Not so.
IPTV came to limelight with a project called the IMS(IP Multimedia Subsystem). The IMS evolved into several other projects such as NGN, EPG etc. A popular Open Source implementation of the IMS was called OpenIMS from a research lab Fraunhofer in Germany.
There are equivalent open source projects for NGN(Next Generation Networks) and EPG(Electronic Programme Guide). Do look up OpenEPG and OpenNGN. At the same time, the OpenIMSCore playground advanced into EVO/LTE and 5G that the world is talking about today. The terminology used back then was NGN.
There are several clients for consuming the IPTV service, which is one of the services available in the IMS. The VLC you mentioned might have today added a plug-in to its core to support IPTV services.
The underlying protocols was SIP with support for others - SS7, Radius etc.
You must have been referring to Video on Demand (VoD), which didn't reply on SIP but protocols like RSTP.
Yes, you can watch TV via VLC for VoD. And if the streaming service provider (say the TV station or her third party) plug into the supposed NGN network, you will have to use an NGN client with the supported protocol(s). Several existing clients have been upgraded to support NGN services. WebRTC is one of such features integrated into those clients. And there are several dedicated clients today too.
