3.1 Introduction to conversion
The most useful and therefore common signal representation is pulse code modulation or PCM which was introduced in Chapter 1. The input is a continuous-time, continuous-voltage video waveform, and this is converted into a discrete-time, discrete-voltage format by a combination of sampling and quantizing. As these two processes are independent they can be performed in either order. Figure 3.1(a) shows an analog sampler preceding a quantizer, whereas (b) shows an asynchronous quantizer preceding a digital sampler.