Refresh rate related flicker?

[moamoa]

I have a problem (i think) which although is not caused directly by sagetv, is only noticed when using sagetv, so I though someone else here might be able to help.

I have my HTPC connected to a Plasma running 1366x768. When I set the PC to that resolution the PC reports that that resolution is at 60hz. My plasma detects the PC and reports 60hz on it's OSD so I'm sure they are both in sync.

However, when watching TV (I'm using DVB-T in the UK) I notice a nasty visual effect when the picture pans horizontally. The image seems to have a staggered effect where the top half of the image is out by a few pixels from the bottom half of the image on some frames. The general image quality is perfect, but for these panning shots during programs. I think it may have something to do with the 60hz PC<->TV link and the fact the UK tv is PAL which is 50hz? Is this correct?

What can I do to sort this? My PC will ONLY support 60hz at 1366x768 which is the native resolution of my tv.

Any help?

[StephaneM]

Originally Posted by moamoa

However, when watching TV (I'm using DVB-T in the UK) I notice a nasty visual effect when the picture pans horizontally. The image seems to have a staggered effect where the top half of the image is out by a few pixels from the bottom half of the image on some frames.

This is tearing.

I think it may have something to do with the 60hz PC<->TV link and the fact the UK tv is PAL which is 50hz? Is this correct?

I don't think so. Displaying 50Hz video on a 60Hz display will just give you a not smooth panning. This is because some frame need to be inserted but unfortunately not evenly so you'll notice some extraneous frames (and the only way to prevent this is either to feed 50Hz or 75Hz to your display or any multiple of 25Hz)

What can I do to sort this? My PC will ONLY support 60hz at 1366x768 which is the native resolution of my tv.

What is your video card?
From what I know you are more prone to tearing if you have a Nvidia card (and tearing can be removed with those cards by using VMR9 renderer and Full Screen Exclusive mode).

If you have a recent Radeon card, usually tearing will not be a problem but you can also try VMR9, then Full Screen Exclusive mode.

Regards,
Stéphane.

[moamoa]

I have an example java proggy that show the problems i am having.

If you run this (after compiling) you will see scrolling vertical bars. On these bars I see a flicker as they scroll. This is just the same effect I see on my HTPC when watch anything in sage that has a similar pan left to right.

Can anyone else see it?

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Image;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JSlider;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class Pan extends JComponent implements Runnable
{
    int pos = 0;
    int w;
    int s;
    int bars = 4;
    long delay = 60;
    boolean running;
    int step;
    Dimension lastD;
    Image img;
    Graphics img_g;
    long base = System.currentTimeMillis();
    
    public Pan() 
    {
    }
    
    public void paint(Graphics g)
    {
        update(g);
    }
    
    public void setDelay(int d)
    {
        delay = d;
    }
    
    public void update(Graphics g)
    {
        Dimension d = getSize();
        if (!d.equals(lastD)) {
            img = createImage(d.width,d.height);
            img_g = img.getGraphics();
            lastD = d;
            System.out.println("reset");
        }
        img_g.setColor(Color.white);
        img_g.fillRect(0,0,d.width,d.height);
        w = d.width/bars;
        s = d.width/(bars*4);
        step = s/4;
        img_g.setColor(Color.black);
        for (int i=0; i<=bars; i++) {
            img_g.fillRect(pos+(w*i),0,s,d.height);
        }
        g.drawImage(img,0,0,null);       
    }
    
    public void run() 
    {
        running = true;
        while (running) {
            pos += step;
            if (pos>=(w-s)) pos = -s;
            try {
                repaint();
                Thread.sleep(delay);
            }
            catch (Exception ex) {
                ex.printStackTrace();
            }
        }
    }
    
    public void start()
    {
        Thread t = new Thread(this);
        t.start();
    }
    
    public void stop()
    {
        running = false;
    }
    
    public static void main(String[] args) 
    {
        JFrame f = new JFrame("Test");
        JPanel p = new JPanel(new BorderLayout());
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final Pan pan = new Pan();
        f.setContentPane(p);
        p.add(BorderLayout.CENTER,pan);
        f.setSize(600,400);
        f.setVisible(true);
        pan.start();
        final JSlider s = new JSlider();
        s.setValue(60);
        s.setMinimum(10);
        s.setMaximum(1000);
        s.setMajorTickSpacing(10);
        s.setSnapToTicks(true);
        p.add(BorderLayout.SOUTH,s);
        s.addChangeListener(new ChangeListener() {
            public void stateChanged(ChangeEvent ev) {
                pan.setDelay(s.getValue());
            }
        });
        s.revalidate();
    }
}

[Lucas]

Moamoa,

even if your video card driver settings don't show 50Hz as an option, you can set it with powerstrip. The should be the ideal.

The nasty artifact does indeed look like tearing and it probably has to do with an underpowered video card if you are running VMR9.

Even with a recent Nvidia card I sometimes get something that looks like tearing. Can you give us some more info on your video card, drivers, SageTV settings etc?

Have you tried overlay?

[moamoa]

I have tried all major codecs and all possible options in sage and codecs, and nothing really helps.

My system is built around the Abit iL-90MV motherboard;
http://www.abit-usa.com/products/mb/...es=1&model=324
This is Abit VIIV board and is really designed to be a HTPC for HD, so should really be totally up to the job. It uses the onbaord Intel GMA 950, which powerstrip does not support. My case is half height, so I really need to use the onboard card, which should really be ok anyway?

I am not sure it is a refresh problem anyway, as I can set the pc to run 75hz if I select a non native resolution for the display. 75hz should match the 50hz (25 interlaced of the UK). But even with this, I still see the "tearing", so I don't think it is this.

It looks to me as if the PC is half way through drawing a frame, when the monitor decides to draw it. But having tried emerying; codecs, reclock, setting, new drivers... you name it... I'm at a total loss.

[stanger89]

Tearing has nothing to do with refresh rate, it has to do with the card not being able to draw frames to the framebuffer fast enough to keep up with the "page flipping" to output them. As a result you get part of one frame and part of the next.

If anything, increasing the refresh rate could worsen it.

Using overlay, or Fullscreen Exclusive VMR9 may (should) help. But it may be a case where the card is just not up to the task.

[moamoa]

Originally Posted by stanger89

Tearing has nothing to do with refresh rate, it has to do with the card not being able to draw frames to the framebuffer fast enough to keep up with the "page flipping" to output them. As a result you get part of one frame and part of the next.

Yes, this seem to fit the problem.

Originally Posted by stanger89

Using overlay, or Fullscreen Exclusive VMR9 may (should) help. But it may be a case where the card is just not up to the task.

Yes I have tried all these options, with no real improvment. One Interesting this is that is is seems to play the windows HD-WMV better than other mpeg stuff, with less tearing?

If an application, like sagtv, starts to render a page to a buffer, what happens to make sure that only a fully draw frame buffer is swaped to the active display frame?

You can run this;
Demo Test App
When the delay is set to 200ms between frames the tearing scrolls down slowly, other values of delay show different results, no value removes it.

For example, as with the java application above; The application draws an Image to the graphics context, in jave there is no way of knowing when the graphics card is about to (or has) switch page. So what can be done to prevent the graphics card doing a page switch to a framebuffer that the java application was only half way through drawing?