How to Use the FFmpeg anequalizer Filter

This article provides a quick, practical guide on how to use the anequalizer (audio equalizer) filter in FFmpeg. You will learn the basic syntax, the meaning of its key parameters, and how to apply real-world configuration examples to adjust your audio’s bass, treble, and mid-range frequencies.

Understanding the anequalizer Filter

The anequalizer filter is a high-order parametric audio equalizer. It allows you to precisely boost or cut specific audio frequencies. Unlike simpler graphic equalizers, a parametric equalizer gives you control over the center frequency, the gain (volume adjustment), and the bandwidth (how wide of a frequency range is affected).

The basic syntax for the filter is:

ffmpeg -i input.mp3 -af "anequalizer=f=FREQ g=GAIN w=WIDTH t=TYPE" output.mp3

Parameter Definitions

Each frequency band configuration uses the following parameters:

• f (Frequency): The target center frequency in Hz (e.g., 100 for bass, 1000 for mids, 10000 for treble).
• g (Gain): The amount of boost or cut in dB. Positive numbers (e.g., 6) boost the frequency; negative numbers (e.g., -6) cut it.
• w (Width): The bandwidth of the filter in Hz. A smaller width targets a narrow, specific frequency, while a larger width affects surrounding frequencies.
• t (Type): The type of filter band.
  • 0: Peaking / Bandpass (ideal for target frequencies in the mid-range).
  • 1: Low-shelf (ideal for adjusting bass below the target frequency).
  • 2: High-shelf (ideal for adjusting treble above the target frequency).

Practical Examples

1. Boosting the Bass

To boost the low-end frequencies (bass) of an audio file, use a low-shelf filter (t=1) centered around 80 Hz with a gain boost of 6 dB:

ffmpeg -i input.wav -af "anequalizer=f=80 g=6 w=50 t=1" output.wav

2. Reducing High-Frequency Hiss (Treble Cut)

To reduce harsh high frequencies or hiss, use a high-shelf filter (t=2) to cut frequencies above 8000 Hz by 10 dB:

ffmpeg -i input.wav -af "anequalizer=f=8000 g=-10 w=1000 t=2" output.wav

3. Creating a Multi-Band Equalizer

You can apply multiple equalizer bands simultaneously by separating each configuration block with a vertical bar (|).

The following command boosts bass at 100 Hz, cuts muddy mid-range frequencies at 1000 Hz, and boosts high-end clarity at 10,000 Hz:

ffmpeg -i input.wav -af "anequalizer=f=100 g=8 w=50 t=0|f=1000 g=-4 w=200 t=0|f=10000 g=6 w=1000 t=0" output.wav

4. Applying Equalization to Specific Channels

By default, the filter applies to all channels. If you want to target a specific channel, prefix the parameters with c0 (left channel) or c1 (right channel):

ffmpeg -i input.wav -af "anequalizer=c0 f=1000 g=5 w=200 t=0" output.wav