我已经使用MediaRecorder和MediaProjection录制了Android手机的屏幕。如何提高录制视频的质量？

Question

在“我的应用程序”中，我必须打开PDF和文档并在其上涂鸦并记录下来。录制后，由于质量差而看不到PDF和Docs的内容。这是我录制屏幕的代码。这里录制的视频大小不是问题。录制的视频质量很差。我需要为我的应用提供更好的质量。

currentPath = initRec();
 mediaProjectionManager= (MediaProjectionManager)getSystemService(Context.MEDIA_PROJECTION_SERVICE);
startActivityForResult(mediaProjectionManager.createScreenCaptureIntent(),SCREEN_CAPTURE);
mediaRec.start();

private String initRec() {
    mediaRec=new MediaRecorder();
    mediaRec.setAudioSource(MediaRecorder.AudioSource.MIC);
    mediaRec.setVideoSource(MediaRecorder.VideoSource.SURFACE);
    mediaRec.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
    mediaRec.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
    mediaRec.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);
    mediaRec.setVideoEncodingBitRate(3000000);
    mediaRec.setVideoFrameRate(16);
    mediaRec.setVideoSize(480,640);
    //CamcorderProfile cpHigh = CamcorderProfile.get(CamcorderProfile.QUALITY_720P);
    //mediaRec.setProfile(cpHigh);
    String currentPath=getFilePath();
    mediaRec.setOutputFile( currentPath);
    try {
        mediaRec.prepare();
    } catch (IOException e) {
        e.printStackTrace();
    }

return  currentPath;
}

 @Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode==SCREEN_CAPTURE)
    {
        mediaProjectionInstance=mediaProjectionManager.getMediaProjection(resultCode,data);
        virtualDisp=createVirtualDisplay();

    }

    private VirtualDisplay createVirtualDisplay() {
    DisplayMetrics displayMetrics=new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
    //    Surface surface=mediaRec.getSurface();

    VirtualDisplay vd=mediaProjectionInstance.createVirtualDisplay("ABC",
            480,640,
            displayMetrics.densityDpi,
            DisplayManager.VIRTUAL_DISPLAY_FLAG_AUTO_MIRROR,
            mediaRec.getSurface(),null,null);
            return vd;
}