An example illustrating recording video and microphone audio in Unity with NatCorder API and NatDevice API.

VideoRecorder.cs

class VideoRecorder {

    MP4Recorder recorder;       // Recorder that will record an MP4
    CameraInput cameraInput;    // Recorder input for recording video from a game camera
    AudioDevice audioDevice;    // Microphone for recording user audio

    void StartRecording () {
        // Get a microphone
        var query = new MediaDeviceQuery(MediaDeviceCriteria.AudioDevice);
        audioDevice = query.current as AudioDevice;
        // Create recorder
        var clock = new RealtimeClock();
        recorder = new MP4Recorder(1280, 720, 30, audioDevice.sampleRate, audioDevice.channelCount);
        // Stream media samples
        cameraInput = new CameraInput(recorder, clock, Camera.main);
        audioDevice.StartRunning(audioBuffer => recorder.CommitSamples(audioBuffer.sampleBuffer.ToArray(), clock.timestamp));
    }
    
    async void StopRecording () {
        // Stop streaming media to the recorder
        cameraInput.Dispose();
        audioDevice.StopRunning();
        // Finish writing video
        var recordingPath = await recorder.FinishWriting();
    }
}