capture what's exactly coming out of the speakers. This is why I don't know If I can implement a feature directly in my audio application that will get the streams I want with WASAPIs or if I have to code a proper Audio Driver that would make a copy of the streams I want for my application to be able to use these streams.

The documentations I refer to: Audio Drivers design guide Core Audio APIs / WASAPI

Thanks for the help,

Best,

Maxime

1
c++windowsaudiodriverwasapi

1 Answers

0
votes

Sometimes the volume control is implemented in software, and sometimes it is implemented in hardware. You can call IAudioEndpointVolume::QueryHardwareSupport to see if the volume control for the audio endpoint you're working with is implemented in hardware or software.

Sometimes the audio loopback is implemented in software, and sometimes it is implemented in hardware. There is no API to tell which.

If the audio loopback is implemented in software, and the volume control is implemented in hardware, then you will get back the data you want.

If the audio loopback is implemented in hardware, or the volume control is implemented in software, the the audio data you get back has already had the volume adjustment applied.

What does your application do with the audio data it receives? The primary use case for audio loopback data is echo cancelation, where you usually WANT the volume to be applied.