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Aliasing is an effect that causes different signals to become indistinguishable from each other during sampling. Aliasing is characterized by the altering of output compared to the original signal because resampling or interpolation resulted in a lower resolution in images, a slower frame rate in terms of video or a lower wave resolution in audio. Anti-aliasing filters can be used to correct this problem.
In a digital image, aliasing manifests itself as a moiré pattern or a rippling effect. This spatial aliasing in the pattern of the image makes it look like it has waves or ripples radiating from a certain portion. This happens because the pixelation of the image is poor; when our eyes interpolate those pixels, they simply do not look right.
Aliasing can also occur in videos, where it is called temporal aliasing because it is caused by the frequency of the frames rather than the pixelation of the image. Because of the limited frame rate, a fast-moving object like a wheel looks like it’s turning in reverse or too slowly; this is called the wagon-wheel effect. This is determined by the frame rate of the camera and can be avoided by using temporal aliasing reduction filters during filming.
In audio, aliasing is the result of a lower resolution sampling, which translates to poor sound quality and static. This occurs when audio is sampled at a lower resolution than the original recording. When the sinusoidal audio wave is converted to a digital wave using a lower resolution sample, only a few specific points of the wave are taken as data. This results in a wave with a lower frequency than the original, translating to a loss of data and audio quality.