The best way to sign a contract online with international signers is to go with DocuSign or Adobe Sign being the witness to the contract signing.
if the contract is about granting licence for a video, than the video must be referenced unambiguously within the contract. And this is where the problems arise.
Unfortunately, electronic signature providers do not offer functionality of placing videos inside the contract. They do not offer anything, but the most simple text documents and images. basically, if it can't be printed, you can't place it in the contract. That includes zip files.
How do you make a contract including video license permission then? Adding a link of the video is a terrible idea, because web is dynamic, and the content to which the video is pointing may easily change over time.