Oversampling is a technique of digital signal processing that helps audio software plug-ins to minimize the level of artifacts often caused by aliasing distortion.

The process of oversampling is done through means of sampling audio material greater than its Nyquist rate. For example, if you want to capture (or record) high-quality audio with a bandwidth of 20 kHz the sampling rate must exceed 40 kHz. That's why the standard sampling rate for a music CD is 44.1 kHz.

Likewise, when the sampling rate is 44.1 kHz this means the Nyquist rate will be 22.05 kHz. Whereby the information above 22.05 kHz is removed by a steep anti-aliasing filter.

So it goes without saying that the use of recording at 44.1 kHz sample rate isn't necessarily to hear sound up to that frequency range but to avoid the aliasing errors that would rather occur during the time of playback.

Oversampling in audio software plug-ins​

The amount of oversampling depends on the sampling rate of your current project. Therefore, when you set your virtual instrument or a sound effect plug-in to operate at 4x oversampling, this means digital signal processing will occur at a sampling rate of 176.4 kHz assuming your music session has a sampling rate of 44.1 kHz.

However, after the signal has been processed by the plug-in, that same signal needs to be downsampled back to its original 44.1 kHz or whatever the sampling rate of your music project.

Some cons of oversampling​

Even though the option of enabling oversampling on an audio software plug-in may increase processing accuracy for non-linear plug-ins there are trade-offs that are to be encountered such as:
  • Increase in audio latency (with some plug-ins, that is)
  • Increase in CPU usage (you can't oversample every single plug-in)
  • Bad downsampling or anti-aliasing filters can mess up your sound

Examples of some audio plug-ins that support oversampling are:​

  • Fab-Filter Pro-C (compressor)
  • Fab-Filter Pro-L (brickwall mastering limiter or maximizer)
  • Cytomic The Glue (compressor)
  • Image-Line Sytrus (FM synthesizer)
  • Xfer Records Serum (wavetable synthesizer)
  • IK Multimedia Stealth Limiter (brickwall mastering limiter or maximizer)
  • etc (the list is endless, go figure!)
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