Quantcast What to resize 720x576 PAL to? Should I resize? - digitalFAQ Forum
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12-17-2020, 02:18 PM
CZbwoi CZbwoi is offline
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My end goal here is to make these for streaming purposes/playback on devices like phones, TVs, computers.

So for my 720x480 NTSC tapes, for the resizing portion my workflow is to crop out some of the tape noise at the bottom and left hand side, and then add borders equally on all sides to even it out. Afterwards I resize it to 640x480 and bam we're done, an example is something like this:

Code:
#NTSC 720x480 tape for streaming/device playback

Crop(4,0,0,-6).AddBorders(2,2,2,4)
Spline36Resize(640,480)
Nothing new you haven't seen before, standard stuff.

Now what would be the PAL equivalent to that? What would my end goal for those be? I know it's a different aspect ratio (5:4, not 4:3), therefore I probably shouldn't resize those to 640x480. Another thing is, these files on regular playback look like they're sized proportionally correct compared to the 720x480 NTSC tapes where you have to resize horizontally to display correctly for online playback, which leads me to question if resizing is necessary for these as well...or if I should just crop out the black borders/noise and equal it back out to 720x576 and have it remain like that?

Basically, if I were to finalize these PAL ones for the same reason I did the NTSC ones, for optimal playback online and on devices, what should I do? Hopefully you understand what I'm trying to say. Here are 2 screenshots for reference if needed:


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  #2  
12-17-2020, 07:25 PM
mjb2019 mjb2019 is offline
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For 4:3 square-pixel display of NTSC captured at 720◊480, you've got it correct, resizing to 640◊480. For PAL content in a 720◊576 frame, you'll want to resize to 768◊576.

You might want to take into account whether the capture includes horizontal blanking—black stripes down the left and right sides—which is outside of the intended 4:3 picture area. Standard procedure in your workflow, when this is present, is to crop to 704 wide (e.g. 8 pixels off of each side) before resizing the remainder to a width of 640 (NTSC) or 768 (PAL). To be extra precise, you could crop PAL to 702 instead of 704, if it lets you.

What to do with borders and head switching noise at the bottom is a philosophical and aesthetic issue. It is also a practical issue, if your target devices & platforms have specific requirements. Most are pretty flexible these days.
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12-17-2020, 08:19 PM
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Quote:
Originally Posted by mjb2019 View Post
For 4:3 square-pixel display of NTSC captured at 720◊480, you've got it correct, resizing to 640◊480. For PAL content in a 720◊576 frame, you'll want to resize to 768◊576.

You might want to take into account whether the capture includes horizontal blankingóblack stripes down the left and right sidesówhich is outside of the intended 4:3 picture area. Standard procedure in your workflow, when this is present, is to crop to 704 wide (e.g. 8 pixels off of each side) before resizing the remainder to a width of 640 (NTSC) or 768 (PAL). To be extra precise, you could crop PAL to 702 instead of 704, if it lets you.

What to do with borders and head switching noise at the bottom is a philosophical and aesthetic issue. It is also a practical issue, if your target devices & platforms have specific requirements. Most are pretty flexible these days.
That's it.

Crop to 704.
Resize 704 to 640.
Mask overscan noises, which recenters actual content. Cropping for overscan will harm image quality.

I do find 720x540 is much better, that 720>768 incur minor quality loss from upsizing.

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12-17-2020, 09:41 PM
traal traal is offline
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Quote:
Originally Posted by CZbwoi View Post
Another thing is, these files on regular playback look like they're sized proportionally correct compared to the 720x480 NTSC tapes where you have to resize horizontally to display correctly for online playback, which leads me to question if resizing is necessary for these as well...
Don't resize, it reduces resolution, then you have to add sharpness to get it back, but that causes halos.

Instead of resizing+sharpening, just set the Display Aspect Ratio in the metadata. How you do this depends on the container (AVI, MP4, MKV, etc.).
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12-19-2020, 01:01 AM
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Quote:
Originally Posted by traal View Post
Instead of resizing+sharpening, just set the Display Aspect Ratio in the metadata. How you do this depends on the container (AVI, MP4, MKV, etc.).
The problem is DAR isn't respected by all players, and 1:1 is often safest.

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  #6  
02-26-2021, 12:51 PM
CZbwoi CZbwoi is offline
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Sorry to come back to this, but I focused more on my NTSC tapes after this thread and just now got back to PALs. I'm still sort of confused on what to do. Referring to the screenshots in the original post, I cropped out this much - but haven't added borders (masking?) yet. Here's what I did to get rid of all the noise/natural black borders:

Code:
Crop(0,12,-4,-8).AddBorders(0,0,0,0)
I notice that you guys said to crop down to 704, and according to my calculation I didn't crop down to 704 wide. I only took 4 pixels of black border off the width, because that's all that was needed. So what am I missing here, in layman's terms? And I'm still supposed to addborders to balance out what I removed, correct? To preserve the quality and data.

Which would result in:
Code:
Crop(0,12,-4,-8).AddBorders(2,10,2,10)
Spline36Resize(720,540)
Is there something wrong in what I'm doing here..? Cropping too much, even though I literally cropped out all the noise/black bars as I think is correct? Am I supposed to add the equal amount of pixels in borders back to size it back up to the original size it was with all the noise/black bars? Sort of lost as I'm trying to divulge what to do from your conversation where there's 2 differing opinions.
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  #7  
02-26-2021, 05:35 PM
latreche34 latreche34 is offline
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The 704 figure is just to set the PAR correctly, In the real world the active video area differs from one camcorder/VCR to another and from one format to another, sometimes more sometimes less, and sometimes more to the right than the left and vise versa, the same goes to top and bottom. That's why the hardware capture is set to 720x486 in the pro capture devices to make sure no pixel left behind.

If you have more than 704 worth of active video and you want to keep it you can do so by cropping to the last active pixel and set the PAR with the same ratio as 704 with a slight horizontal stretch that won't be noticeable. Most people set it from 720 which is about 3-5% stretch so in your case it is far better.

For the vertical resolution just mask the noise, 480 is the minimum number and you cannot crop any further.
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