Created attachment 179887 [details] Project .kdenlive file which fails to render SUMMARY The attached project renders (slowly) as mp4 until reaching frame 3628 and then rendering hangs there forever. This does not hang kdenlive itself; I can still abort the job and quit kdenlive. I have verified this same result in both flatpak and appimage versions of stable (24.12.3), and the appimage daily build (master-9992). After asking on the Telegram channel for support, they suggested I file a bug report, which is this. I would guess that the problem is related to the composite-and-transform on one of the tracks on the image sequence, since that has quite a lot of manually-added keyframes in it and the project did successfully render in the past before I added that (so rendering as a whole is not broken), but I can't confirm that. SOFTWARE/OS VERSIONS Linux: Ubuntu 24.04 KDE Plasma/Frameworks Version: ? don't know how to find these out Qt Version: ? don't know how to find this out either
Created attachment 179889 [details] A version of the .kdenlive file without the keyframed c-n-t, which renders successfully but slowly I've added a second version of the .kdenlive file as an attachment, which does not have the heavily keyframed composite-and-transform in it. This renders successfully and does not hang, although it does take 40 minutes to render this 4 minute HD video, which seems a very long time.
Updating: the project contains an image sequence of about 40 images, each set to be 2s15f in length with a dissolve of 15f in the Project > Add Image Sequence dialogue which is how I imported it.
(Note also that the images in the image sequence don't dissolve/crossfade cleanly with one another; they seem to fade to a grey/black chequerboard pattern like that used to indicate transparency and then into the next image)
Thanks for your report. Can you give us more info about the images used in the image sequences ? What format and which size (width and height) are the images ? Also, if you try to render just a zone of the project around that problematic frame, like render from 3610 to 3640, does it also hang on the 3628 frame ? Thanks in advance for the feedback
Good questions. > Can you give us more info about the images used in the image sequences ? What format and which size (width and height) are the images ? They're all jpegs. They're mostly fairly high resolution: some are around 4000x3000, and smaller ones are around 768x1024 or similar. > Also, if you try to render just a zone of the project around that problematic frame, like render from 3610 to 3640, does it also hang on the 3628 frame ? No, it does not; it successfully rendered that zone to an mp4 without hanging.
(In reply to Stuart Langridge from comment #3) > (Note also that the images in the image sequence don't dissolve/crossfade > cleanly with one another; they seem to fade to a grey/black chequerboard > pattern like that used to indicate transparency and then into the next image) This, it turns out, is caused by applying effects to an image sequence; if I apply a Transform or Position and Zoom effect to the image sequence on the timeline, and the image sequence was given Dissolve when it was imported, then the images crossfade via the "chequerboard" background. Removing the effect removes the chequerboard. This doesn't seem to have anything to do with the render hang, though.
Thanks a lot for your feedback. I can confirm both issues (render hang) and checkerboard on image dissolve. Regarding the render hang, I have identified the cause - incorrect scaling when combining Transform effect with Composite and Transform composition. It will take a few days to properly fix but working on it. Regarding the checkerboard problem, no idea yet but unrelated to the Transform effect as it also appears with the Position and Zoom effect, so more likely an issue with the luma composition used in image sequences, I will investigate this issue after the first one is fixed.
Upstream fix: https://github.com/mltframework/mlt/commit/74eed6b0949bd9a1f90b68561cbefa96a844abb4
Could you please confirm the rendering hang fix with the 25.04 RC appimage that can be downloaded from here: https://files.kde.org/kdenlive/unstable/
Will mark on gitlab task as done until we have a reply
> Could you please confirm the rendering hang fix with the 25.04 RC appimage that can be downloaded from here: I can confirm that rendering the video that hung with this newer version of kdenlive does not hang. It still takes a very long time to render (much of the rendering is at 1fps or slower, and the whole render took 30m) but it does not hang now, so it seems fixed.