My test/work with Cinelerra are always with Proxy enabled (generally without Scaler) and mpeg or mov codec for "fast" editing on my very old Notebook. Then I don't know if what I am writing may have sense for you. OS: UbuntuStudio_16.04 Project: [email protected] fps. Source video: mp4, [email protected] Proxy Settings: 1/3 (640x360), mpeg, 1800000bps. Settings: Play every frame= checked Timeline shows: abcd|12345|ABCD Two transitions 2sec length: Dissolve and Slide. Cin_Ub16-20181231-static 1) X11-OpenGL: Framerate achieved MIN= 25.4 2) X11 (use direct x11 render if possible): Framerate achieved MIN= 29.3 Cin_Ub16-20190206-static-testing 1) X11-OpenGL: Framerate achieved MIN= 24.7 2) X11 (use direct x11 render if possible): Framerate achieved MIN= 28.5 I think that mpeg file (by Proxy)) help a lot my poor Notebook because video resolution is reduced by 1/3 but also GOP=11. In the source video GOP=90. Then I guess that the ffmpeg/Cin engine have work less with more i-frames. What do you think about? Thanks. IgorBeg Note: The Framerate achieved MIN is the value minimum read in the Setting during three plays