How to Apply DC Offset Correction in Ecasound

This article explains how to correct DC offset in an audio signal using Ecasound. While Ecasound does not have a single dedicated "dc-offset" command, DC offset correction is natively achieved using the high-pass filter operator (-efh), as well as through LADSPA plugin operators (-el). Below is a straightforward guide detailing which operators to use, how they work, and practical command-line examples.

Native Correction: The High-Pass Filter (-efh)

In digital signal processing, DC offset is direct current energy sitting at 0 Hz. The standard native way to remove DC offset in Ecasound is by applying a high-pass filter using the -efh operator:

-efh:cutoff_frequency

Setting the cutoff frequency below the human hearing threshold (typically between 5 Hz and 20 Hz) removes the 0 Hz DC bias completely without attenuating the audible bass content of your audio.

Example Usage

To remove DC offset from an input file named input.wav and output the cleaned audio to output.wav, run:

ecasound -i input.wav -efh:10 -o output.wav

In this command:

• -i input.wav defines the audio source.
• -efh:10 applies a high-pass filter with a cutoff frequency of 10 Hz, blocking the DC offset.
• -o output.wav designates the destination file.

LADSPA DC Correction Operator (-el)

If your workflow requires an algorithmic DC removal filter rather than a standard high-pass filter, Ecasound can host LADSPA plugins via the -el operator:

-el:plugin_label,param1,param2,...

Using Steve Harris’s LADSPA plugin set (SW_PLUGINS), you can load the dedicated DC removal filter (dcRemove):

ecasound -i input.wav -el:dcRemove -o output.wav

Summary

• Built-in Operator: Use -efh:cutoff_frequency (recommended value: 10 to 20) to eliminate DC bias using Ecasound's native filter engine.
• Plugin Operator: Use -el:dcRemove if you prefer dedicated LADSPA plugin processing.