how to keep the last frame in opencv in c++ <p>I need to keep the information in the last frame in a video file and then calculate PSNR between the last and whole frames. the video is running! when I get to the last frame I would miss all the previous frames information. so I can not calculate a formula between the last and the first frame :(</p> <pre><code>float *frames; //this pointer points to the frames float *p; for(int i=0; i&lt;sizeof frames; i++){ ... ; } </code></pre> <p>I do not know how to fill the for-loop :(</p> <p>thanks in advance.. </p>