Video signals constitute a rich source of visual information. They are made of a sequence of images, called frames, that are taken at regular time intervals (specified as the frame rate, generally expressed in frames per second) and show a scene in motion. With the advent of powerful computers, it is now possible to perform advanced visual analysis on video sequences—sometimes at rates close to, or even faster than, the actual video frame rate. This chapter will show you how to read, process, and store video sequences.
We will see that once the individual frames of a video sequence have been extracted, the different image processing functions presented in this book can be applied to each of them. In addition, we will also look at a few algorithms that perform a temporal analysis of the video sequence, compare adjacent frames to track objects, or cumulate image statistics over time in order to extract foreground objects.