Use FFmpeg anequalizer Filter for Custom Parametric EQ

This guide explains how to use FFmpeg’s anequalizer (audio equalizer) filter to design and apply custom second-order parametric filters to your audio files. You will learn the syntax of the filter, the meaning of its key parameters—including how to specify a second-order configuration—and see practical command-line examples for shaping your audio streams.

The anequalizer Filter Syntax

The anequalizer filter allows you to configure high-order and second-order parametric equalizers by defining one or more frequency curves. The basic syntax requires passing a string of configuration parameters to the -af (audio filter) flag. Multiple curves are separated by the pipe character (|).

The syntax structure for a single curve is:

"cQ f=F w=W g=G t=T o=O"

Where cQ specifies the channel, and the remaining letters represent key-value parameters.

Key Parameters for Second-Order Filters

To apply a custom second-order parametric filter, you need to configure the following parameters within your filter string:

• c (Channel): Specifies which channel the filter applies to (e.g., c0 for the first channel/left, c1 for the second channel/right). If omitted, the curve applies to all channels.
• f (Frequency): The center frequency of the filter in Hz.
• w (Width): The bandwidth of the filter in Hz.
• g (Gain): The boost or cut applied at the center frequency, measured in dB.
• t (Type): The filter response type.
  • 0: Butterworth (highly recommended for clean parametric EQ cuts and boosts)
  • 1: Chebyshev Type I
  • 2: Chebyshev Type II
• o (Order): The filter order. Set this to 2 to apply a standard second-order parametric filter.

Practical Command Examples

Apply a Second-Order Boost to All Channels

To apply a \(+6\text{ dB}\) boost at \(1000\text{ Hz}\) with a bandwidth of \(200\text{ Hz}\) using a second-order Butterworth filter across all channels:

ffmpeg -i input.mp3 -af "anequalizer=f=1000 w=200 g=6 t=0 o=2" output.mp3

Apply Channel-Specific Equalization

To target the left channel (c0) and right channel (c1) with different parameters, separate the curves with a |:

ffmpeg -i input.wav -af "anequalizer=c0 f=800 w=150 g=-4 t=0 o=2|c1 f=1200 w=250 g=3 t=0 o=2" output.wav

In this command: * The left channel (c0) gets a \(-4\text{ dB}\) cut at \(800\text{ Hz}\). * The right channel (c1) gets a \(+3\text{ dB}\) boost at \(1200\text{ Hz}\).

Multi-Band Parametric Equalization

You can stack multiple filters on the same channel by defining multiple curves for that channel:

ffmpeg -i input.wav -af "anequalizer=c0 f=100 w=50 g=5 t=0 o=2|c0 f=2000 w=300 g=-6 t=0 o=2" output.wav

This applies both a low-frequency boost (\(100\text{ Hz}\)) and a mid-frequency cut (\(2000\text{ Hz}\)) to the left channel.