"These captions in Chrome are created on-device, which allows the captions to appear as the content plays without ever having to leave your computer. Live Caption also works offline, so you can even caption audio and video files saved on your hard drive when you play them in Chrome.
To turn on Live Caption in Chrome from your desktop, go to Chrome Settings, click on the Advanced section, then go to the Accessibility section. The feature currently supports English and is available globally on the latest release of Chrome on Windows, Mac and Linux devices and will be coming soon to ChromeOS." from https://blog.google/products/chrome/live-caption-chrome/