Bug 507630 - [Perf] Viewport animation on Title Clip with large amounts of text extremely slow to play and render
Summary: [Perf] Viewport animation on Title Clip with large amounts of text extremely ...
Status: CONFIRMED
Alias: None
Product: kdenlive
Classification: Applications
Component: Title Clips & Subtitles (other bugs)
Version First Reported In: 25.07.90
Platform: macOS (DMG) macOS
: NOR normal
Target Milestone: ---
Assignee: Jean-Baptiste Mardelle
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2025-07-29 10:33 UTC by rich
Modified: 2025-08-06 06:41 UTC (History)
1 user (show)

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Description rich 2025-07-29 10:33:36 UTC
SUMMARY
Using large amounts of text with the viewport animation for scrolling text causes performance issue. Rendering is extremely slow. On a recent project render fell to 0fps (1000 frames in 4 hours)

STEPS TO REPRODUCE
1. New Project
2. Add an image to a video track for 20 sec
3. Add a Title Clip to another video track overlapping the image for 10sec with the following settings:
- One A4 side of text (300 words)
- Font: phosphate, size 42, colour solid black
- Outline: 13 white
- Viewport animation: top to bottom

4. Try playback or render - extremely slow.

OBSERVED RESULT
Extremely slow - with animation
Normal - without animation

EXPECTED RESULT
Normal both times

SOFTWARE/OS VERSIONS
macOS: 12.7.6
Comment 1 Ron 2025-07-30 01:35:09 UTC
You're going to need to provide an actual project file with your actual settings,
preferably with just a colour clip instead of an image if that also shows the problem
(since then the project can be self-contained with no external resources, and if
that doesn't show the problem that's good information too).

I tried to create one with your recipe and the time to render with the animated title
is only about 5% slower than just rendering the image track alone (and rendering
just the title without the image is considerably faster than for the image), which
fits well within what I would consider reasonably expected.

So we need the actual test you're running before we can say for sure whether it's
something different about what you're doing, or something different about your system.
Comment 2 rich 2025-07-30 01:49:39 UTC
If you are experiencing significant slowdown you've already reproduced it. Copy and paste your text a few more times (1000 words) and see what happens.
Comment 3 Ron 2025-07-30 04:56:15 UTC
(In reply to rich from comment #2)
> If you are experiencing significant slowdown

I'm not, and I haven't yet found anything that does.
And nobody else has reported a similar issue.

So if you can't or won't produce an example that you claim demonstrates this,
which others can test, then I'm not going to waste any more time on this until
someone can show how to actually reproduce it.
Comment 4 rich 2025-07-31 07:30:09 UTC
Are you using a Mac Ron?
If not it seems none of your testing is relevant.
My original post provides a simple example that demonstrates the issue.
Comment 5 Ron 2025-08-06 05:10:57 UTC
(In reply to rich from comment #4)
> Are you using a Mac Ron?
> If not it seems none of your testing is relevant.

There's no inherent reason to believe this is platform specific, and despite repeated requests
you've provided no example to enable anyone else to deterministically test if it's somehow
specific to something about exactly what you are doing, or simply just to you.

> My original post provides a simple example that demonstrates the issue.

No it doesn't, it just describes the ordinary use of this tool for things like scrolling credits
which plenty of other people do and nobody else has ever yet reported a problem with.

Without a clear reproducer, there is no bug here that we can do anything about.
Comment 6 rich 2025-08-06 06:41:30 UTC
Ron, you have already reported a 5% slowdown for rendering some simple animated text.
Considering this is a tool for high definition video editing that, in my view, constitutes a performance issue in line with my original report.

My example is easily and quickly reproducible by anyone.

Since I have recently helped Jean resolve a bug that was specific to Mac [Bug 507568], your claim that there is no reason to believe this is platform specific is unfounded.

Your claim that nobody else has reported the bug may have something to do with low Mac users due to the availability of iMovie.

1000 frames rendered in 4 hours caused directly by title clip text viewport animation is a significant performance issue that needs resolution.

This needs a second opinion from a Mac user.