QT QGraphicsView, giving very slow framerates...

Hi all,
       I'm developing an ECG plotting device using a mini2440, I tried
using QWT but m facin certain probs implementing the lib on QT4, as a
result I moved to graphicsview...

I've uploaded a video of the same... 

http://www.youtube.com/watch?v=NYa9nSU0yXE

But graphicsview is giving extremely slow results! on the host computer its
running fine, but not on mini2440, The code goes as follows:

#include <QtGui>
#include "plot.h"
#include "ui_plot.h"

plot::plot(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::plot),
    scene1( new QGraphicsScene()),
    view1( new QGraphicsView ()),
    slidery(new QSlider(Qt::Vertical,parent))
{
    view1->setRenderHint(QPainter::Antialiasing);
  
    slidery->setMaximum(100);
    slidery->setMinimum(-100);
    slidery->setValue(0);

    ui->setupUi(this);

    ui->horizontalLayout->addWidget( view1);
    ui->horizontalLayout->addWidget( slidery);

    view1->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
    view1->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);

    scene1->setItemIndexMethod(QGraphicsScene::NoIndex);
  
    x1 = 0;
    x2 = 0;
    y1 = 0;
    y2 = 0;

    view1->centerOn(-100,0);

    savebutton->setFixedHeight(50);
    pausebutton->setFixedHeight(50);
    plotbutton->setFixedHeight(50);

    _Pen.setColor(Qt::gray);
    _Pen.setWidth(1);

   
view1->setBackgroundBrush(QBrush(QColor::QColor(204,51,51,50),Qt::CrossPatter
n));
    view1->setScene(scene1);
    _Pen.setColor(Qt::red);

    view1->show();
    QObject::connect(&clicker, SIGNAL(timeout()), this,
SLOT(StartPlotting()));
    clicker.start(16);
}

plot::~plot()
{
    delete view1;
    delete view2;
    delete view3;
    delete scene1;
    delete ui;
}

void plot::changeEvent(QEvent *e)
{
    QMainWindow::changeEvent(e);
    switch (e->type()) {
    case QEvent::LanguageChange:
        ui->retranslateUi(this);
        break;
    default:
        break;
    }
}

void plot::StartPlotting()
{
    x1=x2;
    y1=y2;
    x2=x1+2;
    y2=-(slidery->value());

    scene1->addLine(x1,y1,x2,y2,_Pen);
    view1->ensureVisible(x2+5,y2,10,100,x2+5,10);
}

regards,
Abhinit