An image is to be compressed using JPEG compression that uses 4x4 blocks instead of 8x8 blocks. The remaining compression steps remain unchanged. One of the 4x4 blocks after Discrete Cosine Transform (DCT) is shown in Figure 4. 63 53 6 6 |43 33 6 6 5 5 00 5 5 00 Figure 4 a) Explain why Discrete Cosine Transform (DCT) is used instead of Discrete Fourier Transform (DFT).

a) In today's environment, digital communication has made technology more pleasant. Discuss the recommended compression techniques for still pictures.b) Among the coding schemes available in communication systems, remark on the one that tries to reduce data size by reducing it.

How much does encoding technique effectiveness vary? Which one is now depended on, and why?

Explain in your own words what is meant by the term "sub-band coding" in the field of acoustics, as well as what part it plays in the compression of MP3 files, and use this information to answer the following question: