read successive frames OpenCV using cvQueryframe

Question

I have a basic question in regards to cvQueryFrame() in OpenCV.

I have the following code:

IplImage *frame1,*frame2;
frame1 = cvQueryFrame(capture         


        

Answer 1

ok following from Laurent's answer: I believe the key is cvCloneImage(). cvCloneImage creates a new copy of the original image including the header, ROI, imageData etc. and then points frame2 to this new data.

Since cvQueryFrame is a wrapper for cvGrabFrame & cvRetrieveFrame together I didn't want to split up the functions, so with a small modification I can still use cvQueryFrame.

Below is my modified solution.

IplImage *frame = cvQueryFrame(capture); //to read properties of frame.
IplImage *frame2 = NULL;


while (1){
    if(frame2) 
        frame = cvCloneImage(frame2); // copy image to allow grabbing next frame
    frame2 = cvQueryFrame(capture); //read next frame
    if(!frame2) break; //if frame cannot be read, EOF so break from loop
}

I hope you understand what I've done here. Feel free to ask any more questions.