Analogue to Digital Conversion. Also referred to as digitisation or quantisation. The conversion of analogue signals into digital data – normally for subsequent use in a digital machine. For TV, samples of audio and video are taken, the accuracy of the process depending on both the sampling frequency and the resolution of the analogue amplitude information – how many bits are used to describe the analogue levels. For TV pictures 8 or 10 bits are normally used; for sound, 16 or 20 bits are common while 24 bits is also possible. The ITU-R BT.601 standard defines the sampling of video components based on 13.5 MHz, and AES/EBU defines sampling of 44.1 and 48 kHz for audio. For pictures the samples are called pixels, which contain data for brightness and colour.

See also: AES/EBU, Binary, Bit, Into digits (Tutorial), Pixel