Problem: Some FFmpeg filters require spaces in the filter configuration. Unfortunately, spaces don't work well with Matterhorn as it tries to split the filter definition and send them to FFmpeg as a list of arguments rather than a single argument.
Make the argument parser of Matterhorn more “intellgent”
Introduce a space-placeholder
Let the user set the FFmpeg command in a way that can easily be parsed (e.g. a JSON array)