Hat Tip: If you are trying to open a JPEG2000 encoded .mov file in After Effects 15.1 or 15.1.1, you might get a “Can’t Load Video Stream” error.
That’s because Adobe is deprecating support for Quicktime frameworks in its effort to transition to 64-bit. Apple deprecated 64-bit support for Quicktime frameworks, leaving developers in a bind.
To solve the problem, you can either convert the files or revert your After Effects to 15.0 which still has support for these (and other eclectic) formats.
By the way, reverting is pretty easy in Creative Cloud. Open the Cloud Menu. Scroll down to After Effects. In the Bubble Button labeled Open, click the little down arrow next to it. Select Other Versions and choose the version you want to install. Woohoo!