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Clipping is a form ofdistortion that limits asignal once it exceeds a threshold. Clipping may occur when a signal is recorded by asensor that has constraints on the range of data it can measure, it can occur when a signal isdigitized, or it can occur any other time ananalog ordigital signal is transformed, particularly in the presence ofgain orovershoot and undershoot.
Clipping may be described as hard, in cases where the signal is strictly limited at the threshold, producing a flat cutoff; or it may be described as soft, in cases where the clipped signal continues to follow the original at a reduced gain. Hard clipping results in many high-frequencyharmonics; soft clipping results in fewer higher-order harmonics and intermodulation distortion components.
In thefrequency domain, clipping produces strong harmonics in the high-frequency range (as the clipped waveform comes closer to asquare wave). The extra high-frequency weighting of the signal could maketweeter damage more likely than if the signal was not clipped.
Manyelectric guitarplayers intentionallyoverdrive their amplifiers (or insert a "fuzz box") to cause clipping in order to get a desired sound (seeguitar distortion).
In general, the distortion associated with clipping is unwanted, and is visible on anoscilloscope even if it is inaudible.[1]
In the image domain, clipping is seen asdesaturated (washed-out) bright areas that turn to pure white if allcolor components clip. In digital colour photography, it is also possible for individual colour channels to clip, which results in inaccurate colour reproduction.
A circuit designer may intentionally use aclipper orclamper to keep a signal within a desired range.
When an amplifier is pushed to create a signal with more power than it can support, it will amplify the signal only up to its maximum capacity, at which point the signal will be amplified no further.
Indigital signal processing, clipping occurs when the signal is restricted by the range of a chosen representation. For example in a system using 16-bitsigned integers, 32767 is the largest positive value that can be represented, and if during processing the amplitude of the signal is doubled,sample values of 32000 should become 64000, but instead they are truncated to the maximum, 32767. Clipping is preferable to the alternative in digital systems — wrapping — which occurs if thedigital hardware is allowed to "overflow", ignoring themost significant bits of the magnitude, and sometimes even the sign of the sample value, resulting in gross distortion of the signal.
The incidence of clipping may be greatly reduced by usingfloating point numbers instead of integers. However, floating point numbers are usually less efficient to use, sometimes result in a loss ofprecision, and they can still clip if a number is extremely large or small.
Clipping can be detected by viewing the signal (on an oscilloscope, for example), and observing that the tops and bottoms of waves aren't smooth anymore. When working with images, some tools can highlight allpixels that are pure white, allowing the user to identify larger groups of white pixels and decide if too much clipping has occurred.
To avoid clipping, the signal can be dynamically reduced using alimiter. If not done carefully, this can still cause undesirable distortion, but it prevents any data from being completely lost.
When clipping occurs, part of the original signal is lost, so perfect restoration is impossible. Thus, it is much preferable to avoid clipping in the first place. However, when repair is the only option, the goal is to make up a plausible replacement for the clipped part of the signal.