基于QT视频软件的开发和学习

马上工作需要做视频软件了，所以准备学习QT来开发，为什么选择QT呢，因为他优点多多（不说了自己网上g一下 ）

        随着高清的不断普及，所有视频软件都向高清这个方向而前进，其中有一款开源跨平台的播放器vlc的特性和功能都是非

常的好，所以想准备学习vlc的源码来看看，在看他源码的时候，发现他还有一个可供开发人员调用的libvlc 媒体库可用(GPL)，而vlc本身使用的GUI就是QT。

        好了不多说了

        先装好QT SDK，然后把环境变量设置一下（不会去G!）

        然后把vlc库加入到mingw里面

        先复制vlc-include.rar解压出来的头文件到Qt\2009.04\mingw\include里面

        在把vlc-lib.rar解压出来的文件放到C:\vlc-lib

        我们在 Qt Creator 里面建立一个空的QT项目

        新建一个Player类 ,会多出player.cpp,player.h 修改成如下

player.cpp

/* 
 * Flie Name  player.cpp
 */
#include "player.h"

#include <QVBoxLayout>
#include <QPushButton>
#include <QSlider>
#include <QTimer>
#include <QFrame>

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()
{
    /* Stop playing */
    libvlc_media_player_stop (_mp, &_vlcexcep);

    /* Free the media_player */
    libvlc_media_player_release (_mp);

    libvlc_release (_vlcinstance);
    raise (&_vlcexcep);
}

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 */
    #if defined(Q_OS_WIN)
        libvlc_media_player_set_drawable(_mp, reinterpret_cast<unsigned int>(_videoWidget->winId()), &_vlcexcep );
        //libvlc_media_player_set_hwnd(_mp, _videoWidget->winId(), &_vlcexcep ); // for vlc 1.0
    #elif defined(Q_OS_MAC)
        libvlc_media_player_set_drawable(_mp, _videoWidget->winId(), &_vlcexcep );
        //libvlc_media_player_set_agl (_mp, _videoWidget->winId(), &_vlcexcep); // for vlc 1.0
    #else //Linux
        libvlc_media_player_set_drawable(_mp, _videoWidget->winId(), &_vlcexcep );
        //libvlc_media_player_set_xwindow(_mp, _videoWidget->winId(), &_vlcexcep ); // for vlc 1.0
    #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=(float)(newPosition)/(float)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);
    }
}

  player.h

/* libVLC and Qt sample code
 * Copyright © 2009 Alexander Maringer <[e-mail]>
 */
#ifndef VLC_ON_QT_H
#define VLC_ON_QT_H

#include <vlc/vlc.h>

#include <QWidget>

class QVBoxLayout;
class QPushButton;
class QTimer;
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;

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

 在新建立一个main.cpp 修改成如下

 

#include <QtGui/QApplication>
#include "player.h"
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Player p;
    p.resize(640,480);
    p.playFile("#填写你要播的文件路径#"); 
    p.show();

    return a.exec();
}

 

然后我们修改  .pro文件 成如下

TARGET = test1
TEMPLATE = app
LIBS += -L'C:\vlc-lib'
LIBS += -lvlc
SOURCES += player.cpp \
    main.cpp
HEADERS += player.h

 然后运行qmake

然后就可以编译了

编译成功以后想要运行，还必须把C:\vlc-lib里面的libvlc.dll，和libvlccore.dll拷贝到生成exe的目录里面才能运行

现在在qt creator里面就可以运行了（单独运行还需要其它dll）

 

haha