In digital signal processing, sampling frequency is the rate at which sampling is done. Sampling frequency is usually measured in hertz, or samples per second.
When converting from analog to digital, the analog signal must usually be sampled -- that is, measured or read -- at discrete intervals of time. The length of the interval depends on the application, but is limited by the Nyquist-Shannon sampling theorem. The sampling frequency is the inverse of this number: the smaller the interval, the higher the frequency, and, in general, higher frequencies imply higher-quality sampling.
In digital audio, common sampling rates are:
When analogue video is converted to digital video, a different sampling process occurs, this time at the pixel frequency. Some common pixel sampling rates are: