No, this time no Khirlov's Codecpar.

My friend is rendering a video project, but unfortunately, effects such as blur, glitch and pixelation only get previewed.

But in the output file, the effects are not applied.

What causes this problem and how to fix it?

That KDENLive18.04.1 is running on Windows 8.1 at the moment (I know, Windows is unpopular in this forum, but it likely affects Linux as well. He also has a Linux partition actually.)

The glitch somehow started working, but the target video bitrate was insufficient to handle it.

However, there is a new problem: A background picture behind a vertical video to fill the screen is not rendered.

Edit: No, that was just due to high playback speeds.

Dear Fsckdsk,

Unfortunately, I don't have a solution for your problem. I can only tell you that I have recently encountered a very similar problem in 18.08 on Linux.
I rendered a project that contained a title clip added on top of a video clip by the means of a "Composite" transition, where i set up a fade-in and fade-out. The preview was normal, but if rendered on 4 CPU threads, this effect would disappear. I rendered again using only one CPU thread and the project was rendered OK.

Looks like some weird melt6 bug.

Best regards,
hendric

jimi wrote:Dear Fsckdsk,

Unfortunately, I don't have a solution for your problem. I can only tell you that I have recently encountered a very similar problem in 18.08 on Linux.
I rendered a project that contained a title clip added on top of a video clip by the means of a "Composite" transition, where i set up a fade-in and fade-out. The preview was normal, but if rendered on 4 CPU threads, this effect would disappear. I rendered again using only one CPU thread and the project was rendered OK.

Looks like some weird melt6 bug.

Best regards,
hendric

Thank you for letting me know.

I wonder how rendering with multiple CPU cores could have any effect on the output file. It should not be anything but spreading the rendering work on multiple cores. How should this affect the effects?

fsckdsk wrote:Thank you for letting me know.

I wonder how rendering with multiple CPU cores could have any effect on the output file. It should not be anything but spreading the rendering work on multiple cores. How should this affect the effects?

Dear fsckdsk,
I actually have not the slightest idea why the number of cores should have any impact. Can you reproduce this behaviour?

Best regards,
Hendric

Hello,
Unfortunately, multi-threading is still marked as experimental in MLT & Kdenlive.
There are some situations where it fails, as this one that you raised.
Testing with latest MLT and reporting precisely the issue (which type of source clips, effects, transitions) on MLT's github issues page may help to progress towards stable operation