Created attachment 121562 [details] kdenlive project file which demonstrates difference in rendering speed SUMMARY Rendering speed is much faster when the kdenlive window is minimized (which means rendering is slower when the window is not minimized). It is >=2x faster when minimized. Render time: kdenlive minimized: 1 minute, 10 seconds kdenlive maximized: 3 minutes, 54 seconds STEPS TO REPRODUCE 1. Create a project from some pictures, apply some complex effects to the pictures (Wave/Dust/Blur/Pixelize) 2. Render project using H.264 in the Lossless/HQ section. Click "Render to File" 3. After clicking "Render to File" minimize the kdenlive window 4. Repeat the same process (with a unique output filename) while keeping the kdenlive window open OBSERVED RESULT Render time is much longer when kdenlive window is not minimized. Lower CPU utilization of the rendering can also be observed in Windows' Task Manager. EXPECTED RESULT Render time would be similar when kdenlive window is open or minimized. SOFTWARE/OS VERSIONS Windows: Windows 10 (version 1709), OS Build 16299.1217 KDE Frameworks Version: 5.52.0 Qt Version: 5.11.3 (built against 5.11.2) ADDITIONAL INFORMATION The difference in render speed between minimized/not minimized has been seen in other projects as well.
Created attachment 121563 [details] Image showing rendering speed difference of the same project when kdenlive window is minimized/not minimized
Thanks for reporting. Version 18.12.1 is not maintained anymore. I tested with 19.08.1. It takes 45sec to render: with or without minimizing the Kdenlive window and switch of "parallel processing" set threads to 0 (zero). Could you test with 19.08.1 as well? Which type of CPU do you have? How much memory installed?
As suggested, this seems to be working in latest versions. Please test and reopen if you encounter the issue.