WindowsAudioEndpoint.cs

[ElDuderinoBerlin]

 /// <summary>
    /// Starts the audio capturing/source device and the audio sink device.
    /// </summary>
    public Task Start()
    {
        if (!_isAudioSourceStarted && _waveInEvent != null)
        {
            StartAudio();
        }

        if (!_isAudioSinkStarted && _waveOutEvent != null)
        {
            StartAudioSink();
        }

        return Task.CompletedTask;
    }

    /// <summary>
    /// Closes the audio devices.
    /// </summary>
    public Task Close()
    {
        if (!_isAudioSourceClosed && _waveInEvent != null)
        {
            CloseAudio();
        }

        if (!_isAudioSinkClosed && _waveOutEvent != null)
        {
            CloseAudioSink();
        }

        return Task.CompletedTask;
    }

    public Task Pause()
    {
        if (!_isAudioSourcePaused && _waveInEvent != null)
        {
            PauseAudio();
        }

        if (!_isAudioSinkPaused && _waveOutEvent != null)
        {
            PauseAudioSink();
        }

        return Task.CompletedTask;
    }

    public Task Resume()
    {
        if (_isAudioSourcePaused && _waveInEvent != null)
        {
            ResumeAudio();
        }

        if (_isAudioSinkPaused && _waveOutEvent != null)
        {
            ResumeAudioSink();
        }

        return Task.CompletedTask;
    }

Have switched/swapped _waveInEvent and _waveOutEvent check logic!

The corrected for Pause() is:

public Task Pause()
{
    if (!_isAudioSourcePaused && _waveOutEvent != null)
    {
        PauseAudio();
    }

    if (!_isAudioSinkPaused && _waveInEvent!= null)
    {
        PauseAudioSink();
    }

    return Task.CompletedTask;
}

Regards

[sipsorcery]

The audio source, which is typically an audio input device such as a microhpone, is represented by the _waveInEvent.

The audio sink, which is typically an audio output device such as a speaker, is represented by the _waveOutEvent.

Anything to do with the audio source needs to be done on the _waveInEvent.

Anything to do with the audio sink needs to be done on the _waveOuEvent.

[ElDuderinoBerlin]

But this:
if (_isAudioSourcePaused && _waveInEvent != null) { ResumeAudio(); }

should then be:

if (_isAudioSourcePaused && _waveOutEvent != null) { ResumeAudio(); }

and for the mic code the same.

[sipsorcery]

The audio source is the microphone.

The original code snippet you've psoted again looks correct. The audio source and _waveInEvent go together. The ResumeAudio method would ideally be ResumeAudioSource but because originally there was only a source that's how it was named. Breaking the public API is undesireable so the name has been kept.