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audioBufferToDataUrl()

Part of the @remotion/media-utils package of helper functions. Available from v2.5.7.

This API takes an AudioBuffer instance and converts it to a Base 64 Data URL so it can be passed to an <Html5Audio /> tag.

API Usage​

import {audioBufferToDataUrl} from '@remotion/media-utils';

const str = audioBufferToDataUrl(audioBuffer);

Example: Rendering a sine tone​

The following composition will render a sine tone with a C4 pitch.

import {audioBufferToDataUrl} from '@remotion/media-utils';
import {useCallback, useEffect, useState} from 'react';
import {Html5Audio, cancelRender, continueRender, delayRender, interpolate, useVideoConfig} from 'remotion';

const C4_FREQUENCY = 261.63;
const sampleRate = 44100;

export const OfflineAudioBufferExample: React.FC = () => {
  const [handle] = useState(() => delayRender());
  const [audioBuffer, setAudioBuffer] = useState<string | null>(null);
  const {fps, durationInFrames} = useVideoConfig();
  const lengthInSeconds = durationInFrames / fps;

  const renderAudio = useCallback(async () => {
    const offlineContext = new OfflineAudioContext({
      numberOfChannels: 2,
      length: sampleRate * lengthInSeconds,
      sampleRate,
    });
    const oscillatorNode = offlineContext.createOscillator();
    const gainNode = offlineContext.createGain();
    oscillatorNode.connect(gainNode);
    gainNode.connect(offlineContext.destination);
    gainNode.gain.setValueAtTime(0.5, offlineContext.currentTime);

    oscillatorNode.type = 'sine';
    oscillatorNode.frequency.value = C4_FREQUENCY;

    const {currentTime} = offlineContext;
    oscillatorNode.start(currentTime);
    oscillatorNode.stop(currentTime + lengthInSeconds);

    const buffer = await offlineContext.startRendering();
    setAudioBuffer(audioBufferToDataUrl(buffer));

    continueRender(handle);
  }, [handle, lengthInSeconds]);

  useEffect(() => {
    renderAudio().catch((err) => cancelRender(err));
  }, [renderAudio]);

  return audioBuffer ? (
    <Html5Audio
      src={audioBuffer}
      trimAfter={100}
      volume={(f) =>
        interpolate(f, [0, 50, 100], [0, 1, 0], {
          extrapolateLeft: 'clamp',
          extrapolateRight: 'clamp',
        })
      }
    />
  ) : null;
};

See also​