[zackoverflow]

For Anno we are using HTML video elements / YouTube embeds which have the same frame inaccuracy from currentTime. For our editor we have a WebGL-based solution that seems to get better frame granularity but still has some floating point rounding errors converting frames <-> seconds

There's also requestVideoFrameCallback() and seekToNextFrame() in the Web APIs but they are still experimental/not supported by all browser. The WebCodecs API is also experimental/not supported to all browsers but would allow you to decode and grab the individual frames from a video and draw them to a canvas