Logarithmic curve for audio correction in ffmpeg

Question

I need to apply only logarithmic amplitude correction to audio files, without time effects influence.

In order to demonstrate how do I want to transform an audio, I synthesed an original triangle waveform (Triangle.wav):

Desired waveform (produced in CoolEdit using "Dynamic processigng") looks so:

Curve used in CoolEdit to produce desired amplitude transformations (attack and release times = 0 ms).

I couldn't achieve the desired result in ffmpeg. Here are several variants of what I tried:

ffmpeg -i "Triangle.wav" -acodec libmp3lame -ar 44100 -ac 1 -ab 64k -af "loudnorm" "Triangle_c.mp3"

-af "compand=0|0:1|1:-90/-900|-70/-70|-30/-9|0/-3:6:0:0:0"

-af "compand=points=-80/-80|-6/-6|0/-3.8|20/3.5"

What are the right parameters?

Answer 1

The all filters you tried are doing time effect influence so that is completely invalid approach. You should use aeval filter instead. But you would need math expression for that to work correctly.