In a digital audio system, in order to recover the analog signal from the digital words, a D/A converter is used. The output of the converter is a stair-step waveform which contains a great deal of high-frequency artifacts called images. To reconstruct a smooth replica of the original signal, the stair-step is passed through a steep lowpass filter, also called an anti-imaging filter. It is similar, or even identical, to the anti-aliasing filter at the input of the A/D converter, but its purpose is very different. Also called an anti-imaging filter. See quantization, decimation, FIR, IIR.