https://bugs.kde.org/show_bug.cgi?id=474567
Bug ID: 474567
Summary: Playback very slow and choppy due to follow playhead
behavior, poor timeline redraw performance
Classification: Applications
Product: kdenlive
Version: 23.08.0
Platform: Debian unstable
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: User Interface
Assignee: j...@kdenlive.org
Reporter: jacklebe...@yahoo.com
Target Milestone: ---
SUMMARY
Unless totally zoomed out, playback will become slow and choppy due to the
timeline viewport following the playhead (which is very slow to redraw).
Although there is an option that sounds like it affects this following
behavior, that option doesn't appear to work. Although sometimes (randomly) the
viewport does not follow the playhead, I've found no way to consistently
enforce that behavior.
This slowdown occurs even when the preview window is fullscreen, covering up
the main window (I would have expected all drawing operations to be
short-circuited when the window is not visible, but maybe this isn't an
optimization QT is capable of doing?)
The result of this is lots of (slow redrawing) zooming in and out in order to
allow both fine-ediitng and relatively smooth playback.
Drawing of the timeline in general seems unreasonably slow (when scrolling
etc). It behaves as if it's drawing the entire timeline and only showing the
part within the viewport, rather than optimizing by only redrawing the part
that's visible. This is somewhat confirmed by audio waveforms extending beyond
the clip end in a flash before being redrawn correctly.
STEPS TO REPRODUCE
1. Have a big project
2. Zoom in
3. Start playback
OBSERVED RESULT
Slow and choppy
EXPECTED RESULT
Smooth.
SOFTWARE/OS VERSIONS
ADDITIONAL INFORMATION
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