It depends on what the contract you sign says. For example, on Streamate: anything that you upload on their site is their property. So- if they had a video upload area, any video you uploaded would then be exclusive to them.
Not sure about Chaturbate- Most cam sites have in their contract that anything on their platform is theirs. Just make sure you read every single line of what you're signing up for.
I do know that unless you click the box making Pornhub have the rights to your videos then they do NOT own the rights, you do. Just make sure you don't click that box.
It looks like this :
"Opt-in To Automatically Protect Your Copyrighted Videos On Other Websites
I will no longer have the right to use or reproduce this content in any way, shape or form, on any free user-generated sites or platforms.
By agreeing to this, I also understand that Pornhub will own all the past and future content I have uploaded on the site as part of the Pornhub Model Program and that Pornhub will send DMCA takedown notices to remove any copies of the videos on free third party sites or free platforms. This means that Pornhub will provide a free service of DMCA takedowns on other free websites or free platforms that are user-generated. Pornhub will remove or disable content from our own website and platform by request of the uploader.
In addition, all your videos will now be added to the "Exclusive" category on Pornhub. If you have any questions or concerns, please contact
models@pornhub.com"