Bug 510059

Summary: Severe timeline lag with many subtitle clips
Product: [Applications] kdenlive Reporter: Nathan Upchurch <nathan>
Component: Timeline & EditingAssignee: Jean-Baptiste Mardelle <jb>
Status: REPORTED ---    
Severity: normal    
Priority: NOR    
Version First Reported In: 25.08.1   
Target Milestone: ---   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Nathan Upchurch 2025-09-29 15:38:49 UTC 
SUMMARY
I am working on a project with ~4 hours of footage, using the automatic subtitler to generate subtitles. The footage is almost entirely dialogue; I have generated subtitles for about half of the footage, and the timeline has slowed to the point that it's close to unusable. 

STEPS TO REPRODUCE
1. Open a project with hundreds of subtitle clips

OBSERVED RESULT
Timeline suffers from extreme lag when moving, zooming, etc. 

EXPECTED RESULT
Timeline remains performant.

SOFTWARE/OS VERSIONS
Operating System: EndeavourOS 
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.18.0
Qt Version: 6.9.2
Kernel Version: 6.16.8-arch3-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 2700X Eight-Core Processor
Memory: 64 GiB of RAM (62.7 GiB usable)
Graphics Processor: AMD Radeon RX 6800