IRE 0-100 sRGB or Rec-709 range?

So as I slowly move from semi-professional to professional editing and coloring, I have been studying the various color spaces and gamma curves across the industry.

I have read around the web that IRE 0-100 is mapped to 16-135, hands down. However, some forums have also described changing the mapping setting in their NLE. So my question is, are the scopes in FCPX mapping to 0-255 or 16-235?

And if not, does H264 automatically map to 16-235? which I have read in some places.

Or will I need a broadcast safe layer?

(Side note: it all began when I tried streaming one of my Vimeo videos from a Roku 3 (outputs 0-255) to an HDTV through HDMI and found unintended contrast and clipping even after all the TV's "enhancing" is off)

Hi there,
Just some clarifications. 0 IRE maps to 16 in 8-bit, and 100 IRE maps to 235 (you probably had a typo). The FCPX scopes are in IRE luminance, and go from -20 to 120. All you have to know is you generally want to keep it within 0 and 100. Technically speaking, you can go from 0-255 RGB on computers, so you don't have to follow "broadcast safe" guidelines, but many of us still do try to follow that even for web-only delivery.

sRGB color space is almost identical to REC-709, so you will generally be safe if you shoot for REC-709 for everything. That all is going to change in the future with the newer deeper color spaces, as soon as all those 4K standards get settled.

Thank you. That's exactly the answer I was looking for and more