Filters

Compressor

Information on how audio dynamic range compression works, and on meaning and function of parameters in this filter is available in this Wikipedia article.

Perspective

With parameter Sense set to value Destination it is possible to set the corners of image anywhere in the destination image but there is visual glitch with sides of image being stretched, this is a known issue described here.

The workaround is to add a Crop filter before Perspective filter and cut atleast 1 pixel from all sides of the image.