Editing Upsampling (section)

{{Short description|Digital signal resampling method}}
In [[digital signal processing]], '''upsampling''', '''expansion''', and '''interpolation''' are terms associated with the process of [[sample rate conversion|resampling]] in a [[multi-rate digital signal processing]] system. ''Upsampling'' can be synonymous with ''expansion'', or it can describe an entire process of ''expansion'' and filtering (''interpolation'').<ref name=Oppenheim/><ref name=Crochiere/><ref name=Poularikas/> When upsampling is performed on a sequence of samples of a ''signal'' or other continuous function, it produces an approximation of the sequence that would have been obtained by sampling the signal at a higher rate (or [[Dots per inch|density]], as in the case of a photograph). For example, if [[compact disc]] audio at 44,100 samples/second is upsampled by a factor of 5/4, the resulting sample-rate is 55,125.

[[File:Multirate_upsampling_(interpolation)_filter.svg|thumb|350px|Fig 1: Depiction of one dot product, resulting in one output sample (in green), for the case L=4, n=9, j=3. Three conceptual "inserted zeros" are depicted between each pair of input samples. Omitting them from the calculation is what distinguishes a multirate filter from a monorate filter.]]