Help in creating video streaming app

[high_flyer]

I would change your code along the lines of:

#
image =  QImage( width,  height, QImage::Format_Rgb32);
unsigned char *buff = image.bits();
 
while(1)
{
 memcpy(buff,(uchar*)deviceAccessTool.nextFrame(),/*size in bytes of the frame*/); //this should be faster then allocating each time a new image
image = myprocessingcode(image); //if you want this to fit in 25hz, then you should take in consideration that grabbing and processing should not be longer then 40ms!
myPixmap = myPixmap.fromImage(image);
myLabel.setPixmap(myPixmap);
window.repaint();
}

#
image =  QImage( width,  height, QImage::Format_Rgb32);
unsigned char *buff = image.bits();

while(1)
{
 memcpy(buff,(uchar*)deviceAccessTool.nextFrame(),/*size in bytes of the frame*/); //this should be faster then allocating each time a new image
image = myprocessingcode(image); //if you want this to fit in 25hz, then you should take in consideration that grabbing and processing should not be longer then 40ms!
myPixmap = myPixmap.fromImage(image);
myLabel.setPixmap(myPixmap);
window.repaint();
}

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Also since I dont have much experiance with qt4, I would suggest to try (and can't say this IS better) the following:
instead of :

myPixmap = myPixmap.fromImage(image);
myLabel.setPixmap(myPixmap);

myPixmap = myPixmap.fromImage(image);
myLabel.setPixmap(myPixmap);

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I would try to use the QPainter with a QImage as paint device (one of the new Qt4 fetures, it could be faster then setPixmap()):

//somewhere declared: QPainter painter(&myLabel);
painter.drawImage(maLabel.rect(),image,image.rect());

//somewhere declared: QPainter painter(&myLabel);
painter.drawImage(maLabel.rect(),image,image.rect());

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So put togeather it would look somthing like:

image =  QImage( width,  height, QImage::Format_Rgb32);
unsigned char *buff = image.bits();
QPainter painter(&myLabel);
 
while(1)
{
 memcpy(buff,(uchar*)deviceAccessTool.nextFrame(),/*size in bytes of the frame*/);
image = myprocessingcode(image); //if you want this to fit in 25hz, then you should take in consideration that grabbing and processing should not be longer then 40ms!
painter.drawImage(maLabel.rect(),image,image.rect());
}

image =  QImage( width,  height, QImage::Format_Rgb32);
unsigned char *buff = image.bits();
QPainter painter(&myLabel);

while(1)
{
 memcpy(buff,(uchar*)deviceAccessTool.nextFrame(),/*size in bytes of the frame*/);
image = myprocessingcode(image); //if you want this to fit in 25hz, then you should take in consideration that grabbing and processing should not be longer then 40ms!
painter.drawImage(maLabel.rect(),image,image.rect());
}

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Please note, under Qt3 I can show you how to do a video stream in a crossplatform way, but under Qt4, this code is only a suggestion I think you shoud try, and take in consideration I didn't test it!
Since drawing in Qt4 is done only in a paint event, this all needs to be in a paint event...

Any comments from you Qt4 experts?