Before implementing the entire system shown in Multirate Processing: Introduction, we recommend you design a system that consists of a cascade of filters FIR 1 and FIR 2 without the sample-rate compressor or expander. After verifying that the response of your two-filter system is correct, proceed to implement the complete multirate system and verify its total response. At first, use fixed compression and expansion factors of D=U=4 D U 4 . After you have verified that the multirate system works at a fixed rate, you should modify your code so that the rate can be changed easily. You must be able to quickly change the compression and expansion factors when you demo your code.