FrameTransform Interface does not match TransformStream transformer Interface

[maikthomas]

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No browser affected, just a code question

Description

While looking into Insertable Streams samples e.g. https://github.com/webrtc/samples/blob/gh-pages/src/content/insertable-streams/video-processing/js/canvas-transform.js
I noticed that the Transformers implement FrameTransform from here:
https://github.com/webrtc/samples/blob/gh-pages/src/content/insertable-streams/video-processing/js/pipeline.js#L73

This Interface is very similar to the transform parameter of the TransformStream constructor:
https://developer.mozilla.org/en-US/docs/Web/API/TransformStream/TransformStream#parameters
See also typed TS def for Transformer: https://github.com/microsoft/TypeScript/blob/main/lib/lib.dom.d.ts#L1734

The differences I see are in these method names:
init -> start
destroy -> flush

Would it make sense for the transformers in this repo to match the interface above? Or am I mixing different concepts here?

Steps to reproduce

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Expected results

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Actual results

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[dogben]

Yes, that would make sense.

In that case createProcessedMediaStreamTrack (and createProcessedMediaStream) could accept the same type. It would change the timing of the init/start and flush/destroy calls, so a few other places in the code need to change as well. As currently written, the FrameTransform objects are reused when the source or sink changes without calling init or destroy; with the Transform interface, I believe start and flush would be called multiple times, which means that each implementation needs to be changed to handle that.

I would prefer either making all of the above changes or leaving things as-is. I don't think it's a good idea to use the Transform interface but manually call start/flush in the Pipeline class.