1.简介
libVLC是一个开源的多媒体框架，它提供了丰富的功能，其中包括一个灵活且强大的事件机制。在libVLC中，事件机制主要用于通知应用程序有关播放、媒体状态更改或其他重要事件的信息。
libVLC的事件模型基于订阅-发布模式，主要包含以下关键组件：
-
事件类型（libvlc_event_type_t）：定义了一系列预定义的事件，如媒体打开、播放、暂停、停止、结束等。
-
事件管理器（libvlc_event_manager_t）：每个libVLC对象（如媒体播放器、媒体列表等）都有一个关联的事件管理器，用于注册和触发事件。
-
注册事件监听器（libvlc_event_attach）：应用程序通过调用此函数来订阅特定类型的事件，并提供一个回调函数，当该事件发生时，libVLC会调用这个回调函数。
-
事件解注册（libvlc_event_detach）：当不再需要监听某个事件时，可以调用此函数取消对该事件的订阅。
2.事件的类型
enum libvlc_event_e {
/* Append new event types at the end of a category.
* Do not remove, insert or re-order any entry.
* Keep this in sync with lib/event.c:libvlc_event_type_name(). */
libvlc_MediaMetaChanged=0,
libvlc_MediaSubItemAdded,
libvlc_MediaDurationChanged,
libvlc_MediaParsedChanged,
libvlc_MediaFreed,
libvlc_MediaStateChanged,
libvlc_MediaSubItemTreeAdded,
libvlc_MediaPlayerMediaChanged=0x100,
libvlc_MediaPlayerNothingSpecial,
libvlc_MediaPlayerOpening,
libvlc_MediaPlayerBuffering,
libvlc_MediaPlayerPlaying,
libvlc_MediaPlayerPaused,
libvlc_MediaPlayerStopped,
libvlc_MediaPlayerForward,
libvlc_MediaPlayerBackward,
libvlc_MediaPlayerEndReached,
libvlc_MediaPlayerEncounteredError,
libvlc_MediaPlayerTimeChanged,
libvlc_MediaPlayerPositionChanged,
libvlc_MediaPlayerSeekableChanged,
libvlc_MediaPlayerPausableChanged,
libvlc_MediaPlayerTitleChanged,
libvlc_MediaPlayerSnapshotTaken,
libvlc_MediaPlayerLengthChanged,
libvlc_MediaPlayerVout,
libvlc_MediaPlayerScrambledChanged,
libvlc_MediaPlayerESAdded,
libvlc_MediaPlayerESDeleted,
libvlc_MediaPlayerESSelected,
libvlc_MediaPlayerCorked,
libvlc_MediaPlayerUncorked,
libvlc_MediaPlayerMuted,
libvlc_MediaPlayerUnmuted,
libvlc_MediaPlayerAudioVolume,
libvlc_MediaPlayerAudioDevice,
libvlc_MediaPlayerChapterChanged,
libvlc_MediaListItemAdded=0x200,
libvlc_MediaListWillAddItem,
libvlc_MediaListItemDeleted,
libvlc_MediaListWillDeleteItem,
libvlc_MediaListEndReached,
libvlc_MediaListViewItemAdded=0x300,
libvlc_MediaListViewWillAddItem,
libvlc_MediaListViewItemDeleted,
libvlc_MediaListViewWillDeleteItem,
libvlc_MediaListPlayerPlayed=0x400,
libvlc_MediaListPlayerNextItemSet,
libvlc_MediaListPlayerStopped,
/**
* \deprecated Useless event, it will be triggered only when calling
* libvlc_media_discoverer_start()
*/
libvlc_MediaDiscovererStarted=0x500,
/**
* \deprecated Useless event, it will be triggered only when calling
* libvlc_media_discoverer_stop()
*/
libvlc_MediaDiscovererEnded,
libvlc_RendererDiscovererItemAdded,
libvlc_RendererDiscovererItemDeleted,
libvlc_VlmMediaAdded=0x600,
libvlc_VlmMediaRemoved,
libvlc_VlmMediaChanged,
libvlc_VlmMediaInstanceStarted,
libvlc_VlmMediaInstanceStopped,
libvlc_VlmMediaInstanceStatusInit,
libvlc_VlmMediaInstanceStatusOpening,
libvlc_VlmMediaInstanceStatusPlaying,
libvlc_VlmMediaInstanceStatusPause,
libvlc_VlmMediaInstanceStatusEnd,
libvlc_VlmMediaInstanceStatusError
};找几个常用的事件，如下所示。
switch (ev->type) {
case libvlc_MediaPlayerTimeChanged:
qDebug() << "VLC媒体播放器时间已更改";
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;
}3.代码示例
#pragma once
#include <QtWidgets/QWidget>
#include "ui_showWidget.h"
#include <QMenu>
#include <QActionGroup>
#include <vlc/vlc.h>
#include <QDebug>
#include <QFileDialog>
#include <QThread>
class showWidget : public QWidget
{
Q_OBJECT
public:
showWidget(QWidget *parent = nullptr);
~showWidget();
private slots:
void slotOpenFile();
void slotPlay();
private:
//事件处理回调
static void vlcEvents(const libvlc_event_t *ev, void *param);
private:
Ui::showWidgetClass ui;
private:
libvlc_instance_t *vlc_base = nullptr;
libvlc_media_t *vlc_media = nullptr;
libvlc_media_player_t *vlc_mediaPlayer = nullptr;
};
#include "showWidget.h"
#include <QTimer>
#pragma execution_character_set("utf-8")
showWidget::showWidget(QWidget *parent)
: QWidget(parent)
{
ui.setupUi(this);
this->setWindowTitle("视频播放器");
connect(ui.btnOpen, &QPushButton::clicked, this, &showWidget::slotOpenFile);
connect(ui.btnPlay, &QPushButton::clicked, this, &showWidget::slotPlay);
}
showWidget::~showWidget()
{
libvlc_release(vlc_base); //减少libvlc实例的引用计数，并销毁
}
void showWidget::slotOpenFile()
{
/*选择文件*/
QString filename = QFileDialog::getOpenFileName(this, "选择打开的文件", "D:/", tr("*.*"));
std::replace(filename.begin(), filename.end(), QChar('/'), QChar('\\'));
vlc_base = libvlc_new(0, NULL);
vlc_media = libvlc_media_new_path(vlc_base, filename.toUtf8().data());
if (!vlc_media) {
return;
}
// 创建libvlc实例和媒体播放器
vlc_mediaPlayer = libvlc_media_player_new_from_media(vlc_media);
if (!vlc_mediaPlayer) {
return;
}
libvlc_media_parse(vlc_media);
//获取事件管理器
libvlc_event_manager_t *em = libvlc_media_player_event_manager(vlc_mediaPlayer);
// 注册事件监听器
libvlc_event_attach(em, libvlc_MediaPlayerTimeChanged, vlcEvents, this);
libvlc_event_attach(em, libvlc_MediaPlayerEndReached, vlcEvents, this);
libvlc_event_attach(em, libvlc_MediaPlayerStopped, vlcEvents, this);
libvlc_event_attach(em, libvlc_MediaPlayerPlaying, vlcEvents, this);
libvlc_event_attach(em, libvlc_MediaPlayerPaused, vlcEvents, this);
libvlc_media_player_set_hwnd(vlc_mediaPlayer, (void *)ui.widgetShow->winId());
QTimer::singleShot(1000, this, &showWidget::slotPlay);
}
void showWidget::slotPlay()
{
libvlc_media_player_play(vlc_mediaPlayer);
}
//事件回调
void showWidget::vlcEvents(const libvlc_event_t *ev, void *param)
{
//处理不同的事件
qint64 pos;
switch (ev->type) {
case libvlc_MediaPlayerTimeChanged:
qDebug() << "VLC媒体播放器时间已更改";
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;
}
}