Music, for instance, may contain high-frequency components that are inaudible to humans. Temporal aliasing is a major concern in the sampling of video and audio signals. Aliasing can be caused either by the sampling stage or the reconstruction stage these may be distinguished by calling sampling aliasing prealiasing and reconstruction aliasing postaliasing. Spatial anti-aliasing techniques avoid such poor pixelizations. If the image data is processed in some way during sampling or reconstruction, the reconstructed image will differ from the original image, and an alias is seen.Īn example of spatial aliasing is the moiré pattern observed in a poorly pixelized image of a brick wall.
When a digital image is viewed, a reconstruction is performed by a display or printer device, and by the eyes and the brain.
For spatial anti-aliasing, the types of anti-aliasing include fast sample anti-aliasing (FSAA), multisample anti-aliasing, and supersampling.ĭots in the sky due to spatial aliasing caused by halftone resized to a lower resolution Suitable reconstruction filtering should then be used when restoring the sampled signal to the continuous domain or converting a signal from a lower to a higher sampling rate. moiré patterns in digital images) this type of aliasing is called spatial aliasing.Īliasing is generally avoided by applying low-pass filters or anti-aliasing filters (AAF) to the input signal before sampling and when converting a signal from a higher to a lower sampling rate. It can also occur in spatially sampled signals (e.g. It also often refers to the distortion or artifact that results when a signal reconstructed from samples is different from the original continuous signal.Īliasing can occur in signals sampled in time, for instance digital audio, or the stroboscopic effect, and is referred to as temporal aliasing. In signal processing and related disciplines, aliasing is an effect that causes different signals to become indistinguishable (or aliases of one another) when sampled. Halfway through the 24-second loop, the objects appear to suddenly shift and head in the reverse direction, towards the left. The speed of the "camera", moving towards the right, constantly increases at the same rate with the objects sliding to the left. The motion of the 'camera' at a constant shutter speed creates temporal aliasing known as the wagon wheel effect.
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