Adding to Craig’s excellent advice.
Quicktime for Windows is dead. I am suspecting that less development is going into it for Mac too.
There can be a number of issues, mainly security related or the original could have been produced using a specialist codec from companies like BlueFish444 or other similar board/camera manufacturers. These can be purchased.
I find with VLC on “professional file codecs” that it often on playback does not show an accurate colour space (gamma).
Out of interest, have you tried to export it out of VLC?
It will only give you MP4, but the quality might be high enough for your needs.
The alternative could be to try out Adobe Media Encoder or HandBrake (although the latter takes a fair bit of work to get going.
In my tool-box I have WinXConverter which should be able to do the job too – they also sell a Mac version of it – starts from free:
Hope that it works out for you.