Pulse code modulation, or PCM for short, is a process that converts a time- and value-continuous analog signal into a time- and value-discrete digital signal.
- Sampling of the analog signal with a constant sampling rate over time. The sampling rate must be more than twice as large as the highest frequency component occurring in the signal course.
- This is followed by quantization to discrete values with a finite number of digits. The quantization assigns a certain symbol to a certain range of values.
- Generation of the digital signal by assigning the individual symbols by means of coding. In many practical applications, the binary code is chosen for PCM.
Sampling rate – Sampling frequency – Sampling rate – Sampling frequency
The sampling rate or sampling frequency, also sampling rate, sampling rate or sampling frequency, is the frequency with which an analog signal is sampled in a given time. The unit is hertz (Hz). For sampling human speech, 8000 Hz is required. For audio CDs, a sampling rate of 44.1 kHz is used.
The sample is the determined/sampled value per time unit per channel. It is specified in bits or bytes.
- 8-bit: the sampled values are converted into the range 0 … 256 or -127 … 0 … 127.
- 16-bit: the sampled values are converted into the range -32768 … 0 … 32767.
For each channel (mono/stereo/5.1/ etc.) one sample (8-bit/1 byte, 16-bit/2 byte etc.) is calculated. The data rate is the total number of samples per time unit.