Pulse-code modulation

Pulse-code modulation (PCM) represents an analog signal as a sequence of numerical values measured at regular intervals. It encodes each sample as a discrete value, commonly using binary digits.

Sampling (signal processing): Sampling measures a continuous-time signal at discrete time intervals to produce a sequence of values. PCM begins by measuring the analog signal at evenly spaced instants.
Analog signal: An analog signal varies continuously in time or amplitude and can represent changing physical quantities. PCM converts this continuous representation into regularly spaced numerical measurements.
Linear pulse-code modulation: Linear pulse-code modulation assigns quantization levels at uniformly spaced intervals of signal amplitude. It is the common PCM form used for uncompressed digital audio.
Differential pulse-code modulation: Differential pulse-code modulation encodes differences between predicted and actual signal samples rather than each sample independently. It reduces the number of bits needed by exploiting similarity between successive PCM samples.
Quantization (signal processing): Quantization maps values from a continuous or large set to a finite set of discrete levels. PCM rounds each sample to one of a finite number of representable levels.
Digital signal: A digital signal represents information using discrete values rather than a continuously varying range. PCM produces a digital sequence from an analog input.
A-law: A-law is a logarithmic companding standard used to encode speech signals in digital telephone systems. It applies nonuniform quantization to PCM speech in many telephone networks.
Adaptive differential pulse-code modulation: Adaptive differential pulse-code modulation varies its quantization step size while encoding differences between successive signal values. It improves on basic PCM efficiency by adapting to changing signal levels.
Binary encoding: Binary encoding represents information using sequences of bits, each taking the value zero or one. PCM commonly stores each quantized sample as a binary word.
Bit depth: Bit depth is the number of bits used to represent each digital sample or pixel value. It determines how many quantization levels PCM can assign to each sample.

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