Looks like there is a SIP firmware for the VTO2111D doorbell! I don't have mine anymore, but this was just what i was looking for...
https://share.dahuasecurity.com:8080/Index.aspx?name=FCFA47E1A015A9EA1D750AC48AFAC038&system=FCFA47E1A015A9EA85387DD5C18BFEF1
Všechny firmware pro zařízení...