[vlc-devel] libvlc_media_player_stop

David Hoyt dhoyt at llnl.gov
Mon Oct 27 21:10:38 CET 2008

Using JVLC and SWT, do:

1. Make sure you have a working SWT environment (use eclipse or get the SWT
jars - http://www.eclipse.org/swt/)

2. Create a class named "Utilities" in the org.videolan.jvlc package. Put
this in:

package org.videolan.jvlc;

import org.videolan.jvlc.internal.LibVlc.LibVlcInstance;

public class Utilities {
	public static LibVlcInstance getNativeInstance(JVLC vlc) {
		return vlc.getInstance();

3. Create a class named "Main" in the default package. Put this in:

import java.io.File;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Button;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.FileDialog;
import org.eclipse.swt.widgets.Shell;
import org.videolan.jvlc.JVLC;
import org.videolan.jvlc.MediaPlayer;
import org.videolan.jvlc.Utilities;
import org.videolan.jvlc.internal.LibVlc;

class Main {

    public static void runMessageLoop(Shell shell) {
        if (shell == null) {
            throw new IllegalStateException("Please define the shell before

        Display display = shell.getDisplay();
        if (display != null && !display.isDisposed()) {
            while (!display.isDisposed() && !shell.isDisposed()) {
                if (!display.isDisposed() && !display.readAndDispatch()) {

     * @param args the command line arguments
    public static void main(String[] args) {
        //<editor-fold defaultstate="collapsed" desc="GUI objects">
        final Display display = new Display();
        final Shell shell = new Shell(display);
        shell.setLayout(new FillLayout());
        final Button btnSwitch = new Button(shell, SWT.PUSH);
        btnSwitch.setSize(100, 40);

        final Canvas[] canvases = new Canvas[24];
        final JVLC[] vlcs = new JVLC[canvases.length];
        final MediaPlayer[] mps = new MediaPlayer[canvases.length];

        for (int i = 0; i < canvases.length; ++i) {
            canvases[i] = new Canvas(shell, SWT.NONE);
            vlcs[i] = new JVLC(new String[]{
                "--plugin-path=" + new File(".").getAbsolutePath() + "\\" +

        btnSwitch.addSelectionListener(new SelectionAdapter() {

            FileDialog fd = null;

            public void widgetSelected(SelectionEvent e) {
                if (fd == null) {
                    fd = new FileDialog(shell, SWT.OPEN);
                    fd.setText("Select Media File");
                    fd.setFilterExtensions(new String[]{
                    fd.setFilterNames(new String[]{
                        "Motion JPEG Files (*.mjpg)",
                        "AVI Files (*.avi)",
                        "MPEG Files (*.mpeg, *.mpg)",
                        "MPEG2 Files (*.mpeg2, *.mpg2)",
                        "MPEG4 Files (*.mpeg4, *.mp4)",
                        "PNG Files (*.png)",
                        "JPEG Files (*.jpg, *.jpeg)",
                        "All Files (*.*)"

                String file = "";
                if ((file = fd.open()) != null && !"".equals(file)) {
                    final File f = new File(file);
                    if (!f.exists()) {
                    for (int i = 0; i < canvases.length; ++i) {
                        if (mps[i] != null) {
                        if (mps[i] == null) {
, canvases[i].handle, new LibVlc.libvlc_exception_t());
                        mps[i] = vlcs[i].play(f.getAbsolutePath());



4. Run the class.
5. Click on the "Switch" button and open up a video (I was testing w/ MPEG
and WMV videos).
6. Repeat step 5.

You'll see the videos freeze after about 4-5 panels. I can reproduce this
behavior pretty much every time I run it. If you're able to pause your
debugger, you'll see that it's stuck in the call to
libvlc_media_player_stop(). I haven't tested it out in Linux (Ubuntu) and so
I'm not sure if it will show the same behavior. But in Windows XP at least,
the app freezes up.

-----Original Message-----
From: vlc-devel-bounces at videolan.org [mailto:vlc-devel-bounces at videolan.org]
On Behalf Of Pierre d'Herbemont
Sent: Saturday, October 25, 2008 3:49 AM
To: Mailing list for VLC media player developers
Subject: Re: [vlc-devel] libvlc_media_player_stop

On Oct 25, 2008, at 1:43 AM, David Hoyt wrote:

> I've got an interesting error that I've tried everything I know how to 
> resolve it. Ultimately, it comes down to the fact that I'm just not 
> that familiar w/ the VLC internals.
> I'm trying to use vlc in java through the java bindings (JVLC). The 
> app freezes on me, however, in libvlc_media_player_stop and sometimes 
> in libvlc_media_player_release on Windows XP SP2.
> I can't release any example code without going through an exhaustive 
> review and release process. So I'm stuck explaining the problem.
> Here are some others with the same problem:
> http:// forum.videolan.org/viewtopic.php?f=2&t=51509
> http:// 
> forum.videolan.org/viewtopic.php?f=14&t=47385&st=0&sk=t&sd=a&start=60
> I've got 12+ videos going on a single dialog using SWT. I start them 
> out all playing the same video. They then reach the end of the 3- 
> second long clip and all stop. I then tell one panel to play a video. 
> It plays just fine. Then I tell it to switch and play another video 
> while it's still playing (my code asks it to stop first and then play) 
> and it freezes. Java tells me it's stuck on the call to 
> libvlc_media_player_stop(). This freezes up my app.
> I've tried running all the commands on the GUI thread and then also on 
> separate threads and no luck. My guess is that it's stuck on line
> 689 of https:// 
> trac.videolan.org/vlc/browser/src/control/media_player.c

> I've also run into another error if you try and call
> libvlc_media_player_stop() from the endReached event handler. It 
> freezes there as well. That's not a tough one to get around, but it 
> shouldn't lock up on you.

Could you provide a backtrace, or a sample code that shows the issue?

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