I am new to Kdenlive (15.07.90) as I recently switched from Final Cut Pro. As a Kdenlive newbie, I would like to know what the best workflow would be for making a 4K video based on 2K clips.

My source clips are all 2K 2048x1080 (DCI) 24fps captured with FiLMIC Pro on iPhone 6.
Desired output is 4K 4096x2160 24fps.

Can I just use 4K 4096x2160 in my project settings, import the 2K footage as-is and work from there, or should I resize the clips to 4K before importing?
Or should I just use 2K 2048x1080 in my project settings, import the 2K clips and rescale to 4K when rendering?

Any ideas would be greatly appreciated!

I am just wondering what you are hoping to achieve by making a 2k source into a 4k file? I think yes if you make your project settings ultra hi res you might get a file that thinks it is 4k. But will it really have the same resolution as a genuine 4k file? I think not. Kdenlive can not create resolution that is not there to start with.

I would check the most simple solution first: Rescale when rendering.

If you want to play the movies on normal 4K screens, you may want to render 2K and leave the upscaling to the (usually well working) upscalers of the screen.

Thanks ttguy and capslock.

@ttguy: I know that upscaling 2K to 4K doesn't create a resolution that wasn't there to start with, but (please correct me if I'm wrong) upscaling to a higher resolution before applying effects will give you better results compared to upscaling after applying effects.

Another reason (I forgot to mention) to upscale upfront is that I also want to add some 4K DSLR stills, in which I would like to keep as much detail as possible.

renesmaal wrote:(please correct me if I'm wrong) upscaling to a higher resolution before applying effects will give you better results compared to upscaling after applying effects.

Hmm. I don't know if you are wrong or right. Maybe you should do a little test to see the answer to this question. I guess if you upscale first you are going to have to make sure you output to a lossless codec other wise you are going to loose quality because of double encoding. And you are going to generate huge files. And you might not gain anything. That is why I think an experiment might be in order.

The test results confirmed my assumption. From FreeDCP.net I took a 2K test pattern (Framing_uncorrected_DP2K.PNG).

First, I started a project with 2K settings (see below), imported the clip, added a Box Blur effect (Horizontal 1, Vertical multiplicator 1, Blur factor 2) and rendered (settings see below).

Then I repeated the procedure with 4K settings, using the exact same source clip. The differences are significant: the 4K settings produce way better results than the 2K settings. I would love to attach my test results but unfortunately that option seems to be disabled at the time.

Note: using the still only in my timeline, rendering ended up in an empty clip, so as a workaround I had to add a short filler clip before and after the still.


[2K Project settings]

Profile 2K 1080p 24fps
Size: 2048x1080
Frame rate: 24/1
Pixel aspect ratio: 1/1
Display aspect ratio: 17/9
Colorspace: ITU-R 709


[4K Project settings]

Profile 4K 2160p 24fps
Size: 4096x2160
Frame rate: 24/1
Pixel aspect ratio: 1/1
Display aspect ratio: 17/9
Colorspace: ITU-R 709


[Rendering]
MP4 H.264/AAC High Profile
Scanning auto
Encoder threads 2
Video quality 100

Hello,

1st, when using the very fresh Kdenlive 15.08, be warned that you may encounter bugs and won't be able to use your projects with older safer Kdenlive releases (for the moment as there is not yet export to old format).

Then, if you want to keep quality for some 4k clips (that don't need upscaling, photos in your case) then you should use a 4k profile. Upscaling in the end certainly is lower quality (in case of using effects).

Thank you vpinon. Yes, using the latest version certainly comes at a cost; I surely wouldn't use it (yet) for a huge project - curiosity killed the cat (but satisfaction brought it back).

So what I learned by experimenting is that, regardless of the resolution of the footage, best practice would be to always start a new project in the highest desired (render-time) output resolution, instead of matching the project settings to the resolution of the source clip(s) and upscaling at render-time. Giving the effects more pixels to chew on indeed seems to make a difference!