TheRTCTransformEvent of theWebRTC API represent an event that is fired in a dedicated worker when an encoded frame has been queued for processing by aWebRTC Encoded Transform.

The interface has atransformer property that exposes a readable stream and a writable stream.A worker should read encoded frames fromtransformer.readable, modify them as needed, and write them totransformer.writable in the same order and without any duplication.

At time of writing there is just one event based onRTCTransformEvent:rtctransform.

Instance properties

SinceRTCTransformEvent is based onEvent, its properties are also available.

RTCTransformEvent.transformerRead only

Returns theRTCRtpScriptTransformer associated with the event.

Transform event types

There is only one type of transform event.

rtctransform

Thertctransform event is fired at the worker global scope on construction of an associatedRTCRtpScriptTransform, and whenever a new encoded video or audio frame is enqueued for processing.

You can add artctransform event listener to be notified when the new frame is available using eitherDedicatedWorkerGlobalScope.addEventListener() or theonrtctransform event handler property.

Example

This example creates an event listener for thertctransform event.

The example assumes we have aTransformStream with anoptions object passed from aRTCRtpScriptTransform constructor in the main-thread.The code at the end shows how the stream is piped through the transform stream from thereadable to thewritable.

addEventListener("rtctransform", (event) => {  let transform;  // Select a transform based on passed options  if (event.transformer.options.name === "senderTransform") {    transform = createSenderTransform(); // A TransformStream (not shown)  } else if (event.transformer.options.name === "receiverTransform") {    transform = createReceiverTransform(); // A TransformStream (not shown)  }  // Pipe frames from the readable to writeable through TransformStream  event.transformer.readable    .pipeThrough(transform)    .pipeTo(event.transformer.writable);});

Note that this code is part of a more complete example provided inUsing WebRTC Encoded Transforms.

Specifications

Browser compatibility

• Using WebRTC Encoded Transforms
• TransformStream