Qt Data transfer

[A Former User]

hello! I have 2 unrelated questions:

1. Is there a way to hold the main in a wait mode?
   meaning the main will pass the return a.exec(); (a is a Qapplication) and enter a wait mode until his subprocesses will end(the gui for example).

2. I'm streaming a video through netcat to a socket. from that socket I need to stream the data to an mplayer process.
   I've managed to do that through this code:
   void ClientVidless::run()
   {
   socket = new QTcpSocket(this);
   QStringList args1;

   args1 += "-fps";
   args1 += "60";
   args1 += "-cache";
   args1 += "1024";
   args1 += "-slave";
   args1 += "-wid";
   args1 += QString::number((int)ui->widget->winId());
   args1 += "-";

   process1 = new QProcess(0);

   process1->start("C:\Program Files (x86)\MPlayer for Windows\mplayer.exe",args1);

   qDebug() << "Connecting...";

   socket->connectToHost("192.168.1.109",5001);

   if (!socket->waitForConnected(1000))
   qDebug() << "Error:" << socket->errorString();

   connect(socket,SIGNAL(connected()),this,SLOT(connected()));
   connect(socket,SIGNAL(disconnected()),this,SLOT(disconnected()));
   connect(socket,SIGNAL(bytesWritten(qint64)),this,SLOT(bytesWritten(qint64)));
   connect(socket,SIGNAL(readyRead()),this,SLOT(readyRead()));

}

void ClientVidless::readyRead()
{

Data = socket->readAll(); //Data is a QByteArray

qDebug() << " Data in: " << Data;

process1->write(Data);

}

simply when ready read is emitted the socket is read and then writing to the process.
The problem is that the video is really slow with a lot of lag.
What is the best and fastest way in transferring data into a process?
What is the difference between read/write to readdata/writedata functions, and how to use them(they're virtual protected)?
Thanks for the helpers.