How to Use FFmpeg anequalizer Filter for Parametric EQ

This article provides a straightforward guide on how to use the FFmpeg anequalizer audio filter to apply high-quality parametric equalization to your audio files. You will learn the core syntax of the filter, understand its key parameters—such as frequency, gain, bandwidth, and filter type—and explore practical command-line examples for single-band, multi-band, and channel-specific EQ configurations.

Understanding the anequalizer Syntax

The anequalizer filter allows you to configure one or more equalizer bands by defining their specific parameters. The basic structure of a single band configuration in the audio filter (-af) looks like this:

anequalizer=f=FREQUENCY:w=WIDTH:g=GAIN:t=TYPE

Here is a breakdown of the essential parameters you need to configure:

• f (Frequency): The center frequency of the band in Hz (e.g., f=1000 for 1 kHz).
• w (Width/Bandwidth): The width of the band. By default, this is measured in Hz.
• tb (Width Type): Specifies how the width (w) is interpreted. Set tb=0 for Hz (default), tb=1 for octaves, or tb=2 for Q-factor.
• g (Gain): The boost or cut in dB (e.g., g=6 to boost by 6 dB, g=-4 to cut by 4 dB).
• t (Filter Type): The type of filter band:
  • 0: Bandpass filter
  • 1: Peaking/EQ filter (most common for parametric EQ)
  • 2: Low-shelf filter
  • 3: High-shelf filter
• c (Channel): The channel index to apply the filter to (e.g., c0 for the first channel/left, c1 for the second channel/right). If omitted, the filter applies to all channels.

Practical Examples

1. Single-Band Peaking EQ

To boost a specific frequency (e.g., 1000 Hz) by 6 dB with a bandwidth of 200 Hz across all audio channels, use the following command:

ffmpeg -i input.mp3 -af "anequalizer=f=1000:w=200:g=6:t=1" output.mp3

2. Multi-Band Parametric EQ

To apply multiple EQ bands at once, separate each band configuration with a pipe character (|). The following command applies three bands: a low-shelf boost at 100 Hz, a peaking cut at 2500 Hz, and a high-shelf boost at 12000 Hz:

ffmpeg -i input.wav -af "anequalizer=f=100:w=50:g=4:t=2|f=2500:w=500:g=-5:t=1|f=12000:w=1000:g=3:t=3" output.wav

3. Using Q-Factor Instead of Bandwidth in Hz

If you prefer to define your EQ bands using a standard Q-factor (e.g., a Q of 1.4) instead of bandwidth in Hz, set the width type (tb) to 2:

ffmpeg -i input.mp3 -af "anequalizer=f=800:tb=2:w=1.4:g=-6:t=1" output.mp3

4. Channel-Specific Equalization

You can target individual audio channels by prefixing the band configuration with the channel parameter. For example, to apply a 5 dB boost at 400 Hz only to the left channel (c0):

ffmpeg -i input.wav -af "anequalizer=c0 f=400 w=100 g=5 t=1" output.wav