Delay of 20 milliseconds in the left channel of an audio file (e.g mp3) using ffmpeg?

Question

How do I make a delay of 20 milliseconds in the left channel of an audio file (e.g mp3) using ffmpeg ??

I usually enable this option under ffdshow audio processor while playing audio using MPC-HC

Is it possible to do the same in howlerjs (a strong textjavascript audio library) ? (I mean this audio effect)

Somewhat like this kind of effect: Just delay the either channel by 20ms Like we do in Adobe Audition

Answer 1

Use the adelay filter:

ffmpeg -i input.mp3 -af "adelay=20|0" output.mp3

Answer 2

You could grab the left source of the file, add delay using -itsoffset and mix the final output https://trac.ffmpeg.org/wiki/AudioChannelManipulation.