downsampling

n. act of reducing the resolution of a digital image; act of reducing the quality of a digital sound file by lowering the frequency of the sampling rate

v. reduce the resolution of a digital image; reduce the quality of a digital sound file by lowering the frequency of the sampling rate

In signal processing, downsampling (or "subsampling") is the process of reducing the sampling rate of a signal. This is usually done to reduce the data rate or the size of the data.The downsampling factor (commonly denoted by M) is usually an integer or a rational fraction greater than unity. This factor multiplies the sampling time or, equivalently, divides the sampling rate. For example, if compact disc audio is downsampled by a factor of 5/4 then the resulting sampling rate goes from 44,100 Hz to 35,280 Hz, which reduces the bit rate from 1,411,200 bit/s to 1,128,960 bit/s (assuming that a 32 bit value is sample each time).
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