avconv -i 20201020-f-en.mp4 -vn -acodec libmp3lame -ac 1 -ab 32k -ar 22050 20201020-f-en.mp3

avconv -i 20201020-f-si.mp4 -vn -acodec libmp3lame -ac 1 -ab 32k -ar 22050 20201020-f-si.mp3

avconv -i 20201020-f-ta.mp4 -vn -acodec libmp3lame -ac 1 -ab 32k -ar 22050 20201020-f-ta.mp3