I concur with danrossi. I provided some critical insight, testing and workarounds to users and developers on this exact bug report, and was publicly shunned by one of apple's own developers. Completely and utterly disrespectful and unprofessional, considering that the bug has not be fixed or assigned in the 2 YEARS since its been filed, and very little response otherwise on a status how/when it will be fixed.
VR is exploding right now. Many of us companies and developers who have created VR technologies for web and apps are being held back because Apple has not yet fully embraced compliancy with the way CORS should work. All other major browsers now fully support CORS correctly for webgl video textures (FF, Chrome, Edge, Opera), which I have personally tested and verified. However, with Apple Safari failing to support CORS correctly for webgl and holding 50% of the marketshare, we cannot develop a unified solution for our technologies. Our clients need solutions and we can't provide any, or any timeline for that matter.
Bottom line, here is how I understand the issue with webgl video texturees as it stands: To paint a video frame on to the webgl texture, typically the video needs to be on the same domain as the renderer itself (e.g. www.example.com). However, in reality this concept is completely dated. No one serves video or images for that matter off their webservers anymore. We use CDNs and other media services (e.g. cdn.example.com). Because the sub-domain does not match the parent domain, this causes Safari to crap out. Typically the way around this is to set the header on the cdn to: "Access-Control-Allow-Origin: http://www.example.com" and then in the <video> tag setting video.crossOrigin="anonymous" and that should work. In fact it does for all major browsers listed above, except Safari on OSX and iOS.
Now, from what I understand, there is a back and forth between webkit and AVFoundation on who's to blame for the lack of support. Supposedly, AVFoundation is what loads the video and does not support CORS, so it ends up tainting the cavas. There doesn't seem to be proper support or communication between webkit and AVFoundation to handle initial and subsequent video handling to make this work. From an engineering standpoint, this should have been handled by the webkit browser and not AVFoundation. They are two completely separate systems.
So we're all stuck right now until Apple decides to make VR and WebGL a priority and get this resolved. I would really appreciate some response from Apple on this, and a timeline on when it will be fixed. Otherwise, a workaround would be in order. The use of a reverse proxy is just not feasible for a scaled solution.
Thanks for your attention to this matter.