Best way to resize 640x480 to DVD standard?

[monzie]

Mogshaz:

Using 704 on 720 wide (both 480 high) will add borders L&R as do most commercial DVD's, its their to keeps the AR (DAR) exact as 720 X 480 its not true 4:3...and allow a little head room for overscan....the line length is the same (at the TV end).

You can calculate this yourself if you want

640 (your avi's width) divided by 10/11, or as a decimal 0.909 (an NTSC mpeg TV 'pixel' aka 0.91)

= 640 divided by 0.909 = 704 mpeg pixels wide.

Everyone else:

TV resolutions (talking anologue broadcast based) are measured by the number of STANDARD scanlines (480 max NTSC and 576 PAL...vertical res in 'our' language) available...the horizontal res IS NOT directly comparable to digital formats as its usually express using the circle rule (75% of the screen width for 4:3 TV's).... BUT the scanline length (or horizontal res in 'our' terms) is governed by governmental restrictions to allow for more than one or two TV stations..due to bandwith requirements... so a TYPICAL NTSC broadcast may be said to use only 330 lines of resolution (or 75 % of the available..as defined by the circle rule...or 440 if taking into account the missing 25%) as scanline lengths are not 'fixed' as such....they are 'elastic'.. as long as they occupy the same space.

If you cant get you head around it think of this (ignore the circle rule for this example):

I have 2 lengths of string each 2 feet long (or 60cm) and each has beads a long their length:

One length of string has 24 beads..the other 48 beads.....each piece of string is the same overall length.....in a nutshell thats how TV res works..the string length (TV scanline length) is the same but the information it carries (or the number of 'pixels' in pc terms) differs...the string with only 24 beads can easily carry more beads but is restricted by default.

Which is the WHOLE POINT of DVD in the first place.....it carries more information (a long the horizontal) than typical terrestial broadcast TV allows (though over here in the UK its debateable if DVD actually offers anything as we only have 5 stations and as long as you get a good TV signal its debateable if DVD is any better than terrestial TV ....other than 5.1 audio...)...due to the decreasing 'percieved' information (to the human eye) as the resolution increases (given the same original TV screen size).

[funkguy4]

Go find me a 640x480 TV. Go on. I dare ya.

TV's have about 400 pixels both ways. Hence ANY image is going to not match up in size. Your DVD player will convert 352, 704, or 720 to the appropriate number of scan lines horizontally. It will NOT convert 640 to the appropriate size.

I think what you're referring to is overscan (where you do'nt get to see the whole frame). 640 IS the appropriate size. You just don't get to see all of it. TV "pixel"s are wider than they are high. There aren't really "pixels" per say, but horizontal scan lines with color info distributed accross on them. Take a fullscreen movie and watch it on an analog TV, then watch it on the computer. You'll see that all sides of the screen have more of the frame on the computer. TV's have 525 scan lines in NTSC world. Of those, we see a little less than 480. Hence, the 720x480 resolution choice for our DVDs. The same goes for PAL world where their DVDs' resolutions are 720 x 576, because they got 625 scan lines (lucky bastards).

[lordsmurf]

That's not it either. Scanlines and overscan have no relationship. Your x480 resolution in digital includes overscan, which is the easiest flaw to see on that incorrect information.

The canvas portion seen on a tv, the "safe" area, is about 660x455 or so (660x510 for 4:3 image editing of 720x540 BMP for menus). If you want the FULL VIDEO to show, then resize your video to that size, but keep it inside the 720x480 frame. If using another res, use a calculator, not hard to figure out. Of course, most source have junk in the overscan, so probably best to leave it alone, unless it's FILM source (perfect, no noise), which is what many people see and use as the basis for these flawed thoughts.

[Gurm]

Look, all other arguments aside, it all boils down to this:

If you have a 640x480 video on your PC, and you plop it, as-is, into a DVD which is marked as having 720x480 video, it will look all squished. PERIOD.

[monzie]

That's not it either. Scanlines and overscan have no relationship. Your x480 resolution in digital includes overscan, which is the easiest flaw to see on that incorrect information.

The canvas portion seen on a tv, the "safe" area, is about 660x455 or so (660x510 for 4:3 image editing of 720x540 BMP for menus). If you want the FULL VIDEO to show, then resize your video to that size, but keep it inside the 720x480 frame. If using another res, use a calculator, not hard to figure out. Of course, most source have junk in the overscan, so probably best to leave it alone, unless it's FILM source (perfect, no noise), which is what many people see and use as the basis for these flawed thoughts.

You are quite correct Lordsmurf, in my above post I tried my hardest to avoid mentioning OVERSCAN so as not to confuse issues to people just starting out in video work, its hard enough trying to explain how TV scanlines work without throwing overscan into the explanation...people start getting paranoid about sizing issues....let those who understand overscan compensate for it if required (which I'm sure most of the regulars here do anyway when resizing).

[Nilfennasion]

I'm just going to stick my head in and say "okay, I got it wrong" before this argument about the difference between TV and computer monitor gets any further out of hand. I forgot that the old rule about how adding pixels to any dimension doesn't make the picture look any better is a bit more flexible when it comes to TV.

[monzie]

Look, all other arguments aside, it all boils down to this:

If you have a 640x480 video on your PC, and you plop it, as-is, into a DVD which is marked as having 720x480 video, it will look all squished. PERIOD.

Correct, if no resizing takes place and the original avi is just encoded 'as is' (ie using 640 X 480 on 720 x 480) then the TV picture will be out of AR by 10% (regardless of how much of the picture you actually see on the TV screen due to overscan).

[funkguy4]

alrite then lets get back to the question? What's the best way? just to stretch the 640 x 480 into a 720 x 480 frame and set the aspect ratio in the file to 4:3, forgetting about overscan compensation?

[lordsmurf]

alrite then lets get back to the question? What's the best way? just to stretch the 640 x 480 into a 720 x 480 frame and set the aspect ratio in the file to 4:3, forgetting about overscan compensation?

Yes. However, you keep confusing yourself when you say "stretching". The conversion from 640x480 1:1 will be the same as 720x480 4:3.

[Gurm]

You just... upsize it. In your favorite program. Lots of things are faster than TMPGEnc. I personally use Mainconcept, although if I have to do something OTHER than resize it, I'll probably do it all in VirtualDub just to save time.

[funkguy4]

Yes. However, you keep confusing yourself when you say "stretching". The conversion from 640x480 1:1 will be the same as 720x480 4:3.

I only say stretch coz ur increasing the horizontal resolution. I know that the final product won't replay all skewed up. But thx, sry for the bad terminology/malapropism(s).