libvlc视频播放器: 播放rtsp/rtmp视频流

一、功能介绍

libvlc播发器引擎除了能播放本地视频外，也支持播放各种协议的流媒体视频，比如常见的RTMP、RTSP格式视频。

在前面几篇文章里陆陆续续介绍了libvlc的常用的使用方法，这篇文章继续介绍libvlc的知识点: 播放指定协议的视频。

libvlc提供了两种直接打开视频的方法:

/**
 * Create a media with a certain given media resource location,
 * for instance a valid URL.
 *
 * \note To refer to a local file with this function,
 * the file://... URI syntax <b>must</b> be used (see IETF RFC3986).
 * We recommend using libvlc_media_new_path() instead when dealing with
 * local files.
 *
 * \see libvlc_media_release
 *
 * \param p_instance the instance
 * \param psz_mrl the media location
 * \return the newly created media or NULL on error
 */
LIBVLC_API libvlc_media_t *libvlc_media_new_location(
                                   libvlc_instance_t *p_instance,
                                   const char * psz_mrl );

/**
 * Create a media for a certain file path.
 *
 * \see libvlc_media_release
 *
 * \param p_instance the instance
 * \param path local filesystem path
 * \return the newly created media or NULL on error
 */
LIBVLC_API libvlc_media_t *libvlc_media_new_path(
                                   libvlc_instance_t *p_instance,
                                   const char *path );

其中 libvlc_media_new_path 用于打开本地视频文件,可以直接传入本地磁盘路径。
例如:

libvlc_media_new_path(vlc_base,"D:\\work\\test.mp4");

注意: windows下使用libvlc_media_new_path 函数传入的路径要注意斜杠问题，必须保证传入的是双右斜杠，如果默认选择的路径是左斜杠，可以使用std::replace函数转换一下。

filename="D:/work/test.mp4";
std::replace(filename.begin(), filename.end(), QChar('/'), QChar('\\'));

另一个libvlc_media_new_location 函数用于打开协议，这个函数更加强大，可以支持很多协议，本地视频也可以使用该函数打开，更加通用一点，而且使用该函数时，路径斜杠使用常规左斜杠就行(linux风格)，不需要进行转换。

下面介绍几个常用的使用示例:

打开本地文件: libvlc_media_new_location (inst, "file:///D:/work/test.mp4");
打开RTSP流媒体:libvlc_media_new_location (inst, "rtsp://10.0.0.4:554/cam");
打开RTMP流媒体:libvlc_media_new_location (inst, "rtmp://10.0.0.4:554/cam");
播放当前桌面屏幕: libvlc_media_new_location (inst, "screen://");

注意: 使用 libvlc_media_new_location 函数打开路径之后不要使用std::replace转换路径。

播放桌面屏幕的效果:
libvlc_media_new_location (inst, "screen://")

播放rtmp流效果

libvlc_media_new_location (inst, "rtmp://media3.scctv.net/live/scctv_800")

二、完整代码示例

#include "widget.h"
#include "ui_widget.h"

Widget* Widget::pThis = nullptr;

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    pThis=this;

    ui->setupUi(this);
	
    //创建并初始化libvlc实例
    vlc_base=libvlc_new(0,nullptr);

    this->setWindowTitle("libvlc设计的视频播放器");

}


Widget::~Widget()
{
    delete ui;
}

//选择视频
void Widget::on_pushButton_open_clicked()
{
    /*选择文件*/
    filename=QFileDialog::getOpenFileName(this,"选择打开的文件","D:/",tr("*.*"));

    filename="file:///"+filename;

    /*停止媒体文件*/
    if(vlc_mediaPlayer)libvlc_media_player_stop(vlc_mediaPlayer);
    //QThread::msleep(5000);

    /*为特定文件路径创建媒体*/
    if(vlc_media)libvlc_media_release(vlc_media);
   // vlc_media=libvlc_media_new_path(vlc_base,filename.toUtf8().data());
    vlc_media=libvlc_media_new_location (vlc_base,filename.toUtf8().data());
    if(vlc_media==nullptr)
    {
        qDebug()<<"libvlc_media_new_path 执行错误.";
        return;
    }


    /*根据给定的媒体对象创建一个播放器对象*/
    if(vlc_mediaPlayer)libvlc_media_player_release(vlc_mediaPlayer);
    vlc_mediaPlayer=libvlc_media_player_new_from_media(vlc_media);

    //忽略事件处理(这样libvlc就捕获不到鼠标和键盘事件了)
    if (vlc_mediaPlayer)libvlc_video_set_mouse_input(vlc_mediaPlayer, false);
    if (vlc_mediaPlayer)libvlc_video_set_key_input(vlc_mediaPlayer, false);


    //创建事件管理器
    eventManager = libvlc_media_player_event_manager(vlc_mediaPlayer);

    //订阅事件
    attachEvents(eventManager);

    /*设置给予媒体播放器媒体输出的win32/win64窗口句柄*/
    libvlc_media_player_set_hwnd(vlc_mediaPlayer, (void *)ui->widget->winId());

    /*播放媒体文件*/
    if(vlc_mediaPlayer)libvlc_media_player_play(vlc_mediaPlayer);

    //等待VLC解析文件.否则下面的时间获取不成功
    QThread::msleep(500);

    //获取媒体文件总长度 ms
    libvlc_time_t length = libvlc_media_player_get_length(vlc_mediaPlayer);
    qDebug()<<"媒体文件总长度:"<<length;
    ui->label_t2->setText(QTime(0, 0, 0,0).addMSecs(int(length)).toString(QString::fromLatin1("HH:mm:ss:zzz")));
    ui->horizontalSlider_pos->setMaximum(length);
    ui->horizontalSlider_pos->setMinimum(0);
}


//暂停与继续
void Widget::on_pushButton_pause_clicked()
{
    if(vlc_mediaPlayer)libvlc_media_player_pause(vlc_mediaPlayer);
}

//停止
void Widget::on_pushButton_stop_clicked()
{
    if(vlc_mediaPlayer)libvlc_media_player_stop(vlc_mediaPlayer);
}


//订阅事件
void Widget::attachEvents(libvlc_event_manager_t *eventManager)
{
    // 事件列表
    QList<libvlc_event_e> events = {
        libvlc_MediaPlayerPositionChanged,
        libvlc_MediaPlayerTimeChanged,
        libvlc_MediaPlayerLengthChanged,
        libvlc_MediaPlayerPaused,
        libvlc_MediaPlayerPlaying,
        libvlc_MediaPlayerStopped,
        libvlc_MediaPlayerEndReached,
        libvlc_MediaParsedChanged
    };

    // 订阅事件
    for (const libvlc_event_e &e : events)
    {
        libvlc_event_attach(eventManager, e, vlcEvents, nullptr);
    }
}


void Widget::vlcEvents(const libvlc_event_t *event, void *param)
{
    qint64 pos=0;
    switch (event->type){
    case libvlc_MediaPlayerTimeChanged:
         //获取当前媒体播放的位置
         pos=event->u.media_player_time_changed.new_time;
         pThis->ui->label_t1->setText(QTime(0, 0, 0,0).addMSecs(int(pos)).toString(QString::fromLatin1("HH:mm:ss:zzz")));
         pThis->ui->horizontalSlider_pos->setValue(pos);
         qDebug()<<"pos:"<<pos;
         break;
    case libvlc_MediaPlayerPositionChanged:
         //qDebug() << "Position: " << event->u.media_player_position_changed.new_position << endl;
         break;
    case libvlc_MediaPlayerLengthChanged:
         qDebug() << "Length:"<< event->u.media_player_length_changed.new_length;
         break;
    case libvlc_MediaPlayerEndReached:
         qDebug() << "VLC播放完毕.";
         break;
    case libvlc_MediaPlayerStopped:
         qDebug() << "VLC停止播放";
         break;
    case libvlc_MediaPlayerPlaying:
         qDebug() << "VLC开始播放";
         break;
    case libvlc_MediaPlayerPaused:
         qDebug() << "VLC暂停播放";
         break;
    case libvlc_MediaParsedChanged: //获取媒体信息
          qDebug() << "获取媒体信息";
         break;
    }
}