Maybe this helps in creating a matrix:

DCI-P3

Gamma 2.6

White point
x 0.314
y 0.351 
Red
x 0.680
y 0.320
Green
x 0.265
y 0.690
Blue
x 0.150
y 0.060

From what I understand now, xyz is the storage format within the DCP, while P3 is the color space used by DCI projector itself. When a server plays a DCP, it transmits xyz to the projector. The projector will convert to and show P3.

In a grading situation with a projector connected directly to the grading workstation for realtime playout, the xyz conversion is omited and P3 is played directly from the grading workstation into the projector. A DCI projector therefore needs at least two different input profiles - P3 1:1, or xyz->P3.

Now if you say you have a file sitting in P3 color space - what does that mean? Is it the color space associated with the editing project, or do you have a file rendered out in P3 - if so, which container/codec?

- Carsten