Tracking a target in a raw image may not provide the best tracking performance in all cases. Often tracking a target in a processed image is better. The pre-processing may be edge detection such as a Sobel filter (shown here), or setting a threshold, noise filtering etc.
Using the Set Memory control the original image is saved to memory. The pre-processing (convolution) is performed on the main pixels. The target is tracked in the processed image, but the crop that is passed to the next control is extracted from the image in memory (if it exists). The type of pre-processing will vary depending on the video used.