How to Normalize Audio to 0 dBFS in Ecasound

Normalizing audio amplitude to zero decibels full scale (0 dBFS) in Ecasound requires using the volume analysis operator, -ev, in combination with the amplification operator, -ea. Because Ecasound is designed as a real-time, stream-based audio processor, it does not scan ahead in a single pass to automatically normalize peak levels. Instead, peak normalization to 0 dBFS is achieved through a standard two-step process: analyzing the signal with -ev to determine the maximum peak and required gain, then applying that gain with -ea.

The Operators Explained

The Analysis Operator: -ev

The -ev (envelope volume) operator analyzes the audio stream and outputs statistical volume data without altering the audio. When executed on an audio file, it calculates:

The Amplification Operator: -ea

The -ea:multiplier operator applies linear amplification across all channels. The parameter represents an amplitude scaling factor (where 100 represents 100% / unity gain, and values above or below amplify or attenuate accordingly).

Step-by-Step Normalization Process

Step 1: Analyze the Peak Level

Run Ecasound with the -ev operator directed to null output to inspect the file:

ecasound -i input.wav -ev

At the end of processing, Ecasound outputs volume statistics in the terminal, including a line indicating the peak amplitude and the required scaling value:

(eca-chainsetup) Volume analysis results:
...
-- multiplier for max peak: 1.45 (or percentage equivalent)

Step 2: Apply the Normalization Gain

Take the calculated multiplier and apply it using -ea to render the normalized file:

ecasound -i input.wav -o output.wav -ea:145

If the output provides a direct percentage or floating-point multiplier, adjust the parameter so the peak reaches exactly 1.0 (100% / 0 dBFS).

Alternative: Real-Time Peak Limiting with -eal

If dynamic peak control is needed in a single real-time stream rather than two-pass linear normalization, Ecasound provides the -eal:max-limit-% operator.

ecasound -i input.wav -o output.wav -eal:100

Setting -eal:100 restricts the maximum signal amplitude to 100% (0 dBFS). However, -eal operates as a limiter (compressing or clipping peaks that exceed the threshold) rather than applying uniform gain adjustment across the entire recording. For true linear normalization to 0 dBFS without altering dynamics, the -ev and -ea workflow remains the correct approach.