OpenGL frame rate issue

[PeterG]

Hi everyone,

I am working on TI AM5728 EVM board, linux from TI SDK.

I have an simple Qt openGL widget that just scroll a 1920*640 image on the screen, and the image is preloaded.

When I set the widget window to 800640 which is the default of the EVM screen, the time between each frame is 16-17ms, or 60 Hz, which is good. And when I connect to a external HDMI display(the monitor is set at 19201080) and the widget stay at 800*640, the time is still 16-17ms, it is normal and reasonable so far.

but when I increase the resolution to 1000640 and add little by little (1100640 1200640,etc) the strange thing starts.
@1000640: 16-17ms.
@1100640: 16-17ms.
@1200640: 90% of the time 16-17ms, 10% of the time 33-34 ms, which is 30Hz
@1300*640: 80% of the time 33-34ms, 20% of the time 16-17 ms.
@1300+ *640: all 33-34 ms.

It seems like somewhere around at resolution 1200640, there is a limit, once I cross the limit, it half the FPS.
My goal is to run it at 1920640@60fps.
Please help.

There is the part of my code. modified from an example.

MainWidget::MainWidget(QWidget *parent) :
    QOpenGLWidget(parent),
    geometries(0),
    texture(0),
    angularSpeed(0)
{
}

MainWidget::~MainWidget()
{
    // Make sure the context is current when deleting the texture
    // and the buffers.
    makeCurrent();
    delete texture;
    delete geometries;
    doneCurrent();
}


void MainWidget::timerEvent(QTimerEvent *)
{
        movement=(movement>2)?0:movement+0.006;
      int t=timer0.elapsed()-temp;
      if((t<16)||(t>17))
       qDebug() << t << "milliseconds";
        temp=timer0.elapsed();
    update();
}

void MainWidget::initializeGL()
{

    QSurfaceFormat format;
    format.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
    format.setSwapInterval(1);

    setFormat(format);
    initializeOpenGLFunctions();
   glClearColor(1.0f,1.0f,1.0f,1.0f);
    setGeometry(0, 0, 1300, 640);

    initShaders();
    initTextures();

    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    geometries = new GeometryEngine;
   timer.start(0, this);

}


void MainWidget::initTextures()
{

    // Load image
    Image = QImage(800, 640, QImage::Format_RGB888);
    Image = QImage(":/Test.bmp");
    texture = new QOpenGLTexture(Image.mirrored());
   // texture->setFormat(QOpenGLTexture::RGB8U);

    // Set nearest filtering mode for texture minification
    //texture->setMinificationFilter(QOpenGLTexture::Nearest);

    // Set bilinear filtering mode for texture magnification
    //texture->setMagnificationFilter(QOpenGLTexture::Linear);

    // Wrap texture coordinates by repeating
    // f.ex. texture coordinate (1.1, 1.2) is same as (0.1, 0.2)
    //texture->setWrapMode(QOpenGLTexture::Repeat);
}

void MainWidget::resizeGL(int w, int h)
{
    // Calculate aspect ratio
    //qreal aspect = qreal(w) / qreal(h ? h : 1);

    // Set near plane to 3.0, far plane to 7.0, field of view 45 degrees
    const qreal zNear = 1.0, zFar = 5.5, fov = 28;

    // Reset projection
    //projection.setToIdentity();

    // Set perspective projection
    projection.perspective(fov, 1, zNear, zFar);
}

void MainWidget::paintGL()
{
    texture->bind();
    // Calculate model view transformation
    QMatrix4x4 matrix;
    matrix.translate(movement, 0.0, -5.0);
    //matrix.rotate(rotation);

    // Set modelview-projection matrix
    program.setUniformValue("mvp_matrix", projection * matrix);
    // Use texture unit 0 which contains cube.png
    program.setUniformValue("texture", 0);
    // Draw cube geometry
    geometries->drawCubeGeometry(&program);

}
//your code here

[A Former User]

Hi! Why do you think this issue is related to Qt? Maybe the GL hardware (or driver) just isn't capable enough.