An ADC (analog-to-digital converter) is the chip that turns the continuous voltage from a microphone or line input into the discrete numbers of digital audio. It does the two defining operations together: sampling, measuring the voltage at a fixed rate such as 48,000 times a second, and quantization, rounding each measurement to the nearest value the bit depth allows. An anti-aliasing filter sits in front of it to remove frequencies above the Nyquist limit, which would otherwise fold into the audio as aliasing. The quality of an ADC — its clock stability, linearity, and noise floor — sets the real ceiling on capture, no matter how high the numbers on the spec sheet.
The book · Volume 4 of 7
Audio for Video: A Complete Guide to Sound in Video Products: From PCM and Codecs to Loudness, Accessibility, and Real-Time Voice Processing
The ADC is where audio quality is fixed for good: clipping, noise or a wrong sample rate here cannot be repaired later in the pipeline. Volume 4 covers the ADC in detail: sampling and sample rates, bit depth and dynamic range, quantization, aliasing and the PCM formats that carry captured audio into a video product. Written by Nikolay Sapunov, CEO at Fora Soft.
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