Weird thing to discover for a job
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Only two video codecs support alpha blending: uncompressed AVI, and Quicktime .mov, the latter of which is technically considered a dead format and has been since 2016. (The former will produce files in the hundreds of gigabytes)
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When you install Quicktime, you have the option to install Quicktime itself, the Quicktime movie player, and/or the Quicktime plugin for browsers and such. You would think just installing Quicktime itself would give you the Quicktime codec, since that's the core of the whole format, but no: you have to install the Quicktime player to get the codec.
