Configure FFmpeg asupercut Filter Cutoff Frequency

This article explains how to configure the cutoff frequency in the FFmpeg asupercut audio filter. You will learn the exact syntax, the key parameters including cutoff and order, and practical command-line examples to apply this high-order, steep low-pass Butterworth filter to your audio files.

Understanding the asupercut Filter

The asupercut filter is a steep low-pass filter designed to cut off high frequencies above a specified threshold. Unlike standard low-pass filters, asupercut uses a high-order Butterworth design, allowing for an exceptionally sharp drop-off at the cutoff point.

To configure this filter, you primarily use two parameters: * cutoff (or c): Sets the cutoff frequency in Hz. Frequencies above this limit will be drastically attenuated. The default value is 20,000 Hz. * order (or o): Controls the steepness of the filter curve. The value must be an even integer between 4 and 20. The default is 20, which provides the sharpest cutoff.

Command Syntax and Examples

To apply the filter, use the -af (audio filter) flag followed by asupercut and your desired parameters.

Basic Cutoff Configuration

To set the cutoff frequency to 15,000 Hz while keeping the default filter order of 20, use the following command:

ffmpeg -i input.mp3 -af "asupercut=cutoff=15000" output.mp3

You can also use the short-hand parameter names:

ffmpeg -i input.mp3 -af "asupercut=c=15000" output.mp3

Adjusting Cutoff and Order

If you want to change both the cutoff frequency and the steepness of the curve, separate the arguments with a colon. For example, to set the cutoff to 8,000 Hz with a lower filter order of 12:

ffmpeg -i input.wav -af "asupercut=cutoff=8000:order=12" output.wav

Controlling Input Level

If the filtering process affects the overall volume of your output, you can use the level parameter to scale the input level (the default is 1):

ffmpeg -i input.wav -af "asupercut=c=12000:o=16:level=0.95" output.wav