It’s possible using Accessibility Service. Remote call recorder and BoldBeast both record perfectly both side voice in Android 10 (Pixel 3A) without having to root or being a system app. Both of them use Accessibility service. Detailed info here in this link.
Here is a simple video recording example using the MediaRecorder: public class VideoCapture extends Activity implements OnClickListener, SurfaceHolder.Callback { MediaRecorder recorder; SurfaceHolder holder; boolean recording = false; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); requestWindowFeature(Window.FEATURE_NO_TITLE); getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN); setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE); recorder = new MediaRecorder(); initRecorder(); setContentView(R.layout.main); SurfaceView cameraView = (SurfaceView) findViewById(R.id.CameraView); holder = cameraView.getHolder(); holder.addCallback(this); holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); cameraView.setClickable(true); … Read more