Waveform

Extract audio amplitude data for visualization — useful for building waveform displays in audio/video editors and players.

Quick example

import { ffmpeg } from "ffmpeg-kit";

const result = await ffmpeg.waveform({
  input: "audio.wav",
  fps: 10,
});

console.log(result.samples);    // Float32Array of amplitude values
console.log(result.sampleRate); // Samples per second (same as fps)
console.log(result.duration);   // Total duration in seconds

Function signature

function waveform(options: WaveformOptions): Promise<WaveformResult>;

Options

Parameter	Type	Default	Description
input	string	—	Input audio or video file path
fps	number	10	Samples per second in the output data
channel	number | "mix"	"mix"	Channel to extract (0 = left, 1 = right, "mix" = downmix)
normalize	boolean	true	Normalize amplitude values to [-1, 1] range

Result type

interface WaveformResult {
  samples: Float32Array;   // amplitude values, one per (1/fps) seconds
  sampleRate: number;      // = fps
  duration: number;        // total audio duration in seconds
  channels: number;        // channel count of source audio
  peakAmplitude: number;   // max absolute value in samples
}

Rendering a waveform

The samples array has one value per 1/fps seconds. For a 60-second file at fps: 10, you get 600 samples.

const result = await ffmpeg.waveform({ input: "podcast.mp3", fps: 20 });

// Canvas-based rendering example
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
const { samples, duration } = result;

const width = canvas.width;
const height = canvas.height;
const midY = height / 2;
const stepX = width / samples.length;

ctx.beginPath();
for (let i = 0; i < samples.length; i++) {
  const x = i * stepX;
  const amplitude = Math.abs(samples[i]) * midY;
  ctx.fillRect(x, midY - amplitude, stepX - 1, amplitude * 2);
}

Related

• Audio — normalize and process audio
• Silence Detection — detect quiet regions