1080p 1080i 720p (IE the i/p suffix) denotes a SMPTE resolution and timing.
HD/FHD/UHD (720,1080,2160 respectively) also denote SMPTE resolutions and timings.
These are SMPTE ST2036-1 standards, which are 16:9 and have defined (but not arbitrary) frame rates up to 120fps.

4k DCI is still a SMPTE timing, but used for cinema and is generally 24fps (tho can be 48fps for 2k DCI).
It's SMPTE 428-1.

There are other "4k" standards, but not nearly as common.

If you have arbitrary resolutions or timings outside of the SMPTE standards, and generally fall into VESA standard resolution/timings or custom EDID resolution/timings.
Chances are your computer is actually running 1920x1080@60 CVT-RB rather than 1080p60.

Whilst 1080p60 and 1920x1080@60 seem like they should be the same, some displays (and devices) might only support SMPTE timings or VESA timings.
So, although a display is 1920x1080 it might expect SMPTE, but the device can only output VESA.

[–] billwashere@lemmy.world 2 points 1 year ago (1 children)

Wow. This was very informative. Thanks!

[–] towerful@programming.dev 2 points 1 year ago

No problem.
Displays, resolutions, framrates, edids are all very complex. And marketing muddies the water!

I've encountered this issue before when using BlackMagic equipment.
What I was plugging into was described to me as "1080p".
Laptop directly into it would work, and it looked like 1080p in windows display management.
Going through BlackMagic SDI converters (SDI is a SMPTE standard protocol, so these boxes went hdmi->sdi, sdi cable, sdi->hdmi, and would only support SMPTE resolutions/timings), the display wouldn't work.
Because the display was VESA only.

I then read a lot about SMPTE, VESA, and EDIDs!