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Crop Reduces Video Quality of Some Inputs
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Jaroorda [Avatar]
Newbie Private Message Joined: Jul 11, 2020 16:14 Messages: 5 Offline
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I am wondering if anyone know why the Crop / Zoom / Pan tool seems to reduce the video quality of the input video and what I can do to stop that.

First, let me say that I am well acquaintedwith the topics of resolution, compression, etc. The video used below looks great in its raw form. For demonstration, I dragged two copies of this video onto the timeline and set them side by side. On the right I just resized the video, but otherwise left it alone. On the left, I used the Crop / Zoom / Pan tool to crop out a portion of the video. I resized these in the preview window to be about the same size for comparison.

This is the end result in the rendered video, there is much more artifacting on the cropped video than on the raw video. This is best seen on the baton and the shirt lettering. Certain videos seem to be worse than others and this example is far from the worst I have seen. I suspect it might be due to source format, but I have yet to find a way to completely eliminate the issue other than to avoid cropping videos.

I have tried turning on and off every acceleration option I can find. The artifacting is present in the preview and in H264, H265, and XAVC outputs. Any fixes or ideas would be much appreciated.

Background Info: I'm running PD 365 V 19.0.2108.0 (64-bit)


Comparison of Cropped vs Uncropped
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optodata
Senior Contributor Private Message Location: California, USA Joined: Sep 16, 2011 16:04 Messages: 5938 Offline
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Thanks for the details, the sample screenshots and the list of things you've tried. The first thing to do is to run the App Manager and get the latest version of PD365 (19.0.2222.0) which was released last week.

I'll run some tests on my end and see if I can replicate the issue over here.
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Jaroorda [Avatar]
Newbie Private Message Joined: Jul 11, 2020 16:14 Messages: 5 Offline
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FIrst things first, I am now running version 19.0.2222.0. I started a fresh project and was still able to duplicate the issue. No suprises there, but one can hope.

I have noticed that the effect is most prominent when the videos are reduced to only take up a small portion of the screen. Unfortunitely, I'm making a virtual band video with 45 videos on screen at once, so that's my end game. For context here is my last video: https://youtu.be/gN0AH0PJcFQ?t=102

The quality difference based on size is notable. Here is a side by side cropped and uncropped with each video roughly as tall as the canvas. I can see a tiny bit of degredation, but it isn't bad.

Full Height Example

Here is the same videos but reduced to about 20% of canvas height. The difference is substancial.



I also confirmed it only happens with some videos. I wasn't able to replicate it with the sample videos that ship with PD. I looked at the video properties, but I don't see anything that seems to predict what videos will show the issue. I also tried transcoding this video from H264 to MPEG4 and H265 with handbrake and it still did the same thing.

I have built up all my past vidos as four quadrant videos that I render separately and stich togather into a 4K master. I had to do this previously because I didn't have enough RAM to load all the videos without crashing. I now have more RAM at my disposal and decided to do all the layout at once. In doing so I made all the vidoes half their former size, and thus I believe I exacerbated this issue. I may have to go back to my old method as a fallback.

Thanks again for any suggestions.
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optodata
Senior Contributor Private Message Location: California, USA Joined: Sep 16, 2011 16:04 Messages: 5938 Offline
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I've used the C/Z/P tool extensively when editing my daughter's sports videos and haven't ever run into this issue - although given that you're working with many different clips from many different sources it seems more likely that you'd run into it than I would.

I might help if you were willing to share your project and all source clips as that would be the best way to determine if the issue is actually with PD, with specific source clips, or with your computer. It would also help to see the dxDiag report which will contain important technical details of your PC. See the Read Me Before Posting guide for the required steps.

To do that, go to File > Pack Project Materials and save everything to a cloud folder then paste a publicly shareable link to it here. Please see this forum post for more info.

If you don't have sufficient space on any of your accounts you can PM me and I'll send you a link to a OneDrive folder on my account.
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Jaroorda [Avatar]
Newbie Private Message Joined: Jul 11, 2020 16:14 Messages: 5 Offline
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Thanks!

I'll trim down one of the bad video clips and put it in a project by itself so that everything is nice and compact before posting. It will probably be a few days before I get around to this. I'm going to complete my current video first via the quadrant method I know works so that I don't have to worry about trying to troubleshoot to a deadline.
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Jaroorda [Avatar]
Newbie Private Message Joined: Jul 11, 2020 16:14 Messages: 5 Offline
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I finally had time to get around to putting together a small demo. The zip file below has the project and the single video file.

https://drive.google.com/file/d/1J3O1YKcN95eKcsmJlg7_NHz0jbRY1Ugq/view?usp=sharing

Yes, the video is mirrored. I don't know why my phone decided to do that, but I left it that way just to keep things as simple as possible. If you are looking for the artifacts in the output, I woud suggest rendering at 4K. They are present at 2K, but not terribly pronounced.
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ynotfish
Senior Contributor Private Message Location: N.S.W. Australia Joined: May 08, 2009 02:06 Messages: 9810 Offline
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Hi Jaroorda -

The difference is obvious in the screenshots you posted, but I think I must have missed something...

I downloaded your Demo project & used the Testvideo-1.m4v in a similar way, with the video duplicated on two tracks. Track 1 clip was resized in PiP Designer & Track 2 clip had Crop/Pan/Zoom applied. I left then at full screen height to make any flaws more clear.

Here's what it looks like in Preview.

Here's a VLC Player snapshot from the 2K produced version

Here's a VLC Player snapshot from the UHD produced version

Here are the two produced files: 2K version & UHD version

So, as far as I can tell, I think there's more to it than the difference between Resizing & using Crop/Zoom. What am I missing?

Cheers - Tony
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optodata
Senior Contributor Private Message Location: California, USA Joined: Sep 16, 2011 16:04 Messages: 5938 Offline
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Thanks for sharing the project.

After some testing I now fully understand what's going on. It's not an issue with clip format, bitrate, resolution, encoding or any of PD's settings - it's because you're using the Crop/Pan/Zoom tool instead of masking off the unwanted portions.

While using that tool seems like the obvious choice for cropping clips, the tool is actually meant for full-screen clips and it will also shrink or enlarge the clip to fill the full frame - especially when using the Freeform cropping setting.

In this case, you had trimmed a bit off the left and right edges so the tool automatically enlarged the clip to fill the entire canvas. That's why the clip on Track 2 is a little more zoomed in than the Track 1 clip.

This results in a lower quality image because the C/Z/P tool is working with the reduced pixel size output from the PiP Designer and not the original clip, so it's actually magnifying the flaws in the reduced pixel version.

The more appropriate tool for cropping tiny slivers of video is the Mask Designer because it operates on the full resolution version of original clip just like the PiP Designer and simply masks off the unwanted sections.

As you can see in this screenshot from the attached project, you'll have full quality on a cropped, reduced-size image when using a mask rather than the C/Z/P tool:



Try out the test project and I'm sure you'll see what I've described here. If you go back to your current project, all you have to do is open up each of the affected clips in the C/Z/P tool and click on the Reset button at the lower left to remove all the settings.

I imagine you'll see those clips clear up immediately, then you can open each one in the Mask Designer and apply a standard rectangular mask. It may help to check the Only show the selected track button to remove unrelated clips from the screen, and you'll also want to uncheck the Maintain mask aspect ratio box (under Object Settings) so you aren't stuck with a 9:16 mask.

Hopefully you'll have no more trouble making crystal clear, virtual concert videos from now on
 Filename
Mask Demo.pds
[Disk]
 Description
Run this project with your Testvideo-1.m4v clip
 Filesize
165 Kbytes
 Downloaded:
6 time(s)
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Jaroorda [Avatar]
Newbie Private Message Joined: Jul 11, 2020 16:14 Messages: 5 Offline
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Thank you optodata! That explanation makes sense and explains what I was seeing. The mask tool will give me the good looking results I expected. laughing

Tony, to answer your question, when you did this "I left then at full screen height to make any flaws more clear." you actually eliminated the problem. It is somewhat counterintuitive, but the smaller the video clips are the worse the impact is.

I will say, using the mask tool is more cumbersome (at least for my application) because the PIP designer still works with the dimensions of the unmasked video. This means that if I get a bunch of different videos that need different amounts of cropping I need to do some subtraction and scaling math for the PIP settings to compensate for the masking to get all the videos the same size and in line. I could eyeball it, but that's not my style. With CZP, the dimensions in PIP designer are those of the cropped video clip, so it is trivial to make a bunch of cropped videos all the same size and all aligned.

It seems to me that ideally the CZP tool would, at least when rendered, resample from the original source file and avoid this potential degredation. I am going to submit this as a suggestion and maybe someday it will get picked up.
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