When working with raw video images in video processing applications, many times the data structure that represents the image has a stride field. The stride is usually the number of bytes from one row of the video image to the next. This is different from the width which is usually the number of pixels in a row.
There are various reasons for the stride field to exist. For one, many video libraries allocate large buffers anticipating the need for high-resolution images even if lower-resolution images are actually used. If the stride field exists, it is important to use it properly.