Ecasound Fixed Band Graphic Equalizer Operator

In Ecasound, graphic equalization with fixed frequency bands is provided by the -el (or -eli) operator, which integrates external LADSPA equalizer plugins. While Ecasound features an internal three-band equalizer operator (-e3), its low and high crossover frequencies are adjustable rather than fixed. Consequently, dedicated fixed-band graphic equalization relies on the -el operator loading a standardized multi-band plugin such as Steve Harris's 15-band mbeq.

The -el Operator and Fixed-Band Graphic EQ

Ecasound offloads complex multi-band graphic equalization to the LADSPA architecture using two operator formats:

• -el:plugin_label,param1,param2,...: Loads a plugin using its textual label.
• -eli:plugin_unique_id,param1,param2,...: Loads a plugin using its unique numerical identifier.

To achieve standard graphic equalization with fixed frequency centers, the most common solution is the LADSPA mbeq (Multiband EQ, plugin ID 1197). This plugin provides 15 fixed frequency bands centered at 50Hz, 100Hz, 156Hz, 220Hz, 311Hz, 440Hz, 622Hz, 880Hz, 1.25kHz, 1.75kHz, 2.5kHz, 3.5kHz, 5kHz, 10kHz, and 20kHz.

Usage Syntax

To apply a 15-band fixed graphic equalizer in an Ecasound signal chain, pass the gains (in dB) for each of the 15 fixed bands:

ecasound -i input.wav -o output.wav -el:mbeq_1197,0,0,0,2,4,4,2,0,0,-2,-4,-4,-2,0,0

In this command:

• -el:mbeq_1197 calls the fixed-band equalizer.
• The comma-separated values represent the gain changes applied sequentially from the lowest frequency band (50Hz) to the highest frequency band (20kHz).

Native Alternative: The -e3 Operator

If external LADSPA plugins are unavailable, Ecasound includes a native three-band equalizer operator, -e3:

-e3:gain_low,gain_mid,gain_high,freq_low,freq_high

While -e3 can be treated as a fixed-band equalizer by holding freq_low and freq_high constant (e.g., standard points like 200Hz and 2000Hz), it is technically a semi-parametric shelving and peaking filter. For comprehensive graphic equalization across standard octaves or 1/3-octave fixed intervals, the -el LADSPA operator remains the standard mechanism in Ecasound.