Create a subfolder in source folder

Currently, SoundConverter offers to either place the new files in the source folder or to manually specify an output folder. A useful feature would be if the program also offered an option to automatically create a subfolder in the source folder where the converted files will be placed, so as to avoid mixing the input and output files. This is useful when the user wants to quickly convert files in a folder without having to manually specify an output, but doesn't want to delete the input files either so as to prevent the mixup of the two.