Nvidia able to decode Resolve PC H.264, but not Mac H.264

I'm using Nividia's Cuda video decoder to parse and decode MP4/H.264, as exported from Resolve, and am able to parse exports from the PC version of Resolve (and stream that to the hardware decoder), but the same parser is unable to understand exports from the Mac version of Resolve. What would be the difference between the two?

So this is embarrassing. Found the issue wasn't any difference in the files at all. The issue was that my parser was only accepting filenames without spaces in them, and rejecting the file if it did. On the Mac the test filename had spaces in it, but on the PC the test filename didn't.

C