Hello everyone,,
I recently connected a 4K Apple TV to an HDMI-to-component converter that only supports HDCP 1.4. To my surprise, all of the content I’ve tried to play so far (from iTunes and Netflix) works.

This leaves me confused about HDCP compatibility rules. Under what situations will HDCP prevent HDMI transmission?

1st it has HDCP (doesn't matter the version) so content is always going to play, because it is authorized. The 2 HDCP devices communicate (handshake) and exchange keys to validate each other.

2nd you are converting to component video, which means you are NOT going to get 4K. 1080p is the most you can get with component video. This is within the HDMI 1.4 standard, so it works.

HDCP prevents transmission when there is no handshake happening for the encoded encryption. So if a device doesn't support HDCP at all, then encrypted content will not pass.