Footage is blurry after downscaling from 4K despite Playback Resolution being on full

[JulianGPublicInfo]

Just shot an interview in 4K UHD on a Ninja V with the DNxHR HQX codec. Ingested into Premiere at that resolution and played back with no problems. However, I want to downscale to 1080p since that resolution is not necessary for delivery (just for the edit). Whenever I do though, the footage plays back and exports blurrily, despite the playback resolution being set to full.

The sequence is set to 1080p and I select "Set to frame size" for each clip. The renderer is set to Mercury Playback Enginge GPU Acceleration (CUDA). The crispness and clarity I want is there whenever I pause, and yet whenever I play the footage back, large swaths of the image blur (not enormously, but just enough to notice and to look off when playing back and upon export). 

Editing on the latest version of Premiere Pro 2021 (V15.2). 

HP Z8 G4 Workstation

Intel(R) Xeon(R) Platinum 8180

32 GB RAM

NVIDIA Quadro P6000

[Richard TOULON]

Hi,

For playback in Premiere , look what is your playback resolution in the Source and Program Monitor. By default it's 1/2 meaning that you will play half resolution.When you stop playback it gets back to full res ( you can set this up easily )

For export, it always use the full res independently of your playback settings with your monitors...so, it probably come from your exports settings.

Give us more infos with screenshots.

[JulianGPublicInfo]

Hi Richard,

Thanks for your response. Unfortunately, I've already checked playback resolution, it plainly states "Full" whether it's in playback or pause on both. Upon export, the files seem to match the discrepancy between the paused, unaffected image, vs. the played back, blurrier image.

I've attached photos of what they essentially look like when it's downscaled (played back in a 1080p sequence with "set to frame size" checked) vs when it is played back at full resolution in a 4K UHD sequence. There looks, to my eye, a noticeable drop in quality in both the exports and in the playbacks. In the 1080 interview image, that was exported with a bitrate of 20mbps and with Use Maximum Render Quality checked, settings which haven't facilitated such a drastic drop in quality when I've shot in 4K and exported to 1080p before (I've never downscaled to 1080p while working on a project, just edited in 4K and exported straight to 1080p depending on client needs). In the second image, the 4K one, it was exported with the YouTube 2160 settings, nothing else checked.

Is the drop in quality supposed to be that noticeable when downscaling? Am I approaching it incorrectly?

[Richard TOULON]

Can you give us the codec used for your export try ?

H264 ? H265 ? Other ?

Do you have a 4K monitor ?

I've never experienced such problems with blurry export from 4k to 1080p. This is pretty difficult to judge but my first thought was that the original footage was a little bit out of focus. The characteristic of this is the light reflection in the eyes, a little bit soft. Have you the ability to monitor your edit in full screen ?

I'm trying some exports from 4k UHD files to 1080p with different scenarios and I'll get back to you.

[Richard TOULON]

After multiple tests ( all tests done with " Use maximum render quality" OFF )  , the only thing I can see is that from an UHD sequence, if you want to export to UHD 2160p, you should better use H265 instead of H264. The render was a little bit more crisp than H264 since this codec is made for UHD exports ( and other stuff ).

Concerning the process, it's pretty simple. If you don't know the client needs at the end ( 4k or HD for example ), always create a 4k sequence and just export in whatever format the client ask. You loose the ability to scale in the frame of course but it prevent to move or re-scale everything back if you had an HD sequence with 4K resized assets inside.

All I can say now, is make sure that your original file was crisp at 100% zoom in your timeline. If it's ok, there is no reason to have a big quality gap on your exports from the original 4k file. Have you tried to increase a little bit more the bitrate of your codec ? 

[JulianGPublicInfo]

Hi Richard,

Thank you for your thorough responses, I've been troubleshooting and haven't understood how to check back with the forums (my apologies for the delay).

I exported to H264 in the previous images. For reference, here are two videos of clips of the interview, one in 1080p and one in 4K (once again, sorry for the delay):

https://youtu.be/V0g6f6tio4g (1080p)

https://youtu.be/VYLwEnf4rHA (4K)

I do know that my client wants a 1080p file at the end, plus much of the edit is going to be effects/graphics heavy, and I wanted to work with the smaller resolution to expedite render times and make it easier for my machine to work. Since I was going to be jumping back and forth between wide shots and close ups, I wanted the ability to work in 4K, which is why we shot it as such. Given that information, would an H265 export still be recommended, despite there being a 1080p deliverable?

I do have a 4K monitor, and once again, to my eye, the interview looks crisp in a 4K sequence. It's possible that it could be a little out of focus around the eye, that much I could concede, but it feels, given the YouTube exports, that the difference in quality between the rest of her face, the hair, and the clothes, is a bit much. Most of the time, I edit in a 4K sequence and export to 1080p depending on the situation (mostly to have a higher bitrate 4K deliverable for myself and my own purposes). I've never used a workflow in which I downscaled to 1080p ahead of the export, so my inexperience in terms of the settings could play a part. One thing that did help was checking an option in the program monitor called "High-Quality Playback," which seemed to give me a little bit more confidence in the image (though that has nothing to do with the eventual export).

[Richard TOULON]

No need to apologize.

First, 

"Given that information, would an H265 export still be recommended, despite there being a 1080p deliverable?"

H265 should give a better compression and is more efficient than H264 and will be able to encode more high resolution than H264 without extrem file size and some better handeling for streaming purpose. But I don't think this is the main issue or helper here. 

You work on a 1080p sequence with 4k files only if you attempt to reframe some videos, like for an interview for example. But if your client finaly wants a 4k export...you'll need to reframe everything, loosing of course, the ability to resize your interview. So this is very important to know what will be the final export resolution before even start the production. If you're not sure, use two 4k cameras with different focals so you can edit in 4k all the way.Now if needed you can export a 1080 video from the 4k timeline. You can give a try to the " Use maximum Render Quality" in the Render settings panel and see if your render is any better with or without. It uses an other scaling algorithm than standard upscaling or downscaling algorithm if I remember well. Try and see.

This being said, you have a 4k monitor meaning that if you look a 1080p video especially in full screen, it won't be as crisp as a 4k file since the pixels will be upscaled. 

After a brief look at your two examples on youtube on my 1920x1080 monitors, there is almost no differences.

"One thing that did help was checking an option in the program monitor called "High-Quality Playback," which seemed to give me a little bit more confidence in the image ".

High quality playback is meant for two main things ( as far as I know ). By default, when you use text and launch playback, the text will be a little bit pixelated to preserve computing, the same for some FX you may add on your videos. If you enable " High quality playback", the text and FX will play at full quality. Put a text on your timeline and have a try with and without.

I don't know if it's clearer now, but hope it helps.

[JulianGPublicInfo]

Sorry if I am not commmunicating it clearly, but my client wants a 1080p deliverable at the end. I adjusted the sequence settings to match the output. This was done because A) I didn't want after effects to be working on 4K compositions when I did graphic work, and B) I wanted to reframe shots over the course of the video without a significant loss in quality.

However, much of the information you gave me really helps. Thank you for testing out these issues with me and for providing recommendations for how to approach this, as well as instilling confidence in my workflow for when I do make deliverable files for viewing.

[Richard TOULON]

I'm not english so sometime I may misunderstand informations too. 

So ok I fully understand your process. Just export like you do. Did you send the videos to a friend with a 1080 monitor to have an other point of view. I think you should not be too woried about that. I have done this so much time. Shot in 4k and use a 1080p sequence. A pleasure if I could help you in any way.