c++ - g_main_loop_run 阻塞 Qthread 并且不允许停止视频

Question

我为 gstreamer 创建了一个单独的类来流式传输视频。
此类通过使用 moveToThread() 在单独的线程上运行。
我正在使用 Qt5.5 进行开发。
当我在主线程上发出 startcommand 时，Qthread 启动并且 gstreamer 使用 g_main_loop_run 流式传输视频。这绝对没问题。但不知何故 g_main_loop_run 阻塞了线程，当我发出信号以停止来自主线程的视频时，它不会执行 gstreamer 类中的插槽。

有人可以告诉我如何解决这个问题吗？我可以用其他命令替换 g_main_loop_run 或者可以使用 g_main_loop_quit( gloop );以另一种方式。

void StreamingVideo::slotStartStream() // this slot called on start of thread from main thread
{

    if( !isElementsLinked() )
    {
       qDebug() << " we are emitting in dummy server ";
        //emit sigFailed( "elementsFailed" ); // WILL CONNECT IT WITH MAIN GUI ONXCE CODE IS FINISHED
        return;
    }

    gst_bus_add_watch( bus, busCall, gloop );
    gst_object_unref( bus );

    //proper adding to pipe
    gst_bin_add_many( GST_BIN( pipeline ), source, capsFilter, conv, videoRate, capsFilterRate,
                      clockDisplay, videoEnc, udpSink, NULL
                     );

    //proper linking:
    gst_element_link_many( source, capsFilter, conv, videoRate, capsFilterRate, clockDisplay, videoEnc, udpSink, NULL );

    g_print("Linked all the Elements together\n");
    gst_element_set_state( pipeline, GST_STATE_PLAYING );
    // Iterate
    g_print ("Running...\n");
    emit sigStartStream(); // signal to main thread to issue success command . works fine
    g_main_loop_run( gloop );
    g_print ("Returned, stopping playback\n");
    //gst_element_set_state (pipeline, GST_STATE_NULL);
    if( g_main_loop_is_running( gloop ) )
    {
        qDebug() << " in g_main_loop_is_runnung  emiting signal ";
        emit sigStartStream();
    }
    if( !g_main_loop_is_running( gloop) )
    {
        qDebug() << "in not gmain running thread id";
        qDebug() << QThread::currentThreadId();
    }

}



void StreamingVideo::slotStopStream() // THIS SLOT IS NOT CALLED WHEN VIDEO RUNNING
{
    qDebug() << " we are planning to stop streaming  stramingVideo::slotStopStream ";
    g_print ("Returned, stopping playback\n");
    g_main_loop_quit( gloop );
    gst_element_set_state (pipeline, GST_STATE_NULL);
   // g_main_loop_quit( gloop );
    releaseMemory();
    emit sigStopStream(); // signal to main thread to issue message saying video has stopped.
}

//主线程某处

 threadStreaming = new QThread();
 streamVideo    = new StreamingVideo( "127.0.0.1"); // we will automate this ip address later on

        streamVideo->moveToThread( threadStreaming );

        connect( threadStreaming, SIGNAL( started() ),        streamVideo,     SLOT( slotStartStream() ) );
        connect( streamVideo,     SIGNAL( sigStopStream() ),  threadStreaming, SLOT( quit() ) );
        connect( streamVideo,     SIGNAL( sigStopStream() ),  streamVideo,     SLOT(deleteLater() ) );
        connect( threadStreaming, SIGNAL( finished() ),       threadStreaming, SLOT(deleteLater() ) );

        connect( streamVideo,     SIGNAL( sigStartStream() ), this, SLOT( slotTrueStreamRun()  ) );
        connect( streamVideo,     SIGNAL( sigStopStream() ),  this, SLOT( slotFalseStreamRun() ) );

        connect( this,            SIGNAL( sigMopsCamStopCmd() ), streamVideo, SLOT(slotStopStream() ) );
        threadStreaming->start();

Answer 1

无需依赖GMainLoop。如果没有 g_main_loop_run()，管道应该可以正常运行。

您需要注意的一件事是，您的主 Qt 应用程序循环要么必须轮询管道的总线以获取消息，要么使用 gst_bus_set_sync_handler 为要调用的总线设置回调函数消息到达。对于后者，您必须注意，然后从管道的线程而不是应用程序的线程调用此函数。不过在这里发出信号应该没问题。

如果您想采用线程方式，则必须在您的应用程序中手动创建一个运行 GMainLoop 的线程。也有可能——不过，上述方法对我来说似乎更简单、更干净。