ffmpeg -framerate 6 -loop 1 -i orange.png -i Voice102.ogg -c:v libx264 -preset veryfast -c:a copy -shortest voice102.mkv
The purpose of this command is to convert an audio-only file (e.g. Voice102.ogg) into a movie file. Someone knowledgeable about ffmpeg gave me the above command when I asked for best ffmpeg command in terms of (1) not altering the audio and (2) not increasing file size so much and (3) not taking a long time for the command to be completed.
orange.png is a 4x4 png that is in the same folder. (I basically copy this tiny PNG into every folder containing audio files I want to run this command on. But I could have just one orange.png in /home/Pictures/orangepixel/orange.png for the sake of this GUI way.
voice102.ogg is the file that I want to "convert" into a movie file.
Now, what I want is this process;
In Nemo file manager (I use Mint Cinnamon 18.3), I right click on the audio file,
Choose a new context menu item with a name like "Moviefy" or "Create movie file from this audio file"
Then I wait for a short period.
If I select more than one audio file (batch selection), I want every selected audio file to have a "movie-file equivalent".