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Slideshow grainy

User avatar unhammer
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Slideshow grainy

Wed Feb 21, 2018 3:59 pm
I'm using the Slideshow Clip, seems to work well except the images get really *grainy* compared to the originals. I tried exporting using various of the built-in qualities, even lossless, but even the 5.3G file (for 47 images / 4 minutes) has really grainy images.

The images are e.g. 5760*3840px.

Should the images be a certain file size or something?

Is there a hidden setting I need to apply?

I'm using the Kdenlive-17.12.0d-x86_64.AppImage on Xubuntu 17.10.
User avatar unhammer
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Re: Slideshow grainy

Wed Feb 21, 2018 7:03 pm
So it seems resizing the images (outside kdenlive) to max-width 1920 before exporting to the default HD mp4 removes most of the problem, though I see some moiré that wasn't there before.
Stetsbequem
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Re: Slideshow grainy

Fri Feb 23, 2018 4:24 pm
It's in the nature of things. The dimensions of the pictures (as well as all other values) should correspond to those of the project. Otherwise the program takes over and scales them with "nearest neighbour".
- https://www.mltframework.org/plugins/FilterRescale/


Either you choose the right job for the tool, or the right tool for the job.
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Re: Slideshow grainy

Sat Feb 24, 2018 9:12 am
OK, I got the best result by first doing
Code: Select all
convert -resize '1920x1080>'
to resize so it's at most 1920w/1080h. The stripier images still have a little moiré that isn't there when just viewing the (resized) image in geeqie – would that be due to the filter running regardless, or the video format / compression?

I don't think it has to be the nature of things. A few mitigations that come to mind – in order of difficulty:

  1. The documentation on https://userbase.kde.org/Special:MyLang ... show_clips could say that you should `convert -resize '1920x1080>'` if exporting to 1920x1080 to avoid the low-quality built-in resize filter
  2. The dialog under Project→Add Slideshow Clip could mention that images should first be resized
  3. The dialog under Project→Add Slideshow Clip could warn when added images have file sizes that differ a lot from the frame size under Project Settings
  4. The Slideshow Clip could run resizing before rendering using a better algorithm
  5. There could be a better FilterRescale that users could optionally choose to use everywhere, or that Slideshow Clip could always use
Stetsbequem
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Re: Slideshow grainy

Sat Feb 24, 2018 12:09 pm
The actual work is done by MLT, that's what I mean. ;) Actually, this (picture dimensions equal to project dimensions) is nonsense for slideshows. As soon as the "Kenn Burns" is used in the zoom, a correspondingly high resolution should be available for the images. And of course you're right. Things that are built in must also work. In addition, one can also ask why the size is changed arbitrarily.

A few years ago, I had expressed the wish to give the user control over whether his material would be scaled during the import process or whether the dimensions would be maintained. Just like professional editors do. The developers didn't take it up. Today I'm just looking for the right tool for my job.

- https://wiki.ubuntuusers.de/Diashows_erstellen/
- HOWTO: slideshow "Ken Burns" effect


Either you choose the right job for the tool, or the right tool for the job.

 
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