Video scalers solve resolution compatibility issues between different sources and destinations. The quality of the scaling determines that a source with a certain resolution will be displayed correctly on a screen that does not support that resolution. If the scaling engine is not good, we will see artifacts such as blocks of pixels that make it impossible to read text or blinking pixels that distorts colors, among others.
Presentation scalers are a group within scalers, which have several inputs, usually in different formats, and perform clean switching between them, even if the input resolutions are different. It can be a clean switching that allows mixing two signals or passing through black, in which case the switching is done when there is no visible output signal.
In both cases, Blustream has professional products to perform the resolution change with the best quality.