[1] Application areas include image scaling[2] and audio/visual systems, where different sampling rates may be used for engineering, economic, or historical reasons.
Sample-rate conversion prevents changes in speed and pitch that would otherwise occur when transferring recorded material between such systems.
The term multi-rate digital signal processing is sometimes used to refer to systems that incorporate sample-rate conversion.
In method 1, a slow pre-computation (such as the Remez algorithm) can be used to obtain an optimal (per application requirements) filter design.
This was based on a TV rate camera viewing a monitor displaying the Apollo slow-scan images.