Xamarin Android - Slow Motion Video

Question

I am trying to use MediaRecorder to record 240fps slow motion video on a Galaxy S9 (Android 8 - Can't get it to update to newer). The built-in camera app does this no problem with the "Slow Motion" selection. I'm compiling using API26. This, set for 30fps, works:

    recorder = new MediaRecorder();    
    recorder.SetVideoSource(VideoSource.Camera);
    recorder.SetOutputFormat(OutputFormat.Mpeg4);
    recorder.SetVideoFrameRate(30);
    recorder.SetVideoSize(1920, 1080);
    recorder.SetVideoEncodingBitRate(17000000);
    recorder.SetVideoEncoder(VideoEncoder.H264);
    recorder.SetOutputFile(path);
    recorder.SetPreviewDisplay(viewer.Holder.Surface);

But I can not increase the VideoFrameRate > 30. I've tried a variety of values for the above, removed some settings, etc with no luck.

I have also tried the CamcorderProfile approach, but this doesn't work either. In particular these:

    CamcorderProfile.HasProfile(CamcorderQuality.HighSpeed1080p)
    CamcorderProfile.HasProfile(CamcorderQuality.HighSpeed720p)

return false. Though its clear the camera can do it.

Some posts I've read say that Camera2 is needed, however I've tried a variety of sample xamarin projects for Camera2... none of these work. I've not been able to find the Xamarin_Android version of Android-Slow-Motion-Camera2.

My goal is to record 240fps and play back at 30fps. Which I think requires some use of SetCaptureRate, but since I can't get it to record 240fps, I haven't gotten that far. SetVideoEncodingBitRate likely needs to be some other value too.