Can I upload multimedia from subscription access journals to third party websites
Update:

After further emails and confusions settled, IOP was more than happy to grant me permissions to use the videos. One thing I discovered is that technically, even if you're just using one or two of the figures from your paper for a poster you should ask permission from IOP. I'm not sure how common this is.

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The email response to my specific case was:

"Under the copyright form, IOP Publishing only take a non-exclusive licence from you to use and publish the video abstract (clause 1.3). Therefore we do not control what you do with the video abstract. Please note, if you have used any third party material in your video, you may need to consider whether the permission you were granted was wide enough to use that content on YouTube."

One thing to note is she is talking about the video abstract and not video figures, but I'm personally going to say that's enough of a green light for me.