Frame type, ratios and non-square pixel rendering?

westlight · Post by **westlight** » Mon Dec 17, 2007 4:36 pm

Editing with VS 11 Plus.

I'm using the Canon HG 10. Looking at the captured video properties it list "Upper Field First" as video type. When I start a new project the default frame type list "Lower Field First".

First off I'm not sure what the difference is and am I correct to switch the project settings to match the captured video settings?

I'm also shooting in 16:9 ratio. VS 11 defaults to 4:3 which I change to 16:9. The video attributes are 24 bits, 1440 x 1080, 16:9. In the project settings I cannot change the frame size to match the video manually and it defaults to 720 x 480? Am I correct to assume that this is just for preview/editing purposes and not final output?

Should "Perform non-square pixel rendering" be checked (which it defaults to) or unchecked when shooting this format?

Thanks, David

Post by **Ron P.** » Mon Dec 17, 2007 6:39 pm

The difference in Lower and Upper fields, is basically which gets painted to your TV screen first. It is very important to match your Project Properties field order with that of your source video. Reversing this will result in jerkiness and poor quality.

You can go into the Preferences (File>Preferences or press F6), and set the default field order. That way if most of your work is with video that is Upper Field First, every time you open VS, the default will be Upper Field First. Also while you're there place a check in the box beside Show Message when inserting first video clip into the timeline. With this enabled, VS will prompt you if the project properties are different than that of the video clip being inserted. Be advised for this work, there needs to be audio in the video clips being inserted.

The first screen that you see when you start VS, has a couple of checkboxes in the lower left corner, unless you previously checked the one that says not to show this screen. If so, in the Preferences, just check the box beside Show Start up screen. Close and re-open VS. Now you can place a check beside the one that says 16:9. This will make your project's ratio set at 16:9.

What you're probably running up against with the Frame Size reverting back to 720 x 480, is the NTSC DVD setting. To change that in the Project Properties dialog, make sure the File type is set to MPEG, the press the Edit button. Go to the Compression tab. Where it says NTSC DVD, change that to MPEG2. Now you can go back to the General tab, change the Frame size, aspect ratio, and Frame Type.

That should get you where you need to be to start editing...

westlight · Post by **westlight** » Mon Dec 17, 2007 7:18 pm

Thanks for information. I'll give this a try when I'm back at my home PC.
Did you have an opinion on whether I should check "Non-square pixel rendering"? I do not have any still shots in the project, yet, and no text, again...yet. Not sure if either will be added and not sure if it matters.

I'll search the forum a bit more regarding when this option should or shouldn't be used.

So far playback of the samples of my project that I've rendered for PC use and for my website have played back just fine. I haven't gotten close to burning a disk and trying it on the wide screen HDTV. I'll open that can of worms later.

Thanks, David

www.westlight.net

etech6355 · Post by **etech6355** » Tue Dec 18, 2007 1:09 am

whether I should check "Non-square pixel rendering"?

Yes, this setting should be checked ON because your source video is 1440x1080 16:9 which uses a PAR (pixel aspect ratio) of 1.3333

sjj1805 · Post by **sjj1805** » Tue Dec 18, 2007 1:19 am

Non Square Pixel Rendering.

I admit that this used to confuse me for quite a while until eventually the penny dropped - so let me explain it in laymans language.

Think of a screen size - any screen size will do, for arguments sake we will say that our screen size is 100 x 100.
If we use Square pixels then we will have a perfect 100 x 100 square like a sheet of graph paper.
If we use non square pixels then these pixels could be oblong in shape.
Therefore the 100 x 100 will not be square.

To clarify that even further lets put some sizes to those pixels.
Let us say that our square pixels are 1" x 1" (OK a pixel isn't an inch - I am just trying to make things clear)
so we have a 100 x 100 square measuring 100" x 100"

In our non square pixel example each pixel is 1" high x 2" wide
so now our 100 x 100 grid is in fact 100" x 200" (Oblong)

Both examples contain a 100 x 100 grid but in the square one it is "Square" - the non-square one is "Oblong".

westlight · Post by **westlight** » Tue Dec 18, 2007 1:43 am

Thanks for describing in layman's terms. So given your explanation, unless I'm work in a perfectly square video format I should always use the "Non-square pixel rendering"? I'm guessing there are times when that would not be the case? I think the "penny has dropped" it just hasn't landed in my pocket yet. I do understand your example and once again thanks!

sjj1805 · Post by **sjj1805** » Tue Dec 18, 2007 1:46 am

Generally speaking you use square pixel rendering when looking at a standard computer monitor, you use non square rendering when viewing it on a TV.

etech6355 · Post by **etech6355** » Tue Dec 18, 2007 3:24 am

HighDefintion modes can make this confusing because 1280x720 and 1920x1080 use square pixels.

Another way to describe this is the video picture information is stored in each pixel. The amount of pixels across and how high determines the screen size.

Whats' nice about 1280x720 or 1920x1080 is these framesizes use square pixels
16/9=1.7777
1280/720=1.7777
1920/1080=1.7777

1280x720 Screen Size
So if you took 1280 square blocks and lined them up across in one row.
And you made 720 rows of these (720 rows of 1280 blocks).
You would have a 16:9 widescreen picture.
Same with 1920x1080 screensize.
That would be using square pixels.

Non-Square Pixels (They simply are not square)
Everyone knows what a concrete block looks like (I think), they are wider than higher. Most foundations and buildings are built on or from these blocks.
You could consider one of these blocks similar to a non-square pixel, it simply isn't square.
These non-square blocks are what a 720x480 widescreen 16:9 pixel looks like (close enough for an example, no comments/wisecracks blockheads)

Is there an easier way to explain this?
LEGO BLOCKS!!

sjj1805 · Post by **sjj1805** » Tue Dec 18, 2007 3:28 am

etech6355 wrote:..... no comments/wisecracks blockheads.....
Is there an easier way to explain this?
.....

Sorry but couldn't resist this!!!

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