Main Page | See live article | Alphabetical index A quadrature mirror filter is a filter which splits an input signal into two bands which are subsampled by a factor of 2. The upper band has inverted frequencies, i.e. low frequencies are encoded as high frequencies and vice versa. Frequencies in the transition band are encoded in the low passed and the high passed band with different amplitudes. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.