Scan lines vs Pixels

[Eric Barker]

Pixel Height and Scan Line Height are the same. In older TV technology (CRTs in pre-HD formats like NTSC), due to the fact that lines are drawn slightly appart from each other (and interlaced), the common lingo is that TVs use “scan lines”, for heigh dilleniation. In actuality, all monitors have pixels, there’s no fundimental difference that makes older TVs have scan lines, it’s just that because of that visual separation, the lingo is slightly different. In HD, that’s all moot because HD TVs are basically identical to computer monitors.

So when they ask for 23 scan-lines high, you can think of 23 pixels high. Also, keep in mind, that because of overscan, you’re going to lose the bottom 20 or so pixels on most TVs, so turn on the title/action safe guides (little crosshairs button in the preview monitor), and make sure that the disclaimer is cleanly within the title safe area (inner guide). I guarentee that if they have line height criteria, they will also require that the text be within the title safe area.

[Jim Wilcox]

Know all about safe etc, but if you’re working in a D1 comp (720×486) and old standard def TVs have 525 lines, 23 pixels high isn’t a 1:1 ratio, no? We’re just looking for a way to have this person comfortable with their legal folks. 23 pix high is pretty whopping large for disclaimer…

[Steve Roberts]

525 includes non-image area.

525 = 480 image (“active scan lines”) + 45 blanking.

[Steve Roberts]

This may or may not help:

https://members.aol.com/ajaynejr/vidres.htm

I recommend you visit the Broadcast Video COW forum.

[Steve Roberts]

This may or may not help:
https://members.aol.com/ajaynejr/vidres.htm

I recommend you visit the Broadcast Video COW forum for more info.

[Eric Barker]

Nope, lines to pixels IS a 1:1 ratio. You’re talking about the non-visual fields as well. The visible area on NTSC format is 720×480, along with 6 additional virtical which is used (for lack of a better term) “metadata”, things like closed captioning, digital information, etc. All YOU need to worry about, though is 480 lines, which translates exactly to 720×480 pixels. DV has nothing to do with it, that’s just a digital standard for encoding video for NTSC playback. The extra pixels you are talking about are basically the equivelent to the space between frames on a film reel. You don’t even need to think about that area… I commonly forget it exists.

Basically the ONLY thing you need to worry about (and worry is probably too strong of a word), is the transition from square pixel computer monitors to 1×0.9 sized pixels on an NTSC TV screen.

[Steve Roberts]

Yeah, I thought somebody would catch me on that. If I recall, the 480 has more non-active lines, rather than the 486 having less non-active lines. 😉

Want pain?
https://lurkertech.com/lg/big/howbig.html
https://lipas.uwasa.fi/~f76998/video/conversion/

Look here under “active picture”:
https://www.quantel.com/resource.nsf/Files/Quantel_Digital_Factbook/$FILE/Quantel_Digital_Factbook.pdf

… all this leading us to re-assert our long-held belief that a line is a pixel. If you need confirmation or denial (not me!) check out the Broadcast Video COW.

Now … the confusion may arise from past discussions that a font’s point size is not a line/pixel size. Set ups guides in the comp and work within those. Measure twice, typeset once. 🙂

[Jim Wilcox]

Agree with you all regarding the relative relevance of pix vs line. What we are really trying to do is help her with the legal dept who is demanding the 23 (which would probably chatter like crazy anyway) scan line disclaimer lines. I did just lay it out (FEC requires 4% of height which works out to about 22 pix). Freaked her right out as its pretty huge when you are looking at 5-7 lines of offer disclaimer. PErhaps will be just an academic exercise for this project.

[David Bogie]

If their legal department is like mine, you can’t show them numbers. You can cite government sources and scholarship but you can’t just tell them anything. Convert non-square to square, D1 to DV, MPEG2 or WMV and you will be looking at a sea of blank faces , lawyers who smell trouble.

If you cannot find the documentation to support your position., try this: Create the graphics. Compose your disclaimers in various type sizes and export to the formats you are targeting. Take your waveform with you and count the lines for them. Show clearly 16, 18, 20, 22, 23, 24, and 26 pixel text. Use outlines or shadows as required. Here’s a gotcha: If you have a 1.5 pixel outline, can you use 18 pixel text? If you use 23 pixels text and a 2 pixel edge, that’s 27 pixels. Does the drop shadow count?

bogiesan