Available in print from (now McGraw Hill India) and on e‑commerce sites like Amazon, Flipkart. Some older editions are on archive sites for personal reference (check copyright).
A. Nagoor Kani’s Digital Signal Processing succeeds because it respects the difficulty of the subject matter. It acknowledges that DSP is hard and offers a scaffolded approach to learning it. While it may lack the expansive theoretical depth of Oppenheim, it wins on accessibility and clarity. For the undergraduate student staring down a semester of DSP, it is often the difference between confusion and confidence. digital signal processing by nagoor kani