I used to use Nero Burning ROM's virtual recorder to create NRGs of my originals.
At the time, this seemed to be the easiest solution to me to create such images.
Most virtual CD drives on Windows had read support for NRG, also.
Unfortunately, NRG isn't received very well in the open source community.
Perhaps due to its proprietary nature or because Nero no longer is popular, not sure.
Edit: On the Macintosh platform, Toast used to be a very popular piece of CD/DVD authoring software.
It could handle images with both Mac/PC sessions.
Edit: If you're really curious about the details, please read about "The Apprentice" for Philips CD-i.
It used an obscure format (data in pregaps) that only a few programs like legendary CloneCD could handle correctly.
https://en.wikipedia.org/wiki/The_Appre ... ideo_game)
PS: In fact, that Nero virtual recorder was a great help to me converting the CD to an emulator friendly ISO image (I do have a real CD-i with original games, also, btw).
"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel
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