Audio

To create an empty audio block, use:

const blockId = engine.block.create('audio');

Use engine.block.createAudioFromVideo(blockId, trackIndex: number);.

This example:

1. Extracts the first audio track (1) from a video.
2. Appends it to the page for further manipulation.

const audioBlockId = engine.block.createAudioFromVideo(videoBlockId, 0);
// Attach to the page so it’s part of the scene
engine.block.appendChild(pageId, audioBlockId);

This example:

1. Creates an audio block.
2. Attaches the audio block to the page.
3. Sets the source for the audio from a remote URL.

// Create an audio block
  const audioBlockId = engine.block.create('audio');
  await engine.block.appendChild(pageId, audioBlockId);
  engine.block.setString(
    audioBlockId,
    'audio/fileURI',
    'https://cdn.img.ly/assets/demo/v3/ly.img.audio/audios/far_from_home.m4a'
  );

For details on loading sources, check the dedicated guide.

This example exports the audio block in mp4 format:

engine.block.exportAudio(blockId, {
  mymeType: 'audio/mp4'
  }
);

This example exports the audio in wav format:

const audioData = await engine.block.exportAudio(blockId, {
  mimeType: 'audio/wav'
  }
);

Use engine.block.setPlaybackTime(blockId, time: number).

This example sets the current playback at 3 seconds:

engine.block.setPlaybackTime(blockId, 3)

Use engine.block.setVolume(blockId, volume: number);.

This example sets the volume at 1 (max value):

engine.block.setVolume(blockId, 1);

Use engine.block.setMuted(blockId, muted: boolean);.

This example mutes the audio of the block:

engine.block.setMuted(blockId, true);

Use engine.block.setPlaybackSpeed(blockId, speed: number);.

This example multiplies the speed by 0.25:

engine.block.setPlaybackSpeed(blockId, 0.25);

If the audio has an offset of:

• 0 s → It plays immediately when the scene starts.

• 2 s → The CE.SDK waits 2 seconds before playing it.

• 10 s → The audio only starts at the 10-second mark.

Use engine.block.setTimeOffset(blockId, offset: number).

This example starts the audio at 2 s in the composition:

engine.block.setTimeOffset(blockId, 2);

Use engine.block.setDuration(blockId, duration: number).

This example sets the audio duration for 300 seconds:

engine.block.setDuration(blockId, 300)

Use engine.block.setTrimLength(blockId, length: number);.

This example creates a new trim that:

1. Starts at the second 2 of the audio content.
2. Plays for 10 seconds.

engine.block.setTrimOffset(blockId, 2)
engine.block.setTrimLength(blockId, 10);

Use:

engine.block.generateAudioThumbnailSequence(
  blockId,
  samplesPerChunk: number,
  timeBegin: number,
  timeEnd: number,
  numberOfSamples: number,
  numberOfChannels: number)

numberOfSamples is the total number of samples to produce per channel, and samplesPerChunk is how many of them arrive in each callback. The engine emits ceil(numberOfSamples / samplesPerChunk) chunks, and the last one may be shorter than the rest.

The example below covers seconds 8 through 18 of the audio, producing 512 samples per channel in stereo, delivered as 8 chunks of 64 samples. Because the data is interleaved, each chunk carries 64 × 2 = 128 floats, starting with the left channel.

const cancelAudioThumbnail = engine.block.generateAudioThumbnailSequence(
  audioBlockId,
  64, // samplesPerChunk
  8, // timeBegin
  18, // timeEnd
  512, // numberOfSamples (per channel)
  2, // numberOfChannels (1 for mono, 2 for stereo)
  (chunkIndex, result) => {
    if (result instanceof Error) {
      // An error ends the whole sequence — no further chunks arrive.
      console.error('Thumbnail chunk failed', result);
      return;
    }
    // The Float32Array is a view into engine memory. Copy it before storing it.
    const samples = new Float32Array(result);
    console.log(`Chunk ${chunkIndex}`, samples);
  }
);

Call cancelAudioThumbnail() to stop generation early, for example when the user navigates away.

The values are a normalized amplitude envelope in the range 0 to 1, not raw PCM, so you can draw them directly by mirroring each value around a centerline. For the full waveform and filmstrip workflow, see Thumbnail Previews.