Isolating Frequently Changed Nodes

A common use case for Revideo is adding subtitles to a video. Often, this gets handled like this:

Press play to preview the animation

import ...

export default makeScene2D(function* (view) {
  const words = [
    'Here',
    'are',
    'some',
    'subtitles',
    'added',
    'to',
    'the',
    'video',
  ];

  yield view.add(
    <>
      <Video
        src={'https://revideo-example-assets.s3.amazonaws.com/beach-3.mp4'}
        play={true}
        size={['100%', '100%']}
      />
    </>,
  );

  for (const w of words) {
    const textRef = createRef<Txt>();
    yield view.add(
      <Txt
        fontFamily={'Sans-Serif'}
        fill={'white'}
        fontSize={40}
        ref={textRef}
        text={w}
      />,
    );
    yield* waitFor(0.3);
    textRef().remove();
  }

  yield* waitFor(1);
});

Speed up Rendering by not adding <Txt/> to view

The implementation shown above can be made significantly faster, especially when we have more words in our subtitles:

The existing implementation repeatedly modifies the view node by always adding new <Txt/> elements to it. All of these operations will cause Revideo to reload the view node and therefore also reload the <Video/> tag, which takes up a lot of time.

The solution to this is to not add <Txt/> elements to the view node directly, but to a child container of view that is not a parent of our <Video/> element. Now, we will not reload all children of view during every <Txt/> change:

Press play to preview the animation

import ...

export default makeScene2D(function* (view) {
  const textContainer = createRef<Layout>();
  const words = [
    'Here',
    'are',
    'some',
    'subtitles',
    'added',
    'to',
    'the',
    'video',
  ];

  yield view.add(
    <>
      <Video
        src={'https://revideo-example-assets.s3.amazonaws.com/beach-3.mp4'}
        play={true}
        size={['100%', '100%']}
      />
      <Layout size={['100%', '100%']} ref={textContainer} />
    </>,
  );

  for (const w of words) {
    const textRef = createRef<Txt>();
    yield textContainer().add(
      <Txt
        fontFamily={'Sans-Serif'}
        fill={'white'}
        fontSize={40}
        ref={textRef}
        text={w}
      />,
    );
    yield* waitFor(0.3);
    textRef().remove();
  }

  yield* waitFor(1);
});

Of course, this does not just apply to <Txt/> nodes, but any node that you modify frequently.