Created attachment 142114 [details] Comparative images of correct & incorrect behaviour SUMMARY Preview rendering does not scale correctly for 4K footage on a 4K VDU, magnifying the content for the previewed segment (within the 'green bar' region) then jumping back to normal (correct) scaling outside the preview rendered region. STEPS TO REPRODUCE 1. In a 4K project on a 4K VDU (on Windows 10) place some material on the material on the timeline. 2. Using the drop down menu next to to the 'Preview rendering' button above the timeline, make sure 'Automatic preview' is off and click on 'Remove all preview zones'. 3. Play out the timeline - it should play out correctly and be scaled correctly. 4. Now go back and set 'Add 'Preview render zone' then set 'Automatic preview' on. 5. This should set part of the timeline to a render zone which should turn the render progress line from red to green when it's done OBSERVED RESULT Play out the timeline - on my machine the xegment that is pre-dendered, and only the segment that is pre-rendered, will ge scaled incorrectly, seeming to be magnified or scaled up incorrectly. EXPECTED RESULT Obviously, this simply shouldn't happen. SOFTWARE/OS VERSIONS Windows: 10 Home OS build: 19043.1237 kdenlive: v21.08.1, default installation (portable) ADDITIONAL INFORMATION Clearing caches etc, does not solve the issue.