**5.1 Two main approaches**

In this chapter we discussed the use of saliency-based methods on two main approaches to image and video compression. The first one uses the result of the saliency maps to compress the signal but it does not modify the original spatial (frame resolution) and temporal (video length) size of the signal. The second one uses saliency maps to crop or reduce the spatio-temporal resolution of the signal. In this latter case, the compression is not obtained through signal quality reduction, but through quantity reduction. Of course, both methods can be used together and they are more or less interesting depending on the application.
