Ecasound Downsampling and Bit-Crushing Chain Operator

Ecasound is a versatile command-line digital audio workstation and signal processor that supports complex sound design effects. While Ecasound includes built-in operators for amplitude, filtering, and time delays, downsampling and bit-crushing effects are handled through external plugin chain operators. This guide identifies the specific chain operator required, details its parameter syntax, and provides a clear example of how to implement real-time sample rate decimation and bit reduction in an audio chain.

The Chain Operator: -el (LADSPA Plugin Integration)

Ecasound achieves downsampling and bit-crushing through the -el (LADSPA by label) or -eli (LADSPA by ID) chain operator. Because Ecasound does not feature a hardcoded internal bit-crusher, it uses its LADSPA host operator to load modular audio destruction tools—most notably the SWH (Steve Harris) decimator plugin (ID 1202).

For users utilizing LV2 plugins instead of LADSPA, the corresponding operator is -elv2.

Syntax and Parameters

When loading the decimator plugin via the -el chain operator, pass the effect parameters as a comma-separated list directly after the plugin label:

-el:decimator,bit_depth,sample_rate

• bit_depth: Specifies the bit resolution (typically ranging from 1 to 24). Lowering this value quantizes the audio, creating harsh digital distortion and reducing dynamic range.
• sample_rate: Specifies the decimated target sampling rate in Hertz (e.g., 8000 or 4000). Reducing this value removes high-frequency detail and introduces heavy aliasing distortion.

Practical Example

To process an audio file named input.wav, reduce its bit resolution to 8-bit, decimate its effective sample rate to 8,000 Hz, and save the result to output.wav, run:

ecasound -i:input.wav -el:decimator,8,8000 -o:output.wav

If referencing the plugin by its unique numerical identifier instead of its name, use the -eli operator:

ecasound -i:input.wav -eli:1202,8,8000 -o:output.wav

This operator allows continuous modulation inside interactive Ecasound sessions, letting you automate or adjust the bit depth and decimation rates in real time.