LibVLC SampleCode Qt

This sample code will render a video into a Qt QWidget.

This was tested with vlc-0.9.9 and Qt 4.5.1 on WinXP.

main.cpp:

/* libVLC and Qt sample code
 * Copyright © 2009 Alexander Maringer <maringer@maringer-it.de>
 */

#include "vlc_on_qt.h"
#include <QtGui/QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Player p;
    p.resize(640,480);
    p.playFile("rtp://@:2626");
    p.show();
    return a.exec();
}

vlc_on_qt.h:

/* libVLC and Qt sample code
 * Copyright © 2009 Alexander Maringer <maringer@maringer-it.de>
 */
#ifndef VLC_ON_QT_H
#define VLC_ON_QT_H

#include <vlc/vlc.h>

#include <QWidget>

class QProcess;
class QVBoxLayout;
class QWidget;
class QSizePolicy;
class QPushButton;
class QTextEdit;
class QCloseEvent;
class QTimer;
class QDebug;
class QFrame;
class QSlider;

#define POSITION_RESOLUTION 10000

class Player : public QWidget
{
    Q_OBJECT
    QSlider *_positionSlider;
    QSlider *_volumeSlider;
    QFrame *_videoWidget;
    QTimer *poller;
    bool _isPlaying;
    libvlc_exception_t _vlcexcep;
    libvlc_instance_t *_vlcinstance;
    libvlc_media_player_t *_mp;
    libvlc_media_t *_m;
    libvlc_media_list_t *_ml;
    libvlc_media_list_player_t * _mlp;

public:
    Player();
    ~Player();
    void raise(libvlc_exception_t * ex);

public slots:
    void playFile(QString file);
    void updateInterface();
    void changeVolume(int newVolume);
    void changePosition(int newPosition);

};
#endif

vlc_on_qt.cpp:

/* libVLC and Qt sample code
 * Copyright © 2009 Alexander Maringer <maringer@maringer-it.de>
 */
#include "vlc_on_qt.h"

#include <QVBoxLayout>
#include <QWidget>
#include <QSizePolicy>
#include <QPushButton>
#include <QTextEdit>
#include <QSlider>
#include <QCloseEvent>
#include <QTimer>
#include <QDebug>

Player::Player()
: QWidget()
{
    //preparation of the vlc command
    const char * const vlc_args[] = {
              "-I", "dummy", /* Don't use any interface */
              "--ignore-config", /* Don't use VLC's config */
              "--extraintf=logger", //log anything
              "--verbose=2", //be much more verbose then normal for debugging purpose
              "--plugin-path=C:\\vlc-0.9.9-win32\\plugins\\" };

    _videoWidget=new QFrame(this);

    _volumeSlider=new QSlider(Qt::Horizontal,this);
    _volumeSlider->setMaximum(100); //the volume is between 0 and 100
    _volumeSlider->setToolTip("Audio slider");

    // Note: if you use streaming, there is no ability to use the position slider
    _positionSlider=new QSlider(Qt::Horizontal,this); 
    _positionSlider->setMaximum(POSITION_RESOLUTION);

    QVBoxLayout *layout = new QVBoxLayout;
    layout->addWidget(_videoWidget);
    layout->addWidget(_positionSlider);
    layout->addWidget(_volumeSlider);
    setLayout(layout);

    _isPlaying=false;
    poller=new QTimer(this);

    //Initialize an instance of vlc
    //a structure for the exception is neede for this initalization
    libvlc_exception_init(&_vlcexcep);

    //create a new libvlc instance
    _vlcinstance=libvlc_new(sizeof(vlc_args) / sizeof(vlc_args[0]), vlc_args,&_vlcexcep);  //tricky calculation of the char space used
    raise (&_vlcexcep);
    
    // Create a media player playing environement 
    _mp = libvlc_media_player_new (_vlcinstance, &_vlcexcep);
    raise (&_vlcexcep);

    //connect the two sliders to the corresponding slots (uses Qt's signal / slots technology)
    connect(poller, SIGNAL(timeout()), this, SLOT(updateInterface()));
    connect(_positionSlider, SIGNAL(sliderMoved(int)), this, SLOT(changePosition(int)));
    connect(_volumeSlider, SIGNAL(sliderMoved(int)), this, SLOT(changeVolume(int)));

    poller->start(100); //start timer to trigger every 100 ms the updateInterface slot
}

//desctructor
Player::~Player(){}

void Player::playFile(QString file)
{
    //the file has to be in one of the following formats /perhaps a little bit outdated)
    /*
    [file://]filename              Plain media file
    http://ip:port/file            HTTP URL
    ftp://ip:port/file             FTP URL
    mms://ip:port/file             MMS URL
    screen://                      Screen capture
    [dvd://][device][@raw_device]  DVD device
    [vcd://][device]               VCD device
    [cdda://][device]              Audio CD device
    udp:[[<source address>]@[<bind address>][:<bind port>]]
    */

    /* Create a new LibVLC media descriptor */
    _m = libvlc_media_new (_vlcinstance, file.toAscii(), &_vlcexcep);
    raise(&_vlcexcep);
    
    libvlc_media_player_set_media (_mp, _m, &_vlcexcep);
    raise(&_vlcexcep);

    // /!\ Please note /!\
    //
    // passing the widget to the lib shows vlc at which position it should show up
    // vlc automatically resizes the video to the ´given size of the widget
    // and it even resizes it, if the size changes at the playing
    
    /* Get our media instance to use our window */
    #ifdef Q_OS_WIN
        libvlc_media_player_set_drawable( _mp, reinterpret_cast<unsigned int>(_videoWidget->winId()), &_vlcexcep );
    #else
        libvlc_media_player_set_drawable( _mp, _videoWidget->winId(), &_vlcexcep );
    #endif
    raise(&_vlcexcep);

    /* Play */
    libvlc_media_player_play (_mp, &_vlcexcep );
    raise(&_vlcexcep);

    _isPlaying=true;
}

void Player::changeVolume(int newVolume)
{
    libvlc_exception_clear(&_vlcexcep);
    libvlc_audio_set_volume (_vlcinstance,newVolume , &_vlcexcep);
    raise(&_vlcexcep);
}

void Player::changePosition(int newPosition)
{
    libvlc_exception_clear(&_vlcexcep);
    // It's possible, that the vlc doesn't play anything
    // so check before
    libvlc_media_t *curMedia = libvlc_media_player_get_media (_mp, &_vlcexcep);
    libvlc_exception_clear(&_vlcexcep);
    if (curMedia == NULL)
        return;

    float pos=(newPosition)/POSITION_RESOLUTION;
    libvlc_media_player_set_position (_mp, pos, &_vlcexcep);
    raise(&_vlcexcep);
}

void Player::updateInterface()
{
    if(!_isPlaying)
        return;

    // It's possible, that the vlc doesn't play anything
    // so check before
    libvlc_media_t *curMedia = libvlc_media_player_get_media (_mp, &_vlcexcep);
    libvlc_exception_clear(&_vlcexcep);
    if (curMedia == NULL)
        return;

    float pos=libvlc_media_player_get_position (_mp, &_vlcexcep);
    int siderPos=(int)(pos*(float)(POSITION_RESOLUTION));
    _positionSlider->setValue(siderPos);
    int volume=libvlc_audio_get_volume (_vlcinstance,&_vlcexcep);
    _volumeSlider->setValue(volume);
}
void Player::raise(libvlc_exception_t * ex)
{
    if (libvlc_exception_raised (ex))
    {
         fprintf (stderr, "error: %s\n", libvlc_exception_get_message(ex));
         exit (-1);
    }
}