1) Sampling: sampling is the reduction of a continuous-time signal to a discrete-time signal. A common example is the conversion of a sound wave, a continuous signal, to a sequence of samples, a discrete-time signal.
2) Quantization: quantization is the proces of mapping input values from large set(often continuous set) to output values in a (countable) smaller set, often with a finite number of elements. Rouding and Truncation are typical examples of quantization processes.
3) Encoding : After each sample is quantized and the number of bits per smaple is decided, each sample can be changed to an nb-bit code word. The number of bits for each sample is determined from the number of quantization levels. If the number of quantization level is L
, the number of bits is nb=log2.L