Since DF hasn't put up their full Far Cry 4 analysis yet, "Globalisateur" on the Beyond3d forum analyzed some XB1 gameplay and this is what he came up with:
https://forum.beyond3d.com/threads/...ad-the-first-post.44653/page-105#post-1808938
https://forum.beyond3d.com/threads/...ad-the-first-post.44653/page-106#post-1809029
Fix the PC version if old.
If find ~1400x1080.
Jaggies are more noticeable than on PS4 but maybe it's because of the lower resolution, still not sure yet.
https://forum.beyond3d.com/threads/...ad-the-first-post.44653/page-105#post-1808938
Here we have 34 horizontal edges (steps) for a 46 pixels wide image:
34 * 1920 / 46 = ~1419
Hence my ~1400x1080 approximation.
https://forum.beyond3d.com/threads/...ad-the-first-post.44653/page-106#post-1809029
Fix the PC version if old.