Rushs in 50p export to 25p : how to better blend images

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Gregory_DUBUS

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Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 9:43 am

Hello,

I have an issue in DVR 17. I shot my rushs in 50p UHD 3840x2160 (with a GH5), and i edited a 60 minutes film with a 50p timeline.
My export in 50 mp4 is great (normal), but i need to do DCP for cinema and theaters in 25p only.
So i added my 50p timeline of the edited film in a 25p timeline and exported it. BUT, my issue is that this 25p export have jerks (saccades in french), there are frame jumps (since Resolve is taking only 1 frame on 2).
Is there a way to "better blend" images to avoid these frame jumps please ? Or a better way to export in 25p with fluidity ?

PS : i do not want slow motions, i want my video & audio to play at 100% normally.

Thank you very much for your help.
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Uli Plank

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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 11:51 am

Try to set Frame interpolation to Blend. You'll notice some double contours, though.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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Gregory_DUBUS

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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 1:51 pm

Uli Plank wrote:Try to set Frame interpolation to Blend. You'll notice some double contours, though.

Thanks but i tested multiple things exporting each time but i do not see any difference, trying frame blend or optical flow in the project settings
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 2:07 pm

very strange, it seems the file is looking great reading with other video player than VLC.
I just updated VLC to the last version but no difference, VLC is usually great as video player, but there are image jumps when reading a mp4 export in 25p compared to the 50p. All other video player are reading correctly the 25p and the 50p. Now i can't understand why !
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 2:23 pm

Try another codec.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 2:31 pm

Try to add the motion blur effect
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 2:33 pm

Uli Plank wrote:Try another codec.

Same issue.

I just hope the DCP is good and it will play correctly on theaters. I installed DCP-O Matic to read and test the DCP i created on Davinci, it all seems OK, but...
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 2:47 pm

panos_mts wrote:Try to add the motion blur effect

Adding a blur motion effect doesn't helped.

More and more i guess it's the VLC player only and not the file itself... I hope.
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 3:05 pm

Gregory_DUBUS wrote:Adding a blur motion effect doesn't helped.
Keep in mind that motion blur is a temporal effect and needs to be applied directly to the clips, if you added the effect to a nested timeline/compound clip/adjustment clip then is not going to work.
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 3:07 pm

panos_mts wrote:
Gregory_DUBUS wrote:Adding a blur motion effect doesn't helped.
Keep in mind that motion blur is a temporal effect and needs to be applied directly to the clips, if you added the effect to a nested timeline/compound clip/adjustment clip is not going to work.


Thank you, yes i added the effect to the clip itself and it didn't work
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 5:27 pm

Gregory_DUBUS wrote:
Uli Plank wrote:Try another codec.

Same issue.

I just hope the DCP is good and it will play correctly on theaters. I installed DCP-O Matic to read and test the DCP i created on Davinci, it all seems OK, but...


I don't quite understand. If you play it in DCP-o-matic player, does it still look "jerky" i.e. the same as in VLC?
VLC is good on Android but I'd rather use MPC-HC in Windows.

Also it is good practice to test the DCP on a real projector.
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 5:47 pm

Mario Kalogjera wrote:I don't quite understand. If you play it in DCP-o-matic player, does it still look "jerky" i.e. the same as in VLC?
VLC is good on Android but I'd rather use MPC-HC in Windows.

Also it is good practice to test the DCP on a real projector.

When playing on DCP-o-matic, i can play it but not fluid enough to see it without image jumps/jerks. I've read somewhere that DCP-o-matic only use 1 heart of the computer and so can't read with sufficient fluidity a film.

I do not have access to cinema projector 7 days before the first projection, this is why i wanted to be sure of my file if there was an issue with it.

But thanks all for your help !
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Re: Rushs in 50p export to 25p : how to better blend images

PostMon Jan 17, 2022 9:25 pm

My guess is that what you are seeing is a problem of displaying 25 frames per second on a Computer monitor display at 60 frames per second (60 Hz). This can lead to the impression of jumpiness, because you can’t divide 60 by 25 without fractions.

If you got a TV capable of playing MP4 files:
Export a few minutes of your film and encode that into a mp4. Play that file on your TV (set to 50 Hz). If it looks smooth, then it will look smooth as a DCP in the cinema too.
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 8:49 am

Gregory_DUBUS wrote:
Mario Kalogjera wrote:I don't quite understand. If you play it in DCP-o-matic player, does it still look "jerky" i.e. the same as in VLC?
VLC is good on Android but I'd rather use MPC-HC in Windows.

Also it is good practice to test the DCP on a real projector.

When playing on DCP-o-matic, i can play it but not fluid enough to see it without image jumps/jerks. I've read somewhere that DCP-o-matic only use 1 heart of the computer and so can't read with sufficient fluidity a film.

I do not have access to cinema projector 7 days before the first projection, this is why i wanted to be sure of my file if there was an issue with it.

But thanks all for your help !


So when it plays fluidly is only when you export as mp4?

What processor do you have? You need to be able to play the DCP fluidly if you intend to skip projector test. I see around 50% activity on the R7 3700X processor when playing in DCP-o-matic player, most cores are at considerable load so it uses multicore processing. Granted, it doesn't render to display in a fluid manner.

I'd re-import the DCP into Resolve, let Resolve set timeline framerate according to the DCP and build mp4 from that and check the fluidity as Robert suggested above.

P.S. Did you get the EasyDCP player demo? It allows only for 15 seconds of playback, but it should be enough to get a rock steady proof that your DCP will play fluidly. Drop the quality level if your CPU is too slow, only motion is relevant.
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 10:05 am

MPC-HC is also able to play back DCPs. On a modern CPU it will play 2k DCPs without any struggles (haven’t tried 4K yet).
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 11:30 am

Making DCP with 50 to 25p blending? Not sure who would approve such a DCP.
You think blended looks better than Nearest ? Hm... you must have plenty of pans etc. as normally simple every 2nd frame drop looks way better than blend, which is crap.

Have you actually seen 25p with Nearest on projector? This looks way better than on PC screen. For such a work you need proper monitoring at native fps, not a PC preview with fixed 60Hz refresh rate. Make MP4 and play it on TV as Rober said (then think that on projections it should look even "smoother").
Blend should be last choice, nearest should work fine specially on projector.
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 12:42 pm

Uli Plank wrote:Try to set Frame interpolation to Blend. You'll notice some double contours, though.
Hmm am I correct in my assumption that both Blend and Optical Flow modes are suitable for upscaling the frame rate only (say from 25 to 50) but for downscaling they have no effect, just every second frame is dropped (Nearest mode) but whatever frames are kept, they are kept intact? Or am I mistaken? Just curious...
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 12:47 pm

You are right, but from the description it was not really clear what's going on.
Stuttering, judder, or whatever.
That's why I suggested to provoke some optical flow. But if the hardware can keep up with playing back 25 fps (or a straight multiple) it should look alright, as Andrew wrote.
No, an iGPU is not enough, and you can't use HEVC 10 bit 4:2:2 in the free version.

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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 12:54 pm

stesin wrote:Hmm am I correct in my assumption that both Blend and Optical Flow modes are suitable for upscaling the frame rate only (say from 25 to 50) but for downscaling they have no effect, just every second frame is dropped (Nearest mode) but whatever frames are kept, they are kept intact? Or am I mistaken? Just curious...
This only applies if you reduce the framerate from 50fps to 25fps or from 60fps to 30fps etc. If you downscale from 60fps to 25fps and you have optical flow or blend enabled, new in-between frames will be generated.
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 12:55 pm

stesin wrote:
Uli Plank wrote:Try to set Frame interpolation to Blend. You'll notice some double contours, though.
Hmm am I correct in my assumption that both Blend and Optical Flow modes are suitable for upscaling the frame rate only (say from 25 to 50) but for downscaling they have no effect, just every second frame is dropped (Nearest mode) but whatever frames are kept, they are kept intact? Or am I mistaken? Just curious...


You may be right that for 50p to 25p both ways may give identical end result. It may depend on implementation though.
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Re: Rushs in 50p export to 25p : how to better blend images

PostTue Jan 18, 2022 4:55 pm

panos_mts wrote:If you downscale from 60fps to 25fps and you have optical flow or blend enabled, new in-between frames will be generated.
Thanks a lot for the info. I'd better avoid this kind of rate mismatch as a whole in the future...
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Re: Rushs in 50p export to 25p : how to better blend images

PostThu Jan 20, 2022 3:17 pm

Also be mindful that when you shoot 50 fps, your automatic shutter is faster and produces less motion blur which is no problem for motion @ 50 fps but creates judder (stutter or whatever we call it) @ 25 fps, caused by too low a framerate and is especially "impactful" in high contrast picture content. You either need to shoot with slow shutter or introduce motion blur which can be troublesome.
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