Tachyon1979's profile - activity

After a lot of tests with ffmpeg and try to understand how i can get access to the webcam features in opencv. I found out that my cam is a so called "dshow" device which is provided from Windows Standard Webcam Driver.

So to get deeper access to the device I have to start the capture with this flag.

capture.set(Videoio.Cap_DSHOW + 0); // instead of capture.set(0);

The FourCC flag is also necessary.

    int fourcc = VideoWriter.fourcc('M', 'J', 'P', 'G');
    capture.set(Videoio.CAP_PROP_FOURCC, fourcc);

Now this line has an effect..

capture.set(Videoio.CAP_PROP_FPS,60);

After this changes i can capture with 58 fps and have almost no latency!

Hope this helps someone!

hi everybody

i have a problem with capturing a webcam (logitech c922) video stream. the webcam provides a stream at 60fps at a resolution of 720p.

right now i initialize a capture convert it from BGR2toGray send the frame to an ImageView object.

here is my code.

    public void startCapture(ImageView realView, int frameWidth, int frameHeight){

    moveCoordSystemToCenter(frameWidth/2, frameHeight/2);  

    if (!this.capture.isOpened()){
        capture.open(0);

        int fourcc = VideoWriter.fourcc('M', 'J', 'P', 'G');
        capture.set(Videoio.CAP_PROP_FOURCC, fourcc);   
        capture.set(Videoio.CAP_PROP_FRAME_WIDTH,1280);
        capture.set(Videoio.CAP_PROP_FRAME_HEIGHT,720);
        System.out.println(capture.get(Videoio.CAP_PROP_FRAME_WIDTH));

            TimerTask frameGrabber = new TimerTask(){
                public void run(){

                    long time = System.currentTimeMillis();
                    Image tmp =  grabFrame();

                    Platform.runLater(new Runnable(){   
                        int Counter = 1;
                        long res = 1;

                        public void run(){
                                realView.setImage(tmp);
                                res = res + System.currentTimeMillis()-time;
                                System.out.println("Fps = " + 1000 / (res/Counter)) ;
                                Counter++;
                        }
                    });
                }
            };      
                            this.timer = new Timer();       
                            timer.scheduleAtFixedRate(frameGrabber, 0, 1); // has no effect
    }
    else
    {
        if (this.timer != null){
            this.timer.cancel();
            this.timer = null;
        }
    this.capture.release();
    }       
}

private Image grabFrame() {

    Image imageToShow = null;
    Mat frame = new Mat();

    if ( this.capture.isOpened()){
            try
            {

                this.capture.read(frame);
                if (!frame.empty()){
                    imageToShow = mat2Image(frame);
                }
            }
            catch (Exception e){
            }
    }
    return imageToShow; 
}

private Image mat2Image (Mat frame){
    MatOfByte buffer = new MatOfByte();
    Mat frameGray = new Mat();
    Imgproc.cvtColor(frame, frameGray, Imgproc.COLOR_BGR2GRAY);
    Imgcodecs.imencode(".png",frameGray, buffer);
    return new Image (new ByteArrayInputStream(buffer.toArray()));

}

i use opencv3.1 Java, Eclipse neon, JavaFx

my problem is i can´t get more than 30 fps out of this thing i Need the 60 fps for my application. to set the codec to M J P G brings up speed from 15 fps to 30fps and MJPG is the only Codec which holds my resolution all others fall back to 640 / 480

so i play with some formats of video- and Picture codecs stuff.

Jpg an Png is simular stable at 30 fps bmp is a little faster but not so stable 28- 36 fps

i already tried to set the fps via capture.set(CAP_PROP_FPS,60) which has no effect for values above 30.

I read some stuff about ffmpeg but i don´t understand how the pipeline should work.

can anyone help.

greetz