Bug 425260

Summary: Interpolation is always applied on resulting video (but not in preview)
Product: [Applications] kdenlive Reporter: Grzesiek11 <grzesiek11>
Component: Monitors & PlaybackAssignee: Jean-Baptiste Mardelle <jb>
Status: REPORTED ---    
Severity: normal CC: fritzibaby, snd.noise
Priority: NOR    
Version First Reported In: 21.04.0   
Target Milestone: ---   
Platform: Debian unstable   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description Grzesiek11 2020-08-12 15:15:38 UTC 
SUMMARY
After rendering, clips in resulting video are scaled using some kind of interpolation (if resolution is low (eg. in pixelarts), they look very blurry). This doesn't happen when looking at the preview though.

STEPS TO REPRODUCE
1. Get a low resolution image (for example, this pixelart: https://i.imgur.com/0UGgh9K.png).
2. Create a new Kdenlive project (I used 1280x720 resolution, it shouldn't matter as long as it's bigger than images resolution).
3. Add this image as a clip.
4. Insert it into the timeline.
5. Check out the preview (here is mine: https://i.imgur.com/bmKvJ2s.png).
6. Render the project (I used H264/AAC renderer, but it shouldn't matter).
7. Check out the result (here is mine: https://youtu.be/f6bNdG30_Do).

OBSERVED RESULT
Preview shows sharp image, without interpolation.
Rendered video shows blurry image, with interpolation.

EXPECTED RESULT
Preview shows sharp image, without interpolation.
Rendered video shows sharp image, without interpolation.

SOFTWARE/OS VERSIONS
Operating System: Debian GNU/Linux 
KDE Plasma Version: 5.17.5
KDE Frameworks Version: 5.70.0
Qt Version: 5.14.2
Kernel Version: 5.7.0-8.3-liquorix-amd64
OS Type: 64-bit
Processors: 4 × Intel® Core™ i5-2400 CPU @ 3.10GHz
Memory: 7,7 GiB

ADDITIONAL INFORMATION
I suggest adding an option to disable or enable interpolation in clip preferences, like in GIMP for example. Preview also needs to be fixed to display right interpolation.
Comment 1 Grzesiek11 2021-01-16 18:16:00 UTC 
Still the case for 20.12.1.

Also checked with the official AppImage (https://download.kde.org/stable/kdenlive/20.12/linux/kdenlive-20.12.1-x86_64.appimage).
Comment 2 farid 2021-03-09 17:14:45 UTC 
In the menu go to Monitor -> Monitor config -> Interpolation and change to a better setting. Does that work better?
Comment 3 Bug Janitor Service 2021-03-24 04:33:46 UTC 
Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!
Comment 4 Bug Janitor Service 2021-04-08 04:33:38 UTC 
This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!
Comment 5 Grzesiek11 2021-05-10 23:24:27 UTC 
(In reply to farid from comment #2)
> In the menu go to Monitor -> Monitor config -> Interpolation and change to a
> better setting. Does that work better?

Well, it makes the preview blurry too, so it is *consistent* with the resulting render, but still isn't *good*:

https://grzesiek11.stary.pc.pl/files/images/Screenshot_20210511_011827.png

Ideally, I want to be able to choose how a specific clip will be interpolated (so I can choose "none" for a pixelart, and "cubic" for a photo), and both the monitor and rendered file will be consistent with that setting.

So I'll say it's still the case in 21.04.0.

PS. Sorry for being that late, but I didn't notice the e-mail in my inbox...
Comment 6 Grzesiek11 2021-11-23 18:54:03 UTC 
I think I should close this ticket and open a new one as a feature request. Is that correct?