Operating system: Windows-10-10.0.17763 64 Bits
Graphics card: Intel(R) UHD Graphics 600 Intel 4.5.0 - Build 18.104.22.16837
Broken: version: 2.80 (sub 75), branch: master, commit date: 2019-07-29 14:47, hash: rBf6cb5f54494e
Duplicate the scene(with a camera inside).
Select the new scene.
Open the Video Editor workspace.
Add a scene strip from the first scene.
Set the Render Resolution to 100.
Save the file.
Do the same thing in 2.80.
Open both files in two different instances of Blender 2.80 and compare the playback speed, after setting both to Workspace > View Transform > Standard.
The file generated in 2.79 I get a playback rate of 16-20 fps.
The file generated in 2.80 I get a playback rate of 9-11 fps.
I tried to look through the settings to find any differences, but I couldn't find any, but there must be a difference in the settings causing this regression?
A gif of the playback rates: