Opus is tricky, it&#x27;s royalty free but it&#x27;s not a &quot;free (as in free software)&quot; standard, it&#x27;s based on Patents held by the likes of Broadcom and MSFT which make them available without royalties.<p>This is what I&#x27;ve mentioned earlier there are quite a few royalty free but they are still based on held patents which are offered without royalties.<p>That said honestly I&#x27;m not sure how big royalties are HDMI has quite steep royalties DisplayPort doesn&#x27;t and with pretty much all devices that come with a single&#x2F;mono-cultured display interface will use HDMI rather than DisplayPort.