Avanti GUI is a free front-end for FFmpeg with the option to insert AviSynth as pre-processor. It offers user friendly control over all basic and advanced FFmpeg options. A number of template examples are included. No need to be familiar with AviSynth to use the predefined Avanti/AviSynth pre-processor options. Avanti comes as a portable application packed in a zip folder and doesn't require installation.