When does a browser change a <video> player to the first video frame?

Currently working on a website and trying to control the UX of a videoplayer in it.

Using various events I'm trying to swap out the poster image for the video but only if the entire video can be played. With \`canplay\` and \`canplaythrough\` events, I'm trying to control holding of playback (and displaying the poster image) until the **entire** video is loaded.

What I'm noticing is (or it appears to be this way from my testing), as soon as *some* playable data has loaded, the videoplayer swaps to displaying the initial video frames.

Is there a way for me to control when/how the poster is swapped for the actual video?