NTSC vs. NTSC widescreen

drw wrote on 2/15/2014, 6:33 PM

I just compared rendering some video shot in 720p MP4 to a standard def DVD. In one case I used NTSC program stream, in the other case I used NTSC widescreen. When I bring the clips into DVD Architect, create a DVD menu, bring them into the menu, and then preview them using the DVDA preview screen, they both look almost identical. I took a couple of screenshots of the two versions in the preview screen and brought the files into Photoshop, and because I'm able to overlay them exactly, I can see there's a very small difference in the vertical dimensions of the image, but its so small as to be virtually meaningless. If I had to watch them live I'm sure I wouldn't be able to tell the difference between viewing the two versions one after the other.

Mediainfo shows both files as 720x480, as you would expect, with one aspect ratio at 4:3, and the other at 16:9. Both files show letterboxing at the top/bottom of the frame and appear to have the same visible aspect ratio, regardless of what the file info says.

So a couple of questions, first would I see anything different if I had actually burned the DVD and watched it on my TV? I suspect not, but figured I'd ask. Second, what is the practical (or even theoretical) difference of using NTSC vs. NTSC widescreen when the rendered image is going to be 720x480 either way?

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Comments

Chienworks wrote on 2/19/2014, 11:43 AM

Video card likely has nothing to do with it at all. It's entirely up to the player software to read the PAR info and use it, ignore it, or allow the user to override it.

videoITguy wrote on 2/19/2014, 1:53 PM

Videocards themselves have little to do with the PAR ratio you are examining on the PC output display. If you'll notice on modern LED/LCD screens (some 16:9 others better at 16:10 for the SAR) they can smartly interpret your need to display something in SAR terms but the PAR is not "interpreted".

What you are doing is going back to the display test you did in Photoshop - you are letting the screen interface be your guide and that is just terribly wrong. Photoshop has the ability to understand PAR - but what you see on the screen viewer may get your eyes crossed - give it up.

drw wrote on 2/19/2014, 7:46 PM

videoITguy, there's nothing to give up, I'm done. All I wanted to do is figure out why my DVDA previews looked so similar, and I finally figured that out. They also looked similar when viewed in VLC, but at least there I could see the visible effect of changing the displayed aspect ratio. That allowed me to determine that what I was seeing in the DVDA preview was nothing more than an artifact of my computer display. The DVDA preview mystery now has an explanation, so I'm done with the experiment.

from the comments here it seems everyone thought I was wasting my time, but I felt it was worth the effort, and I learned a thing or two in the process about how the computer displays things.

Chienworks wrote on 2/19/2014, 9:13 PM

Probably what would have benefited you a lot right up front would have been the response, "If they look identical to you then something is wrong with your playback process. They should look different." Then we could have explored what you needed to know right away.