The duration read-only property of the EncodedVideoChunk interface returns an integer indicating the duration of the video in microseconds.

An integer.

In the following example the duration is printed to the console.

const init = {
  type: "key",
  data: videoBuffer,
  timestamp: 23000000,
  duration: 2000000,
};
chunk = EncodedVideoChunk(init);

console.log(chunk.duration); //2000000