Sampling resolution and upsampling demonstrated

Updated: May 10 2010. Copyright (C) 2010 Jussi Laako. All rights reserved.

Since sampling resolutions and over-/up-sampling is hard to demonstrate over web, it is better explained using equivalent image processing technologies. These are very closely related to audio processing equivalents.

As a reminder, oversampling is mathematically equal to upsampling, but typically means more constrained variant.

192/24 hires

As a first example we take hires version of the sample, this is traditionally what is used in studios and sometimes available as FLAC download. This is equivalent of 192/24 audio file.

44.1/16 CD

This is how the reduced resolution on a CD looks like. This is equivalent of 44.1/16 audio file, before D/A conversion.

Filterless NOS

Now as a comparison, let's take a very minimalistic D/A conversion without oversampling or filtering. Some people prefer these "filterless NOS" DACs. Some artefacts can be clearly seen due to lack of needed sharp filtering.

NOS DAC with filtering

For NOS dac with steep enough filter the result would be like this.

4x oversampling, poor filtering

A traditional old school oversampling without heavy filtering yields following type of result. This is with 4x oversampling. Note that it is almost invisble that the dot patterns cosists of dots of different sizes. All dots look to be the same size. Straight lines and curves are rough and blocky with steps, completely unlike the original.

4x oversampling with filtering

Typical affordable proper oversampling and filtering results in fairly good results. Not very good resolution, but otherwise correct.

Audiophile upsampling

Typical audiophile upsampling produces slightly constrained results, but with quite good resolution.

Highend upsampling

At last, cost-no-object high-end upsampling. All the false steps/blocks from straight lines is gone. Smooth curves on the logo, just like in the original. No inconsistency in the dot pattern of the logo's lower edge or red area.