RTCEncodedAudioFrame

Constructor

RTCEncodedAudioFrame()

Copy constructor. Creates a new and independent RTCEncodedAudioFrame object from a frame, optionally overwriting some of the copied metadata.

Instance properties

RTCEncodedAudioFrame.timestamp Read only

Returns the timestamp at which sampling of the frame started.

RTCEncodedAudioFrame.data

Return a buffer containing the encoded frame data.

Instance methods

RTCEncodedAudioFrame.getMetadata()

Returns the metadata associated with the frame.

Examples

Transforming an encoded audio frame

This code snippet shows a handler for the rtctransform event in a Worker that implements a TransformStream, and pipes encoded frames through it from the event.transformer.readable to event.transformer.writable (event.transformer is a RTCRtpScriptTransformer, the worker-side counterpart of RTCRtpScriptTransform).

If the transformer is inserted into an audio stream, the transform() method is called with a RTCEncodedAudioFrame whenever a new frame is enqueued on event.transformer.readable. The transform() method shows how this might be read, modified using a fictional encryption function, and then enqueued on the controller (this ultimately pipes it through to the event.transformer.writable, and then back into the WebRTC pipeline).

addEventListener("rtctransform", (event) => {
  const transform = new TransformStream({
    async transform(encodedFrame, controller) {
      // Reconstruct the original frame.
      const view = new DataView(encodedFrame.data);

      // Construct a new buffer
      const newData = new ArrayBuffer(encodedFrame.data.byteLength);
      const newView = new DataView(newData);

      // Encrypt frame bytes using the encryptFunction() method (not shown)
      for (let i = 0; i < encodedFrame.data.byteLength; ++i) {
        const encryptedByte = encryptFunction(~view.getInt8(i));
        newView.setInt8(i, encryptedByte);
      }

      encodedFrame.data = newData;
      controller.enqueue(encodedFrame);
    },
  });
  event.transformer.readable
    .pipeThrough(transform)
    .pipeTo(event.transformer.writable);
});

Note that more complete examples are provided in Using WebRTC Encoded Transforms.

Specifications

Browser compatibility