Generate White Noise of Specific Duration in FFmpeg

This guide demonstrates how to generate white noise of a specific duration in FFmpeg using audio source filters. While the sine source is designed for pure tones, the aevalsrc (expression evaluation) source is the primary tool for mathematically generating custom white noise. Below, you will find direct commands to create white noise using the evaluation source, alongside the standard native noise generator.

Generating White Noise with the Eval Source (aevalsrc)

The expression evaluation source (aevalsrc) allows you to generate audio using mathematical formulas. To generate white noise, you can use a random number generator scaled to the standard audio amplitude range of -1.0 to 1.0.

Run the following command to generate 10 seconds of white noise:

ffmpeg -f lavfi -i "aevalsrc=-1+random(0)*2:duration=10" output.wav

Parameter Breakdown: * -f lavfi: Forces the input format to use FFmpeg’s Libavfilter input virtual device. * aevalsrc=: The audio evaluation source filter. * -1+random(0)*2: The mathematical formula. random(0) produces a pseudo-random number between 0 and 1. Multiplying this by 2 and subtracting 1 scales the output to a range between -1.0 and 1.0, creating white noise. * duration=10 (or d=10): Sets the duration of the generated audio to exactly 10 seconds.

Why the sine Source is Not Used for White Noise

The sine source in FFmpeg is designed to generate a pure, single-frequency sine wave.

# This generates a pure 440Hz tone, NOT white noise:
ffmpeg -f lavfi -i "sine=frequency=440:duration=10" output.wav

By definition, white noise contains an equal intensity at all frequencies across the audible spectrum. Because a sine wave only produces a single frequency, it cannot be used to generate white noise. For mathematical generation, you must use the aevalsrc method shown above.

The Standard Alternative: anoisesrc

While aevalsrc is highly customizable, FFmpeg has a dedicated native source for generating noise called anoisesrc. It is highly optimized and easier to write.

To generate 10 seconds of white noise using the dedicated noise source, use this command:

ffmpeg -f lavfi -i "anoisesrc=color=white:duration=10:samplerate=44100" output.wav

Parameter Breakdown: * color=white: Specifies the noise color (you can also use pink or brown). * duration=10: Sets the audio length to 10 seconds. * samplerate=44100: Sets the output sample rate to 44.1 kHz.